Indian Journal of Geo Marine Sciences Vol. 49 (10), October 2020, pp. 1611-1618 Ocean atmospheric processes over Bay of Bengal during two contrasting northeast monsoon onsets K V Shende* ,a , M R Ramesh Kumar b & K V Kale a a Department of Computer Science & Information Technology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad – 431 001, India b Physical Oceanography Division, National Institute of Oceanography, Dona-Paula, Goa – 403 004, India *[E-mail: kanchan.shende4@gmail.com] Received 18 December 2018; revised 28 November 2019 Conditions leading at the beginning of North-East Monsoon season on the Bay of Bengal studied using various ocean/ atmosphere parameters such as wind speed, shortwave radiation, sea surface temperature, latent heat flux, net surface heat flux and outgoing longwave radiation for two contrasting North-East monsoon onset years such as 1984 (Delayed) and 1999 (Early). During 1984 sea surface temperature is high over the northern portion of the Bay of Bengal but in 1999 which is the early North-East Monsoon year it is high over the south-eastern portion. In the delayed year i.e. in 1984, sea surface temperature over northern portion of Bay of Bengal warms more than an earlier year i.e. 1999, but contrast behaviour is observed in the south-eastern portion, it warms more in 1999 than 1984. From the analysis, it also observed that in delayed year more heat evaporates than an early year. [Keywords: Bay of Bengal, Latent Heat Flux, North-East Monsoon, Outgoing Longwave Radiation, Sea Surface Temperature, Wind Speed] Introduction The term “North-East Monsoon (NEM)” is often used to describe the period from October to December 1 , it’s known as winter monsoon, post- monsoon or retreating southwest monsoon 2 ; one of the significant component of Indian Monsoon cycle 3 . Similar to summer rainy season, NEM perform a significant role not only for agriculture development but also for economic development 4 over Southern Peninsular of India. It mostly affects the southern meteorological sub-divisions of Rayalaseema, Tamil Nadu, Coastal Andhra Pradesh, South Central Karnataka and Kerala 5 . Of these sub-divisions, Tamil Nadu experiences extra rain throughout the NEM season compared to southwest rainy season; it is in the coastal band where the onset and withdrawal activity of NEM are well marked 6 . Tamil Nadu usually receives precipitation because of the development of convective systems like, depressions, deep depressions, low pressure area, cyclonic system which form on the Bay of Bengal (BoB) 1 . The BoB is situated in the eastern region of the north Indian Ocean, it holds rare physical and atmospheric setting 7 . It is observed that rainfall obtained during this period is extremely variable. Therefore, it is necessary to predict the behaviour of rainfall during this period in advance which will be very helpful for industrial and agricultural development 8 . Heat exchange between ocean and atmosphere during the particular season at different time scales might be responsible for the atmospheric condition 9 . Scientists are interested to explore the NEM season and are trying to find the interrelationship of NEM rainfall patterns besides various meteorological parameters. Gibies et al. 10 showed the variation of NEM rainfall over southern peninsular India (SPI) for strong and weak NEM rainfall years from 1951 to 2003 using SST, zonal wind at 850 hPa and sea level pressure (SLP). They concluded that among all parameters SLP between the western pacific and the western Indian Ocean contribute to deciding an intensity of NEM rainfall over SPI. Charlotte et al. 11 studied the different types of fluctuations generated during NEM over SPI, and they observed that NEM of SPI is extremely complicated and it doesn’t follow any easy directive during the season. They also observed that if the SST of BoB is cool & steady for a longer period and if it is hotter than the Arabian Sea then SLP decides the rainfall pattern of SPI. Using NCEP 6-hourly reanalysis data of meridional & zonal brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by NOPR