Mapping of Near-Surface Winds in Hurricane Rita Using Finescale Radar, Anemometer, and Land-Use Data

Abstract

ata collected from a Doppler on Wheels (DOW) mobile radar deployed in Port Arthur, Texas, near the point of landfall of Hurricane Rita (2005) and from two Florida Coastal Monitoring Program 10-m weather stations (FCMP-WSs) are used to characterize wind field variability, including hurricane boundary layer (HBL) streaks/rolls, during the hurricane's passage. DOW data, validated against nearby weather station data, are combined with surface roughness fields derived from land-use mapping to produce fine spatial scale, two-dimensional maps of the 10 m above ground level (AGL) open-terrain exposure and exposure-influenced winds over Port Arthur. The DOW collected ~3000 low-elevation radar sweeps at 12-s intervals for >10 h during the passage of the hurricane. This study focuses on the 2?3-h period when the western eyewall passed over Port Arthur. Finescale HBL wind streaks are observed to have length scales of O(300 m), smaller than previously identified in other HBL studies. The HBL streaks are tracked as they pass over an FCMP-WS located in flat, open terrain and another FCMP-WS located near a subdivision. DOW data collected over the FCMP-WS are reduced to anemometer height, using roughness lengths calculated from DOW and FCMP-WS data. Variations in the radar-observed winds directly over the FCMP-WS are very well correlated, both in their timing and magnitude, with wind gusts observed by the weather stations, revealing directly for the first time the surface manifestation of these wind streaks that are observed frequently by radar >100 m AGL. This allows for the generation of spatially filled maps of small-scale wind fluctuations over Port Arthur during the hurricane eyewall's passage using DOW-measured winds.