Snow and Ice Particle Sizes and Mass Concentrations at Altitudes Up to 9 km (30,000 ft)
FEDERAL AVIATION ADMINISTRATION ATLANTIC CITY NJ AIRPORT AND AIRCRAFT SAFETY RESEARCH AND DEVELOPMENT
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About 7600 nautical miles nm 14,000 km of select ice particle measurements over the United States have been compiled into a single, computerized database for use in characterizing ice crystal and snowflake generally termed ice particle size distributions and mass concentrations at flight altitudes. Data are from 50 research flights by six agencies in eight flight research projects using Particle Measuring Systems one-dimensional 1-D and two-dimensional 2-D particle sizing probes. Primary recorded variables are average particle size distributions in the range 0.1 to 10 mm from each of 1625 microphysically uniform cloud intervals or other convenient distances in wintertime clouds, snowstorms, cirrus, and other high-altitude clouds. The findings are that, generally, the largest particles and the greatest concentrations of total ice particle mass TIPM are confined to altitudes below 20,000 ft 6 km. There, particles of 10 mm in maximum dimension and TIPMs up to about 3 gmexp 3 may be found. Above 20,000 ft, particles are smaller than 2 mm and TIPMs are less than 0.2 gmexp 3 in the cirrus and the upper reaches of deep winter storm clouds that are found at these levels. Exceptions are thunderstorm anvil clouds where 10 mm particles and TIPMs of at least 1 gmexp 3 can be found up to at least 30,000 ft 9 km. Anvil clouds and stratiform clouds associated with warm season mesoscale convective systems have provided some of the largest TIPMs, the greatest particle concentrations, and the largest particle sizes at high and mid altitudes, respectively. In contrast to supercooled cloud droplets where the largest liquid water mass concentrations are confined to short distances of 3 nm or less in convective clouds, the largest average TIPMs in glaciated clouds have been found in layer clouds over distances up to 30 nm.
- Commercial and General Aviation
- Atmospheric Physics
- Snow, Ice and Permafrost