The Response of Geopotential Height Anomalies to El Niño and La Niña Conditions and Their Implications to Seasonal Rainfall Variability over the Horn of Africa  

作　　者：Solomon Gunta Hejamady Gangadhara Bhat Busnur Rachotappa Manjunatha Solomon Gunta;Hejamady Gangadhara Bhat;Busnur Rachotappa Manjunatha(Department of Physics, College of Natural and Computational Sciences, Wolaita Sodo University, Wolaita Sodo, Ethiopia;Remote Sensing and Geo-Informatics Division, Department of Marine Geology, Faculty of Science and Technology, Mangalore University, Karnataka, India)

机构地区：[1]Department of Physics, College of Natural and Computational Sciences, Wolaita Sodo University, Wolaita Sodo, Ethiopia [2]Remote Sensing and Geo-Informatics Division, Department of Marine Geology, Faculty of Science and Technology, Mangalore University, Karnataka, India

出　　处：《Atmospheric and Climate Sciences》2022年第2期475-492,共18页大气和气候科学（英文）

摘　　要：In this study, we unveil atmospheric circulation anomalies associated with the large-scale tropical teleconnections using National Center for Environmental Prediction (NCEP) reanalysis dataset. Composite analyses have been performed to know the impact of large-scale tropical circulations on the Horn of Africa. The composite analysis performed at the geopotential height of 850 Mb and 200 Mb, and precipitation rate (mm/day) during six strong El Niño and La Niña episodes revealed that the large-scale tropical variability induced climate anomalies in space and time. A substantial decrease in upper-level height (200 Mb) has been observed in the study area during El Niño composite years as compared to the La Niña years. During El Niño conditions, the upper-level divergence initiates low-level vertical motion, thereby enhancing convection, however, during La Niña composite years, nearly contrasting situations are noticed in Belg (February to May) season in Ethiopia. However, geopotential height anomalies at 850 Mb are above-normal during the strong El Niño years, suggesting suppressed convection due to vertical shrinking and enhancement of divergence at the lower level. Compared to the Belg (February to May), geopotential anomalies were generally positive during the Kiremt (June to September) season, thereby suppressing the rainfall, particularly in Southern Ethiopia and Northern Part of Kenya. In contrast, an increase in rainfall was observed during the Belg season (February to May).In this study, we unveil atmospheric circulation anomalies associated with the large-scale tropical teleconnections using National Center for Environmental Prediction (NCEP) reanalysis dataset. Composite analyses have been performed to know the impact of large-scale tropical circulations on the Horn of Africa. The composite analysis performed at the geopotential height of 850 Mb and 200 Mb, and precipitation rate (mm/day) during six strong El Niño and La Niña episodes revealed that the large-scale tropical variability induced climate anomalies in space and time. A substantial decrease in upper-level height (200 Mb) has been observed in the study area during El Niño composite years as compared to the La Niña years. During El Niño conditions, the upper-level divergence initiates low-level vertical motion, thereby enhancing convection, however, during La Niña composite years, nearly contrasting situations are noticed in Belg (February to May) season in Ethiopia. However, geopotential height anomalies at 850 Mb are above-normal during the strong El Niño years, suggesting suppressed convection due to vertical shrinking and enhancement of divergence at the lower level. Compared to the Belg (February to May), geopotential anomalies were generally positive during the Kiremt (June to September) season, thereby suppressing the rainfall, particularly in Southern Ethiopia and Northern Part of Kenya. In contrast, an increase in rainfall was observed during the Belg season (February to May).

关 键 词：Geopotential Height Composite Analysis ENSO Atmospheric Circulations NCEP Reanalysis Tropical SST Anomalies TELECONNECTIONS Belg Kiremt 

分 类 号：P73[天文地球—海洋科学]