The behavior of atmospheric electric field in terms of potential gradient (PG) has been studied during the period of 2013 and 2014 at a tropical and urban location Kolkata (22°34′N, 88°22′E), India. The clear-weather PG is influenced by varying concentration of black carbon, which is a major pollutant in urban atmosphere. The diurnal variation of the clear-day PG follows that of the black carbon concentration in all the seasons. It is found that cloud base height and liquid water path correlate well with the PG change in convective events. It is shown that during a convective event the PG change measured over 10-min interval about 30&nbsp;min before the onset of rain can approximate impending rain accumulation. ©2019. American Geophysical Union. All Rights Reserved.

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University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Electric Field Variation in Clear and Convective Conditions at a Tropical Urban Location

Journal of Geophysical Research: Atmospheres

A nowcasting technique has been proposed to estimate the impending rain accumulation using ground-based radiometric measurements at Kolkata (22.65°N, 88.45°E), a tropical location. It has been observed that the normalized variation of brightness temperature (BT) at 31 GHz along with the standard deviation of BT at 22 GHz and instability indices, namely, lifting index, have shown definite changes before rain events. A combination of these three parameters can be effective in predicting rain events both qualitatively and quantitatively. Accordingly, a prediction model is developed and tested on several intense rain events during the period 2014-2015. The model is found to perform reasonably well in predicting intense rain about 70-75 min in advance with an efficiency of 80%. © 1980-2012 IEEE.

IEEE Transactions on Geoscience and Remote Sensing

Prediction of Rain Occurrence and Accumulation Using Multifrequency Radiometric Observations

Owing to the wide rain variability of the tropical region, the Simple Attenuation Model (SAM) estimated rain attenuation values are often found to exhibit substantial deviation from the actual measurements over the location, Kolkata (22°34′N, 88°22′E). This is due to the variability in rain cell sizes resulting from the diverse rain characteristics of the region. Thus, an attempt has been made to model the rain decay parameter in SAM on the basis of the tropical rain characteristics. A model of rain decay parameter in terms of rain rate is proposed which accounts for different types of rain at the present location. The incorporation of the model of decay parameter provides a better estimation of rain attenuation than the existing SAM and ITU-R model. © 2017 COSPAR

Advances in Space Research

Modelling of rain decay parameter for attenuation estimation at a tropical location

In this paper parameters of precipitation profiles obtained from precipitation radar aboard tropical rainfall measuring mission satellite and from ground based micro rain radar observations have been compared for different rain events. The dual frequency radar observations of precipitating atmosphere have been utilized to study the vertical profiles of radar reflectivity and rain rate. It is shown that the inclination of the ray path of the satellite borne radar significantly influences the rain rate measurements. The study demonstrates the efficacy of combining space borne and ground-based measurement in obtaining a complete profile of vertical rain structure. © 2016, Metrology Society of India.

Mapan - Journal of Metrology Society of India

Simultaneous Radar Observations of Vertical Profile of Rain Features from Space and Ground at Ku and Ka Bands at a Tropical Location

Microwave radiometer is an effective instrument to monitor the atmosphere continuously in different weather conditions. It measures brightness temperatures at different frequency bands which are subjected to standard retrieval methods to obtain real time profiles of various atmospheric parameters such as temperature and humidity. But the retrieval techniques used by radiometer have to be adaptive to changing weather condition and location. In the present study, three retrieval techniques have been used to obtain the temperature and relative humidity profiles from brightness temperatures, namely; piecewise linear regression, feed forward neural network and neural back propagation network. The simulated results are compared with radiosonde observations using correlation analysis and error distribution. The analysis reveals that neural network with back propagation is the most accurate technique amongst the three retrieval methods utilized in this study. © 2016

Atmospheric Research

Retrieval of atmospheric properties with radiometric measurements using neural network

In the present study, the effectiveness of nowcasting convective activities using a microwave radiometer has been examined for Kolkata (22.65° N, 88.45° E), a tropical location. It has been found that the standard deviation of brightness temperature (BT) at 22. GHz and instability indices like Lifting Index (LI), K Index (KI) and Humidity Index (HI) has shown definite changes before convective events. It is also seen that combination of standard deviation of BT at 22. GHz and LI can be most effective in predicting convection. A nowcasting algorithm is prepared using 18 isolated convective events of 2011 and in all cases, a marked variation of these parameters has been seen an hour before the event. Accordingly, a prediction model is developed and tested on convective events of 2012 and 2013. It is seen that the model gives reasonable success in predicting convective rain about 7075. min in advance with a prediction efficiency of 80%. © 2015 Elsevier B.V.

Journal	Journal of Geophysical Research: Atmospheres
Publisher	Blackwell Publishing Ltd
ISSN	2169-897X
Open Access	No