Abstract
Rain events can be characterized by rain drop size distribution (DSD) that denotes the number of drops as a function of diameter per unit size interval and per unit volume of space. DSD (at ground level) describes the microstructure of precipitation during different phases of rain varying both spatially and temporally. DSD can be influenced by the nature and origin of rain. The present study investigates the role of continental and maritime airflow in influencing the precipitation features near the land-sea boundary. The data of the rain DSD used in the present analysis are collected from a ground-based disdrometer located at Kolkata, India, near land-sea boundary during the year of 2011–2017. The dataset is divided into two categories, namely, maritime and continental rainfall, based on the airflow trajectories associated with rain events exclusively from Bay of Bengal or land region in the west of Kolkata as derived from TRAJSTAT software. The events with trajectories extending both over land and sea region are excluded for the present study. Variations of the DSD parameters using the gamma model are presented showing the abundance of smaller drops during maritime rain events whereas dominance of larger rain drops in the case of the continental rain events. The Z-R relations are also found to be significantly different for these two types of rain. The present study reveals the microstructures of rain at a location where the influences of both land and sea climatic features prevail.
Highlights
Past studies on rain microstructures are mostly concerned with drop size distribution (DSD) variations with respect to locations and rain types (Rao et al 2001; Tokay and Short 1996; Atlas et al 1999; Rao et al 2009; Rosenfeld and Ulbrich, 2003)
Case studies have been made for two particular rain events depicting maritime and continental rain.The red line indicates the continental air flow as the wind direction fully covers the land mass before rain occurence at Kolkata, while the blue line corresponds to the maritime airflow as the wind contains trajectory coming from Bay of Bengal indicating it picked up moisture from the sea surface
Rain drop size distribution has been studied for rain originating from sea and land seperatly for two such typical days in the month of October, 2017
Summary
Past studies on rain microstructures are mostly concerned with DSD variations with respect to locations and rain types (Rao et al 2001; Tokay and Short 1996; Atlas et al 1999; Rao et al 2009; Rosenfeld and Ulbrich, 2003). The aerosol transports from both land and ocean have significant influence on rain climatology as reported in earlier studies (Rosenfeld and Lensky, 1998; Radhakrishna et al, 2009; Fuentes et al, 2008). Limited studies are reported on the rain DSD difference due to maritime and continental circulation from a coastal location (Das and Chatterjee, 2018). Earlier studies (Maitra et al, 2019; Rakshit et al, 2016; Jana et al, 2018) from Kolkata suggests the location to be important for the study of DSD variations as it is situated near the land-ocean boundary and thereby experiencing a variety of atmospheric processes influencing DSD. The main objective of this study is to understand the role of continental and maritime air motion that influences the precipitation microstructure near the land-ocean boundary
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