BOX 6.1

Improved Understanding of Hydrology and Climate from TRMM

TRMM-based multisatellite data are being used as input into hydrologic models, including the Land Data Assimilation System, to better understand land-atmosphere interactions on scales of days to years (Rodell et al. 2004) and to study variations in river runoff (Fekete et al. 2004). These same data are being used to monitor crops in Central America and elsewhere and as input into river forecast models in South Asia and other locations. Analysis of TRMM precipitation radar data has been used to discover orographic precipitation processes and diurnal cycles of rainfall causing flash floods in headwater streams (Barros et al. 2004). TRMM observations led to the discovery of extremely tall convective towers within the vertical precipitation profiles of tropical cyclones. Kelley et al. (2004) reported that the chance of intensification increases when one or more of these “hot towers” exist in the tropical cyclone’s eyewall (Figure 6.1).

FIGURE 6.1 A cross-sectional view of Hurricane Katrina through the eye of the storm, as observed from TRMM. This image shows the horizontal distribution of rain intensity on August 28, 2005, when Katrina was a Category 3 hurricane with maximum sustained winds of 100 knots (115 mph). Rain rates in the central portion of the swath are from the TRMM precipitation radar, and the rain rates in the outer swath are from the TRMM microwave imager. The rain rates are overlaid on infrared data from the TRMM visible infrared scanner. Two isolated hot towers (in red) are visible: one in an outer rain band and the other in the northeastern part of the eyewall. The height of the eyewall tower is 16 km. Towers of this height near the core are often an indication of intensification as was true with Katrina, which became a Category 4 storm soon after this image was taken. SOURCE: NASA (2005).

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