Estimation of area-average rainfall for frontal rain using the threshold method

摘要: The relationship between area-average rainfall rate and the fractional area covered by radar echoes of intensity greater than a predefined rainfall-rate threshold is investigated using quality-controlled data from United Kingdom Irish radars for period 26 January to 25 February 1990. During this precipitation was predominantly frontal, unlike previous studies that have concentrated upon convective precipitation. A high degree correlation found composite field areas individual within composite. coefficient varies with threshold, peaking at 2.0 mm h−1 when it higher 0.97 all data. order merit six thresholds 2.0, 1.0, 4.0, 0.5, 0.06 80. h−1. spatial temporal stability over studied high, especially h−1%. A linear-regression used estimate observed area. average error in estimation instantaneous areal single 1.0 18.0% 20.0% rates ⩾0.05 Use combined reduces about 14%. Rainfall accumulations are estimated accuracy rates, increasing accumulation period. Five-day areal-average obtained 1 2 an range 8% 11%. Over even produces useful estimate, 18%.