Estimación del efecto del cambio climático en la precipitación de la costa norte del Perú usando simulaciones de modelos climáticos globales

Universidad Nacional Agraria La Molina. Facultad de Ciencias. Departamento Académico de Ingeniería Ambiental, Física y MeteorologíaLa Costa Norte del Perú caracterizada como una zona árida puede llegar a sufrir de intensas precipitaciones debido al calentamiento del mar durante los eventos El Niño. Se conoce que existe una relación no-lineal entre la temperatura superficial del mar (TSM) y la precipitación en los trópicos: para que ocurra precipitación convectiva es necesario que la TSM exceda un valor crítico, de manera que el aire pueda ascender y romper la capa de inversión térmica que controla la estabilidad atmosférica e impide la formación de tormentas. Se espera que este valor crítico aumente bajo escenarios de cambio climático debido al calentamiento de la atmosfera tropical. La generación actual de modelos climáticos proyectan aumento en la lluvia promedio en la costa norte pero estos modelos presentan grandes sesgos positivos de la TSM y precipitaciones en la costa de Sudamérica. Considerando la relación no lineal de la precipitación y temperatura, es probable que estos sesgos sobreestimen la estimación de los cambios futuros de la precipitación en esta región. Para evitar los errores sistemáticos de los modelos, proponemos un modelo empírico que relaciona la precipitación y la TSM mensual observada en la costa norte del Perú. En este modelo, la precipitación incrementa linealmente con la TSM sobre la Temperatura Crítica (Tcrit) y es cero bajo esta. El modelo empírico reproduce bien los resultados de la mayoría de los GCM y cuando se evitan los sesgos correspondientes, se encuentra que el cambio de precipitación futuro varía en un rango de entre 0 y 60% en los últimos cincuenta años del siglo XXI. Esto se traduce en un incremento de 22mm en Tumbes y 8mm en Piura.The northwestern of Peru is characterized which is characterized as an arid zone, may experience strong rainfall due to El Niño warming events. It is known that there is a non-linear relationship between sea surface temperature (SST) and precipitation (PP) in the tropics: to convective precipitation occur is necessary that the SST exceeds a critical value, so air can move up and break the inversion layer that controls the atmospheric stability and prevents the formation of storms. It is expected that this critical value increases under scenarios of climate change due to warming of the tropical atmosphere. The current generation of climate models projects an increase in average rainfall the northwestern coast, but these models have large positive biases of SST and rainfall alongshore of South America. Considering the nonlinear relationship of precipitation and temperature, these biases are likely to overestimate the estimated future changes in precipitation in this region. To correct this effect, we propose an empirical model (MFE) relating monthly precipitation and SST observed in the northern coast of Peru. In this model, precipitation increases linearly with SST over the critical temperature (Tcrit) and the otherwise is cero. The empirical model reproduces well the results of most of the GCM. As the corresponding biases are corrected the change of future precipitation varies in a range between 0 and 60% in the last fifty years of this century. This translates into an increase of 22mm in Tumbes and 8mm in Piura.Tesi

MJO-induced Warm Pool Eastward Extension Prior to the Onset of El Niño: An Observational study

Thesis (Master's)--University of Washington, 2020The Madden-Julian Oscillation (MJO) and El Niño Southern Oscillation (ENSO) are the two most important phenomena in the Tropics that affect global weather and climate on intraseasonal to interannual timescales. Although they occur on different timescales, the MJO-induced SST changes over the western Pacific have spatial scales similar to those of SST anomalies prior and/or during the onset of El Niño. To investigate the MJO-induced SST changes and their contribution to the warm pool eastward extension (WPEE) prior to the onset of El Ni˜no, we use 20 years of Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA), Cross Calibrated Multi-Platform (CCMP) surface winds, and Optimum Interpolated Sea Surface Temperature (OISST) to quantify the time and spatial scales of MJO rain and wind, and the MJO-induced WPEE. The MJO events in the western equatorial Pacific (east of 130°E, 10°S – 10°N) are identified based on the Large-scale Precipitation Tracking (LPT). The intensity of the MJO is measured by total rain volume and zonal surface winds averaged throughout its lifetime. It is found that the majority of the MJOs (65%) induce a WPEE up to 3000 km that can last beyond 15 days. The MJO events prior to the onset of El Niño are generally stronger in convection and winds, and produce significant WPEE beyond the annual cycle. Consecutive MJO events produce much larger WPEE prior to El Niño, which has been observed in every El Niño event from 1998-2019

New insights into the rainfall variability in the tropical Andes on seasonal and interannual time scales

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