Streamflow Intensification Driven by the Atlantic Multidecadal Oscillation (AMO) in the Atrato River Basin, Northwestern Colombia

[EN] The impact of the Atlantic Multidecadal Oscillation (AMO) on the variations in the streamflow in the Atrato River Basin (ARB) during the 1965-2016 period was analyzed here by considering the cold (1965-1994) and warm (1995-2015) 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 1995-2015 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.The first author was supported by the Doctoral Scholarship of the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior-Brazil (CAPES), Finance Code 001 and Universidad del Valle (Cali-Colombia). The Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) of Brazil partially supported the second and third authors under grants 302322/2017-5 and 305942/2015-8, respectively. The fourth author was supported by the CAPES-Brazil and Universidade Federal de Vicosa for doctoral studies. The fifth author was supported by the Program for Strengthening Regional Capacities in Research, Technological Development and Innovation in the department of Narino and the CEIBA Foundation for doctoral studies. The seventh author was supported by the CAPES-Brazil. This research was done partially during an internship of the first and fifth author at the Research Institute of Water and Environmental Engineering of the Universitat Politecnica de Valencia. This work was also supported by the Spanish Ministry of Science and Innovation through Project TETISCHANGE (RTI2018-093717-B-I00).Cerón, WL.; Kayano, MT.; Andreoli, RV.; Avila, A.; Canchala, T.; Francés, F.; Rivera, IA.... (2020). Streamflow Intensification Driven by the Atlantic Multidecadal Oscillation (AMO) in the Atrato River Basin, Northwestern Colombia. Water. 12(1):1-23. https://doi.org/10.3390/w12010216S12312

Does the El Niño-Southern Oscillation Affect the Combined Impact of the Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation on the Precipitation and Surface Air Temperature Variability over South America?

Previous studies have shown that the Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO) have combined effects on the precipitation (PRP) variability over South America. The combined impacts have been assessed considering four mean states as the averages of the variable anomalies during sub-periods overlapping time intervals of the PDO and AMO phases. Since these sub-periods include years under El Niño-Southern Oscillation (ENSO) extremes, the extent to which these years’ occurrence affects the averaged anomaly patterns during different mean states is investigated. The analyses are done for the PRP and surface air temperature (SAT) during the austral winter (June to August) and summer (December to February) of the 1901–2014 period using a composite technique. The nonlinear ENSO response in each mean state for a variable corresponds to the sum of the anomaly composites of the El Niño and La Niña events. In each mean state, the nonlinear PRP and SAT anomalies are not negligible and show similar patterns of the corresponding mean state, with larger magnitudes. For both seasons and all mean states, these similarities are more pronounced for SAT than for PRP. Thus, the ENSO variability affects the mean state’s PRP and SAT anomaly patterns in different ways. As far as we know, analyses of the nonlinear ENSO response of the South American climate during distinct mean states were not performed before. Our results also indicate that the ENSO variability should be considered in the studies of the low-frequency modes and their effects on the mean state over South America. The results presented could be relevant for climate monitoring and modeling studies.Incluye referencias bibliográfica

Trend Pattern of Heavy and Intense Rainfall Events in Colombia from 1981–2018: A Trend-EOF Approach

The Andes mountain range divides Colombia into various climatic regions over the country, as the Andean, Caribbean, Pacific, Amazon, and Orinoco regions. Given this scenario, knowing the current change in total precipitation and their extremes values are relevant. In this study, the main goal is to assess the spatio-temporal trends of heavy and intense rainfall at a seasonal scale during the last 38 years (1981–2018) using the trend empirical orthogonal function (TEOF). An increase in maximum precipitation during five consecutive days (RX5day), Simple daily intensity index (SDII), and the number of days with precipitation above 20 mm (R20mm) and 30 mm (R30mm) during December–February and March–May was observed in most of the Colombian territory, except for the Amazon region for RX5day. A decrease in total rainfall in June–August was observed in the Andean, the Caribbean, and southern Pacific regions, while, in the northern Pacific, it increased, consistent with the trend patterns of RX5day, SDII, and R20mm. During September–November, there was a reduction in rainfall in the Amazon region and the South Pacific, and an increase in RX5day, SDII, R20mm, and R30mm in the Andean, the Caribbean, and North Pacific regions. The TEOF showed more pronounced spatial trend patterns than those obtained with the traditional Mann–Kendall test. The findings offer a better understanding of the climate extremes impacts in tropical latitudes and help planners to implement measures against the future effects of climate change

Trend Pattern of Heavy and Intense Rainfall Events in Colombia from 1981–2018: A Trend-EOF Approach

The Andes mountain range divides Colombia into various climatic regions over the country, as the Andean, Caribbean, Pacific, Amazon, and Orinoco regions. Given this scenario, knowing the current change in total precipitation and their extremes values are relevant. In this study, the main goal is to assess the spatio-temporal trends of heavy and intense rainfall at a seasonal scale during the last 38 years (1981–2018) using the trend empirical orthogonal function (TEOF). An increase in maximum precipitation during five consecutive days (RX5day), Simple daily intensity index (SDII), and the number of days with precipitation above 20 mm (R20mm) and 30 mm (R30mm) during December–February and March–May was observed in most of the Colombian territory, except for the Amazon region for RX5day. A decrease in total rainfall in June–August was observed in the Andean, the Caribbean, and southern Pacific regions, while, in the northern Pacific, it increased, consistent with the trend patterns of RX5day, SDII, and R20mm. During September–November, there was a reduction in rainfall in the Amazon region and the South Pacific, and an increase in RX5day, SDII, R20mm, and R30mm in the Andean, the Caribbean, and North Pacific regions. The TEOF showed more pronounced spatial trend patterns than those obtained with the traditional Mann–Kendall test. The findings offer a better understanding of the climate extremes impacts in tropical latitudes and help planners to implement measures against the future effects of climate change

Pacific and Atlantic Multidecadal Variability Relations with the Choco and Caribbean Low-Level Jets during the 1900–2015 Period

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

Does the El Niño-Southern Oscillation Affect the Combined Impact of the Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation on the Precipitation and Surface Air Temperature Variability over South America?

Previous studies have shown that the Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO) have combined effects on the precipitation (PRP) variability over South America. The combined impacts have been assessed considering four mean states as the averages of the variable anomalies during sub-periods overlapping time intervals of the PDO and AMO phases. Since these sub-periods include years under El Niño-Southern Oscillation (ENSO) extremes, the extent to which these years’ occurrence affects the averaged anomaly patterns during different mean states is investigated. The analyses are done for the PRP and surface air temperature (SAT) during the austral winter (June to August) and summer (December to February) of the 1901–2014 period using a composite technique. The nonlinear ENSO response in each mean state for a variable corresponds to the sum of the anomaly composites of the El Niño and La Niña events. In each mean state, the nonlinear PRP and SAT anomalies are not negligible and show similar patterns of the corresponding mean state, with larger magnitudes. For both seasons and all mean states, these similarities are more pronounced for SAT than for PRP. Thus, the ENSO variability affects the mean state’s PRP and SAT anomaly patterns in different ways. As far as we know, analyses of the nonlinear ENSO response of the South American climate during distinct mean states were not performed before. Our results also indicate that the ENSO variability should be considered in the studies of the low-frequency modes and their effects on the mean state over South America. The results presented could be relevant for climate monitoring and modeling studies

Spatio-Temporal Variability of Hydroclimatology in the Upper Cauca River Basin in Southwestern Colombia: Pre- and Post-Salvajina Dam Perspective

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

Ganglioneurocytoma of the spinal cord: report of a case and review of literature

A case of ganglioneurocytoma of the spinal cord in a 51-year-old man is reported. Patient presented with a progressively worsening back pain and hyposthenia of lower limbs. Magnetic resonance imaging of the spinal cord revealed an intradural lesion in the T10–11 spinal segments, hyperintense on T1-weighted sequences. Complete resection was achieved. The patient did not show evidence of recurrence 12 months after surgery. On histology, the lesion was composed of round to oval cells with fine granular, slightly eosinophilic to clear cytoplasm suggesting a neurocytic differentiation. Some ganglion cells were observed. Neither significant cytologic atypia nor mitoses were present. The neoplastic cells were strongly positive with synaptophysin and negative with glial fibrillary acid protein. Neurocytomas are uncommon tumors typically arising within the lateral ventricles near the foramen of Monro. Extraventricular neurocytomas have been reported at various sites with rare examples in spinal cord. In the present paper, a case of ganglioneurocytoma of the spinal cord is reported with review of literature and discussion of differences compared to neurocytomas of other sites