Assessment of vertical air motion among reanalyses and qualitative comparison with direct VHF radar measurements over the two tropical stations

Abstract. Vertical wind (w) is one of the most important meteorological parameters for understanding different atmospheric phenomena. Only very few direct measurements of w are available and most of the time one must depend on reanalysis products. In the present study, assessment of w among selected reanalyses, (ERA-Interim, ERA-5, MERRA-2, NCEP-2 and JRA-55) and qualitative comparison of those datasets with direct VHF radar measurements over the convectively active regions Gadanki (13.5° N and 79.2° E) and Kototabang (0° S and 100.2° E) are presented for the first time. The magnitude of w derived from reanalyses is 10–50 % less than that from the direct radar observations. Radar measurements of w show downdrafts below 8 to 10 km and updrafts above 8–10 km over both locations. Inter-comparison between the reanalyses shows that ERAi is overestimating NCEP-2 and underestimating all the reanalyses. Directional tendency shows that the percentage of updrafts captured is reasonably good, but downdrafts are not well captured by all reanalyses. Thus, caution is advised when using vertical velocities from reanalyses.