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Attenuation relations for monsoonal rain at the X band from disdrometric measurements: Dependency on temperature, raindrop size distribution and drop shape models
Author(s) -
Narayana Rao T.,
Amarjyothi K.,
Rao S.V.B.
Publication year - 2018
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.3291
Subject(s) - attenuation , monsoon , dependency (uml) , drop (telecommunication) , seasonality , atmospheric sciences , environmental science , climatology , meteorology , geology , mathematics , physics , optics , statistics , computer science , telecommunications , software engineering
Four years of disdrometric measurements made at Gadanki (13.5 ° N, 79.18 ° E), which receives rainfall during both southwest and northeast monsoons, have been used to (a) derive optimal attenuation relations for monsoonal rainfall at the X band, (b) study the impact of seasonal variation in raindrop size distribution (DSD) on attenuation relations and (c) analyze the dependency of these relations on the controlling parameters/models, such as temperature ( T ) and drop shape model. The results clearly show that the coefficients of these relations vary significantly with DSD (season and rain type), T and drop shape model, and are quite different for monsoonal rain than for those obtained elsewhere. The traditional relations that involve a specific attenuation ( A H )‐reflectivity factor at horizontal polarization ( Z H ) and A H ‐rain rate depend heavily on DSD and to some extent on T , while the relations involving a specific differential phase ( K DP ) and differential attenuation ( A DP ) show strong dependency on the drop shape model and DSD, but depend weakly on T . A detailed investigation has been carried out to decipher reasons for the observed intriguing seasonal variation in K DP ‐based relations and their temperature dependency. The resonance scattering effects that are thought to be negligible at the X band in earlier studies appear to play a dominant role here and are primarily responsible for the observed features.