The Variation Of Monsoon Wind Direction And Its Application In Evaluating Monsoon Simulation

Based on the seasonal reversal of wind vectors which is the essential characteristic of monsoon, a new concept, directedly rotary angle, which is quite different from the previous studies of angle between wind vectors has been presented. It reveals the rotation style of monsoon wind vectors with time evolution and its geographical distribution. In addition, the abrupt change of wind direction in monsoon onset and its relationships with other variables (such as zonal wind, OLR, precipitation) are also discussed. Further, this new concept is applied to evaluate the monsoon simulation of the model output of 8 AGCMs of AMIP in IPCC 4th assessment based on the above results. The main results of this study are as follows:(1) The concept of directedly rotary angle can reflect the daily variations of wind direction including the rotary direction and the degree of rotary angle, and reveals the inimitable features of monsoon seasonal evolution. Six categories of wind vectors rotation with seasonal cycle have been detected and classified as follows: (I)Clockwise to counter-clockwise rotation; (II)Counter-clockwise to clockwise rotation; (III)Full clockwise rotation(;IV)Full counter-clockwise rotation;(V)Stable rotation;(VI)Instable rotation. Wind in monsoon regions almost rotates in the forms of the first four categories. The results show that the different rotary style of wind vectors is closed relate to annual evolution of atmosphere circulation.(2) The new concept is applied to evaluate the monsoon simulation of the model output of 8 AGCMs of AMIP in IPCC 4th assessment. The results show that it not only reflects the dynamic process of daily evolution in...