Showing papers by "Animesh Maitra published in 2013"

Multi-technique observations on precipitation and other related phenomena during cyclone Aila at a tropical location

Abstract: A severe cyclone, named Aila, passed over Kolkata on 25 May 2009. The strong convective activities manifested through rainfall during the cyclone were studied with multi-technique observations involving micro rain radar, disdrometer, rain gauges, and a Ku-band satellite signal receiving system. A number of features of precipitation, namely the presence of large rain drops, the large vertical extent of the precipitating layer, an unusual enhancement of cross-polar component, and strong scintillations of the co-polar component of the satellite signal due to strong turbulences associated with the cyclone, were observed. This study leads to a more comprehensive understanding of the precipitation associated with a cyclonic storm.

Diurnal variation of slant path Ka-band rain attenuation at four tropical locations in India

Abstract: Rain attenuation is very severe at Ka and higher frequencies especially in tropical regions. The conventional fade mitigation techniques are not be able to mitigate this severe fade and hence, suitable diversity technique is required for this purpose. In this paper, rain characteristics and slant path rain attenuation at 30 GHz using synthetic storm technique has been presented. Three years of high resolution rain rate data obtained from disdrometer at four tropical and equatorial locations in India have been utilized. The results indicate that the fade margin requirement is very high (above 50 dB at 30 GHz) for 99.99% link availability for these locations. However, the diurnal analysis shows that in most of the places, the rain occurrence is much less in morning/early-morning hours and therefore, the fade margin requirement will be considerably lower (around 30 dB at 30 GHz) in the morning hours compared to the afternoon hours. The result indicates the suitability of using selective time period for high link availability data communication over the locations studied.

Interrelation between microphysical and optical properties of cloud and rainfall in the Indian region

Abstract: Ground and satellite based measurements of microphysical and optical parameters of cloud are analysed for three tropical locations Kolkata, Guwahati and Bangalore during the year 2006 to find an interrelation between cloud optical depth, cloud effective radius, cloud liquid water content and rain. The present study suggests that a relation exists between cloud effective radius and cloud liquid water content. A minimum threshold of cloud optical depth is required for the precipitation to initiate. However, the threshold value depends on weather conditions of the tropical location. Cloud droplets with effective radii above 8 micron are mostly effective for the rain formation. Again, a threshold value of 5 is obtained for cloud optical depth for precipitation formation. There also exists a positive relation of accumulated rainfall with cloud effective radius and cloud optical depth as observed at a particular location.