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Convective Climatology for Central Arizona During the 1995-1999 Monsoon Seasons
Objective
To create a 1-km resolution convective climatology for central Arizona, and examine the role of terrain forcing and synoptic-scale effects on convection initiation, modes and movement for the Phoenix/Flagstaff region.
Project Overview
In the western US, mountainous regions act as focal points for convective initiation. This study focuses on the role terrain plays in producing convection over central Arizona during the monsoon season (July through mid-September). Arizona receives 40-60% of its annual rainfall (Jurwitz 1953) during the monsoon season, and these storms generally produce flooding, severe weather, and lightning. Hence, a better knowledge of areas favorable and unfavorable for development, and the associated synoptic conditions would be useful for forecasters and weather-sensitive operations (utilities, fire managers, farmers, etc.). In order to improve the resolution of Arizona's convective climatology and our understanding of terrain forcing, this study uses high-resolution (1 km) reflectivity mosaics and terrain data to analyze the diurnal cycle of convection in central Arizona for the 1995-1999 monsoon seasons. This study also addresses the hypothesis that certain synoptic regimes regulate the location of convective 'hot spots.'
To address the above goal, areas of repeated convection forced by mountainous terrain require identification. The proposed work is unique because it will use high-resolution, multiple-radar reflectivity data to identify terrain-relative areas of repeated convective initiation. For this study, 1 km reflectivity mosaics will be created using level II radar reflectivity data collected from the Phoenix (KIWA) and Flagstaff (KFSX) WSR-88D's during July and August of 1995-1999. The mosaic technique maps reflectivity data from multiple radars onto a common Cartesian grid (440 x 440 km) using objective analysis techniques, and ensures the data closest to ground level and specified levels above ground are used (MOSAIC). The domain contains Phoenix, the most populated city in Arizona, river basins important to the area's water supply (e.g., Gila and Salt River Basins), and mountainous terrain that affects the area's precipitation variability
Preliminary results for the 1999 diurnal convective climatology are shown here. For a more detailed description of this project and the 1999 preliminary results, click here.
The proposed work is exciting for the field of meteorology because it 1) illustrates a new method for improving the resolution of convection climatologies applicable to most regions in the US (especially mountainous regions), and 2) attempts to identify better ways to forecast convective initiation areas in areas of terrain.
Diurnal frequency of reflectivity >= 40 dBZ for July 1999
Diurnal frequency of reflectivity >= 40 dBZ for July 1-10 1999
Diurnal frequency of reflectivity >= 40 dBZ for July 11-20 1999
Diurnal frequency of reflectivity >= 40 dBZ for July 21-31 1999
Diurnal frequency of reflectivity >= 40 dBZ for August 1999
Diurnal frequency of reflectivity >= 40 dBZ for August 1-10 1999
Diurnal frequency of reflectivity >= 40 dBZ for August 11-20 1999
Diurnal frequency of reflectivity >= 40 dBZ for August 21-31 1999
Fine-Scale Radar Climatology Team
Kenneth W. Howard, NSSL Research Meteorologist/Team Leader
Pamela Heinselman, CIMMS Research Meteorologist
Dr. David Schultz, Ph.D. Advisor
Funding for Radar Climatology was provided by the Salt River Project (SRP).
