Horizontal winds at 850 hPa retrieved using the nonlinear balance equation, where the mass field was determined from AMSU temperature soundings (DeMaria et al. 2004), were compared with the surface wind fields derived from QuikSCAT and Hurricane Research Division H-Wind analyses. From these comparisons it was found that the AMSU-derived wind speeds at 850 hPa have linear relations with the surface wind speeds from QuikSCAT or H-Wind. There are also characteristic biases of wind directions between AMSU and QuikSCAT, or H-Wind. Using this information to adjust the speed and correct for the bias, a new algorithm was developed to estimate a tropical cyclone surface wind field from the AMSU-derived 850 hPa winds.

The algorithm was evaluated in two cases for hurricane Floyd (1999) and Michelle (2001), which were observed simultaneously by AMSU, QuikSCAT and H-Wind. In this evaluation, the AMSU adjustment algorithm for wind speeds showed good results. On other hand, it is understood that the bias correction algorithm for wind direction has room for improvement.