Real time extended range prediction of heat waves over India

Raju Mandal,A Dey,A K Sahai,D R Pattanaik,Susmitha Joseph,R Chattopadhyay,R Phani

doi:10.1038/s41598-019-45430-6

Abstract

Heat waves over India occur during the months of March-June. This study aims at the real-time monitoring and prediction of heat waves using a multi-model dynamical ensemble prediction system developed at Indian Institute of Tropical Meteorology, India. For this, a criterion has been proposed based on the observed daily gridded maximum temperature (Tmax) datasets, which can be used for real-time prediction as well. A heat wave day is identified when either (1) Tmax (a)≥ its climatological 95th percentile (calculated from daily values during March-June and for 1981–2010), (b) >36 °C, and (c) its departure from normal is >3.5 °C, Or, (2) when the Tmax >44 °C. Three heat wave prone regions, namely, northwest, southeast and northwest-southeast regions are recognized and heat wave spells of minimum consecutive six days are identified objectively for each region during 1981–2018. It is noticed that the prediction system has reasonable skill in predicting the heat waves over heat wave prone regions of India. Forecast verification of heat wave spells during 2003–2018 reveals that the prediction system has great potential in providing overall indication about the onset, duration and demise of the forthcoming heat wave spell with sufficient lead time albeit with some spatio-temporal error.

Highlights

The Intergovernmental Panel on Climate Change (IPCC), in its 4th assessment report, states that the type, frequency and intensity of extreme events are expected to change as the Earth’s climate changes, and these changes could occur even with relatively small mean climate changes[1]
Once developed and verified for hindcast data, all the products will be transferred to India Meteorological Department (IMD), which is the authorized Govt. agency to issue the forecasts/warnings, to make them operational in real time
This study makes an attempt to explore the strength of the Climate Forecast System version 2 (CFSv2) based Model Ensemble (MME) forecast system in using a new criterion for the real-time Extended Range Prediction (ERP) of Heat waves (HWs) over Indian region during MAMJ

Summary

Introduction

The Intergovernmental Panel on Climate Change (IPCC), in its 4th assessment report, states that the type, frequency and intensity of extreme events are expected to change as the Earth’s climate changes, and these changes could occur even with relatively small mean climate changes[1]. In India, the HWs occur during the summer season months, March to June (MAMJ), mainly over north, northwest, central and the eastern coastal regions[3]. Using a HW index based on daily maximum temperature (Tmax), researchers[13] have shown that, the frequency of severe HWs will rise by 30 times under the increase in global mean temperature by the end of 21st century. There are no studies that focus on real-time prediction of HWs. Considering the impacts of such events across various sectors of the society, such as health, agriculture etc., there is a need to develop new strategy/criteria for the real time monitoring and prediction of such silent disastrous events over Indian region. The present study proposes a criterion based on the daily gridded Tmax data for the real-time prediction of HWs over India on extended range during the summer season, MAMJ. The proposed HW criterion and the methodologies for identifying the HW spells over different HW-prone regions are discussed in the Methods section

Objectives

Methods

Results

Conclusion