TY - JOUR
T1 - Notes and correspondence the impact of tropical tropopause cooling on sahelian extreme deep convection
AU - Kodera, Kunihiko
AU - Eguchi, Nawo
AU - Ueyama, Rei
AU - Funatsu, Beatriz M.
AU - Gaetani, Marco
AU - Taylor, Christopher M.
N1 - Funding Information:
This work was supported in part by Grants-in-Aid for Scientific Research (25340010, 17H01159, JP18K03743) from the Japan Society for the Promotion of Science. Preliminary analysis of this study was carried out using the Interactive Tool for Analysis of the Climate System (ITACS) provided by the Japan Meteorological Agency. AMSU data was accessed through ICARE with support of the IPSL-ESPRI team. CT was supported by UK NERC/DFID African Monsoon Multidisciplinary Analysis-2050 project (Grant NE/M020428/1). RU was supported by NASA Upper Atmospheric Composition Observations Program.
Publisher Copyright:
©The Author(s) 2021.
PY - 2021
Y1 - 2021
N2 - Previous studies have suggested that the recent increase in tropical extreme deep convection, in particular over Asia and Africa during the boreal summer, has occurred in association with cooling in the tropical lower strato-sphere. The present study is focused on the Sahel region of West Africa, where an increased occurrence of extreme precipitation events has been reported over recent decades. The results indicate that the changes over West Africa since the 1980s involve a cooling trend in the tropical lower stratosphere and tropopause layer, combined with warming in the troposphere. This feature is similar to that which might result from increased greenhouse-gas levels but is distinct from the interannual variation of precipitation associated with the transport of water vapor from the Atlantic Ocean. It is suggested that the decrease in the vertical temperature gradient in the tropical tropopause region enhances extreme deep convection over the Sahel, where penetrating convection is frequent, whereas tropospheric warming suppresses the shallower convection over the Guinea Coast. Therefore, the essen-tial feature of the recent changes over West Africa is the depth of convection rather than the total amount of surface precipitation.
AB - Previous studies have suggested that the recent increase in tropical extreme deep convection, in particular over Asia and Africa during the boreal summer, has occurred in association with cooling in the tropical lower strato-sphere. The present study is focused on the Sahel region of West Africa, where an increased occurrence of extreme precipitation events has been reported over recent decades. The results indicate that the changes over West Africa since the 1980s involve a cooling trend in the tropical lower stratosphere and tropopause layer, combined with warming in the troposphere. This feature is similar to that which might result from increased greenhouse-gas levels but is distinct from the interannual variation of precipitation associated with the transport of water vapor from the Atlantic Ocean. It is suggested that the decrease in the vertical temperature gradient in the tropical tropopause region enhances extreme deep convection over the Sahel, where penetrating convection is frequent, whereas tropospheric warming suppresses the shallower convection over the Guinea Coast. Therefore, the essen-tial feature of the recent changes over West Africa is the depth of convection rather than the total amount of surface precipitation.
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U2 - 10.2151/jmsj.2021-055
DO - 10.2151/jmsj.2021-055
M3 - Letter
AN - SCOPUS:85113704911
VL - 99
SP - 1127
EP - 1139
JO - Journal of the Meteorological Society of Japan
JF - Journal of the Meteorological Society of Japan
SN - 0026-1165
IS - 4
ER -