Colloquium: Thursday, 11/10, 3:00 pm, EN6085A

Abstract: 

CALJET and PACJET studies of 1997-2003 showed winter storms in California and Oregon frequently do not exhibit a melting-layer radar bright band, even when cloud tops are well above the melting level and rainfall is heavy.  The researchers inferred that this kind of “non-brightband” rain has notably different microphysical properties, such as more small drops and fewer large ones, than those of the more familiar kind of brightband rain periods.  The non-brightband periods are more prevalent in orographically-enhanced rain.

The earlier studies relied on observations with vertically pointing S-band Doppler radar profilers and did not have the benefit of actual measurements of drop sizes.  In the winter of 2003-2004, NOAA’s Hydrometeorology Testbed (HMT) again operated S-band profilers at two of the earlier California study sites.  This time however, disdrometers were collocated with the profilers to measure drops sizes at the ground.  The profiling radar data from aloft were again used to objectively classify the rain periods as brightband or non-brightband.  The concurrent disdrometer data are examined in this talk for differences in the drop size distributions and the reflectivity rainfall (Z-R) relations derived from them.