2006 Volume 84 Issue 5 Pages 891-905
A new long-term reanalysis project, JRA-25, has set as one of its main goals the realistic representation of tropical cyclones (TCs) in the reanalysis. To supplement in situ observations near TCs, wind profile data (TCR data) are retrieved based on best track information and assimilated. This paper addresses the benefits of using TCR data for the analysis of TCs.
TC representation in the JRA-25 reanalysis is compared with other reanalysis data, and an experimental reanalysis (Control) without TCR data. The general result is that JRA-25 successfu11y represents the location and intensity of each TC. Among TC basins in the Northern Hemisphere, the TC representation in the JRA-25 data in the eastern North Pacific, and in the tropical Atlantic, where upper observations are sparse, is superior compared to other datasets that did not assimilate TCR data. In the western North Pacific, especially around Japan and the East China Sea, TCR data give little improvement in TC representation, since conventional upper observations are dense there and upstream of the active TCregtons.
TC detection rates in the Northern basins and over the entire globe, are computed using an objective procedure from the reanalysis datasets. The rate in JRA-25 is the highest in all basins among the datasets, and consistent through the period. The high qualified TC representation in intensity and location has a positive effect on a flow field, and hydrologic cycle around TCs. Case studies of TC track forecasts for a recurving TC, in which reanalysis data are used as initial conditions, suggest the JRA-25 data are more realistic than the Control. For these reasons, TCR data is effective in representing TCs and sur rounding atmospheric conditions in JRA-25.