Features of lower troposphere on occasions of contrasting rainfall at a tropical coastal station

The radiosonde data and the synoptic situations relating to pairs of consecutive days of contrasting rainfall recorded at the tropical coastal station, Bombay, were analysed for two contrasting summer monsoons. The synoptic situations relating to the pairs of days were classified into two categories, namely, not similar and nearly similar. The results pointed out that the majority of the higher rainfall days in the pairs, irrespective of the similarity in the synoptic situation, were associated with one or more of the following: (i) higher static stability, (ii) lower convective instability, (iii) higher precipitable water content and (iv) lower lifting condensation level.

The associations noted with (i) and (iii) were not statistically significant on both the categories of synoptic situations. The association with (ii) was significant at the 10% level when the synoptic situations were nearly similar and was not significant when the situations were not similar. The association with (iv) was significant at the 5% level on both categories of days. The features noticed were discussed in the light of the available knowledge for tropical oceanic and land regions.