Cloud Microphysical Measurements in Thunderstorm Outflow Regions During Allied/BAE 1997 Flight Trials

Microphysical properties of clouds in thunderstorm outflow regions, derived from measurements of a specially instrumented test aircraft at approximately 8.8 km and -28°C are presented. Although the heaviest echo regions were not penetrated, measurements in areas adjacent to the red-echo region of the pilot’s radar showed clouds with maximum ice water contents in excess of 1.3 gmM3 , and often sustained ice water contents in excess of 0.5 gmm3. It was concluded that at most trace amounts of supercooled liquid water content were present. Although ice particles of up to 10 mm were observed, mass was concentrated at small sizes and number concentrations were surprisingly high, with average median mass diameter and concentration of 43 pm and 90 cm” respectively for a 47 minute case study. Some unexpected conflicting indications from conventional aircraft cloud physics probes were experienced, and are also discussed.