Abstract Four-dimensional variational (4D-Var) data assimilation (DA) experiments using
Global Positioning System (GPS)-derived precipitable water vapor (PWV) were conducted
for the tropical cyclone (TC) Nargis in 2008. In order to analyze the initial field at 1200 UTC
30 April 2008, 12, 24, 36, and 48 h sequential DA experiments with 3 h assimilation
windows were performed. The initial fields made by these DA experiments were applied to
subsequent forecast experiments using a nonhydrostatic model (NHM) with a horizontal …

A mesoscale data assimilation (DA) system was developed for low latitudes, and DA
experiments for the tropical cyclone Nargis were conducted. A tropical cyclone bogus (TCB)
procedure was developed for the Bay of Bengal, and the impact was investigated. The Meso
4D-Var system of the Japan Meteorological Agency (JMA), which was designed for
operational mesoscale DA in the mid-latitudes, was modified for DA application in the
tropics. Since the relationship of the geostrophic wind was not available near the equator, a …