Drop size spectra and integral remote sensing parameters in the transition from convective to stratiform rain

Abstract

[1] Several authors have reported the correlation between the shape (m) and slope (L) of the gamma distribution of raindrops to reduce the number of parameters required to measure rainfall by remote sensing methods. However, we find that there are no well-defined m-L, or associated relations between reflectivity (Z) and rain rate (R) or differential reflectivity for all storms or portions thereof. Rather, there is a general behavior such that A and b (in the Z = AR b relation) and median volume drop diameter D o all decrease from convective (C) to stratiform (S) to transition (T) rains. The m-L correlation of the investigators in question appears to be limited to rainfall events which do not include convective rain; it is biased toward S and T rains. They miss the narrow (large m), large D o DSDs of convective rain that are often found to have equilibrium spectra. The dependence of D o on the strength of the updraft and the findings of others concerning the association with the physics, dynamics, and climate regime strongly suggests that it is necessary to characterize the physical and dynamic nature of the storms in order to select the appropriate remote sensing algorithms. Citation: Atlas, D., and C. Ulbrich (2006), Drop size spectra and integral remote sensing parameters in the transition from convective to stratiform rain, Geophys. Res. Lett., 33, L16803,

Differences in raindrop size distribution from southwest monsoon to northeast monsoon at Gadanki

“…Standard algorithms are utilized to convert the DSD into integral rainfall parameters. The pros and cons of the instrument are well known and are discussed in several earlier papers (Tokay et al, 2001;Atlas and Ulbrich, 2006). The JWD measurements are available for four SW (1999SW ( , 2000SW ( , 2006SW ( and 2007 and five NE (1997NE ( , 1999NE ( , 2000NE ( , 2006NE ( and 2007 monsoon seasons.…”

“…The differences in microphysical processes from SW to NE monsoon during the descent of rainfall also play a crucial role in modifying the DSD. The DSD evolves into an equilibrium distribution under the influence of processes such as collision, coalescence and break-up, if the 0 • C isotherm level is sufficiently high (Hu and Srivastava, 1995;Atlas and Ulbrich, 2006). Therefore, if the height of melting level is different in these seasons, it may cause some differences in rain DSD at the surface.…”

Polarimetric Radar Observations of Convection in Northwestern Mexico during the North American Monsoon Experiment

“…The continental archetype is characterized by relatively less dependence on ''warm-rain'' microphysical processes, namely collision and coalescence, for the production of rainfall. Instead, continental convection tends to strongly involve ice-based growth processesin particular, depositional, aggregrational, and riming growth of ice particles, which subsequently melt into rain (Rosenfeld and Lensky 1998;Atlas and Williams 2003;Ulbrich and Atlas 2007). By contrast, the maritime archetype depends more strongly on warm-rain processes (Jorgensen and LeMone 1989;Hu and Srivastava 1995;Rosenfeld and Lensky 1998;Ulbrich 2000, 2006;Ulbrich and Atlas 2007).…”

Retrieval of the raindrop size distribution from polarimetric radar data using double-moment normalisation

“…This assumption is subject to debate (e.g. Zhang et al, 2003;Atlas and Ulbrich, 2006;Moisseev and Chandrasekar, 2007;Cao and Zhang, 2009). The technique, modified by Brandes et al (2003), can provide useful DSD information (Brandes et al, 2004a).…”