Regional variability and change in Extremes :

Application of indices in India

Jayashree Revadekar Indian Institute of Tropical Meteorology

Pashan, Pune

Using RCLIMDEX since 2004

In 2005, worked as resource person for the Global Climate Observing System (GCOS) International

Workshop on Enhancing South Central Asian Climate Change Monitoring and Indices held at

IITM, Pune during 14-19 February 2005

Analysis on Indian Region :

• Preparation and Quality Control of Data

• 27 indices of extremes in daily Tmax, Tmin, Precipitation

• Observational analysis using station data

• Validation and Future scenario using model gridded data

• Trend and variability in each index at station and region

• Role of sea surface temperature in extremes over India

• Impact of change and variability in extremes

• Elevation dependency of extremes

• Reconstruction of past extremes using proxy data

Indices Analysed : Frequency indices e.g.

Hot events Cold Events Heavy rainfall events

Intensity indices e.g.

Hottest day/night temperature Coldest day/night temperature 1-day & 5-day maximum precipitation

Spell duration e.g.

Warm spell duration Cold spell duration Continuous wet/dry days

Summary statistics of stations for increasing and decreasing trends in extremes

Statistical properties of Precipitation Extremes during summer and winter monsoon

1971- 2003

All-India monthly temperature extremes computed over two equal parts of the data period show increase in the frequency of hot events in all the individual months, while those in cold events show opposite patterns. Similarly increase in the temperature is seen in all intensity indices of both hottest and coldest events in maximum and minimum temperature, in all months of recent period

Black : 1971-1986 Red : 1987-2003

Semi-average changes

Red colour indicate increasing trend Blue colour indicate decreasing trend There is a widespread warming through spatial pattern of indices of extremes with : Frequency of hot events increased Frequency of cold events decreased

Revadekar et al., 2012, Natural Hazards

ROLE OF SEA SURFACE TEMPERATURES

IN EXTREMES OVER INDIA

The El Niño and La Niña characterized by typical SST anomaly patterns in tropical central and eastern Pacific Ocean are known to be a major forcing of earth's year-to-year climate variability with significant impacts on regional climatic patterns. Association between ENSO and Summer monsoon rainfall over India has been rigorously studied by several scientists.

The All-India time series of detrended seasonal extremes, correlated with monthly NINO SSTs.

Correlation Coefficients are computed between indices of extremes NINO SSTs

Correlation between Monthly SSTs and Winter Monsoon Precipitation Extremes : 1-day and 5-day maximum precipitation :

Revadekar & Kulkarni, 2008, Int. J. Climatology

Composite anomalies in hot and cold events during El nino and La Nina There is a characteristics change in the ENSO-associated temperature extremes with the onset of summer monsoon in June; El Niño is associated with less frequency of warm extremes during the pre-monsoon months, and higher frequency of warm extremes during the monsoon and post-monsoon season. The opposite features are seen in the case of La Niña;

Top hot events ; bottom cold events

Revadekar, Kothawale & Rupa Kumar, 2009 Int. J. Climatology

Analysis of Extremes using

Climate model data

Climate models provide us the tools to understand the behaviour of the climate system in the most comprehensive manner, through sophisticated numerical representations of the various processes and their interactions. More importantly, they provide us the capability to project the future climate change under various plausible scenarios of climate forcings, both natural and anthropogenic.

Evaluation of Model data in simulating Extremes

Evaluation of Annual cycles of Lowest Minimum/Highest Maximum temperature :

PRECIS shows cold biases. Annual cycles of both minimum and maximum temperature extremes are well captured by the PRECIS.

Revadekar et al., 2012, Natural Hazards

Evaluation of spatial distribution of Seasonal precipitation :

Future of scenarios of Extremes as seen in PRECIS

The changes in winter season are prominent than the rest of year. Similar features are seen in minimum temperature also. The changes in extremes in night temperatures are increasing at faster at rate than the changes in extremes in day temperature.

Daily Maximum Temperature in a calendar year in base line, a2 and change

Revadekar et al., 2012, Natural Hazards

Lowest minimum temperture Both A2 and B2 scenarios show similar patterns of projected changes in the mean climate and extremes towards the end of 21st century. However, B2 scenario shows slight lower magnitudes of the projected changes than that of A2 scenarios. Similar features are seen other intensity indices also

Annual cycle in Coldest night temperature and the changes :

Scenarios for 1-day and 5-day maximum. precipitation

International Conference on "Celebrating the Monsoon", 24-28 July 2007, Bangalore, India 22

IMPACT OF EXTREMES ON FOOD GRAIN OVER INDIA

PRECIPITATION EXTREMES & FOOD GRAIN

Revadekar & Preethi, 2012, Int. J. Climatology

RELATIONSHIP BETWEEN PRECIPITATION EXTREMES & FOOD GRAIN

Revadekar & Preethi, 2012, Int. J. Climatology

EXTREMES & FOOD GRAIN

Preethi & Revadekar, 2013, Int. J. Climatology

Elevation dependency of Extremes

Recent studies suggested a more sensitive response to global warming at higher elevation. High elevation stations are more directly in contact with the free troposphere than low-elevation The snow-albedo feedback can also provide a strong elevation dependent forcing Snow is depleted at high altitude under warming conditions More solar radiation absorbed at the high elevation surface enhance warming

Elevation dependency of Extremes

Revadekar et al, 2013, Int. J. Climatology (APN Project outcome)

Recent study : Reconstruction of past extremes Using proxy data