Migrations Of Atmospheric Mass Between Lands And Oceans In Eurasia-North Pacific Domain In Boreal Autumn And Their Impacts On Climate Anomalies Of China

By using NECP/NCAR monthly reanalysis, the SST datasets from the US National Oceanic and Atmospheric Administration (NOAA) and the daily observation data of 756 stations provided by National Meteorological Information Center for the period of 1961-2010, the interannual variations of migrations of atmospheric mass between lands and oceans (MAMLO) over Eurasia-North Pacific regions and their impacts on the climate of Eurasia are analyzed. On this basis, the circulation anomalies and their possible influences on variations of surface air temperature in China during boreal fall in association with different phase combinations of migrations of atmospheric mass between lands and oceans (MAMLO) and interhemispheric oscillations (IHO), as well as ENSO have been investigated. The results are as follows.It is found that there is significant atmospheric mass exchange between the Eurasian continent and the North Pacific Ocean on an interannual time scale during the fall. The spatial distribution of the MAMLO is characterized by a see-saw-like pattern in the Eurasia-Pacific Ocean region. Atmospheric mass fluxes over the Eurasian continent during the fall converge in the upper troposphere, resulting in downward movement. Meanwhile, an abnormal high forms above the ground. Over the North Pacific Ocean, atmospheric mass fluxes converge in the lower troposphere in association with a cyclonic circulation anomaly. Thus, the atmospheric mass migrations from the Eurasian continent to the North Pacific Ocean region are observed in the lower troposphere. Abnormal diabatic heating of in the air column forms a strong contrast between the continent and ocean regions, which drives the MAMLO during the fall. The effects of the MAMLO on the fall climate of the Northern Hemisphere are significant over Eurasia including the far-eastern region when the MAMLO index is positive, the surface climate there is abnormally cold and dry while a warm and moist anomaly occurs over the North American continent.MAMLO and Interhemispheric Oscillation (IHO) are almost independent of each other in statistical sense. Four types of phase combinations of MAMLO and IHO have been configured. These four types of cases are respectively defined as type-â…  for both MAMLO and IHO indices in positive phases, type-â…¡ for both in negative, type-â…¢ for the MAMLO in positive while IHO in negative, and type-â…£ for the MAMLO in negative while IHO in positive. When type-â…  cases occur, IHO tends to weaken the low pressure in North Pacific and to intensify the high pressure in Eurasian continent by piling more than normal atmospheric mass in these two places, inducing an east-warm-west-cold pattern in North China when the MAMLO in its positive phase. When cases belong to type-â…¡, IHO weakens the positive air mass anomaly in Eurasia and strengthens the negative air mass anomaly in North Pacific, which tends to form a consistent warm pattern in China. Type-â…¢ leads to an east-cold-west-warm pattern contrary to type-â… , while the effect of type-â…£ is some similar to type-â…¡. It is showed that MAMLO plays a primary role in the temperature anomalies in China during boreal fall, whereas IHO makes a disturbing effect on the influence of MAMLO on the temperature anomalies in North China.In statistical sense, MAMLO and ENSO are also almost independent of each other. Six types of phase combinations of MAMLO and ENSO have been configured. These six types of cases are respectively defined as type-â…  for both MAMLO and ENSO indices in positive phases, type-â…¡ for the MAMLO in negative while ENSO in positive, type-â…¢ for the MAMLO in positive while ENSO in negative, type-â…£ for both in negative, type-â…¤(â…¥) for the MAMLO in positive (negative) while no ENSO events occur. The mean climatological surface air pressure distributions in boreal fall can be modified by these six types of events, and hence the surface air temperature in China and in Eurasia-North Pacific sector can be modulated significantly. When type-â…  and type-â…¢ cases occur, the same-signed anomalous temperature patterns tend to happen in China. When cases of type-II and type-IV occur, the air temperature anomalies tend to occur with the opposite signs between east China and west China. When type-V events occur, anomalous surface air temperature will be colder. When the type-VI occur, warmer temperatures will be found over China during boreal fall. MAMLO plays a primary role in the temperature anomalies in boreal autumn of China.