Aircraft and dual polarization radar observations of hydrometeors in light stratiform precipitation

Abstract

AbstractA case study investigating the relationship of ice phase microphysical structure to differential reflectivity is presented. the distribution of ice crystal types in light precipitation is discussed and shown to agree with a theoretical model of an individual precipitation fallstreak. the particle characteristics were found to reflect sorting by size and type associated with fall through weak wind shear as well as growth in regimes of varying temperature and humidity within the fallstreak.The observed differential reflectivities were compared with the in situ particle measurements and the association of high values with planar crystal structures demonstrated. the particle size distribution was found to have a marked influence on radar returns, particularly through the obscuring effects of large particles of indefinite shape. This effect gave rise to relative variations of differential reflectivity which were found to differ from the predictions of monodisperse models. In particular large dendritic crystals of low density were found in this case to be associated with stronger signatures than denser plate‐like crystals which from theoretical studies might be expected to produce the greatest differential reflectivity. Because of these complicating factors under stratiform conditions it was concluded that differential reflectivity data must be interpreted with considerable caution in the absence of in situ measurements or other supporting data.