Effective Path Length for Estimating Rain Attenuation Over an Earth‐Space Path Using Features of Stratiform and Convective Precipitation at a Tropical Location

Abstract

The effective path length (LE) for the rain attenuation estimation over the Earth‐space path depends on rain cell size, rain rate, and rain height which in turn are determined by the types of rain. The present study examines the variation of LE based on the experimental measurements of Ku‐band attenuation and rain rate at a tropical location Kolkata (22°34′N, 88°22′E) in comparison with the ITU‐R. The study also utilizes measurements from a 24‐GHz micro rain Doppler radar to differentiate the precipitation types as stratiform and convective rain on the basis of the presence and absence of a melting layer. Power‐law models of LE in terms of rain rate are proposed for convective and stratiform types of rain. The investigation reveals the physical phenomena behind the variability of LE at low and high rain rates which are associated with stratiform and convective rain respectively. The proposed models provide a significantly better agreement with the experimental data compared to the ITU‐R model and also account for distinguishing features of two types of rain, thus giving a physical basis of the proposed model which is not reflected in the ITU‐R formulations.

Micro Rain Radar and Radiometric Measurements to Unravel Contrasting Features of Rain Microstructure Below and Above the Boundary Layer

“…Near surface DSD information are obtained from the disdrometer (first column), while MRR provides the rain rate and DSD data for 1, 2, 3, and 4 km (second to fourth column) as presented in Figure 3. Here, it may be noted that DSD data corresponding to rain class R6 is not available for stratiform rain as very high rain rates are not found in this case (Rakshit & Maitra, 2022).…”

“…On the other hand, stratiform rain events are favored by lower thermodynamic instabilities causing weaker vertical motions along the atmospheric column (Saha et al., 2022) which in turn helps the formation of a melting layer (Li et al., 2018), thereby suppressing any nonlinearities prevalent in the free troposphere (Chakravarty et al., 2021; Seela et al., 2018). But convective rain cases depict high rain rates and are devoid of bright bands (Rakshit & Maitra, 2022). In this connection, the altitudinal variations of rain rate obtained from MRR for convective and stratiform rain are shown in Figure 4f.…”

“…The present study utilizes the profiles of rain rate ( R ) and rain DSD along with disdrometer measurements in delineating the response of rain microphysical profiles under varied raining conditions. Further, as the paper focuses on the DSD features for the two distinct rain types, the classification of rain into stratiform and convective types are done on the basis of the presence or absence of the bright band signature respectively from the MRR rain rate profiles (Rakshit & Maitra, 2022; Saha et al., 2022).…”

“…The present paper utilizes MRR to identify two distinct rain types namely, convective and stratiform prevalent over the tropical region (Lavanya & Kirankumar, 2021; Maitra et al., 2022; Saha et al., 2022). Highly variable nature of the precipitating environment corresponding to convective and stratiform rain over the tropics leads to varied rain microstructure even for the same rain intensity (Lavanya & Kirankumar, 2021; Rakshit & Maitra, 2022). Hence the study of rain DSD profile needs to be considered separately for convective and stratiform rain respectively.…”