The seasonal cycle of redistribution of atmospheric mass between continent and ocean in the Northern Hemisphere  

作　　者：HU Chao GUAN ZhaoYong LI MingGang 

机构地区：[1]Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science & Technology [2]Meteorological Administration of Tianjin Binhai New Area

出　　处：《Science China Earth Sciences》2014年第7期1501-1512,共12页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant No. 41175062);the Project of Scientific Creation of Post-Graduates of Jiangsu (Grant No. CXZZ12_0485);the Creative Teams of Jiangsu Qinglan Project

摘　　要：Using NCEP/NCAR and ERA-40 reanalyses,we studied the seasonal cycle of redistribution of air mass between continents and oceans over the Northern Hemisphere.Our results demonstrate that air mass in the Northern Hemisphere shifts clearly between continents and oceans when the season cycles.In July,the air mass reaches its lowest over Eurasia and its highest over the Pacific,and the opposite occurs in January.However,a different scenario is observed over the north Atlantic;the accumulated air mass reaches its maximum there in May.The maintenance of the accumulation or loss of air mass in a region is found to be related to the areal mean air mass flux divergence and the difference between precipitation and evaporation in an air column.The zonal-vertical circulations change with season,with the air ascent and decent reversed between land and sea.Besides,there also exists a noticeable difference of water vapor content of the air between continents and oceans,and this difference is season-dependent.Physically,the vapor content is able to significantly affect the atmosphere in absorbing solar short-and earth’s long-wave radiations,hence influencing atmospheric thermal conditions.The land-sea thermal contrasts inclusive of the diabatic heating rate changes their signs with season going on,resulting in the reversal of orientations of the temperature gradient.These thermal forcings not only facilitate the formation of the monsoons but also indirectly induce the seasonal cycle of the air mass exchanging over regions between continents and oceans.Using NCEP/NCAR and ERA-40 reanalyses, we studied the seasonal cycle of redistribution of air mass between continents and oceans over the Northern Hemisphere. Our results demonstrate that air mass in the Northern Hemisphere shifts clearly between continents and oceans when the season cycles. In July, the air mass reaches its lowest over Eurasia and its highest over the Pacific, and the opposite occurs in January. However, a different scenario is observed over the north Atlantic; the accumulated air mass reaches its maximum there in May. The maintenance of the accumulation or loss of air mass in a region is found to be related to the areal mean air mass flux divergence and the difference between precipitation and evaporation in an air column. The zonal-vertical circulations change with season, with the air ascent and decent reversed between land and sea. Besides, there also exists a noticeable difference of water vapor content of the air between continents and oceans, and this difference is season-dependent. Physically, the vapor content is able to significantly affect the atmosphere in absorbing solar short- and earth＇s long-wave radiations, hence influencing atmospheric thermal conditions. The land-sea thermal contrasts inclusive of the diabatic heating rate changes their signs with season going on, resulting in the reversal of orientations of the temperature gradient. These thermal forcings not only facilitate the formation of the monsoons but also indirectly induce the seasonal cycle of the air mass exchanging over regions between continents and oceans.

关 键 词：atmospheric mass seasonal cycle redistribution between continents and oceans land-sea thermal contrast 

分 类 号：P461.2[天文地球—大气科学及气象学]