Cyclonic and anticyclonic circulations of 850 hPa over India and adjoining areas based on highly packed hand drawn streamline charts : part 1 - characteristics

Cyclonic (‘C’) and Anticyclonic (‘A’) circulations play a decisive role in deciding the weather of a region. Therefore, understanding the characteristics of circulation and their spatio-temporal distribution has become important. The present exploratory study characterizes circulations of 850 hPa pressure level over India and adjoining regions. Highly packed wind streamlines are drawn for 850 hPa integrating wind data from satellites, radiosondes, pilot balloons and Doppler Weather Radars. ‘C’ and ‘A’ circulations centre points are identified and the characteristics of their distribution are explored spatially on seasonal, long-term and monthly time scale over the Indian and surrounding regions for 2014 to 2020. Several meteorological significant features are visually manifested in ‘C’ and (‘A’) circulations and their role in dynamics is discussed in the manuscript. Frequency distribution shows wide-spread and large numbers of (‘C’) circulations are present over the north and northwest India, the Indo-Gangetic plain, and in the east equatorial Indian Ocean region. Seasonal analysis reveals an association with the southwest monsoon trough, the head Bay of Bengal lows, heat lows over land and in the southern peninsula. (‘A’) circulation centre point distribution is concentrated further south of the trough region and concentrated mainly on the land. The winter season has noticeably more (‘A’) circulation which could be attributed to the descending limb of the Hadley Cell. Spatial distribution of circulation shows land-sea contrast. The analysis has several applications, including operational weather forecasting, aviation and ballistic meteorology and scope for advanced research.