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A Comparison of COSMIC, AIRS, Terra, and Aqua Temperature and Moisture Profiles against Dropsondes in 2006 Atlantic Tropical Cyclones

Pat Fitzpatrick, Yee Lau, Sachin Bhate, and Chris Hill GeoResources Institute Mississippi State University Stennis Space Center Branch fitz@gri.msstate.edu

Historically, satellites have served as the most crucial tool for monitoring tropical cyclones. Recent advances include the Advanced Microwave Sounding Unit (AMSU) instrument, which can measure the warm core of a hurricane, and the NASA Aqua satellite, which can retrieve profiles via MODIS retrieval algorithms and the AIRS. However, all have trouble with cloudy regions or with heavy precipitation.

Recently (April 14 2006), a new constellation of satellites was successfully launched. These low- orbiting satellites will provide real-time data over thousands of points throughout the globe. Called the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC), these satellites will provide temperature and moisture profiles (Anthes, Ricken, and Kuo 2000; Cucurull et al. 2006). COSMIC relies on a technology known as radio occultation. As radio signals from GPS satellites pass through the atmosphere, the paths of the signals are bent and their progress slowed. The rate of these changes depends on atmospheric density along the signal path. COSMIC's low-Earth-orbiting (LEO) satellites take advantage of this effect by intercepting the GPS radio signals just above Earth's horizon and precisely measuring the bend and signal delay along the signal path. These parameters are then used to compute temperature and moisture information. Because radio signals can pass through thick cloud cover and precipitation, weather conditions will not interfere with data gathering, as often occurs with remote sensing platforms. Therefore, this technology could be very useful to the monitoring of tropical cyclones. More information is available at: http://www.cosmic.ucar.edu.

This study will investigate COSMIC capabilities in studying hurricanes. Analysis of these data, along with NASA satellite data, is underway for 2006 Atlantic tropical cyclones. A validation study of COSMIC data against dropsondes has been performed. The tentative results show:

  • COSMIC temperature profiles in hurricane environment are reasonable. In addition, they provide tropopause and stratosphere information not available from dropsondes.

  • Dewpoint profiles in hurricane environment shows a moist bias in mid and upper troposphere. The low levels appear reasonable.

  • The COSMIC horizontal data distribution is coarse, but the temperature could still be useful in data sparse locations or between reconnaissance flights. COSMIC dewpoint still requires more examination and (apparently) refinement. However, COSMIC dewpoint should still be useful, especially in dry regions.

A comparison between COSMIC, AIRS, and Terra/Aqua soundings to dropsondes is underway, and these results will be reported at the conference.

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