19 Aug 2022
19 Aug 2022
Status: this preprint is currently under review for the journal AMT.

Raindrop Size Distribution (DSD) during the Passage of a Tropical Cyclone NIVAR: Effect of Measuring Principle and Wind on DSDs and Retrieved Rain Integral and Polarimetric Parameters from Impact and Laser Disdrometers

Basivi Radhakrishna Basivi Radhakrishna
  • National Atmospheric Research Laboratory, Department of Space, Govt. of India, Gadanki - 517112, Andhra Pradesh, India

Abstract. Raindrop size distribution (DSD) observations during the passage of landfalling tropical cyclone NIVAR by impact (JWD) and laser (LPM and PARSIVEL) disdrometers are used to unveil the DSD characteristics in the eyewall, inner, and outer rainbands. Disdrometer measurements collected at the same location are used to study the effect of wind, measuring principle, and hardware processing on the DSDs and, in turn, on estimated rain integral and polarimetric parameters. The concentration of raindrops of diameters between 0.7 mm to 1.5 mm increases with rain rate (R) in all the regions of NIVAR, while the magnitude of the increase is high in the eyewall than in the inner and outer rainbands. The DSD characteristics reveal that for a given R, relatively large reflectivity (Z) and mass-weighted mean diameter (Dm) are found in the outer rainband and small Z, and Dm in the eyewall than in other regions of a TC. Raindrops of diameter 3-mm in size are observed frequently in inner and outer rainbands, while infrequent in the eyewall at R greater than 5 mm h−1. The DSDs and estimated rain integral and polarimetric parameters are distinctly different for various disdrometers at similar environmental conditions. Raindrops greater than 3 mm in size are infrequent in the JWD recordings while frequent in the LPM an PARSIVEL indicating JWD underestimates the size of the raindrops than LPM and PARSIVEL due to canting of raindrops in the presence of wind. The wind effect on the recorded DSD and estimated rain integral and polarimetric parameters are not uniform in various regions of NIVAR for different disdrometers as the measuring principle and hardware processing further influence these effects. Along with the differences in measured DSD spectra, the resonance effects at X-band for raindrops greater than 3-mm cause variations in the estimated polarimetric parameters between the disdrometers.

Basivi Radhakrishna

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-209', Anonymous Referee #1, 31 Aug 2022
    • AC1: 'Reply on RC1', Basivi Radhakrishna, 01 Sep 2022
  • RC2: 'Comment on amt-2022-209', Anonymous Referee #2, 16 Sep 2022
  • RC3: 'Comment on amt-2022-209', Anonymous Referee #3, 16 Sep 2022

Basivi Radhakrishna

Basivi Radhakrishna


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Short summary
Raindrop size distributions (DSDs) measured by various types of disdrometers are different in the same environmental conditions. The mass-weighted mean diameter (Dm) measured from JWD is larger, ZDR is smaller than LPM and PARSIVEL due to the resonance effect at X-band frequency. The effect of wind on DSD measured by various disdrometers is not uniform in different regions of a tropical cyclone.