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Mobile Ground-Based Observations of Landfalling Hurricanes: Current Capabilities and Future Plans

Kevin Knupp, Walt Petersen, and Dan Cecil kevin.knupp@nsstc.uah.edu Department of Atmospheric Science and Earth System Science Center University of Alabama in Huntsville (UAH)

UAH has acquired measurements of landfalling tropical storms and hurricanes since 1998. Until now, this activity has been conducted on an occasional basis when facilities and personnel were available. In this short paper, we summarize measurements acquired to date, and outline future plans.

The UAH Mobile Integrated Profiling System (MIPS) has been the primary measurement platform used to acquire measurements of wind profiles, radar reflectivity profiles, turbulence information, cloud base, profiles of temperature and humidity, and surface measurements. Current research instruments include a 915 MHz Doppler wind profiler, a lidar ceilometer, a 12- channel profiling radiometer, and surface meteorological measurements. Data have been acquired from 6 landfalling storms, including 3 hurricanes (Earl 1998, Georges 1998, Ivan 2004) and 3 tropical storms (Helene 2000, Gabrielle 2001, Isidore 2002). Up to this point, primarily boundary layer properties have been analyzed in detail and reported (Knupp et al. 2000, Knupp et al. 2006, Roberts and Knupp 2007).

Ground-based facilities are currently being expanded and upgraded to provide more comprehensive measurements of the boundary layer, precipitation properties, and kinematics of landfalling hurricanes. Two optical disdrometers will provide information on raindrop size distributions and their spatial/temporal variability. The disdrometer data will be used to determine Z-R relations, which will be used to derive improved estimates of rainfall using WSR- 88D radars. A vertically-pointing X-band Profiling Radar (XPR, currently under construction) will serve as a high-resolution boundary layer and precipitation profiler. Disdrometer data will be used to provide an accurate calibration for both the XPR and 915 MHz profiler, which will in turn be used to calibrate WSR-88D radars. We anticipate that this upscale calibration, and use of relevant Z-R relations, will provide superior estimates of rainfall from landfalling systems. A mobile X-band dual-polarization radar (currently under construction) will provide additional details of 3-D precipitation characteristics within landfalling systems.

Aside from the boundary layer and precipitation research thrusts, we will also investigate the thermodynamic and kinematic structure of rainbands and stratiform precipitation region. This research will focus on mesoscale vertical motion patterns and the impact of cold mesoscale downdrafts (within stratiform precipitation) on changes in hurricane intensity around the time of landfall. Wind, temperature, and humidity profiles will also provide insight on rainband kinematics, including the evolution of mini-supercell storms that occasionally produce tornadoes around the time of landfall. We are particularly interested in investigating tornadoes that are spawned near the coast prior to the landfall of the TC inner core region.

Beginning with the 2007 season, we will begin a more aggressive field campaign and deploy on both landfalling tropical storms and hurricanes within an 12-h drive form Huntsville (e.g., between Morehead City NC and Houston TX). Close collaboration with NOAA and other university groups is planned.

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