The efficiency with which drizzle and precipitation sized drops collide with aerosol particles

Values of collision efficiency and scavenging rates for drops interacting with aerosol particles are presented using more accurate flow fields than previous work and for a much greater number of drops than hitherto obtained. All calculations are performed at an ambient temperature 10°C and atmospheric pressure of 900 mb. Computations of collision efficiency are performed for a drop radius range from 50 to 500 micrometre (μm), for particle radius from 0.005 to 10 μm, for relative humidity values of 50, 75, 95 and 100%, and for particle density of 1, 1.5, 2.0 and 2.5 × 10³ kgm^-3. In addition the collision efficiency was also calculated for electric charges on the drop and particle, and for an electric field, representative of typical thundercloud values. Combined use is made of a rigorous trajectory model together with a flux model and comparison is made between them in the overlap size region. Precipitation scavenging rates and the percentage of aerosol particles scavenged by precipitation drops described by Marshall-Palmer size distribution is also calculated.