MIXED-LAYER CHARACTERISTICS AS RELATED TO THE MONSOON CLIMATE OF NEW-DELHI, INDIA

Annual variations of mixed-layer characteristics at New Delhi, India have been studied for a weak monsoon (1987) and a strong monsoon (1988) year. In the weak monsoon year (1987), the maximum mixing depth h(max) was found to have a value of around 3000 m during the pre-monsoon, less than 2000 m during the summer monsoon, around 2000 m during the post-monsoon, and less than 1000 m in the winter season. For the strong monsoon year (1988), h(max) values were less than 1987 values for comparable periods throughout the year. The seasonal and yearly differences of h(max) were explained by the surface energy balance and potential temperature gradient gamma at a time close to sunrise. According to the spatial patterns of gamma obtained by an objective analysis of the 850 to 700 hPa layers, mixed-layer characteristics obtained at New Delhi are representative of the north and central regions of India.