Accession Number : AD0671941

Title :   MEASUREMENT OF SNOWFALL BY RADAR,

Corporate Author : MCGILL UNIV MONTREAL (QUEBEC) STORMY WEATHER GROUP

Personal Author(s) : Carlson,Paul E.

Report Date : MAR 1968

Pagination or Media Count : 41

Abstract : Using wavelength 3.2 cm in dry snow, radar returns from a layer at an average height of 5000 ft were converted to snowfall rates and integrated to obtain isohyets for a 48-hour period, during which snow accumulated to an average depth of 5 inches. First, radar-derived isohyets based on the Z = 2000 R2.0 relation for aggregate snow were mapped to 100-miles range. These were then compared with isohyets based on ground measurements of new-fallen snow at 140 climatological stations. Within 58-miles range, there was good agreement on maximum snowfall amounts (10 inches), most of which fell at high rates; but the radar underestimated the minimum amounts (2 inches), all of which fell at low rates. Agreement between radar and ground measurements was generally improved by applying a modified relation, Z = 1000 R2.67. For this relation, the values of RADAR/CLIMAT ratio (radar-measured to ground-measured amounts) at grid points within 58-miles range had a near-Gaussian distribution, with a mean value of 0.98 and standard deviation of 0.29. Beyond 58-miles range, underestimation by the radar increased with range, particularly for the larger snowfall amounts. Comparison of radar-measured snowfall rates at a fixed point aloft with rates measured by a recording gauge at the ground showed good agreement after allowance was made for horizontal displacement of the snow during its fall. (Author)

Descriptors :   (*SNOW, *METEOROLOGICAL RADAR), ALTITUDE, VOLUME, INTENSITY, WEATHER STATIONS, CLIMATE, WEATHER FORECASTING, DISTRIBUTION, PERIODIC VARIATIONS, TRAJECTORIES, MEASUREMENT

Subject Categories : Meteorology
      Snow, Ice and Permafrost

Distribution Statement : APPROVED FOR PUBLIC RELEASE