MAPR Measurements of Snowfall During ISPA-2001

In February 2001 the Desert Research Institute and NCAR will conduct an experiment to establish the relationship between snowfall rate and aerosol-induced changes in the cloud droplet size distribution. At the Storm Peak Laboratory (SPL) atop Mt. Warner in Steamboat Springs, Colorado, in situ measurements of cloud droplet size distribution, precipication rate, and ice water content will be collected. Also, images will be recorded to identify ice crystal sizes, habits, and rimed mass fractions. Cloud water will also be collected for chemical and isotopic characterization.

NCAR will operate an Integrated Sounding System about 1100 m below the Storm Peak Laboratory. The ISS will include the MAPR spaced antenna wind profiler, GPS rawinsondes, and surface measurements including snowfall rate. MAPR will provide background wind profiles to identify possible source directions for the aerosols, and will also attempt to identify riming heights. MAPR will also be used for the first time to measure snow size distributions, which can be compared with in situ measurements from SPL. It is well suited to this experiment, compared with a standard DBS wind profiler because it operates pointing vertically and so can monitor fall speeds continuously. Also, it has a larger dynamic range and is more likely to record both clear air and precipitation Doppler measurements.

The presentation will emphasize the technique to measure size distributions from MAPR Doppler spectra and ways to use the SPL in situ data to verify these measurements.