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In this article, we propose a novel approach for assessing the effects of sea surface temperature (SST) variations in the eastern Pacific and the Caribbean Sea on the Choco low-level jet (CJ) intensity over the 1900-2015 period that involved defining the interbasin gradient index (IGR) between these 2 oceanic basins. We also studied the effects on rainfall in northwestern South America and Central America in the high CJ season during September-November (SON). Wavelet coherence analysis showed high consistency between CJ and IGR on an interannual scale of 2-8 yr. Precipitation increased over central, western, and northern Colombia and most of Central America during strong CJ (SCJ) and decreased during weak CJ (WCJ) events, which occurred, respectively, in the negative IGR (NIGR) and positive IGR (PIGR) phases. NIGR is associated with anomalous cooling in the tropical Pacific and warming in the equatorial Atlantic; opposite patterns are observed during PIGR. Also, the CJ and the Caribbean low-level jet (CLLJ) showed reversed intensities such that as one strengthened, the other weakened and vice versa. Our results indicate that the low-frequency SST anomalies in the North Atlantic affect the IGR and low-level jet intensities associated with changes in large-scale circulation modulated by the Atlantic multidecadal oscillation (AMO). Indeed, positive precipitation anomalies during the SCJ under NIGR were more accentuated and extensive in the warm AMO (WAMO) than in the cold AMO (CAMO) phase. Conversely, negative precipitation anomalies during WCJ under PIGR were more accentuated and extensive in the CAMO than in the WAMO.

Anomalous seasonal patterns of precipitation variability over South America (SA) associated with El Nino-Southern Oscillation (ENSO) and non-ENSO (residual) conditions were assessed during 1951–2016. Patterns were obtained from empirical orthogonal functions analysis of total and residual precipitation seasonal anomalies. In austral spring and summer, precipitation variability is dominated by a dipolar anomaly mode with a centre extending from northwestern to northeastern SA and another in central-eastern Brazil and part of southeastern SA (SESA) during spring, and a centre in northwestern SA and another extending from northeastern SA to central and eastern Brazil and central SESA, during summer. These modes are associated with ENSO to a greater extent during spring than summer. In summer, there is a strong association of the dipolar precipitation pattern with sea surface temperature (SST) anomalies on the east coast of Brazil, which indicates local influence. In austral fall, SST anomalies in the tropical South Atlantic relate to precipitation anomalies in northeast SA, and those in the tropical north Atlantic (TNA) to precipitation anomalies in northwestern SA, through the intertropical convergence zone anomalous position modulated by SST anomalies. In this same condition, the ENSO acts only to intensify or weaken the dominant precipitation pattern, depending on its phase, mainly over SESA. In contrast, the second variability mode in fall is characterized by positive SST anomalies in the Indian Ocean and equatorial and southern Atlantic Ocean and negative in the TNA. The importance of ENSO and the Indian Ocean in the characterization of the SST dipole in the tropical Atlantic explains the main changes in precipitation patterns over northeastern Brazil not been discussed in previous studies.

The El Nino–Southern Oscillation (ENSO) is the main phenomenon causing interannual rainfall variability in many parts of the globe. Its influence on Southwestern Colombia rainfall was examined using observational and reanalysis data during the 1983–2016 period. In order to focus on the interannual timescale, the data were filtered at the 3–6-year scale. The relations between variables were analyzed with total and partial correlations. The total correlations show consistent relationships between the sea surface temperature (SST) anomalies in the tropical Pacific and the rainfall variations in Colombia such that the rainfall in the Andean Region (AR) relates to the SST anomalies in the central Pacific, and the rainfall in the Pacific Region (PR), or Pacific western plains, relates to the SST anomalies in the eastern Pacific. Partial correlations, excluding the Oceanic Nino Index (ONI) influence, show that AR rainfall is partly modulated by a west–east SST gradient between the eastern tropical Pacific and the tropical North Atlantic (TNA). The partial correlation analyses indicate that the rainfall in the PR is modulated by the SST anomalies in the eastern Pacific; for example, an anomalous SST pattern with simultaneous warming north of 10° S and cooling south of 10° S relates to positive rainfall anomalies in the PR. This SST anomaly dipole in the eastern Pacific is associated with an asymmetric anomalous low-level wind pattern about 5° S, with southeasterlies to the south and southwesterlies to the equator which contribute to increase moisture transport into most of the western plains of Colombia and Ecuador and in part of the western Andes mountain range. Conversely, an opposite-sign SST anomaly pattern in the eastern Pacific and reversed anomaly wind pattern relate to negative rainfall anomalies in the PR. These results establish the foundation for rainfall differential modeling in Southwestern Colombia based on the Pacific SST variations.

This article assesses the consistency of the satellite precipitation estimate CHIRPS v.2 to describe the spatiotemporal rainfall variability in the La Plata Basin (LPB), the second largest hydrographic basin in South America, by (a) pixel-to-point comparison of CHIRPS data with 167 observed monthly precipitation time series using three pairwise metrics (coefficient of correlation, bias and root mean square error) and (b) principal component analysis (PCA) to evaluate the large-scale coherence between CHIRPS and rain gauge data. The pairwise metrics indicate that CHIRPS better represents the rainfall in the coastal, northeastern and southeastern parts of the basin than in the Andean region to the west. The PCA shows that CHIRPS describes most of the observed rainfall variability in the LPB, but contains more variability, especially during December–February and March–May seasons. The two major modes observed are highly correlated spatially (empirical orthogonal functions—EOFs) and temporally (principal components—PCs) with the corresponding CHIRPS modes. The PCA allows the determination of the main rainfall variability modes and their possible relations with climate variability modes. Besides, the analyses of the precipitation anomaly modes show that the El Nino Southern Oscillation explains the first EOF modes of datasets. The PCA provides an alternative and effective means of assessing the consistency of CHIRPS data in representing spatial and temporal rainfall variability in the LPB.

Contrasting effects of the tropical Indian and Pacific Oceans on the atmospheric circulation and rainfall interannual variations over South America during southern winter are assessed considering the effects of the warm Indian Ocean basin-wide (IOBW) and El Niño (EN) events, and of the cold IOBW and La Niña events, which are represented by sea surface temperature-based indices. Analyses are undertaken using total and partial correlations. When the effects of the two warm events are isolated from each other, the contrasts between the associated rainfall anomalies in most of South America become accentuated. In particular, EN relates to anomalous wet conditions, and the warm IOBW event to opposite conditions in extensive areas of the 5° S–25° S band. These effects in the 5° S–15° S sector are due to the anomalous regional Hadley cells, with rising motions in this band for the EN and sinking motions for the warm IOBW event. Meanwhile, in subtropical South America, the opposite effects of the EN and warm IOBW seem to be due to the presence of anomalous anticyclone and cyclone and associated moisture transport, respectively. These opposite effects of the warm IOBW and EN events on the rainfall in part of central South America might explain the weak rainfall relation in this region to the El Niño–Southern Oscillation (ENSO). Our results emphasize the important role of the tropical Indian Ocean in the South American climate and environment during southern winter.

The Cauca River rises in the Colombian Andes and is the main tributary of the Magdalena River, which drains to the Caribbean Sea. The La Balsa station monitors the Upper Cauca basin and is located just downstream of La Salvajina hydroelectric facility. At this station, the discharge time series for November–January during 1950–2019 shows a statistically significant downward break, and change of distribution after 1986 has been documented after La Salvajina started operation. We assessed the spatio-temporal variability of hydroclimatology in the upper Cauca River basin during the pre- and post-Salvajina dam periods to better understand this break. Post-Salvajina, low (high) discharge events are linked to negative (positive) precipitation and soil moisture anomalies that are greater in magnitude and extension than those recorded in the pre-Salvajina period in response to the more intense El Niño events (more intense and frequent central La Niña events) after 1986. Therefore, it is necessary to consider possible future rainfall scenarios and non-infrastructure measures (i.e., reforestation, territorial planning, integrated watershed management, etc.) to mitigate floods and droughts impacts. The contribution of this study is to provide evidence for the need for foresight in the design of any structural or non-structural flood measures.

This study analyzes the variability of the Choco jet (CJ) and Caribbean low-level jet (CLLJ) with consideration of the simultaneous Pacific interdecadal oscillation (PDO) and Atlantic multidecadal oscillation (AMO) low-frequency mean states and their effects on the atmospheric circulation and rainfall in northwestern South America and Central America for the 1900–2015 period, during the seasons with the highest intensities of the CJ (September–November (SON)) and the CLLJ (June–August). Variations in the sea surface temperature (SST) anomaly positioning in the eastern Pacific, tropical North Atlantic (TNA)/Caribbean Sea during different mean states restrict the anomalous circulation, and, consequently, the intensity of the CJ and CLLJ. During the warm AMO (WAMO)/cold PDO (CPDO), the SST gradient from the tropical Pacific into the TNA, accompanied by a cyclonic circulation near the east coast of the Americas, intensifies the west–east circulation in the region, strengthening the CJ and weakening the CLLJ during SON such that rainfall increases over Colombia, Central America and in adjacent oceans. During the cold AMO (CAMO)/warm PDO (WPDO) phase, a relative east/west SST gradient occurs in TNA, consistent with a cyclonic circulation in western TNA, establishing an anomalous southwest–northwestward circulation from the eastern Pacific into the Caribbean basin, forming a well-configured CJ, increasing precipitation over Central America and its adjacent oceans. For the CLLJ, during CAMO phases, the anticyclonic circulations extended over most of the TNA favor its intensification from 30° W to the Caribbean Sea. In contrast, during WAMO, the cyclonic circulation near the east coast of the United States restricts its intensification to the Caribbean Sea region. To the best of our knowledge, the results presented here are new and might be useful in atmospheric modeling and extreme event studies.

An adequate representation by models and reanalyzes is fundamental since the coverage by observational data on the oceans is still limited. Therefore, this paper aims to evaluate the influence of the wind near the surface on the heat fluxes during the southern winter and summer seasons. Datasets from Coupled Model Intercomparison Project Phase 5 (CMIP5) and reanalyzes were used, in comparison to Objectively Analyzed Air - sea Fluxes (OAFlux) for the South Atlantic Ocean (SAO) during 1980-2005. Results point out an overestimation on the CMIP5 models and reanalyzes to reproduce the heat flux latent and sensible fluxes of SAO, mainly at medium and high latitudes. One possibility may be related the underestimating of surface wind speed, causing an impacts on the heat exchange between ocean and atmosphere. It was also possible to verify that the representation of heat flux, specific humidity, and air and ocean temperatures shows small biases (Mean Bias Error (MBE) to specific humidity (±5 kg.kg-1) and sensible heat flux (±10 W.m-2)). To the test Root Mean Square Error (RMSE)-observations Standard deviation Ratio (RSR), air temperature values are less than 1 °C, and for the wind with values greater than 2 m.s-1. There is less precision of CMIP5 models than OAFlux, resulting in low correlation values (between -0.3 and 0.3). On the other hand, the reanalyzes show small biases in air and ocean temperatures (between ±1 °C) and significant correlations (above 0.9) with the best performances for the NCEP and ERA5.

The Colombian Biogeographic Choco (CBC) and the La Plata Basin (LPB) are regions with high biodiversity. However, these areas are characterized by scarce climatological information, complex orography, and rain-gauge network unevenly distributed. Interpolated data from the ground station might overcome these aspects. For this reason, is necessary to identify the best technique for the spatial interpolation of rainfall. Hence, the spatial interpolation techniques were applied to annual and seasonal rainfall in the CBC and LPB. Geostatistical results and deterministic approaches were compared by cross-validation. Cokriging with spherical (gaussian) model is the best interpolator in the CBC (LPB), as indicated by the lowest root mean square error (RMSE) and a standardized RMSE close to one. The CBC shows three rainfall cores: the northern, 9,000 mm/year; the central-southern, 10,000 mm/year; and the southern, 7,000 mm/year. The LPB shows a west-east rainfall gradient, with a minimum to the west (450 mm/year) and a maximum in the mid-west (2,000 mm/year). To the north of the LPB, rainfall reaches 1,500 mm/year, while in the south it reaches only 900 mm/year. The results in our study may be useful for scientists and decision-makers for use in environmental and hydrological models for the CBC and the LPB.

Changes observed in the current climate and projected for the future significantly concern researchers, decision-makers, and the general public. Climate indices of extreme rainfall events are a trend assessment tool to detect climate variability and change signals, which have an average reliability at least in the short term and given climatic inertia. This paper shows 12 climate indices of extreme rainfall events for annual and seasonal scales for 12 climate stations between 1969 to 2019 in the Metropolitan area of Cali (southwestern Colombia). The construction of the indices starts from daily rainfall time series, which although have between 0.5% and 5.4% of missing data, can affect the estimation of the indices. Here, we propose a methodology to complete missing data of the extreme event indices that model the peaks in the time series. This methodology uses an artificial neural network approach known as Non-Linear Principal Component Analysis (NLPCA). The approach reconstructs the time series by modulating the extreme values of the indices, a fundamental feature when evaluating extreme rainfall events in a region. The accuracy in the indices estimation shows values close to 1 in the Pearson's Correlation Coefficient and in the Bi-weighting Correlation. Moreover, values close to 0 in the percent bias and RMSE-observations standard deviation ratio. The database provided here is an essential input in future evaluation studies of extreme rainfall events in the Metropolitan area of Cali, the third most crucial urban conglomerate in Colombia with more than 3.9 million inhabitants.

Improving the accuracy of rainfall forecasting is relevant for adequate water resources planning and management. This research project evaluated the performance of the combination of three Artificial Neural Networks (ANN) approaches in the forecasting of the monthly rainfall anomalies for Southwestern Colombia. For this purpose, we applied the Non-linear Principal Component Analysis (NLPCA) approach to get the main modes, a Neural Network Autoregressive Moving Average with eXogenous variables (NNARMAX) as a model, and an Inverse NLPCA approach for reconstructing the monthly rainfall anomalies forecasting in the Andean Region (AR) and the Pacific Region (PR) of Southwestern Colombia, respectively. For the model, we used monthly rainfall lagged values of the eight large-scale climate indices linked to the El Ni&ntilde, o Southern Oscillation (ENSO) phenomenon as exogenous variables. They were cross-correlated with the main modes of the rainfall variability of AR and PR obtained using NLPCA. Subsequently, both NNARMAX models were trained from 1983 to 2014 and tested for two years (2015&ndash, 2016). Finally, the reconstructed outputs from the NNARMAX models were used as inputs for the Inverse NLPCA approach. The performance of the ANN approaches was measured using three different performance metrics: Root Mean Square Error (RMSE), Mean Absolute Error (MAE), and Pearson&rsquo, s correlation (r). The results showed suitable forecasting performance for AR and PR, and the combination of these ANN approaches demonstrated the possibility of rainfall forecasting in these sub-regions five months in advance and provided useful information for the decision-makers in Southwestern Colombia.

Oceanic-atmospheric phenomena of different time scales concurrently might affect the streamflow in several basins around the world. The Atrato River Basin (ARB) and Pat&iacute, a River Basin (PRB) of the Colombian Pacific region are examples of such basins. Nevertheless, the relations between the streamflows in the ARB and PRB and the oceanic-atmospheric factors have not been examined considering different temporal scales. Hence, this article studies the relations of the climate indices and the variability of the streamflows in the ARB and PRB at interannual and decadal timescales. To this, the streamflow variability modes were obtained from the principal component analysis (PCA), furthermore, their linear dependence with indices of the El Ni&ntilde, o/Southern Oscillation (ENSO), precipitation (PRP), the Choco low-level jet (CJ), and other indices were quantified through (a) Pearson and Kendall&rsquo, s tau correlations, and (b) wavelet transform. The PCA presented a single significant mode for each basin, with an explained variance of around 80%. The correlation analyses between the PC1s of the ARB and PRB, and the climate indices showed significant positive (negative) high correlations with PRP, CJ, and Southern Oscillation Index (SOI) (ENSO indices). The wavelet coherence analysis showed significant coherencies between ENSO and ARB: at interannual (2&ndash, 7 years) and decadal scale (8&ndash, 14), preferably with the sea surface temperature (SST) in the east and west Tropical Pacific Ocean (TPO). For PRB with the SST in the central and western regions of the TPO in the interannual (4&ndash, 8 years) and decadal (8&ndash, 14 years) scales, the decreases (increases) in streamflow precede the El Ni&ntilde, o (La Ni&ntilde, a) events. These results indicate multiscale relations between the basins&rsquo, streamflow and climate phenomena not documented in previous works, relevant to forecast the extreme flow events in the Colombian Pacific rivers and for planning and implementing strategies for the sustainable use of water resources in the basins studied.

This study examines the influence of the Atlantic Multidecadal Oscillation (AMO) on the Choco Low-level Jet (CJ) variations during the 1983&ndash, 2016 period. Considering the September&ndash, November (SON) 925 hPa zonal wind index in the CJ core, a significant breakpoint occurs in 1997 with larger values after 1997. The changes in the CJ and Caribbean Low-Level Jet (CLLJ), and their related ocean-atmospheric patterns and impacts on precipitation over Colombia were analyzed considering separately the 1983&ndash, 1996 and 1998&ndash, 2016 periods, which overlap the cold and warm AMO phases, respectively. During the 1998&ndash, 2016 period, the negative sea surface temperature (SST) anomalies in the tropical Pacific Ocean and the positive ones in the Caribbean Sea and Tropical North Atlantic (TNA) strengthen the CJ and weaken the CLLJ, and moisture is transported into Central and Western Colombia increasing the rainfall there. Our results indicate that part of the CJ strengthening after 1997 was due to a higher percentage of intense CJ events coinciding with La Ni&ntilde, a events during the warm AMO and cold Pacific Decadal Oscillation (PDO) background. However, the AMO-related SST and sea level pressure (SLP) variations in the TNA seem to be more crucial in modulating the CJ and CLLJ intensities, such that CJ is weakened (intensified) and CLLJ is intensified (weakened) before (after) 1997. As far as we know, the relations of the CJ and CLLJ intensities to the AMO phases were not examined before and might be useful for modeling studies.

The impact of the Atlantic Multidecadal Oscillation (AMO) on the variations in the streamflow in the Atrato River Basin (ARB) during the 1965&ndash, 2016 period was analyzed here by considering the cold (1965&ndash, 1994) and warm (1995&ndash, 2015) phases of this oscillation. The mean streamflow increased after 1994 (AMO phase change). This increase is related to the strengthening of the zonal gradients of the sea surface temperature (SST) and sea level pressure (SLP) between the tropical central Pacific and the tropical Atlantic after 1994 (warm AMO phase). These gradients contributed to strengthen the Walker cell related upward movement over northern and northwestern South America, in particular during November-December (ND). Consistently, the frequency (R20 mm) and intensity (SDII) of extreme daily rainfall events increased during the 1995&ndash, 2015 period. Our results show a connection between the AMO and the increase in the streamflow in the ARB during the last five decades. These results contribute to the studies of resilience and climate adaptation in the region.

This paper analyzed the spatio-temporal variability of droughts in Cali, Colombia and their primary relations to the El Nino Southern Oscillation (ENSO). The Standardized Precipitation Index (SPI) was used to detect drought events from monthly rainfall data of 24 stations well spread over Cali during 1971-2011. The SPI provided the drought intensity, magnitude, frequency, and the minimum rainfall thresholds, mainly on an annual scale (SPI-12). Eighty percent of the stations reported four events with dry conditions in Cali: 1976-1977, 1983-1984, 1990-1992 and 2009-2010. The ENSO influence was evaluated using the correlation and wavelet transform analyses. Significant (non-significant) negative correlations between SPI-12 in the northern (southern) part of Cali, the multivariate ENSO Index (MEI), and Sea Surface Temperature (SST) Nino 3.4 and Nino 4 indices were observed. The wavelet coherence analysis showed significant coherencies between ENSO and SPI-12: at interannual scale (4-6 years), the phase difference of-135o generates a lag of 6-9 months between the minimum peak of the SPI-12 and the maximum peak of the indices. On the quasi-biennial scale (2-3 years), the phase difference of-180o suggests that the maximum wet (dry) conditions coincide with the mature stage of the La Nina (El Nino) event; and on the decadal scale (8-16 years), the decreases (increases) in rainfall precede the El Nino (La Nina) mature stage by approximately 10-18 months. These results are relevant for seasonal forecasting, since changes in SST in the equatorial Pacific may take place 6-18 months ahead of the dry conditions in Cali. © 2020 Universidad Nacional Autonoma de Mexico.

This paper examines the effects of the tropical Pacific Ocean (TPO) and Indian Ocean Dipole (IOD) modes in the interannual variations of austral spring rainfall over South America (SA). The TPO mode refers to the El Niño-Southern Oscillation (ENSO). The isolated effects between IOD and TPO were estimated, events were chosen from the residual TPO (R-TPO) or residual IOD (R-IOD), and the IOD (TPO) effects for the R-TPO (R-IOD) composites were removed from the variables. One relevant result was the nonlinear precipitation response to R-TPO and R-IOD. This feature was accentuated for the R-IOD composites. The positive R-IOD composite showed significant negative precipitation anomalies along equatorial SA east of 55° W and in subtropical western SA, and showed positive anomalies in northwestern SA and central Brazil. The negative R-IOD composite indicated significant positive precipitation anomalies in northwestern Amazon, central–eastern Brazil north of 20° S, and western subtropical SA, and negative anomalies were found in western SA south of 30° S. This nonlinearity was likely due to the distinct atmospheric circulation responses to the anomalous heating sources located in longitudinally distinct regions: the western tropical Indian Ocean and areas neighboring Indonesia. The results obtained in this study might be relevant for climate monitoring and modeling studies.

This paper examines the relative role of the Indian Ocean basin-wide (IOBW) mode and El Niño–Southern Oscillation (ENSO) in the atmospheric circulation and rainfall interannual variations over South America (SA) during southern summer of the 1951‒2016 period. The effects of the warm IOBW and El Niño (EN) events, and of the cold IOBW and La Niña (LN) events are examined using partial correlations. The ENSO and IOBW modes, through the associated large-scale and regional anomalous circulation patterns, induce contrasting effects on the rainfall in northeastern SA. The EN without the warm IOBW effect induces anomalously dry conditions over eastern Amazon and part of northeastern Brazil (NEB) through anomalous sinking motions of the EN-related anomalous Walker and Hadley cells and strong moisture divergence associated with a vigorous anticyclone over tropical South Atlantic (TSA) and SA. The warm IOBW without the EN effect induces anomalously wet conditions in NEB, which is marginally related to the anomalous Walker and Hadley cells but is modulated by an anticyclone over SA between the equator and 20° S, and a cyclone in the southwestern Atlantic between 20° S and 40° S. The results here might be relevant for climate monitoring and modeling studies.

Given that the analysis of past monthly rainfall variability is highly relevant for the adequate management of water resources, the relationship between the climate-oceanographic indices, and the variability of monthly rainfall in Southwestern Colombia at different time scales was chosen as the research topic. It should also be noted that little-to-no research has been carried out on this topic before. For the purpose of conducting this research, we identified homogeneous rainfall regions while using Non-Linear Principal Component Analysis (NLPCA) and Self-Organizing Maps (SOM). The rainfall variability modes were obtained from the NLPCA, while their teleconnection in relation to the climate indices was obtained from Pearson's Correlations and Wavelet Transform. The regionalization process clarified that Nari&ntilde, o has two regions: the Andean Region (AR) and the Pacific Region (PR). The NLPCA showed two modes for the AR, and one for the PR, with an explained variance of 75% and 48%, respectively. The correlation analyses between the first nonlinear components of AR and PR regarding climate indices showed AR high significant positive correlations with Southern Oscillation Index (SOI) index and negative correlations with El Ni&ntilde, o/Southern Oscillation (ENSO) indices. PR showed positive ones with Ni&ntilde, o1 + 2, and Ni&ntilde, o3, and negative correlations with Ni&ntilde, o3.4 and Ni&ntilde, o4, although their synchronous relationships were not statistically significant. The Wavelet Coherence analysis showed that the variability of the AR rainfall was influenced principally by the Ni&ntilde, o3.4 index on the 3&ndash, 7-year inter-annual scale, while PR rainfall were influenced by the Ni&ntilde, o3 index on the 1.5&ndash, 3-year inter-annual scale. The El Ni&ntilde, o (EN) events lead to a decrease and increase in the monthly rainfall on AR and PR, respectively, while, in the La Ni&ntilde, a (LN) events, the opposite occurred. These results that are not documented in previous studies are useful for the forecasting of monthly rainfall and the planning of water resources in the area of study.

The Standardized Precipitation Index (SPI) characterizes meteorological droughts of a place, by quantifying the deficit of rainfall in different time periods. Negative SPI values represents drought, while positive values indicate wet periods. The results suggest that negative SPI periods coincide with El Niño years: 82-83, 91-92 and 97-98. The 91-92 event had the largest impact on the region. These results indicate that the most severe droughts in the basin of Dagua, were presented at the quarters of Dec- Jan-Feb, Jan-Feb-Mar, Jun-Jul-Aug and Jul-Aug-Sep. The results have been obtained with geostatistical techniques, and are a basic input to formulate adaptation strategies and ensure food sovereignty of small farmers against drought., El Índice Estandarizado de Precipitación (SPI) caracteriza las sequías meteorológicas de un lugar, mediante la cuantificación del déficit de precipitación en diferentes períodos de tiempo. Valores negativos del SPI representan sequías, mientras valores positivos indican periodos húmedos. Los resultados muestran que los períodos SPI negativos, coinciden con años clasificados como El Niño: 82-83, 91-92 y 97-98, de los cuales, el evento 91-92 presentó los mayores impactos en la región. En general, los resultados indican que las sequías más intensas en la cuenca del Dagua, se presentaron en los trimestres de Dic-Ene-Feb, Ene-Feb-Mar, Jun-Jul-Ago y Jul-Ago-Sep; estos resultados se espacializaron con técnicas geoestadísticas, y son insumo básico para formular estrategias de adaptación y garantizar la soberanía alimentaria de los pequeños agricultores frente a las sequías. [fr] L’Indice de précipitations normalisé (SPI) caractérise les sécheresses météorologiques d’un lieu, en quantifiant le déficit de précipitations à différentes périodes de temps. Les valeurs négatives de SPI indiquent périodes sécheresse, tandis que les positives indiquent des périodes humides. Les résultats montrent que les périodes SPI négatifs obtenus coïncident avec les années «El Niño». Les années en question sont: 82-83, 91-92 et 97-98. L’événement 91-92 montre le plus grand impact sur la région. Ces résultats suggèrent que les sécheresses les plus sévères touchant le bassin de Dagua ont eu lieu lors des trimestres de décembre-janvier-février, janvier-février-mars, juin-juillet- août et juin-août-septembre. Les résultats ont été obtenus à l’aide des techniques géostatistiques et fournissent des outils de base pour l’élaboration des stratégies d’adaptation afin d’assurer la souveraineté alimentaire des petits agriculteurs contre la sécheresse.

The success of many projects linked to the management and planning of water resources depends mainly on the quality of the climatic and hydrological data that is provided. Nevertheless, the missing data are frequently found in hydroclimatic variables due to measuring instrument failures, observation recording errors, meteorological extremes, and the challenges associated with accessing measurement areas. Hence, it is necessary to apply an appropriate fill of missing data before any analysis. This paper is intended to present the filling of missing data of monthly rainfall of 45 gauge stations located in southwestern Colombia. The series analyzed covers 34 years of observations between 1983 and 2016, available from the Instituto de Hidrología, Meteorología y Estudios Ambientales (IDEAM). The estimation of missing data was done using Non-linear Principal Component Analysis (NLPCA); a non-linear generalization of the standard Principal Component Analysis Method via an Artificial Neural Networks (ANN) approach. The best result was obtained using a network with a [45−44−45] architecture. The estimated mean squared error in the imputation of missing data was approximately 9.8 mm. month−1, showing that the NLPCA approach constitutes a powerful methodology in the imputation of missing rainfall data. The estimated rainfall dataset helps reduce uncertainty for further studies related to homogeneity analyses, conglomerates, trends, multivariate statistics and meteorological forecasts in regions with information deficits such as southwestern Colombia. Keywords: Missing data, Monthly Rainfall Data, Artificial neural networks, NLPCA

Contexto: Los eventos climáticos extremos ocasionan grandes retos para la sostenibilidad social, económica y medioambiental, de una región, como es el caso de las sequías que afectan significativamente las actividades agrícolas, aumentando el riesgo de la subsistencia y la seguridad alimentaria de la población rural, principalmente de países en desarrollo. Este estudio tuvo como objetivo caracterizar las sequías meteorológicas en la cuenca del río Dagua, Valle del Cauca. Método: Se estimó la intensidad, magnitud, duración y frecuencia de eventos de sequía mediante el uso del Índice Estandarizado de Precipitación (SPI) para agrupaciones semestrales y anuales, usando el registro de 19 estaciones en el período comprendido entre 1982-2011 Resultados: Al menos una sequía fue identificada en cada serie, mientras el área próxima a la región subxerofítica de la cuenca, presentó mayor frecuencia de sequías extremadamente fuertes y los menores umbrales de precipitación mínima; el mayor porcentaje de cobertura espacial coincidió con la ocurrencia de eventos del fenómeno El Niño, tales como los ocurridos en 91-92 y 09-10. Conclusiones: Los resultados obtenidos sirven como aproximación para la predicción y caracterización de las sequías, y ofrecen insumos para generar estrategias de planificación y mitigación de sus impactos. Context: Extreme climatic events causes great challenges for social, economic and environmental sustainability of a region. Droughts affect agricultural activities significantly thus endangering the livelihoods and food security of rural populations, this is especially crucial for developing countries. The objective of this study is to characterize meteorological drought in Dagua river basin, Valle del Cauca. Method: Intensity, magnitude, duration and frequency of drought events was estimated using the Standardized Precipitation Index (SPI), for semi-annual and annual groupings with records of 19 stations, during the period 1982-2011 Results: At least one drought was identified in each series; the area near to the subxerofític Basin region, exhibits more frequency of extremely strong drought and lower threshold of minimum precipitation; the largest percentage of spatial coverage of drought coincides with El Niño phenomena events, such as those that occurred in 91-92 to 09-10. Conclusions: The results obtained provide an approach for prediction and characterization of drought, and offer inputs to generate strategies for planning and mitigation of their impacts.

El sistema de monitoreo y seguimiento permite identificar, a través de indicadores e índices, la sostenibilidad del recurso hídrico en el sector agrícola de la microcuenca Centella (Dagua-Valle del Cauca). Este modelo de monitoreo permite evaluar continua y sistemáticamente el progreso y los cambios ocasionados por la ejecución de un conjunto de actividades en un período de tiempo determinado. De igual manera, a través de este sistema es posible realizar un seguimiento y verificar en qué medida se cumplen las metas propuestas de sostenibilidad del recurso hídrico en el sector agrícola a nivel: biofísico, tecnológico, político-institucional y socioeconómico.

La identificación de los elementos que permiten evidenciar una visión regional y metropolitana de los municipios del área de influencia inmediata de Cali (Jamundí, Candelaria, Palmira y Yumbo ubicados en el sur del Valle del Cauca y Puerto Tejada localizado en el norte del departamento del Cauca), se realizó apartir de cuatro procesos metodológicos: el primero de ellos llamado Lectura Operativa, en el que se analizó la suficiencia y la articulación de los Planes de Ordenamiento Territorial (POT) en la búsqueda de convergencias regionales, intermunicipales o metropolitanas; el segundo, denominado ensamble cartográfico, con el cual se identificó a partir de los modelos territoriales municipales propuestos en los POT, las perspectivas que plantea cada municipio que permita reconocer una visión regional y metropolitana; tercero, se hizo el estudio de la incorporación de los lineamientos propuestos en la "Carta de Intención de Cooperación Horizontal" en los POT, y por ultimo, la identificación de elementos para la construcción de una visión metropolitana. Los resultados muestran las discontinuidades y fragmentaciones espaciales en los modelos territoriales municipales, lo cual indica una ausencia de visión de conjunto en cada entidad territorial, evidenciando la necesidad de una construcción colectiva de visiones compartidas, soportadas en alguna figura asociativa como las que prevé la Constitución y la Ley colombiana. The identification of the elements that allow a regional and metropolitan view of the municipalities in the área of immediate influence of Cali (Jamundí, Candelaria, Palmira and Yumbo located in southern Valle del Cauca and Puerto Tejada located in the north of Cauca), was made from four methodology: the first one called Operative Reading, which examined the adequacy and implementation of Land Management Plans (POT) in the search for regional, metropolitan, or intermunicipality convergence, the second, called map assembly, were was identified from the municipal territorial models proposed on the POT, the perspectives that propose each municipality to recognize a regional and metropolitan view; third the study of the incorporation of the guidelines proposed in the "Letter of Intent for Horizontal Cooperation" inthePOTwasmade, andfinally, the identification of elements for the construction of metropolitan view. The results show the spatial discontinuities andfragmentation in territorial municipality models, which indi cates a lack of oversight in each territorial entity, highlighting the needfor a collective sharing of visions, supportedby some associative figure as foreseen in the Constitution and Laws in Colombia.

Socioeconomic segregation of urban space has complex relationships according to ethnicity, age, education, culture or immigration status, among others. In this context, a spatial study was conducted in Cali, by multivariate analysis, applying the Guttman scalogram. The results by municipalities show that as the city extends to the periphery, spatial segregation increases towards the slopes in the west and the banks of the Cauca River in the east, which coincides with the location of ethnic groups or people in poverty, unlike privileged socioeconomic groups, which tend to be concentrated in the north and south of the city.

The Sustainability Index of Agricultural Production Systems (SIAPS) was used to assess the ecological integrity of study area in the Centella watershed (Dagua, Valle del Cauca). Four components were evaluated: soil management and hedging, water management, solid waste, and social, economic, political and institutional aspects for a total of 23 indicators. SIAPS was used to compare production systems and to estimate conditions of integrity amongst farms. The results permitted definition of minimum thresholds of ecosystem capacity for supporting anthropogenic use. 38% of the farms were constituted as best performers, 56% are "above the threshold" and only 6% were "below the threshold". The key issue is not that farmers use the exact same techniques used by those of the "headlight", but that they are presented as an example of the management and conservation of resources, planning and promotion of sustainable human development on farms.