The walker circulation and atmospheric water vapour characteristics over the Pacific for two contrasting years

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Abstract
The Walker circulation for two contrasting years 1983 (ENSO year) and 1984 (non ENSO year) is determined. Principal changes in the upper level divergence are noted in the western and central Pacific regions. Thus, this part seems to form the principal branch of the Walker circulation, where a reversal takes place during the two contrasting years. Water vapour characteristics of the atmosphere over the western and central Pacific regions are determined using radiosonde data. During the ENSO event of 1983 an unusual accumulation of water vapour over the central Pacific and a depletion of it over the Indonesian region is noted. Further, the correlation coefficient between the SO index and water vapour variation showed significant values. Another aspect of the tropical atmosphere discussed here is the thermodynamic structure and its implications for the development of convection. Our study revealed a spectacular reversal of atmospheric properties such as the upper level divergence, water vapour, and thermodynamic structure during the two contrasting years.