Study On The Sensitivity Of The East Asian Climate To The Underlying Surface Parameters In The Arid And Semi Arid Area

Arid region accounted for about 40% of the total land area, its surface features are diversity, ecological fragility, and greatly influenced by human activities,land-atmosphere interaction process has a complicated im Pact on the formation and development of the local climate and global atmospheric circulation system. The energy imbalance in the surface layer, caused the energy distribution uncertain between underlying surface and near surface atmosphere, and this makes the land surface process simulation more difficult. The Parameterization scheme of land surface process, which did not consider the influence of energy closure distribution,will not be able to accurately describe land-atmosphere interaction process. So the local atmosphere forecast simulations and the large-scale circulation situation are deviation from actual situation, and long-term climate simulation cumulative error increased. For the study of energy closure on the arid zone how to affect long-term climate numerical simulation, based on the predecessors’ research on the area,respectively introduced the two cases of arid zone underlying surface turbulent transport Parameterization scheme to the regional climate model, study on the different case of land-atmosphere interaction process to climate sensitivity.Reveal arid zone land-atmosphere interaction process to the development of the east Asian monsoon circulation situation, explore the arid land surface process changes to the contribution of climate change.land-atmosphere interaction process is greatly influenced by human activities,such as agricultural plastic film mulching cultivation with large extension in arid areas,and plastic mulching could suppress farmland soil moisture evaporation, change underlying surface for atmospheric water and heat transfer process. Based on underlying surface mulch farmland land-atmosphere interaction research data, In RegCM4 numerical model build a simple plastic film mulching farmland numericalcalculation process for calculating scheme of plastic film mulching, introduced of a new land use type of underlying surface mulch farmland. To explore a wide range of farmland in arid areas laying plastic mulch or not, will have a different effect on land-atmosphere interaction process, the local climate, and the atmospheric circulation situation in the east Asian monsoon region. Based on this, to reveal the climate effect produced by human activity.In this Paper, main conclusions are as follows:(1) Arid region different energy closure schemes climate numerical experiment results show that according to the Energy conservation theory to amendment turbulent transport scheme,the atmosphere energy has increased from underlying surface,increase the energy of the atmospheric and the energy spread to the whole layer of the atmosphere. From the lower troposphere to the upper, atmospheric geopotential height increase over the arid areas and enhancing the airflow divergence, effectively blocking the east Asian monsoon flow northward process, directly reduce of the precipitation in northeast China, at the same time, varying precipitation influence on area south of the Yangtze river.(2) The results of plastic film mulching farmland numerical simulation show that the scheme can accurately simulate the process: by blocking of plastic film mulching,latent heat transport reduced, the sense heat transfer enhanced, and near surface air temperature increased. Based on the dynamic mechanism of plastic film mulching scheme, which has a direct imPact on local convection weather process of the occurrence and development. First, the atmospheric heating effect produced by the plastic film mulching scheme promotes the formation and development of convectional weather; Second, the plastic film mulching scheme block soil moisture transported to atmosphere, make the convectional precipitation process of water vapor in short supply, and inhibits precipitation occurred.(3) Large areas of farmland covered with plastic film lead to the lower troposphere atmospheric heating effect is obvious, prompting the lower troposphere atmosphere uplifting process, and enhancing cyclonic circulation characteristics. In the process of air currents to rise temperature is reduced, and cloted after drops to the dew point temperature. As underlaying surface water vapor transport and latent heat condensation release is reduced, upward movement of air is weakened. Airflow in themiddle upper troposphere divergence process enhanced, the layer of the troposphere airflow presents the anticyclonic circulation characteristics.(4) Due to a wide range of plastic mulching farmland prompted local airflow rise,Enhanced the cyclonic circulation characteristics of the lower troposphere atmosphere,local air pressure reduced, Promotied the Western Pacific subtropical high to the Northwest and influenced the distribution of summer rain belt to our country. This test is ideally, membrane area is much larger than the actual, affected by the effect of membrane, arid zone 850 hpa level pressure is reduced, the subtropical high moved have an impact, shows that plastic mulching fields of study on the climate environment evaluation has practical value.