Small Scale Variability in Warm Season Precipitation Around Louisville, KY

This study examines ground-based precipitation observations recorded by a high-density gauge network located within approximately 40 km of Louisville, Kentucky’s urban center. The network is operated by Louisville’s Metropolitan Sewer District and consists of over 36 active gauges with a 5 min recording frequency. Due to a lack of information regarding gauge maintenance, calibration, and accuracy, additional quality controls steps are taken to filter the data.

An analysis of warm season (April–October) events reveals that precipitation is significantly greater on the downwind side of Louisville compared to the upwind side, particularly when precipitation systems have a westerly component to their motion. The mean difference between downwind and upwind precipitation across all events is 20%. This value is smaller for widespread precipitation events (i.e., most or all gauges detect precipitation) and larger for isolated events (i.e., rain detected by half of gauges or fewer). The largest and most significant differences between upwind and downwind precipitation amounts occur in association with moist moderate, moist tropical, and transitional air masses.