No abstract

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 (AH)‐reflectivity factor at horizontal polarization (ZH) and AH‐rain rate depend heavily on DSD and to some extent on T, while the relations involving a specific differential phase (KDP) and differential attenuation (ADP) 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 KDP‐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.