Climate Variability, Predictability and Applications

Objectives

The objective of understanding mechanisms responsible for Indian monsoon variability on intraseasonal, interannual and inter-decadal time scale is proposed to be achieved through diagnostic studies as well as modelling and simulation studies. In particular

To continue ongoing efforts in identifying regional and global climate drivers for monsoon interannual variability and to identify useful predictors.
To examine the teleconnections of Indian monsoon rainfall on intra-seasonal , interannual to decadal scale.
To develop forecast models for relevant climatic parameters over India on different spatio-temporal scales using empirical/statistical methods as well as downscaling of seasonal forecasts from General Circulation Models (GCMs) with high-resolution regional models.
To understand the role of low-frequency feedbacks involving land-atmosphere interactions relevant to interannual variability of the seasonal mean Indian summer monsoon that is governed by internal dynamics leading to the improvement of the representation of Indian monsoon rainfall, soil moisture etc. in the current generation of earth system models.
To develop regional climate data products such as daily temperature, rainfall etc on district, state and homogeneous regional scales using latest interpolation techniques for improved climate change detection and attribution.
To understand the role of aerosol loading over the Indian region in monsoon interannual variability and its possible implications on the predictability on interannual as well as on intraseasonal time scale.
To quantify the various aspects of climate change and variability on intraseasonal, interannual, decadal and century time scales over India and the neighbouring countries, particularly related to the southwest and northeast monsoons.

About Us

Research efforts of scientists in India and outside, in recent decades, have resulted in a considerable advancement in the understanding of monsoon variability on different spatio-temporal scales and possible role of many global climatic factors responsible for such variability. Intense studies have been made separately for different components of the Asian summer monsoon system (South, Southeast, western North Pacific summer monsoon and East Asian monsoon). We propose to understand the impact of changing global atmospheric conditions on the Asian summer monsoon circulation in general and Indian monsoon circulation and associated rainfall in particular. Predictability of Indian summer monsoon is limited by the ‘climate noise’ or ‘internal’ interannual variability (IAV), generated in the region. In order to improve the prediction skill, it is important to understand the physical processes responsible for the ‘climate noise’. It is proposed to try to unravel the physical processes responsible for ‘internal’ IAV of monsoon

In order to improve the forecast models to achieve the limit on potential predictability of seasonal mean monsoon, it is important to isolate and quantify the contribution from different climate drivers like ENSO, IOD, PDO, AMO, etc. in relation to the ‘internal’ IAV of the monsoon. Using available observations and high resolution coupled-ocean-atmosphere model, we attempt to isolate the contribution of various climate drivers of IAV of the Indian monsoon. The findings of such studies will guide us to develop better model for predicting monsoon climate.

To examine the impact of changing climate , the basic requirement is to understand the climate variability. We examine and try to understand the variability of Indian monsoon on the time scales of intra-seasonal, sub-seasonal, inter-annual to decades.

In view of the large spatial variability of Indian monsoon the efforts are being made to predict the summer monsoon rainfall on smaller spatial scales such as homogeneous regions, sub-divisions etc.

Project Details

Developmental Activities:

Development of web portal CLIMINFO and TEMPINFO: A web portal ‘CLIMINFO and TEMPINFO’ is being developed which will provide all the information on rainfall and temperature variability over a region in one click. The products are being prepared on the spatial scale of sub-divisions, cities and districts and on the time scale of daily, monthly and seasonal. The products are so designed as to be used by the general public as well as farmers. These products would be very useful as inputs to impact assessment groups.

Important Results:

Prediction of summer monsoon rainfall over India and its homogeneous regions

The coherent regions for various meteorological parameters (sea level pressure, temperature, geopotential height and zonal wind anomalies) at the surface, 850, 500 and 200 hPa levels in pre-monsoon months and seasons have been identified by applying the shared nearest neighbour (SNN) algorithm. The time series were constructed by averaging the parameters over the respective clusters. The relationship between these time series and the summer monsoon rainfall over India and over well-defined homogeneous regions over India, (northwest India, central northeast India, northeast India, west central India and peninsular India) was examined during the positive and negative phases of effective strength index (ESI) tendency using multiple regression. Fig. 1 depicts the observed and estimated summer monsoon rainfall over India for 1951-2012. Root mean square error (RMSE) on the domain 1951-2012 is 4.25, whereas CC between the observed and estimated rainfall departure is 0.90.

All estimated rainfall departure values in deficit/excess years are shown in Fig. 2 and it is observed that extreme rainfall departures are qualitatively well predicted. The unprecedented droughts in 2002 and 2009, where all models failed to predict, are quantitatively well captured by this strategy. [Kakade S., Kulkarni Ashwini, Prediction of summer monsoon rainfall over India and its homogeneous regions, Meteorological Applications, 23, January 2016, DOI:10.1002/met.1524]

Fig. 1: Estimated (white column) and observed (black column) summer monsoon rainfall percentage departures over All India (top panel) and subsequently followed over North west India, West central India, Central north east India, North east India and Peninsular India respectively; using separate equations depending upon positive or negative phase of ESI-tendency for 1951-2012.

Fig. 2: Observed (black) and estimated (red) all-India summer monsoon rainfall departures (%) during (a) deficient and (b) excess monsoon years during 1951-2012.

Changes in climate extremes over major river basins of India
High-resolution gridded daily rainfall data (1951-2014) and gridded daily temperature data (1951-2013) are used to examine the temporal changes in the extreme rainfall and temperatures on daily time scales in major river basins of India. Trend analysis is carried out to examine the temporal changes in the frequency, area covered by extreme events and their intensities. Rainfall of 10 cm during summer monsoon (JJAS), maximum temperature of 40°C during summer season (MAM) and minimum temperature of 10°C during the winter season (DJF) were used as the thresholds to define the extreme weather events of rainfall and temperatures. Analysis indicates that during monsoon season, zero rainfall days are increasing in all the river basins except some parts of the Peninsular river basins. River basins located in the central parts of India show significant increase in the area covered by the heavy rainfall episodes and their intensity. Substantial rise in the monthly maximum temperatures is seen in the Krishna, Peninsular and West Coast river basins (Fig. 3). Frequency, area coverage and intensity of hot days during summer season are increasing significantly in the Peninsular river basins, while no substantial change was observed for cold days during winter season in any river basins of the study. [Deshpande N.R., Kothawale D.R., Kulkarni Ashwini, Changes in climate extremes over major river basins of India, International Journal of Climatology, online, February 2016, DOI: 10.1002/joc.4651]

Fig. 3: Annual cycle of monthly maximum temperatures.

Project Highlight

Monsoon variability, the 2015 Marathwada drought and rainfed agriculture

The analysis of 145 years of summer monsoon rainfall over Marathwada shows that the two successive droughts of 2014-2015 and also the good monsoon of 2016 are not the effect of climate change and are well within the limits of monsoon variability over this region. It has also been shown that the Marathwada rainfall has strong relationship with all-India summer monsoon rainfall as well as ENSO. (Ashwini Kulkarni, Sulochana Gadgil, Savita Patwardhan , CURRENT SCIENCE, VOL. 111, NO. 7, 10 OCTOBER 2016)

Recent Publications

Joshi M.K., Rai A., Kulkarni Ashwini, Global-scale interdecadal variability a skillful predictor at decadal-to-multidecadal timescales for Sahelian and Indian Monsoon Rainfall, npj Climate and Atmospheric Science, 5: 2, January 2022, DOI:10.1038/s41612-021-00227-1, 1-8 (Impact Factor 8.624)
Sahoo M., Yadav R.K., Role of equatorial central Pacific sea surface temperature in modulating rainfall over north India during Indian summer monsoon, International Journal of Climatology, 41, November 2021, DOI:10.1002/joc.7165, 6017-6030 (Impact Factor 4.069)
Sahoo M., Yadav R.K., Teleconnection of Atlantic Nino with summer monsoon rainfall over northeast India, Global and Planetary Change, 203: 103550, August 2021, DOI:10.1016/j.gloplacha.2021.103550, 1-10 (Impact Factor 5.114)
Yadav R.K., Relationship between Azores High and Indian summer monsoon, npj Climate and Atmospheric Science, 4: 26, April 2021, DOI: 10.1038/s41612-021-00180-z, 1-9 (Impact Factor 8.624)