The objectives of this research are: (1) modeling and observational studies of intense downdrafts. This will involve extensions to the one-dimensional models already in existence, completion and extension of work on the modeling of axially symmetric downdrafts including detailed microphysics. An extension to three dimensions and inclusion of more complete microphysics (drop coalescence and breakup in addition to melting and evaporation) in all the models is anticipated. The results of the various models will be compared with radar and, in particular, surface meteorological data; (2) A comparison of ZDR measured by a radar, with that calculated from the drop size distribution inferred from profiler observations, and studies of the size spectra of raindrops and raindrop oscillations by means of profiler observations; (3) Numerical simulations and theoretical studies of a dual-radar method of measurement of rainwater content and rainfall rate and tests of the method against observations; and (4) A theoretical calculation of the growth of drops by condensation in very slow updrafts, as in stratiform clouds.
