caa a22 4500 605471061 CHVBK 20210128100331.0 cr unu---uuuuu 210128e20150801xx s 000 0 eng 10.1007/s00382-014-2296-0 doi (NATIONALLICENCE)springer-10.1007/s00382-014-2296-0 Asian summer monsoon onset barrier and its formation mechanism [Elektronische Daten] [Boqi Liu, Yimin Liu, Guoxiong Wu, Jinghui Yan, Jinhai He, Suling Ren] The onset process of Asian summer monsoon (ASM) is investigated based on diagnostic analysis of observations of precipitation and synoptic circulation. Results show that after the ASM commences over the eastern Bay of Bengal (BOB) around early May, the onset can propagate eastwards towards the South China Sea and western Pacific but is blocked on its westward propagation along the eastern coast of India. This blocking, termed the "monsoon onset barrier (MOB)”, presents a Gill-type circulation response to the latent heating released by BOB monsoon convection. This convective condensation heating generates summertime (wintertime) vertical easterly (westerly) shear to its east (west) and facilitates air ascent (descent). The convection then propagates eastward but gets trapped on its westward path. To the east of the central BOB, the surface air temperature (SAT) cools faster than the underlying sea surface temperature (SST) due to monsoon onset. Thus more sensible heat flux supports the onset convection to propagate eastward. To the west of the central BOB, however, the land surface sensible heating over the Indian Peninsula is strengthened by the enhanced anticyclone circulation and air descent induced by the BOB monsoon heating. The strengthened upstream warm horizontal advection then produces a warm SAT center over the MOB region, which together with the in situ cooled SST reduces the surface sensible heating and atmospheric available potential energy to prevent the occurrence of free convection. Therefore, it is the change in both large-scale circulation and air-sea interaction due to BOB summer monsoon onset that contributes to the MOB formation. The Author(s), 2014 Monsoon onset barrier nationallicence Bay of Bengal summer monsoon nationallicence Gill-type response nationallicence Air-sea interaction nationallicence Liu Boqi State Key Lab of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China aut Liu Yimin State Key Lab of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China aut Wu Guoxiong State Key Lab of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China aut Yan Jinghui China Meteorological Administration, 100081, Beijing, China aut He Jinhai State Key Lab of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China aut Ren Suling State Key Lab of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China aut Climate Dynamics Springer Berlin Heidelberg 45/3-4(2015-08-01), 711-726 0930-7575 45:3-4<711 2015 45 382 https://doi.org/10.1007/s00382-014-2296-0 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00382-014-2296-0 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Liu Boqi State Key Lab of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China aut NATIONALLICENCE 700 1- Liu Yimin State Key Lab of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China aut NATIONALLICENCE 700 1- Wu Guoxiong State Key Lab of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China aut NATIONALLICENCE 700 1- Yan Jinghui China Meteorological Administration, 100081, Beijing, China aut NATIONALLICENCE 700 1- He Jinhai State Key Lab of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China aut NATIONALLICENCE 700 1- Ren Suling State Key Lab of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China aut NATIONALLICENCE 773 0- Climate Dynamics Springer Berlin Heidelberg 45/3-4(2015-08-01), 711-726 0930-7575 45:3-4<711 2015 45 382