Migration Of Atmospheric Mass Over Regions Between Lands And Oceans In Boreal Spring And Its Impacts On Climate Anomalies

Using NCEP/NCAR monthly mean reanalysis and CMAP (CPC Merged Analysis of Precipitation) precipitation data over period from 1979 to 2013, by defining an index of the Migration of Atmospheric Mass over Regions between Lands and Oceans (MAMLO), we have investigated the interannual variability of spring MAMLO in Eurasia-North Pacific (EP) domain and MAMLO in North Pacific-North America (PA) region and their impacts on climate anomalies over Eurasia and North America. At the same time, according to different configuration of two indexes, the atmospheric circulation characteristics and their impacts on climate over Eurasia and North America are also analyzed. The conclusions are as follows:The spring MAMLO-EP is mainly characterized by a seesaw like structure in surface air pressure anomalies, which can be referred to Eurasia-North Pacific teleconnection pattern. The MAMLO-EP index varies with a long-term trend, and the distinct interannual and interdecadal changes. It is found that anomalous vertical circulation bridges Eurasia and North Pacific, with the migration of atmospheric mass between these two regions. The wave activity fluxes show that the wave energy propagate from the Western Europe eastward into the North Pacific, facilitating the maintenance of the anomalous geopotential height disturbances there. In spring, The MAMLO-EP index IMAMLO-EP is highly correlated with the anomalous rainfall and surface air temperature over Eurasia. When the IMAMLO-EP is positive, the precipitation decreases significantly over the north of East Asia, the west of Okhotsk Sea and the coastal Western Europe, as opposed to the increase over the west of Eurasia and northern of China. The anticyclonic circulation in Siberia and cyclonic circulation in North Pacific in lower troposphere induce the anomalously high surface air temperature in northern Eurasia, along with the anomalous lower temperature in regions of East of Siberia, Northeast China, North China, Yangtze-Huaihe River valley, Korea and the south of Japan. The surface air temperature anomalously decreases in much of Western Europe and northwestern China.The spring MAMLO-PA is also mainly characterized by a seesaw like structure in surface air pressure anomalies over North Pacific and North America, with its index varying with the periodicities of 2-4 yrs, and the distinct interdecadal changes, besides a weak up-trend. It is found that the anomalous horizontal spatial distributions of atmospheric mass fluxes bridge North Pacific and North America. The wave activity fluxes show that the wave energy propagate from the subtropical Eastern North Pacific eastward into the North America, manifesting the existence of circulation variation connections over there. When the IMAMLO-PA is positive, the precipitation increases significantly over the USA, Mexico and Labrador Plateau, as opposed to the decrease over the central of Canada. The anomalous northerly airflow in lower troposphere induces the anomalously high surface air temperature in North America. The cyclonic circulation in Eastern North Pacific induces the anomalously high surface air temperature in the west coast of North America, along with the anomalous lower temperature in its east-central areas. The MAMLO-PA is different from PNA with a weak positive correlation, and their spatial distributions and formation mechanisms are also significantly different.The MAMLO-EP and MAMLO-PA are almost independent of each other in statistical sense, with the correlation of 0.03. Four types of phase combinations of them have been configured:++,--,+-,-+. There are different distributions in air mass flow, wave activity, precipitation, surface air temperature and diabatic heating with different phase combinations. The convergence and dispersion of wave energy over North pacific bridge Eurasia and North America, with the migration of atmospheric mass between these two regions. When the two indexes are positive, the structures of heating fields in East Asia, east coast of China and Mexico show that the radiation, surface sensible heat flux and latent heat transport are strengthened, besides the latent heating, corresponding to the increased precipitation. However, the structures of heating fields in Baikal, Alaska and coastal plain of Hudson’s bay are opposite, corresponding to the decreased precipitation. The surface air temperature in East Asia, central of North America controlled by anomalously circulation decreases significantly and the opposite situations are observed in Siberia, Kamchatka peninsula-Alaska. When MAMLO-EP is in positive phase, with MAMLO-PA in negative, the cooling downdraft induces anomalous less precipitation, with the anomalous low temperature in Eurasia. But the surface air temperature anomalously increases in North America.