论文信息 - Upper‐tropospheric relative humidity observations and implications for cirrus ice nucleation

Upper‐tropospheric relative humidity observations and implications for cirrus ice nucleation

Relative humidity (RH) measurements acquired in orographic wave cloud and cirrus envi- ronments are used to investigate the temperature- dependent RH required to nucleate ice crystMs in the upper troposphere, RH,c(T). High ice- supersaturations in clear air- conducive to the main- tenance of aircraft contraills yet below RH,½ and there- fore insufficient for cirrus formation- are not uncom- mon. Earlier findings are supported that RH, in mid-latitude, continental environments decreases from water-saturation at temperatures above-39oC to 75% RH at-55oC. Uncertainty in determining RH, below -55oC results in part from size detection limitations of the microphysical instrumentation, but analysis of data from the SUCCESS experiment indicates that RH,, below -55oC is between 70 and 88%. A small amount of data acquired off-shore suggests the possibility that RH, may also depend on properties of the aerosols.

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