Relationship of convective precipitation with atmospheric heat flux — A regression approach over an Indian tropical location Swastika Chakraborty a , Upal Saha b,c , Animesh Maitra b,c, ⁎ a Department of Electronics and Communication Engineering, JIS College of Engineering, Kalyani, West Bengal, India b S. K. Mitra Centre for Research in Space Environment, Institute of Radio Physics and Electronics, University of Calcutta, Kolkata, India c Institute of Radio Physics and Electronics, University of Calcutta, Kolkata, India abstract article info Article history: Received 29 January 2015 Received in revised form 2 April 2015 Accepted 5 April 2015 Available online 16 April 2015 Keywords: Convective precipitation Latent heat Sensible heat Bowen ratio Surface evaporation The response of atmospheric heat fluxes and sea surface temperatures on the convective precipitation over the tropics has been an important area of research in recent decades. A long-term observation (1979–2008) of the increase in convective precipitation in relation to the latent and sensible heat fluxes on a tropical location, Kolkata, has been investigated in the present study. Invigoration of convective precipitation has been caused by vertically integrated divergence of moisture flux, rise in sea surface temperatures, convective cloud cover and surface evaporation rate over the tropical region. A convective precipitation estimation (CPE) index is proposed, con- sidering the Bowen ratio, surface evaporation rate, sea surface temperature and temperatures at 500 hpa pressure level during the pre-monsoon season (March–May), to estimate the amount of convective precipitation over the tropics using multiple linear regression technique is also another aim of this study. A good agreement is obtained between the results from the proposed model and the MERRA observations during the years 2009–2013. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Moist convection over the continent is significantly associated with the heat fluxes of the atmosphere. In terms of the heat fluxes there exists a definite coupling between land surface and the atmosphere which leads to the convection (Alfieri et al., 2008). Sensitivity of the convective rainfall frequency to the partitioning of sensible heat flux and latent heat flux over North America has been analyzed (Berg et al., 2013) using North American Regional Reanalysis (NARR) data. Most of the general circulation model (GCM) and other models (Chakraborty and Maitra, 2012, 2013) successfully predict mean rainfall but fail to estimate precipitation intensity and frequency. The European Centre for Medium-Range Weather Forecasting (ECMWF) model is used to study the triggering algorithm of diurnal cycle of convective precipitation over tropical South America and Africa where a strong diurnal cycle is observed (Bechtold et al., 2004). The North American Mesoscale (NAM) Forecast System model is used over the Carolina Sand hills region to predict the summer convective rainfall as mesoscale and local scale effects are prominent during summer (Wootten et al., 2010), and they are enhanced by surface heat fluxes. Convective rainfall triggering mechanism is explained (Juang et al., 2007) by a semi analytical model using surface heat flux and moisture. The model performance is not satisfactory during night, but boundary layer growth and boundary layer development plays a triggering phenomenon for the convection to be happened (Gentine et al., 2013). According to the atmospheric ther- modynamics, hydrological cycle is very much dependent on the interaction between land and atmosphere during warm season. Evapotranspiration (Schär et al., 1999) process successfully explains the water vapor balance of the planetary boundary layer. Intense trans- fer of moisture at the near surface atmosphere causes enhanced convec- tive precipitation. Bowen ratio, i.e. the ratio of surface heat flux to latent heat flux, and potential evaporation rate have a very good impact on convective precipitation. Dryness of the soil moisture results in shallow cumuli and thereby deep convection. Explanation of continental moist convection will be incomplete without considering the partitioning of heat flux (Gentine et al., 2013). Tropical precipitation is mostly dominated by convective phenome- non followed by stratiform precipitation (Houze, 1997). As the tropics is in close vicinity of the equator getting direct heating from the sun, clouds are of mostly cumulonimbus and cumulus types. Precipitation particles from vigorous convective region of cumulonimbus gather mass by collecting cloud water and break down into heavy shower. Over the last few years an increase of convective precipitation at pre- monsoon (warm) season is the main motivation behind this study. In the last decade, the study on convective precipitation around the world has been a topic of prior interest to the mesoscale research com- munity (Soriano and Pablo, 2003; Guo et al., 2006; Dimitrova et al., Atmospheric Research 161–162 (2015) 116–124 ⁎ Corresponding author at: Institute of Radio Physics and Electronics, University of Calcutta, Kolkata, India. E-mail address: animesh.maitra@gmail.com (A. Maitra). http://dx.doi.org/10.1016/j.atmosres.2015.04.008 0169-8095/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Atmospheric Research journal homepage: www.elsevier.com/locate/atmos