O. P. Sreejith

• PhD
• Managing Director at India Meteorological Department

Seasonal rainfall prediction for the Indian Summer Monsoon remains a challenging task for climate models, with regional-scale forecasts proving even more difficult than predicting the all-India averaged seasonal rainfall. In this study, we evaluate the performance of eight models from the Copernicus Climate Change Service (C3S) in simulating and pr...

IMD was created to act as the nodal agency in the country on weather and climate matters. This article broadly covers the journey of Climate Services becoming a separate branch with direct linkages to sectoral applications and is not an exhaustive documentation. Notionally, weather and climate differ in the former being a time specified information...

This study comprehensively assesses the predictive capabilities of the Monsoon Mission Coupled Forecasting System (MMCFS) output for El Niño-Southern Oscillation (ENSO) conditions and its transitions in the various phases. The MMCFS model is being run for the operational seasonal forecast at the India Meteorological Department (IMD), and understand...

The El Niño-Southern Oscillation (ENSO) is considered as the primary driver of interannual variability in the all India summer monsoon rainfall (ISMR). Recently, La Niña conditions were experienced during three consecutive years (2020-2022), which is widely known as the 'triple-dip' La Niña episodes and ISMR during all these three years was normal...

The El Niño-Southern Oscillation (ENSO) is the most important driver of the Indian summer monsoon rainfall (ISMR) interannual variability. In recent years, there have been three consecutive La Niña years (2020–2022), which are widely known as the ‘triple-dip’ La Niña. This study discusses the observed variations in SST and ISMR during these triple-...

Tropical cyclones affect millions of lives in the Indian subcontinent which makes the region highly vulnerable to cyclones. Classifying the region’s vulnerability greatly helps the stakeholders involved in the disaster management associated with tropical cyclones. This study is a comprehensive assessment of India’s vulnerability to cyclones of diff...

Northeast Monsoon of South Asia

This study attempts to understand the asymmetry in the Indian Summer Monsoon Rainfall (ISMR) response to two types of La Niña whether they evolved from El Niño or La Niña in the previous boreal winter season. It was seen that nine La Niña years during the monsoon season were preceded by El Niño (hereafter ELLA) whereas eight were preceded by La Niñ...

In this paper, various methods used by the India Meteorological Department (IMD) to issue Long-Range Forecast (LRF) of Southwest monsoon rainfall and its current status are discussed. IMD started issuing long-range forecast for rainfall in 1886 using conditions like snow cover. Since then, several forecast techniques were developed for improving th...

The post‐monsoon (October–November–December) tropical cyclone (TC) over the Bay of Bengal is one of the most devastating natural disasters causing economic and human losses over India and its neighbouring countries. This study discusses a hybrid statistical/dynamical model developed to forecast the post‐monsoon cyclone activities over the Bay of Be...

This paper studies the summer monsoon 2017 and examines the number of parameters which we believe were important in understanding why monsoon failed in second half over India. The list of parameters includes monthly mean or anomalies of the following fields : sea surface temperature, outgoing longwave radiation, stream function of lower and upper a...

Floods are one of the most devastating natural hazards across the world, with India being one of the worst affected countries in terms of fatalities and economic damage. In-depth research is required in order to understand the complex hydrometeorological and geomorphic factors at play and design solutions to minimize the impact of floods. But the e...

The Tropical Atmosphere Ocean (TAO) and Triangle Trans-Ocean Buoy Network (TRITON) buoys deployed in the tropical Pacific play a significant role in monitoring tropical Pacific conditions such as El-Niño/La-Niña in real-time. Earlier studies have illustrated the importance as well as irrelevance of moored buoy observations towards the prediction of...

Kerala, located at the southwest tip of India, witnessed disastrous floods during the monsoon seasons of two consecutive years, 2018 and 2019. This paper provides a detailed analysis of these two flood events using data from multiple sources. The unusually unstable and convective nature of the 2019 event, as detectable in its higher cloud tops and...

Andaman & Nicobar in the Bay of Bengal and Lakshadweep Islands in the Arabian Sea are integral parts of India which are situated in climate hazardous areas influenced by monsoonal rain bursts and tropical cyclonic disturbances formation. In order to examine various rainfall variability and trend features over India, long time series of daily gridde...

Floods are one of the most devastating natural hazards across the world, with India being one of the worst affected countries in terms of fatalities and economic damage. In-depth research is required in order to understand the complex hydrometeorological and geomorphic factors at play and design solutions to minimize the impact of floods. But the e...

Heavy rainfall (≥ 100 mm or HR) events and moderate rainfall (≥ 5 mm to 100 mm or MR) events over Kera-la for June-September were analysed statistically to understand the influence of climate change in MR and HR events for the period 1901-2019 and its two different parts; 1901-1970 and 1971-2019. Most parts of coastal Kerala receive more than 50 HR...

2 1 Introduction 3 2 Data and Methodology 6 3 Results and discussions 3.1 Rainfall Climatology and Trend for various months and seasons 7 3.2 Influence of ENSO and IOD over the region during various months and seasons 12 3.3 Verification of Seasonal Rainfall Forecasts 17 Acknowledgements 19

Development of A New (1o x 1o) (1981-2019) Monthly Gridded Rainfall Data Set Over South Asian Region This report discusses development of a new monthly gridded rainfall data set at a spatial resolution (1ox1o, latitude x longitude) covering a period of 39 years (1981-2019) over the South Asian region by merging various rainfall data sets over the...

Extreme weather and climate events are affecting societies worldwide. Associated with the projected climate variability and change, intensity and frequency of these extreme events are likely to increase and posing significant challenges and threat to the planet. Seasonal prediction of rainfall and temperature plays an important role in helping vari...

Bulletin of the Indian Meteorological Society Pune chapter Annual Monsoon Workshop (AMW-2018) And Prof. D. R. Sikka Memorial National Symposium on “Role of Weather & Climate Observations and Forecasting on increasing Agricultural Productivity & Risk Management”. _____________________________________________________________________ Authors: IMSP...

The extensive coastal belt of India is very vulnerable to the deadly storms known as tropical cyclones (Mohapatra et al., Nat Hazards 63:1601–1620. doi:10. 1007/ s11069-011-9891-8, 2012; Mohapatra, J Earth Syst Sci 124:515–526. doi:10. 1007/ s12040-015-0556-y, 2015). These systems form initially as low-pressure areas (when the maximum sustained sur...

The Indian summer monsoon rainfall (ISMR) depicts large inter-annual variability strongly linked with El Niño Southern Oscillation (ENSO). However, many of the El Niño years were not accompanied by deficient ISMR. The results from the study reveal the significant role of coupled air-sea interaction over the tropical Indian Ocean (IO) in modifying t...

The study evaluates various sea surface temperature (SST) indices and their teleconnections with Indian summer monsoon rainfall (ISMR) simulated by Japan Meteorological Agency (JMA) coupled general circulation model (CGCM). The indices considered for evaluations are Niño indices (Niño 4, Niño 3.4, Niño 3 and Niño 1 + 2) of Pacific Ocean (PO) and In...

The performance of a dynamical seasonal forecast system is evaluated for the prediction of summer monsoon rainfall over the Indian region during June–September (JJAS) by using hindcast of the Japan Meteorological Agency (JMA) seasonal ensemble prediction system (EPS) model, based on five ensembles of March, April and May initial states for a period...

The study discusses development of a new daily gridded rainfall data set (IMD4) at a high spatial resolution (0.25° × 0.25°, latitude × longitude) covering a longer period of 110 years (1901-2010) over the Indian main land. A comparison of IMD4 with 4 other existing daily gridded rainfall data sets of different spatial resolutions and time periods...

The occurrence of exceptionally heavy rainfall events and associated flash floods in many areas during recent years motivate us to study long-term changes in extreme rainfall over India. The analysis of the frequency of rainy days, rain days and heavy rainfall days as well as one-day extreme rainfall and return period has been carried out in this s...

At present, India Meteorological Department (IMD) issues various monthly and seasonal operational forecasts for the south-west monsoon season using models based on latest statistical techniques with useful skill. Operational models are reviewed regularly and improved through in house research activities. For the forecasting of the south-west monsoo...

The summer monsoon rainfall over India exhibits strong intraseasonal variability. Earlier studies have identified Madden Julian Oscillation (MJO) as one of the most influencing factors of the intraseasonal variability of the monsoon rainfall. In this study, using India Meteorological Department (IMD) high resolution daily gridded rainfall data and...

Satellite based daily fields of Pathfinder SST (PFSST) and blended-analysed fields like National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) and Reynolds weekly SST data were compared with the in situ measurements obtained from several drifting buoys and a moored buoy in the north Indian Ocean. The mean...

Hydrographic observations in the eastern Arabian Sea (EAS) during summer monsoon 2002 (during the first phase of the Arabian Sea Monsoon Experiment (ARMEX)) include two approximately fortnight-long CTD time series. A barrier layer was observed on occasions during the two time series. These ephemeral barrier layers were caused by in situ rainfall, a...

The annual and inter-annual variability of precipitation over the tropical Indian Ocean is studied for the period 1979–1997, using satellite data from a variety of sensors. The Climate Prediction Center Merged Analysis Precipitation (CMAP), Microwave Sounding Unit (MSU) estimates of rainfall had better correlation with the island rainfall data than...

Measurement of Sea Surface Temperature (SST) using satellite based sensors have matured during the last decade. The infrared measurements, using the AVHRR sensor, flown onboard the NOAA satellites, have been used for the generation of high resolution operational products on daily basis, since 1982. However, the intrinsic problem of the infrared rad...