Correlation of pressure changes at the surface with those in the upper atmosphere over India and neighbourhood

Abstract

The nature of the relationship between the pressure changes in the atmosphere at the 300 and 200-mb levels and the concurrent and subsequent pressure changes at the surface have been examined in this paper, analysing the data for 15 radiosoride stations in India and neighbourhood, during the period July 1944 to June 1945. The correlation between the changes aloft and the surface changes 24 and 48 hours later have been found to be generally negative. Tetrachoric correlation coefficients have been worked out to assess the magnitude of such out of phase correlation and these have been compared with the corresponding values in the U.S.A. The correlation data have been dispersed with respect to the different seasons of the year and the major regions comprising the Indian area. It has been found that the negative correlation is maximum during the period November to March and minimum when convective activity is predominant. It is felt that a study of the pressure fluctuations at the coastal radiosonde stations in the field of depressions and storms in the Bay of Bengal and the Arabian Sea might materially help in anticipating the courses these may subsequently take.