On the Distribution of Mean Static Stability and Mean Richardson Number in Tropical Atmosphere

Abstract

Mean tropospheric soundings over different regions of the tropical belt lying between 30°N
and S during different periods of the year are constructed and used to compute mean static
stability (SS) over all regions and mean Richardson number (Ri) over monsoon regions in different
isobaric layers. The results show that the vertical distribution of moist static stability based on
values of equivalent potential temperature is remarkably similar in all regions, with high negative
values near surface and high positive values in the upper troposphere, the level of transition from
negative to positive value occurring at a level between about 700 and 500mb. However, the
investigation reveals the following regional and seasonal characteristics in values of mean static
stability: (a) in any particular region, the lower troposphere is statically more unstable and
instability extends to greater heights during the summer than during the winter; (b) during a
particular season, the regions lying in the summer hemisphere show greater static instability
extending to greater heights than those lying in the winter hemisphere: and (c) in any particular
hemisphere, the atmosphere over the region/area lying near the equator is statically more unstable
than that lying away from the equator.
The vertical distribution of Ri as judged by values in monsoon regions appears to exhibit
similar variation with seasons and between regions as static stability.