Dynamical analysis of precipitation and temperature change over arid central asia in recent 50 years

Abstract

The rainy and rainless years, and the higher and lower temperature years in arid central Asia were divided by using the gridded monthly air temperature and precipitation data from the Climate Research Unit (CRU) and the Tyndall Center, University of East Anglia, UK. And the mechanisms of temperature and precipitation change in these typical years were analyzed by using the NCEP/NCAR data from the National Centers for Environmental Prediction and the National Center for Atmospheric Research of USA. The results show that in the rainy years, the ascending motion areas are located in the west part of arid central Asia in winter and in the east part in summer. No matter in the rainy or rainless years, the sinking motion areas are located in the east part of arid central Asia in winter and in the west part in summer. For precipitation, in winter, the dynamical structure of rainy years presents decreasing of the Ural pressure ridge and East Asian trough in association with the deepening of East European trough. In opposite, the Ural pressure ridge and East Asian trough has a stiffness condition and the meridional airflow strengthening in the rainless years. In summer, the dynamical structure of rainy years presents the strengthening of East European high pressure ridge and the western Pacific subtropical high ridge in association with the western-spread of subtropical ridge. For temperature, in winter, the west part of arid central Asia is affected by south-west warm airflow and the east part is affected by north-west airflow in higher temperature years. However, the whole arid central Asia is controlled by north-west airflow in lower temperature years. In summer, the intensity and location of the west Pacific subtropical high pressure play an important role in determining the higher or lower temperature years. It should be higher temperature years when the subtropical high pressure strengthens and western-spreads. It should be lower temperature years when the subtropical high pressure decreases and withdraws eastward.