Tropical Cyclone Intensity in Relation to SST and Moisture Variability: A Global Perspective
Robbie Berg, RSMAS/Univ. of Miami, Miami, FL
Tropical cyclone intensity forecasting remains one of the most difficult tasks in an operational setting. Many factors affect a tropical cyclone's intensity, some of which include environmental shear, oceanic heat content (often in the form of sea surface temperature), and atmospheric moisture content or instability. New technologies have been employed to grasp each of these factors when attempting to make an intensity forecast. In particular, TRMM (Tropical Rainfall Measuring Mission) Microwave Imager (TMI) data has emerged as an exceptional tool for measuring atmospheric water vapor content, liquid cloud water, and precipitation rates in the tropics. It must also be noted that TRMM data for sea surface temperatures (SST) is available, but this data set has remained largely untouched since its inception in 1997. Clouds are transparent at 10.7 GHz - one of the frequencies used by TRMM - and so it is a useful tool for monitoring SST on a daily basis even when clouds normally obscure the view. Although SST and atmospheric relative humidity have been used in idealized models to study the Maximum Potential Intensity (MPI) in the past, they have not been used to examine the interactive nature of tropical cyclones with SST and moisture variability.
The goal of this study is to acquire a global perspective of tropical cyclone intensity with respect to oceanic heat content (SST) and moisture availability by comparing SST and moisture changes in each of the major ocean basins due to storm interaction. We categorize tropical cyclones by intensity as weak storms (tropical depressions or tropical storms), moderate storms (Category 1 or 2 hurricanes, or the equivalent), and strong storms (Category 3, 4, or 5 hurricanes, or the equivalent). The TRMM SST and moisture content data are from 1997 to the present, and thus only tropical cyclones over the past four tropical cyclone seasons will be considered. To validate our TRMM data analysis, we use in situ aircraft dropsondes (both atmospheric and oceanic AXBTs) obtained from Atlantic hurricane field programs.
Extended Abstract (80K)
Session 16C, Tropical Cyclone Air-Sea Interaction III (Parallel with Sessions 16A and 16B)
Friday, 3 May 2002, 8:30 AM-10:30 AM
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