Stratiform and Convective Precipitation Observed by Multiple Radars during the DYNAMO/AMIE Experiment

Abstract

In this study, methods of convective/stratiform precipitation classification and surface rain-rate estimation based on the Atmospheric Radiation Measurement Program (ARM) cloud radar measurements were developed and evaluated. Simultaneous and collocated observations of the Ka-band ARM zenith radar (KAZR), two scanning precipitation radars [NCAR S-band/Ka-band Dual Polarization, Dual Wavelength Doppler Radar (S-PolKa) and Texas A&M University Shared Mobile Atmospheric Research and Teaching Radar (SMART-R)], and surface precipitation during the Dynamics of the Madden-Julian Oscillation/ARM MJO Investigation Experiment (DYNAMO/AMIE) field campaign were used. The motivation of this study is to apply the unique long-term ARM cloud radar observations without accompanying precipitation radars to the study of cloud life cycle and precipitation features under different weather and climate regimes. The resulting convective/stratiform classification from KAZR was evaluated against precipitation radars. Precipitation occurrence and classified convective/stratiform rain fractions from KAZR compared favorably to the collocated SMART-R and S-PolKa observations. Both KAZR and S-PolKa radars observed about 5% precipitation occurrence. The convective (stratiform) precipitation fraction is about 18% (82%). Collocated disdrometer observations of two days showed an increased number concentration of small and large raindrops in convective rain relative to dominant small raindrops in stratiform rain. The composite distributions of KAZR reflectivity and Doppler velocity also showed distinct structures for convective and stratiform rain. These evidences indicate that the method produces physically consistent results for the two types of rain. A new KAZR-based, two-parameter [the gradient of accumulative radar reflectivity Z e (GAZ) below 1 km and near-surface Z e ] rain-rate estimation procedure was developed for both convective and stratiform rain. This estimate was compared with the exponential Z-R (reflectivity-rain rate) relation. The relative difference between the estimated and surface-measured rainfall rates showed that the two-parameter relation can improve rainfall estimation relative to the Z-R relation.

Evaluation of the Near Real-Time Forecasts Using a Global Nonhydrostatic Model during the CINDY2011/DYNAMO

“…The MJO initiation, which had been a difficult aspect of MJO forecasting, was the primary target. Intensive observations were conducted over the Indian Ocean (hereafter, IO) during the period from 1 October 2011 to 15 January 2012, and a large amount of high-quality data was collected (Ciesielski et al 2014a;Deng et al 2014;Feng et al 2014;Moum et al 2014;Y13). The observations captured many important processes that would be key to a complete understanding of the MJO, such as (1) the deep moistening which led to MJO convective initiation Johnson and Ciesielski 2013;Johnson et al 2015;Y13), (2) the evolution of populations of different cloud types in each stage of the MJO (Bellenger et al 2015;Feng et al 2014;Powell and Houze 2013;Ruppert and Johnson 2015;Zuluaga and Houze 2013;Xu and Rutledge 2014), and (3) the sub-daily to seasonal upper ocean variations Moum et al 2014;Seiki et al 2013;Yokoi et al 2014;Y13).…”

Evolution, Properties, and Spatial Variability of MJO Convection near and off the Equator during DYNAMO

“…Measurements from the three radars (Ka, C, and S band) deployed on Gan were merged into a precipitating and nonprecipitating radar echo dataset (Feng et al 2014). A convective and stratiform precipitation product based on the Ka-band cloud radar (KAZR) was also developed (Deng et al 2014). These studies provided key information on the role of shallow and congestus clouds in the initiation of the MJO.…”

Atmospheric thermodynamics and dynamics during convective, stratiform and nonprecipitating clouds over the metropolitan area of Rio de Janeiro – Brazil

“…In contrast, stratiform clouds are characterized for being shallow and presenting greater horizontal homogeneity, possibly extending for hundreds of kilometers. Stratiform clouds present weak vertical air movement and generate light rains (Hong et al, 1999;Deng et al, 2014). Different microphysical cloud processes can be related to drop size growth.…”