Measurements of the Charge, Size, and Type of Thunderstorm Precipitation Particles

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9311749 Marshall The objective of this research is to see if the charge on precipitation is primarily responsible for the electricity in thunderstorms. Toward this end, the investigators propose to analyze data of the charge, size, and two-dimensional shape of precipitation particles collected inside ten Florida thunderstorms during the 1991 Convection and Precipitation/Electrification Experiment (CaPE). These data are especially important because of the measurements in the temperature range from -5o to -20oC; this region has not been well studied despite suggestions that much of the charge in storms is generated there. From the shape measurements the proposers can determine the type of precipitation particle: raindrop, snowflake, hailstone, or graupel. They can then determine the polarity and amount of charge carried on different types of particles. The PIs will collaborate with colleagues at the National Center of Atmospheric Research (NCAR) to look for influences on particle charges by temperature, cloud liquid water content, cloud particle types and numbers, updrafts and downdrafts, position in the cloud, etc. They will compare the electric fields measured by the sailplane to the electric field expected from the measured particle charges; comparable fields will suggest the precipitation carries most of the charge in that part of the storm. The PIs will collaborate with NCAR colleagues and other CaPE researchers using radar data to place the precipitation measurements in their correct storm context by superimposing sailplane tracks on reflectivity data and on wind fields from multiple Doppler radar analyses. ***