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Transcript of Poveda Alvarez Rueda
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Hydro-climatic variability over the Andes of Colombia associatedwith ENSO: a review of climatic processes and their impact on one
of the Earths most important biodiversity hotspots
German Poveda Diana M. Alvarez
Oscar A. Rueda
Received: 25 October 2009 / Accepted: 11 October 2010
Springer-Verlag 2010
Abstract The hydro-climatic variability of the Colom-
bian Andes associated with El NinoSouthern Oscillation(ENSO) is reviewed using records of rainfall, river dis-
charges, soil moisture, and a vegetation index (NDVI) as a
surrogate for evapotranspiration. Anomalies in the com-
ponents of the surface water balance during both phases of
ENSO are quantified in terms of their sign, timing, and
magnitude. During El Nino (La Nina), the region experi-
ences negative (positive) anomalies in rainfall, river
discharges (average and extremes), soil moisture, and
NDVI. ENSOs effects are phase-locked to the seasonal
cycle, being stronger during DecemberFebruary, and
weaker during MarchMay. Besides, rainfall and river
discharges anomalies show that the ENSO signal exhibits a
westerly wave-like propagation, being stronger (weaker)
and earlier (later) over the western (eastern) Andes. Soil
moisture anomalies are land-cover type dependant, but
overall they are enhanced by ENSO, showing very low
values during El Nino (mainly during dry seasons), but
saturation values during La Nina. A suite of large-scale
and regional mechanisms cooperating at the oceanatmo-
sphereland system are reviewed to explaining the identi-
fied hydro-climatic anomalies. This review contributes to
an understanding of the hydro-climatic framework of a
region identified as the most critical hotspot for biodiver-sity on Earth, and constitutes a wake-up call for scientists
and policy-makers alike, to take actions and mobilize
resources and minds to prevent the further destruction of
the regions valuable hydrologic and biodiversity resources
and ecosystems. It also sheds lights towards the imple-
mentation of strategies and adaptation plans to coping with
threats from global environmental change.
Keywords Tropics Hydro-climatology Andes
Colombia ENSO Biodiversity
1 Introduction
1.1 Threats from deforestation and biodiversity loss
in the tropical Andes
Colombia is located in northwestern South America amidst
complex geographical and hydro-climatological features
arising from its equatorial setting, in combination with: (1)
strong topographic gradients of the three branches of the
Andes crossing from southwest to northeast, (2) atmo-
spheric circulation patterns over the neighboring tropical
Pacific and Caribbean Sea, (3) its share of the Amazon and
Orinoco River basins hydro-climatic dynamics, and (4)
strong landatmosphere feedbacks.
Since a decade ago, the tropical Andes have been
identified as the most critical hotspot for biodiversity on
Earth (Myers et al. 2000), or the region subject to the
highest rates of biodiversity loss in the planet. Such situ-
ation is caused by human encroachment, deforestation,
land use/land change for agriculture, mining, and extensive
cattle ranching. Current rates of deforestation amount to
G. Poveda (&) D. M. Alvarez O. A. Rueda
School of Geosciences and Environment,
Universidad Nacional de Colombia, Medelln, Colombia
e-mail: [email protected]
D. M. Alvarez
e-mail: [email protected]
Present Address:
O. A. Rueda
Grupo HTM, Medelln, Colombia
e-mail: [email protected]
123
Clim Dyn
DOI 10.1007/s00382-010-0931-y
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340,000 ha per annum (R. Lozano, pers. comm., 2010).
Colombia is one of the top countries in biodiversity rich-
ness worldwide, but the ongoing deterioration of the tropi-
cal Andes constitutes an serious threat to the regions
sustainable development.
The purpose of this review is twofold. First, it aims
at providing a scientific framework to understand the
dynamics of the regions hydro-climatic variability atinterannual timescales, which are mainly controlled by the
two phases of the El Nino/Southern Oscillation (ENSO)
system: El Nino (warm phase) and La Nina (cold phase).
This knowledge necessarily has to be taken on board to
anticipating, mitigating and coping with the effects from
global environmental change (Poveda and Pineda 2009),
and their concomitant environmental, social and economic
losses.
Second, it constitutes a wake-up call for scientists and
policy-makers alike, aimed at taking action and mobilizing
resources and minds to set back the further destruction of
the regions valuable hydrologic and biodiversity resour-ces. Such situation needs to be tackled from the political
and institutional arenas, but also from the science of
endangered ecosystems. Structural and non-structural
measures, legislation, conservation programs and projects
need to be implemented, based on scientific research of the
regions hydrology and water resources (Poveda 2004a),
atmospheric sciences, climatology, carbon and other trace
gases budgets, biogeochemical cycles, atmospheric chem-
istry, etc. Equally needed are studies about interactions
between natural ecosystems and social systems, and on the
increasingly relevant issue of compensation for ecosystems
services, among others. Research must be funded to pre-
vent further deforestation and degradation of the regions
fragile but precious ecosystems. These tasks need to con-
form a scientific program aimed at implementing decision-
making tools and knowledge-based systems and actions,
and public policies to face the urgent challenges brought
about by deforestation and biodiversity loss over the
tropical Andes.
With the aim of providing a broader context, we review
the main climatic features of the tropical Andes of
Colombia, and provide a short literature review on the
linkages between ENSO and the regions hydro-climate
variability. Further sections quantify the effects of both
phases of ENSO on the variables making part of the
regions surface water balance.
1.2 Hydro-climatology of the Colombian Andes
In terms of the spatial distribution of precipitation Snow
(1976) describes the Andes as a dry island in a sea of
rain, but a detailed understanding of atmospheric
dynamics and precipitation over the Andes covering a wide
range of time and space scales is missing. The three
branches of the Andes house a broad range of ecosystems
and life zones including tropical rainforests, cloud forests,
paramos, glaciers, dry forests, deserts, and large intra-
Andean valleys in a predominant northerly direction.
Rainfall over the Andes deserves a careful analysis,
since the role of topography on the genesis and dynamics
of weather patterns and rainfall cannot be overstated. Deepconvection developed over strong topographic gradients
leads to deep convection that triggers highly intermittent
and intense storms in space and time. Thereby, the space
time distribution of rainfall over the tropical Andes exhibit
quite a strong variability, evidenced by markedly different
diurnal cycles even at nearby raingauges (Poveda et al.
2005). The three branches of the Andes exhibit elevations
surpassing 5,000 m, and house rapidly receding tropical
glaciers on the verge of extinction (Poveda and Pineda
2009), and long and skinny intra-Andean valleys. Extreme
precipitation amounts are witnessed over the Pacific coast
of Colombia, including one of the rainiest regions on Earth(averaging 10,00013,000 mm per year), which can be
explained through ocean-atmosphere-topography interac-
tions enhanced by the action of a low-level westerly jet
(Poveda and Mesa 2000).
On seasonal timescales, central and western Colombia
experience a bimodal annual cycle of precipitation (Fig. 1)
with marked high-rain seasons (AprilMay and Septem-
berNovember), and low-rain seasons (DecemberFebru-
ary and JuneAugust), mainly driven by the double passage
of the intertropical convergence zone (ITCZ) (Eslava 1993;
Meja et al. 1999; Leon et al. 2000; Poveda et al. 2007).
Rainfall exhibits a uni-modal annual cycle (May
October) at the northern Caribbean coast of Colombia and
at the Pacific flank of the southern isthmus, reflecting the
northernmost position of the ITCZ over both the continent
and the eastern equatorial Pacific, respectively (Hastenrath
2002; Poveda et al. 2006). Another single annual peak
(JuneAugust) occurs at the eastern slope of the eastern
Andes, resulting from the encounter of the moisture-laden
trade winds from the Amazon with the Andes. The
meridional migration of the ITCZ is strongly intertwined
with other atmospheric phenomena, including: (1) the
westerly low level Choco jet off the Pacific coast of
Colombia (Poveda and Mesa 2000; Stensrud 1996; Mapes
et al. 2003a, 2003b; Xie et al. 2008; Sakamoto et al. 2009),
(2) mesoscale convective systems (Velasco and Frisch
1987; Poveda and Mesa 2000; Meja and Poveda 2005), (3)
the low level jet in the Caribbean trade winds (Poveda and
Mesa 1999; Magana et al. 1999; Mestas-Nunez et al. 2005;
Wang 2007; Munoz et al. 2008; Amador 2008), and (4) the
easterly portion of the South American low level circula-
tion embedding a low level jet, which influences the
Colombias eastern Andes (Montoya et al. 2001), before
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veering and heading southwesterly to southern South
America and reaching to La Plata River basin (Marengo
et al. 2004).
At intra-seasonal time scales, the westerly and easterly
phases of the 4050 day intra-seasonal oscillation (Poveda
et al. 2005; Arias 2005), and the dynamics of tropical
easterly waves during the boreal summer-autumn areknown to affect precipitation regimes over different
regions of Colombia (Martnez 1993). At shorter time-
scales, the diurnal cycle of maximum rainfall exhibits
sharp differences even among nearby raingauges (Poveda
et al. 2005), while hourly and 15-min rainfall exhibit
fractal behavior in space and time (Hurtado and Poveda
2009; Poveda 2010).
1.3 ENSO-driven interannual variability
El Nino/Southern Oscillation (ENSO) is the main forcing
mechanism of interannual climate variability from hours to
seasons to decades. In general, the warm phase of ENSO
(El Nino) begins during the boreal spring, exhibiting a
strong phase locking with the annual cycle, and encom-
passing two calendar years characterized by increasing sea
surface temperature (SST) anomalies during the boreal
spring and fall of the onset year (Year 0), peaking in winter
of the following year (Year ? 1). Anomalies then decline
in spring and summer of the ensuing year (Year ? 1).
Details of ENSO dynamics and their impacts worldwide
can be found at http://www.cdc.noaa.gov/enso/.
The hydro-climatic effects of ENSO in the tropical
Americas have been investigated by Hastenrath (1976,
1990), Hastenrath et al. (1987), Waylen and Caviedes
(1986), Ropelewski and Halpert (1987), Aceituno (1988,
1989), Kiladis and Diaz (1989), Marengo (1992), Poveda
and Mesa (1997), Marengo and Nobre (2001), Ronchail
et al. (2002); Poveda and Salazar (2004), Ropelewsky and
Bell (2008), Grimm and Tedeschi (2009), Nobre et al.
(2009), Misra (2009) and Xavier et al. (2010), among
others. Physical mechanisms of ENSO-related hydro-
climatic anomalies over the region are discussed by Poveda
et al. (2006). In particular, the effects of ENSO on
Colombia are studied by Poveda (1994, 2004b); Poveda
and Mesa (1997), Gutierrez and Dracup (2001), Waylen
and Poveda (2002), Poveda et al. (1999, 2001a, 2003,
2006), Tootle et al. (2008), and Aceituno et al. (2009),
among others.
This work reviews a suite of hydro-climatic anomalies atinterannual timescales, with emphasis on the Colombian
Andes during the extreme phases of ENSO. For estimation
purposes, anomalies of precipitation, river discharges, soil
moisture, and vegetation index (NDVI) are statistically
linked with different ENSO indices, and their spacetime
consistence is discussed in Sects. 24. Section 5 summa-
rizes the physical mechanisms of the regions ocean-
atmosphereland surface system that cooperate to explain
the identified ENSO-driven hydro-climatic anomalies in
the tropical Andes of Colombia.
2 Precipitation
2.1 EOF and correlation analysis
Figure 2 shows iso-correlations between 3-month running
means of sea surface temperature (SST) anomalies over the
Indo-Pacific and the first Principal Component of monthly
standardized records of 88 raingauges along the Andes of
Colombia. High quality data, with very few missing
monthly records were provided by IDEAM and Empresas
Publicas de Medellin. The highest correlations appear over
the Nino-4 and Nino-3 regions, but also over the eastern-
most fringe of the Pacific Ocean by the tropical Americas.
Nevertheless, correlations shown in Fig. 2 are lesser than
those with the first Principal Component of river discharges
in the Andes of Colombia (Fig. 8 of Poveda and Mesa
1997), which evidences that ENSO signal is stronger for
river flows and weaker in rainfall records. Such conclusion
can be explained by the higher temporal persistence in
the former ones, and a higher intermittency of rainfall in
time, but also because river discharges result from the
Fig. 1 Annual cycle of average
precipitation during the
19721998 period at diverse
raingauges located in the central
Andes of Colombia, within the
the 1150N7460N latitudinal
band. From Poveda et al. 2001c
G. Poveda et al.: Hydro-climatic variability over the Andes of Colombia associated with ENSO
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cooperative effects of rainfall, evapotranspiration, soil
moisture and infiltration in river basins, which contribute
altogether to filter out rainfalls high frequency variability.
The said study of Poveda and Mesa (1997) showed that
ENSOs influence on anomalies of river discharges
appears earlier (later) over the western (eastern) Andes,proceeding in a wave-like westerly propagating fashion.
Such conclusion was obtained through cross-correlation
analysis between 3-month running means of the Southern
Oscillation Index (SOI) and standardized monthly river
flows. No explanation has been provided for such
behavior. Here, we contribute towards that explanation by
examining whether it is also the case for rainfall ano-
malies. Figure 3 shows cross-correlations between 3-month
running averages of the Southern Oscillation Index (SOI)
and standardized rainfall records at five raingauges in
Colombia, for the period 19581994. The SOI corre-
sponds to the traditional (Standardized TahitiStandard-
ized Darwin) sea level pressures, as is defined by the US
Climate Prediction Center (http://www.cpc.ncep.noaa.gov/
data/indices/). Cross-correlations indeed exhibit maximum
values at earlier (later) time lags over the western (eastern)
Andes, confirming the wave-like westerly-propagating
ENSO signal on monthly rainfall anomalies. As a conjec-
ture, such spatial rainfall dynamics could be attributed to
the intra-seasonal oscillation over the region (Arias 2005),
or by a combination of the direct effects of ENSO on sea
surface temperatures over the eastern Pacific, thus weak-
ening the strength of the winds of the Choco low level jet,
and by long-distance teleconnections affecting the Amazon
and eastern Colombia during both phases of ENSO, which
are reviewed in Sect. 5.
2.2 ENSOs effect on the diurnal cycle of rainfall
Rainfall in the Colombian Andes exhibit clear-cut diurnal
(24 h) and semi-diurnal (12 h) cycles, with seasonally
shifting diurnal maxima, while peak hours are extremely
sensitivity to raingauge location (Poveda et al. 2005). The
effects of both phases of ENSO on the amplitude of the
diurnal cycle are consistent throughout the Andes, as the
hourly and daily precipitation decreases during El Nino,
and increases during La Nina. For illustration, we used an
hourly data set of 55 raingauges located on the Andes of
Colombia, covering the period 19721999, with no morethan 5% of missing records. Figure 4 shows the diurnal
cycle of rainfall at 19 selected raingauges over the northern
Correlation map SSTs vs. PC No. 1 monthly rainfall in Colombia
-10
-10
-10
0
0
10
10
10
10 20
-40
-30
-30-20-1
0-30
-30
-30
-20
-2
0
-10
-10
0
0
10
10
-1000
020
0
20 -40
-40
-20
-50
20 3
0
Fig. 2 Iso-correlations (%) between sea surface temperatures and the first principal component of the Colombian standardized monthly rainfall
at 88 raingauges, for the 19581998 period
Fig. 3 Behavior of cross-correlations between 3-month running
averages of the Southern Oscillation Index (SOI) and standardized
rainfall at five raingauges in Colombia, estimated for the period
19581994. From west to east: Ansermanuevo, La Bella, Cabrera,
Monterredondo and Ramiriqu. Negative lags correspond to the SOI
leading the hydrology, and the y-scale in each diagram goes from
-1.0 to 1.0. Notice that the peaks of correlations ( P[ 0.95) occur
later in raingauges located farther east
G. Poveda et al.: Hydro-climatic variability over the Andes of Colombia associated with ENSO
123
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Fig. 4 Average diurnal cycle of rainfall intensity at selected raingauges over the northern Andes during El Nino (red), and La Nina (blue). The
study period corresponds to 19721999. Error bars are not shown for clarity
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Andes, as well as the consistent effect of both phases of
ENSO on the diurnal cycle of rainfall. Overall, a clear-cut
decrease in rainfall intensity is witnessed during El Nino
(red), and an increase and La Nina (blue).
2.3 River discharges
2.3.1 Average monthly river flows
Figure 5 shows the evolution of bi-monthly averaged
standardized anomalies of the Nare River at Santa Rita
(Department of Antioquia) alongside the (negative) Mul-
tivariate ENSO Index. Very good quality river discharges
data set was provided by Empresas Publicas de Medellin. A
statistically significant correlation of 0.60 indicates that El
Nino (La Nina) is strongly associated with negative
(positive) monthly river discharge anomalies. Seasonal
correlations (next section) exhibit even larger values. Suchstrong association provides an excellent prediction tool of
average monthly river discharges in Colombia (Poveda
et al. 2003, 2008), and makes ENSO an excellent early
warning system for multiple applied sectors in Colombia
including disaster preparedness and mitigation, hydro-
power generation (Poveda et al. 2003), agriculture (Poveda
et al. 2001a), water supply, fluvial transport, infrastructure
construction, and human health outcomes of malaria and
dengue (Poveda and Rojas 1996; Poveda et al. 2001b),
among others. In spite of that knowledge, the ongoing La
Nina (October 2010) has affected more than 1,000,000
people, causing 92 deaths and 122,000 flooded houses atmore than 400 municipalities in 28 out 32 Departments
country-wide.
The strong association between ENSO and river dis-
charges anomalies are reflected in their probability distri-
bution functions (PDF). Frequency histograms were
estimated for different phases of ENSO, using the classi-
fication defined by NOAA (http://www.cpc.noaa.gov/
products/analysis_monitoring/ensostuff/ensoyears.shtml),
and taking the hydrological year from June (Year 0) to May
(Year ? 1). Figure 6 illustrates the frequency histograms
for La Vieja River (Cartago, Valle del Cauca), with data
from 1958 to 1996 provided by IDEAM. The identified
changes in the PDFs of river discharges confirm the col-
lapse of stationarity as one of the fundamental tenets in
hydro-climatological time series analysis.
Fig. 5 Simultaneous evolution
of bi-monthly averaged
standardized anomalies of the
Nare River at Santa Rita
(Antioquia; 6200N, 75100W),
along with the negative of the
Multivariate ENSO Index
(MEI). The correlation
coefficient is 0.60, statistically
significant at 99%
Fig. 6 Frequency histograms of monthly river flows of La Vieja
River at Cartago (Valle del Cauca; 4460N, 75540W), during ENSO
phases: Normal (top), El Nino (center), and La Nina (bottom). Each
panel contains the estimated values of the sample mean (m) and
standard deviation (sd). The study period corresponds to 19581996
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2.3.2 ENSOs effects on the annual cycle
ENSO affects the amplitude of the annual cycle, although
not so the phase. Figure 7 shows the estimated average
annual cycle of the Cauca River at Salvajina, during both
phases of ENSO for the 19581998 period, estimated with
monthly data provided by IDEAM. The amplitude increa-ses during La Nina, and decreases during El Nino, although
the phase remains the same.
Furthermore, the effects of ENSO on river flows vary
with the seasonal cycle. Figure 8 shows estimates of sea-
sonal lagged correlations between the Multivariate ENSO
Index (MEI) and river discharges throughout Colombia,
with very good quality data sets provided by IDEAM and
Empresas Publicas de Medellin. In general, very large
negative simultaneous and lagged seasonal correlations
appear, in particular for the MEI during September
November (SON) and river flows in DecemberFebruary
(DJF).
2.3.3 Different flavors of El Nin o-related anomalies
The relationship between ENSO and the regions hydro-
climatology is rather complex. Although both phases of
ENSO exhibit robust dynamical features, they vary in
duration, magnitude and timing (Trenberth 1997), and so do
ENSO-related hydrological anomalies. Figure 9 shows the
evolution of standardized discharge anomalies (averages
depicted with thicker line) during past El Nino events, at
four separated rivers in central Colombia, estimated with
data provided by IDEAM. El Nino-driven hydrological
anomalies differ in timing, amplitude and duration, although
their averages (thicker line) exhibit the featured robust
negative anomalies. Such behavior of El Nino-driven
hydrologic anomalies demands continuous research to
understand the physical mechanisms driving their relation-
ship, which in turn can contribute to develop much better
river discharges forecasting methods, a highly relevant task
for planning and management of hydropower generation
(Poveda et al. 2003 and 2008), among other sectors.
2.3.4 Maximum annual and monthly flows
Extreme hydrological events are also affected by both
extreme phases of ENSO, such that in general, droughts
(floods) are amplified during El Nino (La Nina). Figure 10
shows the annual cycle of average maximum daily flows at
diverse river gauges throughout Colombia, for the
19702000 period. Good quality data sets were provided byIDEAM. Colors denote ENSO phases: El Nino (red), La
Nina (blue). The hydrological year is considered from June
(Year 0) to May (Year ? 1), as those months are the least
impacted by the onset or demise of El Nino and La Nina. As
in the case for average monthly flows, the annual cycle of
average maximum daily flows indicates that ENSO effects
are larger and felt earlier over the western Andes, whereas
effects are smaller and felt later over the eastern Andes.
We have discussed that ENSO imposes a non-stationarity
and persistent dynamics in time series of river discharges,
which invalidates the stationarity and independence
hypotheses required by traditional probabilistic estimationof annual peak flows. Thus, estimation of floods needs to be
conditioned on ENSO phase. Figure 11 shows the ENSO
phase-dependant PDFs of maximum annual (hourly) river
flows of the Negro River at Colorados (Cundinamarca),
during the 19602006 period, estimated with the procedure
introduced by Waylen and Caviedes (1986).
3 Soil moisture
Soil moisture plays an important role in tropical South
America climate dynamics at seasonal and interannual
timescales (Poveda and Mesa 1997), and makes part of
ENSO-related hydro-climatic anomalies, owing to its role
in controlling land surface-atmosphere interactions, through
processes like evapotranspiration, latent heat and sensible
heat fluxes, and atmospheric boundary layer dynamics.
Soil moisture data gathered at different land-cover types
over the tropical Andes show a remarkable dynamics at
seasonal and interannual timescales. Soil moisture data
consists in averaged daily records at Cenicafe research
station (5000N, 75360W, 1,425 m a.s.l.) on the the Central
Andes of Colombia during two consecutive extreme phases
of ENSO: El Nino 199798, and La Nina 19982000. Data
were gathered at three different land cover types: second-
ary forest, sunlit coffee, and shade coffee. Data shows that
annual and interannual (ENSO) cycles are strongly cou-
pled. Figure 12 shows the time series of 10-day average
soil moisture content for the three land cover types at
20-cm depth, along with their sample frequency histograms.
Values of 40-cm depth soil moisture contents (not shown)
are a bit larger than those at 20-cm, due to the stronger
effects of evapotranspiration at 20-cm depth. During the
Fig. 7 Annual cycle of average flows of the Cauca River at Salvajina
(Valle del Cauca; 4450N, 75500W) during ENSO phases: La Nina
(blue), Normal (black), and El Nino (red). The study period
corresponds to 19581998
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Fig. 8 Estimates of seasonal lagged correlations between the MEI
and river discharges throughout Colombia. First row MEI in March
May (MAM) versus river flows in MAM and ensuing seasons, second
row MEI in JuneAugust (JJA) and river flows in JJA and ensuing
seasons, third row MEI in SeptemberNovember (SON) and river
flows in SON and ensuing seasons, and fourth row MEI in December
February (DJF) and river flows in DJF and ensuing seasons. Filled
circles denote statistically significant correlations with respect to the
circles shown at the bottom. From Poveda et al. 2002
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Fig. 9 Time evolution of standardized anomalies at four noted river gauging stations, during past El Nin o events depicted with different color
marks, for the previous year (-1), onset year (0), and following year (?1). The black thick line denotes average of anomalies
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less rainy seasons (JulySeptember 1997 and December
1997March 1998), soil moisture reached minimum values
owing to 19971998 El Nino. During the ensuing
19982000 La Nina, soil moisture did not exhibit the
normal annual bi-modality, reaching saturation values
throughout the whole year. Under sunlit coffee, soil
moisture exhibited much more pronounced deficits than
under shade coffee and forest, which indicates that the
former is more prone to water stress. Thus, El Nino-related
dry spells might be mitigated via land cover and land use,
which is also a relevant conclusion bearing on the possible
effects of climate change.
A detailed analysis of the statistical parameters of
10-day soil moisture time series indicates that:
1. Estimated values of the mean, l, indicate that shade
coffee exhibits greater soil moisture values than forest
and sunlit coffee.
2. Estimated values of the mean, l, and standard devi-
ation, r, for sunlit coffee evidence larger dispersion
Fig. 10 Annual cycle of average maximum daily flows during El Nin o (red), La Nina (blue) for selected rivers throughout Colombia. The
abscissa axis denote the annual cycle from June (Year 0) to May (Year ? 1). The average study period corresponds to 19702000
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and unimodal probability distribution functions (PDF).This behavior can be attributed to higher intermittency
of soil moisture for sunlit coffee.
3. Higher values of the standard deviation, r, and the
kurtosis, j, for sunlit coffee indicate more extreme
values of soil moisture, and therefore fatter tails,
higher intermittency, a lower capacity of soil water
retention, and bimodal PDFs.
4. Soil moisture contents at secondary forest and shade
coffee exhibit similar values and temporal behavior,
with values around the mean, owing to a larger water
regulation capacity. Water stress also depends on land-
cover type.
These observations show that soil moisture constitute an
active key variable of climate variability during ENSO in
the tropical Andes, owing to its strong control of evapo-
transpiration, and therefore on recycled precipitation, as
well as of percolation (Rueda et al. 2010).
4 Vegetation activity (NDVI) as a surrogate
for evapotranspiration
Up to now we have reviewed the effects of ENSO on the
regions precipitation, river discharges, and soil moisture
dynamics. The effects on actual evapotranspiration should
be quantified to cover all the variables involved in the
surface water balance. Towards that end, we use the Nor-
malized Difference Vegetation Index (NDVI) as a surro-
gate measure for evapotranspiration. The NDVI is a
satellite-derived index defined as the ratio of (NIR - Red)
and (NIR ? Red), where NIR is the surface-reflected
radiation in the near-infrared band (0.731.1 lm), and Red
is the reflected radiation in the red band (0.550.68 lm).
NDVI represents the photosynthetic capacity or photo-
synthetic active radiation (PAR) absorption by green
leaves, and therefore it is linked to evapotranspiration and
plant growth. Theoretically, NDVI takes values in the
range from -1 to 1, but the observed range is usually
smaller, with values around 0 for bare soil (low or no
vegetation), and values of 0.9 or larger for dense
vegetation.The NDVI data set was obtained from the NASA Global
Inventory Modeling and Mapping Studies (GIMMS NDVI)
at 8 km spatial resolution during the July 1981November
2002 period (Tucker et al. 2005). The GIMMS NDVI data
set exhibits diverse improvements with respect to previous
NDVI data sets, including corrections for: (1) residual
sensor degradation and sensor inter-calibration differences,
(2) distortions caused by persistent cloud cover in tropical
evergreen broadleaf forests, (3) solar zenith angle and
viewing angle effects, (4) volcanic aerosols; (5) missing
data in the Northern Hemisphere during winter using
interpolation; and (6) short-term atmospheric aerosoleffects, atmospheric water vapor effects, and cloud cover.
Estimates of lagged seasonal correlations between the
Southern Oscillation Index (SOI) and NDVI data for the
July 1981November 2006 period are shown in Fig. 13.
Redish colors represent high positive correlations, while
bluish colors represent high negative correlations, indicat-
ing that NDVI is strongly reduced during El Nino, but
enhanced during La Nina. A detailed analysis of seasonal
correlations evidences high positive simultaneous correla-
tions (panels on the main diagonal), in particular during
DecemberFebruary (DJF), and September-November
(SON), although less over the eastern and southern parts of
Amazonia during MarchMay (MAM). One season lagged
correlations (above the main diagonal and left bottom
panels) indicates that SOI in MAM exhibit high positive
correlations with NDVI in JJA from north-east Brazil to the
Andes, and high negative correlation between the SOI in
JJA and NDVI in SON in northern South America. The
SOI in SON exhibits high positive correlations with NDVI
in DJF all over tropical South America.
Figure 13 denotes the continental-scale effect of ENSO
on vegetation activity over tropical South America.
Assuming that NDVI is an appropriate surrogate for
evapotranspiration, the observed correlations are in agree-
ment with the observed anomalies in precipitation, river
discharges, and soil moisture during both phases of ENSO
over the region.
5 Physical mechanisms associated with El Nino
The previously discussed ENSO-related hydro-climato-
logical anomalies in the tropical Andes of Colombia result
Log-NormalDistribution
0
500
1000
1500
2000
2500
3000
0,0 0,2 0,4 0,6 0,8 1,0
Non-excedenceProbability
Nio Nia Normal
Data Data Data
Disc
harge(m3/s)
Fig. 11 Log-Normal probability distribution functions for annual
floods of the Negro River at Colorados (Cundinamarca; 530N,
74340W), fitted for the three phases of ENSO. Study period is
19602006
G. Poveda et al.: Hydro-climatic variability over the Andes of Colombia associated with ENSO
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from diverse physical mechanisms co-operating at the
regions oceanatmosphereland surface system, summa-
rized as follows:
1. The reduction of the SST gradient over the eastern
Pacific between El Nino 1 ? 2 region and the Colom-
bian Pacific weakens the winds of the Choco jet, thus
reducing moisture advection inland (Poveda and Mesa
2000; Poveda et al. 2001a), as well as the number and
intensity of mesoscale convective systems (MCS)
(Velasco and Frisch 1987; Zuluaga and Poveda 2004;
Mejia and Poveda 2005). In general, the opposite
situation occurs during La Nina, with the concomitant
intensification of the Choco jet winds and number of
MCSs. Negative anomalies in moistureadvection by the
Choco jet winds contribute to explain negative rainfall
anomalies reported over central and western Colombia.
2. Perturbations in the tropical atmospheric circulation
patterns during El Nino lead to the establishment of an
Fig. 12 Time series of 10-day
soil moisture content under
three different land cover types
at Cenicafe research station
(5000N, 75360W, 1,425 m
a.s.l.) along with their sample
frequency histograms. Panels
a, b, and c correspond to 20-cm
soil moisture at forest, shade
coffee, and sunlit coffee,
respectively. Statistical
parameters of the series are
shown at the bottom right of
each panel as follows: mean (l),
variance (r2), standard
deviation (r), and kurtosis (j)
G. Poveda et al.: Hydro-climatic variability over the Andes of Colombia associated with ENSO
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anomalous Hadley cell over tropical South America.
The subdued ascent of moist air and associated
reduction in convective precipitation explain the
anomalously high surface pressure over the region,
particularly during DecemberFebruary, as noted by
Rasmusson and Mo (1993) during 19821983,
19861987, and 19911992 El Nino events, and
diagnosed by Yasunari (1987) and Aceituno (1988).
Diverse characteristics such as position, and horizon-
tal and vertical structure of thermal forcing over the
tropical Pacific during boreal winters appear as
important determinants of the phase and amplitude
of ENSO-related anomalies over the tropical Ameri-
cas (Ambrizzi and Magana 1999).
3. Atmospheric pressure changes over tropical South
America during El Nino contribute to the shift the
centers of convection within the ITCZ over the
eastern Equatorial Pacific towards the south-west of
their normal positions (Pulwarty and Diaz 1993).
4. It has been suggested that precipitation anomalies
over the region during ENSO events are caused by an
anomalous eastward shift of the Walker cell, which
would produce an anomalous rising motion over the
equatorial eastern Pacific and a sinking motion over
the tropical Atlantic (Kousky et al.1984). Although
there have been attempts to describe the entire zonal
circulation of the tropics (Flohn and Fleer 1975;
Wang 1987), it seems that the Walker cell is not well
defined beyond the Pacific region (Hastenrath 1991,
p. 210). It has been recognized that ENSO influences
the large-scale eastwest and meridional circulations
in the global tropics that have implications over
Fig. 13 Estimates of seasonal lagged correlations between the
Southern Oscillation Index (SOI) and the Normalized Difference
Vegetation Index (NDVI) over tropical South America. First row SOI
in DecemberFebruary (DJF) versus NDVI in DJF and ensuing
seasons, second row SOI in MarchMay (MAM) and NDVI in DJF
and ensuing seasons, third row SOI in JuneAugust (JJA) and NDVI
in DJF and ensuing seasons, and fourth row SOI in September
November (SON) and ensuing seasons. Correlations are quantified
according to the color bar on the bottom. The study period is July
1981 through November 2006
G. Poveda et al.: Hydro-climatic variability over the Andes of Colombia associated with ENSO
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tropical South America (Misra 2008; Grimm 2003,
2004).
5. Weakened feedbacks between precipitation and sur-
face convergence in tropical South America are
associated with the aforementioned anomalies in the
Hadley cell circulation (Numaguti 1993) and in the
trade winds over the Caribbean. Also, during ENSO
there is a large-scale anomalous upper-level diver-gence over continental tropical South America.
6. The featured wave-like westerly propagation ENSO
signal on hydrological anomalies cause a disruption
of landatmosphere interactions, owing to the strong
coupling between precipitation, soil moisture, vege-
tation, and evapotranspiration anomalies (Nepstad
et al. 1994; Jipp et al. 1998; Poveda and Mesa 1997;
Zeng 1999; Poveda et al. 2001a; Poveda and Salazar
2004; Nobre et al. 2009). A reduction in evapotrans-
piration also contributes to diminish the amount of
recycled precipitation. Diminished cloudiness pro-
motes increased solar irradiance and surface tempera-tures, thus reinforcing dry conditions. Even in wet
tropical climates, water stress can be imposed on
tropical forests, as in the case of strong El Nino
events (Oren et al. 1996; Marengo et al. 2008).
7. Land surface-atmosphere feedbacks are important
mechanisms to explaining anomalies in precipitation
and upper level divergence over northern South
America (Poveda and Mesa 1997; Misra 2009).
8. The interannual anomalies in precipitation (Lau and
Sheu 1988; Hsu 1994; Kousky and Kayano 1994) are
associated with negative anomalies in soil moisture
(Nepstad et al. 1994; Jipp et al. 1998; Poveda andMesa 1997; Fisher et al. 2008). The hydrological
connection between soil moisture and river dis-
charges validates the conclusions drawn from the
isocorrelation maps shown in Fig. 8.
9. Negative anomalies in evapotranspiration in tropical
South America (Nepstad et al. 1994; Vorosmarty
et al. 1996; Poveda and Mesa 1997; Malhi et al.
2002; Meir et al. 2009; Phillips et al. 2009; Meir and
Woodward 2010) lead to further precipitation defi-
cits, as large proportions (2550%) of rainfall in the
Amazon basin have been estimated as derived from
evapotranspiration recycling (Shuttleworth 1988;Elthair and Bras 1994; Trenberth et al. 2003). This
is a crucial aspect of the land-atmosphere feedback
mechanisms during ENSO over tropical South
America.
10. Negative anomalies in evapotranspiration over tropi-
cal South America during El Nino may also
contribute to weaken the pumping effect of atmo-
spheric moisture exerted by the Amazon forest, a
physical mechanism put forward recently by
Gorshkov and Makarieva (2007), and Makarieva
et al. (2009).
11. During the boreal summer of Year 0, the northeast
trade winds intensify (weaken) during El Nino (La
Nina). However, in concordance with the noted
changes in surface pressures during the boreal winter
(3), the winds weakens and even reverse in Year ? 1,
triggering a change in sea surface temperatures overthe Caribbean and the tropical North Atlantic (Has-
tenrath 1976; Curtis and Hastenrath 1995).
12. SSTs positive anomalies and the strength of the trade
winds over the Caribbean play an important role in
decreasing the intensity and number of tropical
easterly waves and tropical storms (Frank and Hebert
1974; Gray and Sheaffer 1991), thus contributing to
diminish precipitation over the Caribbean and north-
ern South America, including Colombia.
6 Final remarks
The ENSO-driven hydro-climatic variability of the tropical
Andes of Colombia at interannual timescales was
reviewed. The strong seasonality of such an influence has
been quantified on precipitation, average and extreme river
discharges, soil moisture, and NDVI as a surrogate of
evapotranspiration. Extreme phases of ENSO constitute the
main driver of hydro-climatic anomalies, resulting from the
combined effects of SSTs anomalies off the Pacific coast
off Colombia, in addition to atmospheric teleconnections
and land surfaceatmosphere feedbacks. The Nino 3 andNino 4 regions over the central tropical Pacific exhibit the
highest correlations with rainfall in the tropical Andes.
Seasonal cross-correlation analyses confirm that El Nino
(La Nina) produces drier (wetter) than normal and more
prolonged dry (wet) seasons in the Andes of Colombia.
River discharge and rainfall data show that the effects of
ENSO appear earlier (later) and stronger (weaker) over the
western (eastern) Andes. Seasonal correlations indicates
that ENSO indices become important and valuable tools to
forecast many hydro-climatological variables in the region.
We have also shown that soil moisture dynamics is a key
component of climate variability over the tropical Andesfrom seasonal to interannual timescales. Both El Nino and
La Nina affect the dynamics of soil moisture on the region,
and their effect depends on land cover type. The coupling
between the vegetation-soil system and land cover strongly
modulates (space-) time hydro-climatic variability in the
tropical Andes, and therefore El Nino-related dry spells
might be ameliorated via land cover and land use. This in
turn suggests an appropriate adaptation strategy to cope
with the effects of climate change.
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Besides ENSO, other macro-climatic phenomena affect
the hydro-climatic variability of the tropical Andes. Among
them, there are significant statistical correlations between
the NAO and Colombias hydrology (Poveda et al. 1998),
as well as with the PDO and sea surface temperatures over
the tropical Atlantic (Poveda 2004b). The nonlinear inter-
actions of such macro-climatic phenomena with the ITCZ,
the Choco and Caribbean low-level jets, and with otherphysical mechanisms acting at intra-annual timescales
(intra-seasonal oscillation, tropical easterly waves, etc.),
coupled with land surface-atmosphere interactions produce
the featured hydro-climatic variability pattern at the
Colombian Andes. This knowledge contributes to improve
hydro-climatic predictability, with important practical
implications for agriculture, hydropower generation, fluvial
transport, natural hazards and disasters, and human health
outcomes in the region.
Our study sheds light to understand how the interannual
hydro-climatic variability could affect a suite of biological
and ecological processes in two critical regions, namely thetropical Andes and the headwaters of the Amazon, a river
basin of global hydro-ecological and biodiversity impor-
tance. A fundamental research programme for the region
will have to deal with implications for biodiversity and
ecosystems functioning arising from feedbacks between
global warming, deforestation, land use/land change, and
the reviewed ENSO-related interannual hydro-climatic
variability.
Acknowledgments This research was supported by COLCIEN-
CIAS and Universidad Nacional de Colombia through the GRECIA
Research Programme. We thank Instituto de Hidrologa, Meteoro-loga y Estudios Ambientales de Colombia (IDEAM), Empresas
Publicas de Medelln (EPM), and Cenicafe for providing hydrological
data sets. NDVI data set was provided by C.J. Tucker and J. Pinzon
from the NASA Goddard Space Flight Center. We are grateful to
H.A. Moreno, O.O. Hernandez, C.D. Hoyos, V. Toro, A. Ceballos,
and L.A. Acevedo for their help with some figures, and to Peter
Bunyard, the Editor, Dr. Edwin K. Schneider, and the anonymous
reviewers for their valuable comments and insights to improve the
manuscript.
References
Aceituno P (1988) On the functioning of the Southern Oscillation in
the South American sector. Part I. Surface climate. Mon Wea
Rev 116:505524
Aceituno P (1989) On the functioning of the Southern Oscillation in
the South American sector. Part II. Upper-air circulation. J Clim
2:341355
Aceituno P, Prieto M, Solari ME, Martinez A, Poveda G, Falvey M
(2009) The 18771878 El Nino episode: Climate anomalies in
South America and associated impacts. Clim Change
92:389416
Amador JA (2008) The intra-Americas sea low-level jet. Overview
and future research. Ann NY Acad Sci 1146:153188
Ambrizzi T, Magana V (1999) Dynamics of the impact of El Nino/
Southern Oscillation on the Americas climate. In: Proceedings
of 14th Conference on Hydrology. AMS, Dallas, pp 307308
Arias PA (2005) Intra-seasonal variability of Colombias hydro-
climatology with emphasis on the Madden-Julian Oscillation (in
Spanish). M.Sc thesis, Graduate Program in Water Resources,
Universidad Nacional de Colombia at Medellin
Curtis S, Hastenrath S (1995) Forcing of anomalous sea surface
temperature evolution in the tropical Atlantic during Pacific
warm events. J Geophys Res 100(C8):15,83515,847
Elthair EAB, Bras R (1994) Precipitation recycling in the Amazon
basin. Quart J Roy Meteor Soc 120:861880
Eslava J (1993) Some climatic particularities of Colombias Pacific
region (in Spanish). Atmosfera 17:4563
Fisher RA, Williams M, de Lourdes Ruivo M, Costa AL, Meir P
(2008) Evaluating climatic and soil water controls on evapo-
transpiration at two Amazonian rainforests sites. Agric For
Meteorol 148:850861
Flohn H, Fleer H (1975) Climate teleconnections with the equatorial
Pacific and the role of ocean/atmosphere coupling. Atmosphere
13:96109
Frank NL, Hebert PJ (1974) Atlantic tropical systems of 1973. Mon
Wea Rev 102:290295
Gorshkov VG, Makarieva AM (2007) Biotic pump of atmospheric
moisture as driver of the hydrological cycle on land. Hydrol
Earth System Sci 11:10131033
Gray WM, Sheaffer JD (1991) El Nino and QBO influences on
tropical cyclone activity. In: Glantz WM et al (ed) Teleconnec-
tions Linking Worldwide Climate Anomalies. Cambridge Uni-
versity Press, Cambridge, pp 257284
Grimm AM (2003) The El Nino impact on the summer monsoon in
Brazil: regional processes versus remote influences. J Clim
16:263280
Grimm AM (2004) How do La Nina events disturb the summer
monsoon system in Brazil? Clim Dyn 22:123138
Grimm AM, Tedeschi RG (2009) ENSO and extreme rainfall events
in South America. J Clim 22:15891609
Gutierrez F, Dracup JA (2001) An analysis of the feasibility of long-
range streamflow forecasting for Colombia using El Nino-
Southern Oscillation indicators. J Hydrol 246(14):181196
Hastenrath S (1976) Variations in low-latitude circulations and
extreme climatic events in the tropical Americas. J Atmos Sci
33:202215
Hastenrath S (1990) Diagnostic and prediction of anomalous river
discharges in northern South America. J Clim 3:10801096
Hastenrath S (1991) Climate dynamics of the tropics. Kluwer,
Dordrecht, p 488
Hastenrath S (2002) The intertropical convergence zone of the eastern
Pacific revisited. Int J Climatol 22:347356
Hastenrath S, de Castro LC, Aceituno P (1987) The Southern
Oscillation in the tropical Atlantic sector. Contrib Atmos Physics
60(4):447464
Hsu H-H (1994) Relationship between tropical heating and global
circulation. Interannual variability. J Geophys Res 99(D5):10,47310,489
Hurtado AF, Poveda G (2009) Linear and global space-time
dependence and Taylor hypotheses for rainfall in the tropical
Andes. J Geophys Res 114:D10105. doi:10.1029/2008JD011074
Jipp PH, Nepstad DC, Cassel DK et al (1998) Deep soil moisture
storage and transpiration in forests and pastures of seasonally-
dry Amazonia. Clim Change 39:395412
Kiladis G, Diaz HF (1989) Global climatic anomalies associated with
extremes in the Southern Oscillation. J Clim 2:10691090
Kousky VE, Kayano MT (1994) Principal modes of outgoing
longwave radiation and 250-mb circulation for the South
American sector. J Clim 7:11311143
G. Poveda et al.: Hydro-climatic variability over the Andes of Colombia associated with ENSO
123
http://dx.doi.org/10.1029/2008JD011074http://dx.doi.org/10.1029/2008JD011074 -
7/30/2019 Poveda Alvarez Rueda
16/17
Kousky VE, Kayano MT, and Cavalcanti IFA (1984) A review of the
Southern Oscillation: oceanic-atmospheric circulation changes
and related rainfall anomalies. Tellus 36A:490504
Lau KM, Sheu PJ (1988) Annual cycle, quasi-biennial oscillation, and
Southern Oscillation in global precipitation. J Geophys Res
93(D9):10,97510,989
Leon GE, Zea JA, Eslava JA (2000) General circulation and the
intertropical convergence zone in Colombia (in Spanish).
Meteorol Colomb 1:3138
Magana V, Amador JA, Medina S (1999) The midsummer drought
over Mexico and Central America. J Clim 12:15771588
Makarieva AM, Gorshkov VG, Li B-L (2009) Precipitation on land
versus distance from the ocean: Evidence for a forest pump of
atmospheric moisture. Ecol Complexity 6:302307
Malhi Y, Pegoraro E, Nobre AD et al (2002) The energy and water
dynamics of a central Amazonian rain forest. J Geophys Res 107.
doi:10.1029/2001JD000623
Mapes BE, Warner TT, Xu M, Negri AJ (2003a) Diurnal patterns of
rainfall in northwestern South America. Part I. Observations and
context. Mon Wea Rev 131:799812
Mapes BE, Warner TT, Xu M (2003b) Diurnal patterns of rainfall
in northwestern South America. Part III. Diurnal gravity
waves and nocturnal convection offshore. Mon Wea Rev
131:830844
Marengo JA (1992) Interannual variability of surface climate in the
Amazon basin. Int J Climatol 12:853863
Marengo JA, Nobre CA (2001) The hydroclimatological framework
in Amazonia. In: McClaine ME, Victoria RL, Richey JE (eds)
The Biogeochemistry of the Amazon Basin. Oxford University
Press, New York, pp 1742
Marengo JA, Soares WR, Saulo C, Nicolini M (2004) Climatology of
the low-level jet east of the Andes as derived from the NCEP
Reanalyses. J Clim 17:22612280
Marengo JA, Nobre CA, Tomasella J, Cardoso MF, Oyama D (2008)
Hydro-climatic and ecological behaviour of the drought of
Amazonia in 2005. Phil Trans R Soc B 363:17731778. doi:
10.1098/rstb.2007.0015
Martnez MT (1993) Major sinoptic systems in Colombia and their
influence on weather patterns (in Spanish). Atmosfera 16:110
Meir P, Woodward FI (2010) Amazonian rain forests and drought:
response and vulnerability. New Phytol 187:14698137. doi:
10.1111/j.1469-8137.2010.03390.x
Meir P, and co-authors (2009) The effects of drought on Amazonian
rainforests. AGU Geophys Monogr Ser 186. doi:10.1029/2008
GM000882
Meja JF, Mesa OJ, Poveda G et al (1999) Spatial distribution, annual
and semi-annual cycles of precipitation in Colombia (in Span-
ish). DYNA 127:726
Mejia JF, Poveda G (2005) Atmospheric environments of mesoscale
convective systems over Colombia during 1998 after TRMM and
NCEP/NCAR Reanalysis (in Spanish). Rev Acad Colomb Cienc
29(113):495514
Mestas-Nunez AM, Zhang C, Enfield DE (2005) Uncertainties in
estimating moisture fluxes over the intra-Americas sea. J Hydro-met 6:696709
Misra V (2008) Coupled air, sea, and land interactions of the South
American monsoon. J Clim 21:63896403
Misra V (2009) The amplification of the ENSO forcing over
equatorial Amazon. 1562 J Hydromet 10:15611568
Montoya G, Pelkowski J, Eslava JA (2001) On the northeast trade
winds and the existence of a current along the eastern
Andean piedmont (in Spanish). Rev Acad Colomb Cienc
96:363370
Munoz E, Busalacchi AJ, Nigam S, Ruiz-Barradas A (2008) Winter
and summer structure of the Caribbean low-level jet. J Clim
21:12601276
Myers N, Mittermeier RA, Mittermeier CG, da Fonseca GAB, Kent J
(2000) Biodiversity hotspots for conservation priorities. Nature
403:853858
Nepstad DC, de Carvalho CR, Davidson EA., and co-authors (1994)
The role of deep roots in the hydrological and carbon cycles of
Amazonian forests and pastures. Nature 372:666669
Nobre CA, Obregon G, Marengo J, Fu R, Poveda G (2009)
Characteristics of Amazonian climate: main features. AGU
Geophysical Monograph Series 186:149162
Numaguti A (1993) Dynamics and energy balance of the Hadley
circulation and the tropical precipitation zones: significance of
the distribution of evaporation. J Atmos Sci 50:18741887
Oren R, Zimmermann R, Terborgh J (1996) Transpiration in upper
Amazonia flood plain and upland forests in response to drought-
breaking rains. Ecology 77:968973
Phillips O et al (2009) Drought sensitivity of the Amazon rainforest.
Science 323:13441347
Poveda G (1994) Rainfall in Colombia: Correlation with the climate
of the Pacific Ocean and empirical orthogonal function analysis
(in Spanish). Proc 16th Latin American Hydraulics and Hydrol-
ogy Meeting, IAHS, Santiago de Chile, vol 4:93105
Poveda G (2004a) Science priorities ignore Colombias water needs.
Nature 431:125
Poveda G (2004b) The hydro-climatology of Colombia: a synthesis
from inter-decadal to diurnal timescales (in Spanish). Rev Acad
Colomb Cienc 28(107):201-222
Poveda G (2010) Mixed memory, (non) Hurst Effect, and maximum
entropy of rainfall in the Tropical Andes. Adv Water Resour
(Submitted)
Poveda G, Mesa OJ (1997) Feedbacks between hydrological
processes in tropical South America and large-scale oceanic
atmospheric phenomena. J Clim 10:26902702
Poveda G, Mesa OJ (1999) The low level westerly jet (CHOCO jet)
and two other jets in Colombia: climatology and variability
during ENSO phases (in Spanish). Rev Acad Colomb Cienc
23(89):517528
Poveda G, Mesa OJ (2000) On the existence of Lloro (the rainiest
locality on Earth): enhanced ocean-atmosphere-land interaction
by a low-level jet. Geophys Res Lett 27:16751678
Poveda G, Pineda K (2009) Reassessment of Colombias tropical
glaciers retreat rates: are they bound to disappear during the
20102020 decade? Adv Geosci 22:107116
Poveda G, Rojas W (1996) Impacts of El Nino phenomenon on
intensification of malaria in Colombia (in Spanish). Proc XII
Colomb Hydrol Meeting, Sociedad Colombiana de Ingenieros,
Bogota, pp 647654
Poveda G, Salazar LF (2004) Annual and interannual (ENSO)
variability of spatial scaling properties of a vegetation index
(NDVI) in Amazonia. Rem Sens Environ 93:391401
Poveda G, Gil MM, Quiceno N (1998) El ciclo anual de la hidrologia
de Colombia en relacion con el ENSO y la NAO. Bull Inst Fr
Etud And 27(3):721731
Poveda G, Gil MM, Quiceno N (1999) The relationship between
ENSO and the annual cycle of Colombias hydro-climatology.10th Symposium on Global Change Studies. Am Met Soc, Dallas
Poveda G, Jaramillo A, Gil MM, Quiceno N, Mantilla R (2001a)
Seasonality in ENSO related precipitation, river discharges, soil
moisture, and vegetation index (NDVI) in Colombia. Water
Resour Res 37(8):21692178
Poveda G, Rojas W, Vlez ID, et al (2001b) Coupling between annual
and ENSO timescales in the malaria-climate association in
Colombia. Environ Health Persp 109:489493
Poveda G, Moreno HA, Vieira SC, et al (2001c) Characterization of
the diurnal cycle of precipitation in the tropical Andes of
Colombia. Proc. IX Ibero-American Meteorological Meeting,
Buenos Aires, Argentina, 711 May
G. Poveda et al.: Hydro-climatic variability over the Andes of Colombia associated with ENSO
123
http://dx.doi.org/10.1029/2001JD000623http://dx.doi.org/10.1098/rstb.2007.0015http://dx.doi.org/10.1111/j.1469-8137.2010.03390.xhttp://dx.doi.org/10.1029/2008GM000882http://dx.doi.org/10.1029/2008GM000882http://dx.doi.org/10.1029/2008GM000882http://dx.doi.org/10.1029/2008GM000882http://dx.doi.org/10.1111/j.1469-8137.2010.03390.xhttp://dx.doi.org/10.1098/rstb.2007.0015http://dx.doi.org/10.1029/2001JD000623 -
7/30/2019 Poveda Alvarez Rueda
17/17
Poveda G, Velez JI, Mesa OJ (2002) Hydrological Atlas of Colombia
(in Spanish). Graduate Programme in Water Resources, Uni-
versidad Nacional de Colombia at Medellin
Poveda G, Mesa OJ, Waylen PR (2003) Non-linear forecasting of
river flows in Colombia based upon ENSO and its associated
economic value for hydropower generation. In: Diaz H, More-
house B (eds) Climate and water. Transboundary challenges in
the Americas. Kluwer, Dordrecht, pp 351371
Poveda G, Carvajal LF, Ochoa A, Velez JI (2008) Assessment of
diverse monthly mean streamflow forecasting models involving
macro-climatic indices and hydrologic persistence in Colombia.
HYDRO PREDICT 2008-international and interdisciplinary
conference on predictions for hydrology, ecology, and water
resources management, September 1518, Prague, Czech
Republic
Poveda G, Mesa OJ, Salazar LF et al (2005) The diurnal cycle of
precipitation in the tropical Andes of Colombia. Mon Wea Rev
133:228240
Poveda G, Velez JI, Mesa OJ et al (2007) Linking long-term water
balances and statistical scaling to estimate river flows along the
drainage network of Colombia. Jour Hydrol Eng 12(1):413
Poveda G, Waylen PR, Pulwarty R (2006) Modern climate variability
in northern South America and southern Mesoamerica. Palaeo-
geo Palaeoclim Palaeoecol 234:327
Pulwarty RS, Diaz HF (1993) A study of the seasonal cycle and its
perturbation by ENSO in the tropical Americas. Preprints, Fourth
Int Conf on Southern Hemisphere Meteorology and Oceano-
graphy, Hobart, Australia. Amer Meteor Soc 262263
Rasmusson EM, Mo K (1993) Linkages between 200-mb tropical and
extratropical circulation anomalies during the 19861989 ENSO
cycle. J Clim 6:595616
Ronchail JG, Cochonneau G, Molinier M, Guyot J-L et al (2002)
Interannual rainfall variability in the Amazon basin and sea-
surface temperatures in the equatorial Pacific and the tropical
Atlantic Oceans. Int J Climatol 22:16631686
Ropelewski CF, Halpert MS (1987) Global and regional scales
precipitation associated with El Nino-Southern Oscillation. Mon
Wea Rev 115:16061626
Ropelewsky CF, Bell MA (2008) Shifts in the statistics of daily
rainfall in South America conditional on ENSO phase. J Clim
21:849865
Rueda OA, Poveda G, Jaramillo A (2010) Probabilistic modelling of
soil moisture dynamics at seasonal and interannual timescales
over the tropical Andes of Colombia. (in preparation)
Sakamoto MS, Ambrizzi T, Poveda G (2009), Life cycle of
convective systems over western Colombia. In: Proceedings
MOCA-09 IAMAS, IAPSO and IACS Joint Assembly, 1929
July, Montreal
Shuttleworth WJ (1988) Evaporation from Amazonian rainforest. Phil
Trans R Soc London B 233:321346
Snow JW (1976) The climate of northern South America. In:
Schwerdtfeger W (ed) Climates of Central and South America.
Elsevier, Amsterdam, pp 295403
Stensrud DJ (1996) Importance of low-level jets to climate: a review.
J Clim 9:16981711
Tootle GA, Piechota TC, Gutirrez F (2008) The relationships between
Pacific and Atlantic Ocean sea surface temperatures and
Colombian streamflow variability. J Hydrol 349(3-4):268276
Trenberth KE (1997) The definition of El Nino. Bull Am Meteorol
Soc 78:27712777
Trenberth KE, Dai A, Rasmussen RM, Parsons DB (2003) The
changing character of precipitation. Bull Amer Meteor Soc
84:12051217
Tucker CJ, Pinzon JE, Brown ME et al (2005) An extended AVHRR
8-km NDVI dataset compatible with MODIS and SPOT
vegetation NDVI data. Inter J Remote Sens 26(20):44854498
Velasco I, Frisch M (1987) Mesoscale convective complexes in the
Americas. J Geoph Res 92(D8):95919613
Vorosmarty CJ, Willmott CJ, Choudhury BJ et al (1996) Analyzing
the discharge regime of a large tropical river through remote
sensing, ground-based climatic data, and modeling. Water
Resour Res 32:3,1373,150
Wang C (2007) Variability of the Caribbean low-level jet and its
relations to climate. Clim Dyn 29(4):411422
Wang S-W (1987) A version of the circulation scheme in the
equatorial zone. Beitr Phys Atmosph 60:478487
Waylen PR, Caviedes C (1986) El Nino and annual floods on the
north Peruvian littoral. J Hydrol 89:141156
Waylen PR, Poveda G (2002) El Nino-Southern Oscillation and
aspects of western South America hydro-climatology. Hydrol
Proc 16:12471260
Xavier L, Becker M, Cazenave A, and co-authors (2010) Interannual
variability in water storage over 20032008 in the Amazon
Basin from GRACE space gravimetry, in situ river level and
precipitation data. Rem Sens Environ 114:16291637
Xie S-P, Okumura Y, Miyama T, Timmermann A (2008) Influences
of Atlantic climate change on the tropical Pacific via the Central
American isthmus. J Clim 21:39143928
Yasunari T (1987) Globalstructure ofthe El Nino/SouthernOscillation.
Part I. El Nino composites. J Meteor Soc Japan 65:6779
Zeng N (1999) Seasonal cycle and interannual variability in the
Amazon hydrologic cycle. J Geophys Res 104(D8):90979106
Zuluaga MD, Poveda G (2004) Diagnostics of mesoscale convective
systems over Colombia and the eastern tropical Pacific during
1998-2002 (in Spanish). Avances en Recursos Hidraulicos
11:145-160
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