Assimilation of GPS Refractivity and Other Satellite Data

Assimilation of GPS Refractivity and Other Satellite Data for Hurricane Prediction Xiaoyan Zhang 1, Ying-Hwa Kuo 1 , Zaizhong Ma 2, and Qingnong Xiao 1 1. National Center for Atmospheric Research, Boulder, Colorado 2. LASG, Institute of Atmospheric Physics, Chinese Academy of Science, Beijing China

B SACC 1509 UTC 2 Oct. GPS Ref QSCAT, Bogus 0. 5 h 02/12 Z 15: 09 Cloud drift Wind 12: 00, 13: 15, 16: 45 3 h Assimilation Window 02/18 Z

Difference between GPS and No. GPS at initial time (1200 UTC 2 October 2002) 600 h. Pa Q 300 h. Pa Vorticity SLP + surface wind 500 h. Pa UV +T

Time series of forecast Sea Level Pressure

Difference between GPS and No. GPS at 12 h and 24 h forecast 12 h 600 h. Pa Q difference 24 h vorticity difference and SLP 24 h 300 h. Pa UV difference and SLP 24 h rainfall difference

Conclusion 1. MM 5 4 D-Var system successfully assimilated one single GPS RO sounding, together with other satellite data. 2. The assimilation of one GPS RO sounding increased the low level moisture in the vicinity of Hurricane Lili, deepened the surface pressure, and increased the cyclonic vorticity of the storm. 3. As a result, the intensity and track of Hurricaen Lili was significantly improved. The 36 -h track error was reduced from 219 km to 128 km. This shows that even one single GPS RO sounding can improve the prediction of a hurricane, despite the fact that many other satellite data have already been used