The impact of multisatellite data on the initialization and simulation of Hurricane Lili's (2002) rapid weakening phase

• Published in: Monthly weather review 2007-02, Vol.135 (2), p.526-548
• Main Authors: XIAOYAN ZHANG, QINGNONG XIAO, FITZPATRICK, Patrick J
• Format: Article
• Language: English
• Subjects: Atmospheric research; Cyclones; Data assimilation; Data collection; Dry air; Earth, ocean, space; Exact sciences and technology; External geophysics; GOES satellites; Hurricanes; Kalman filters; Low temperature; Mathematical models; Meteorological satellites; Meteorology; MODIS; Moisture effects; Numerical experiments; Precipitation; Predictions; Remote sensing; Remote sensing systems; Satellite data; Satellite tracking; Satellites; Simulation; Sounding; Spectroradiometers; Storm tracks; Storms; Storms, hurricanes, tornadoes, thunderstorms; Surface wind; Temperature; Vortices; Water vapor; Water vapour; Weather analysis and prediction; Wind; Wind data; Winds
• ISSN: 0027-0644; 1520-0493
• DOI: 10.1175/mwr3287.1

Numerical experiments have been conducted to examine the impact of multisatellite data on the initialization and forecast of the rapid weakening of Hurricane Lili (in 2002) from 0000 UTC to landfall in Louisiana on 1300 UTC 3 October 2002. Fifth-generation Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) Mesoscale Model (MM5) 4DVAR sensitivity runs were conducted separately with QuikSCAT surface winds, the Geostationary Operational Environmental Satellite-8 (GOES-8) cloud drift-water vapor winds, and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) temperature-dewpoint sounding data to investigate their individual impact on storm track and intensity. The results were compared against a simulation initialized from a Global Forecast System background interpolated to the MM5 grid. Assimilating QuikSCAT surface wind data improves the analyzed outer-core surface winds, as well as the inner-core low-level temperature and moisture fields. Substantial adjustments of winds are noted on the periphery of the hurricane by assimilating GOES-8 satellite-derived upper-level winds. Both track forecasts initialized at 1200 UTC 2 October 2002 with four-dimensional variational data assimilation (4DVAR) of QuikSCAT and GOES-8 show improvement compared to those initialized with the model background. Assimilating Aqua MODIS sounding data improves the outer-core thermodynamic features. The Aqua MODIS data has a slight impact on the track forecast, but more importantly shows evidence of impacting the model intensity predicting by retarding the incorrect prediction of intensification. All three experiments also show that bogusing of an inner-core wind vortex is required to depict the storm's initial intensity. To properly investigate Lili's weakening, data assimilation experiments that incorporate bogusing vortex, QuikSCAT winds, GOES-8 winds, and Aqua MODIS sounding data were performed. The 4DVAR satellite-bogus data assimilation is conducted in two consecutive 6-h windows preceding Lili's weakening. Comparisons of the results between the experiments with and without satellite data indicated that the satellite data, particularly the Aqua MODIS sounding information, makes an immediate impact on the hurricane intensity change beyond normal bogusing procedures. The track forecast with the satellite data is also more accurate than just using bogusing alone. This study suggests that dry air intrusion played an important role in Lili's rapid w