heartland conference on climate change chicago may 21-23 2012 indian monsoon variability &...

Heartland Conference on Climate Change Chicago May 21-Heartland Conference on Climate Change Chicago May 21-23 201223 2012

Indian Monsoon Variability & Indian Monsoon Variability & Global WarmingGlobal Warming

Madhav Khandekar CANADAMadhav Khandekar CANADA

Expert Reviewer IPCC 2007 Climate Expert Reviewer IPCC 2007 Climate Change Change

Heartland Conference on Climate ChHeartland Conference on Climate Change Chicago May 21-23 2012ange Chicago May 21-23 2012

AbstractAbstract

An analysis of Indian Summer An analysis of Indian Summer Monsoon Rainfall (ISMR) reveals that Monsoon Rainfall (ISMR) reveals that droughts and floods have occurred droughts and floods have occurred irregularly throughout a 200-year irregularly throughout a 200-year long excellent dataset with NO Link long excellent dataset with NO Link to “global warming OR climate to “global warming OR climate change” at this point in time.change” at this point in time.


Monsoon: General NotesMonsoon: General Notes

Indian/Asian monsoon is the largest seasonal abnormality in Indian/Asian monsoon is the largest seasonal abnormality in the global climate systemthe global climate system

Indian/Asian monsoon affects about 4 billion people of Indian/Asian monsoon affects about 4 billion people of south Asia. Timely arrival and well distributed rainfall during south Asia. Timely arrival and well distributed rainfall during the summer season (May-October) is critical for the summer season (May-October) is critical for agriculturally dominated countries of south Asia.agriculturally dominated countries of south Asia.

Climate models have achieved only a limited success so far Climate models have achieved only a limited success so far in simulating many features of global and regional in simulating many features of global and regional monsoon. Most climate models project monsoon circulation monsoon. Most climate models project monsoon circulation to intensify in a warmer future climate. In reality, Monsoon to intensify in a warmer future climate. In reality, Monsoon circulation has weakened in the last fifty years. circulation has weakened in the last fifty years.


Basic Facts on Indian Summer Basic Facts on Indian Summer Monsoon Monsoon

1.1. Summer (June-September) rains most important for whole Summer (June-September) rains most important for whole of India for agriculture & water supplyof India for agriculture & water supply

2.2. Mean rainfall ~90 cm; On west coast ( Mumbai-Goa-Mean rainfall ~90 cm; On west coast ( Mumbai-Goa-Kerala Coast)~ 150-200 cm; central India ~100-125 cm; Kerala Coast)~ 150-200 cm; central India ~100-125 cm; northwest India ~50 cmnorthwest India ~50 cm

3.3. Monsoon onset on west coast tip of India ~June 7Monsoon onset on west coast tip of India ~June 7thth

4.4. Despite year-to-year variability, this onset date is robust: Despite year-to-year variability, this onset date is robust: Over Bay of Bengal & northeast, monsoon arrival ~1-12 Over Bay of Bengal & northeast, monsoon arrival ~1-12 JuneJune

5.5. By 25 June, monsoon spreads over most of India By 25 June, monsoon spreads over most of India


Highest/Lowest RainfallHighest/Lowest Rainfall

Highest One Year Rainfall: Cherrapunji 2646 cmHighest One Year Rainfall: Cherrapunji 2646 cm Aug 1860- July 1861Aug 1860- July 1861

Highest One Month Rainfall: Cherrapunji 930 cm Highest One Month Rainfall: Cherrapunji 930 cm July 1861July 1861

Highest 2-day Rainfall: 41 in ( ~105 cm) Mumbai Highest 2-day Rainfall: 41 in ( ~105 cm) Mumbai July 2005July 2005

Lowest seasonal Rainfall: 33mm (1918), 49mm (1899) in West Lowest seasonal Rainfall: 33mm (1918), 49mm (1899) in West Rajasthan: Both the years ( 1899 &1918 ) were severe drought Rajasthan: Both the years ( 1899 &1918 ) were severe drought years over whole of Indiayears over whole of India


Major drought years 1868, 1877, 1899, 1918, 1951, 1972, 1987

Major Flood Years 1892, 1917, 1933, 1961, 1970, 1975


Large-scale controls of Indian Large-scale controls of Indian MonsoonMonsoon

ENSO phase in the equatorial Pacific (El Nino linked to ENSO phase in the equatorial Pacific (El Nino linked to drought)drought)

Eurasian snow cover, previous winter (Heavy snow cover Eurasian snow cover, previous winter (Heavy snow cover weakens monsoon)weakens monsoon)

Equatorial stratospheric wind oscillation (QBO: quasi-Equatorial stratospheric wind oscillation (QBO: quasi-biennial oscillation)biennial oscillation)

Indian Ocean Dipole (IOD)Indian Ocean Dipole (IOD)

These large-scale controls and their various phases, produce These large-scale controls and their various phases, produce major droughts/floods in summer monsoon major droughts/floods in summer monsoon


Depressions traveling along Monsoon trough

Regional controls of Monsoon

Low Pre

ssure

s strength

en w

estcoast rain

Axis of Monsoon trough

Weste

rn G

hats


ENSO (El Nino-Southern Oscillation) phases in the equatorial Pacific


The 1997/98 El Nino structure at about Sep 1997


Equatorial stratospheric wind oscillation (QBO) at ~20-22 km levelwith about 26-month (east-west) period.


A schematic of Indian Ocean Dipole (IOD)Positive phase: warmer SSTs in west equatorial oceanNegative phase: warmer SSTs in east equatorial ocean


Eurasian winter snow coverEurasian winter snow cover

Blanford (1884) first identified adverse impact of Blanford (1884) first identified adverse impact of heavy winter snow cover on subsequent monsoon heavy winter snow cover on subsequent monsoon rainsrains

Sir Gilbert Walker used snow cover as one of the Sir Gilbert Walker used snow cover as one of the important parametersimportant parameters

Barnett et al (1989) simulated snow/monsoon Barnett et al (1989) simulated snow/monsoon adverse relationship using climate modelsadverse relationship using climate models

In general, heavier snow cover produces weaker In general, heavier snow cover produces weaker monsoon and vice-versamonsoon and vice-versa


This jet (peak winds ~100 knots at 15 km level) is due to reversal of north-south temperature gradient. The jet disappears by October.


Indian monsoon exhibits decadal variability and is not influenced by Global Warming at this time

Indian Monsoon Rainfall standardized values 1871-2001 (Top)Cramer’s t-statistic for 11-year running mean depicting decadalvariability and epochs (Bottom)


Major floods/droughts (1813-Major floods/droughts (1813-2010)2010) FLOODSFLOODS

1818 (1036 mm)1818 (1036 mm)

1861 (1051 mm)1861 (1051 mm)

1874 (1033 mm)1874 (1033 mm)

1878 (1039 mm)1878 (1039 mm)

1892 (1050 mm)1892 (1050 mm)

1894 (1032 mm)1894 (1032 mm)

1916 (1034 mm)1916 (1034 mm)

1917 (1079 mm)1917 (1079 mm)

1933 (1042 mm)1933 (1042 mm)

1942 (1037 mm)1942 (1037 mm)

1956 (1007 mm)1956 (1007 mm)

1961 (1088 mm)—1961 (1088 mm)—Most Severe FloodMost Severe Flood

1971 (1002 mm)1971 (1002 mm)

1988 (1047 mm)1988 (1047 mm)

DROUGHTSDROUGHTS 1823 (795 mm)1823 (795 mm) 1824 (770 mm)1824 (770 mm) 1832 (775 mm)1832 (775 mm) 1840 (774 mm)1840 (774 mm) 1844 (788 mm)1844 (788 mm) 1848 (688 mm)1848 (688 mm) 1851 (744 mm)1851 (744 mm) 1860 (733 cm)1860 (733 cm) 1864 (748 mm)1864 (748 mm) 1868 (777 mm)1868 (777 mm) 1877 (609 mm)—Most Severe Drought1877 (609 mm)—Most Severe Drought 1899 (695 mm)1899 (695 mm) 1918 (661 mm)1918 (661 mm) 1920 (786 mm)1920 (786 mm) 1941 (785 mm)1941 (785 mm) 1965 (741 mm)1965 (741 mm) 1972 (708 mm)1972 (708 mm) 1979 (723 mm)1979 (723 mm) 1982 (788 mm)1982 (788 mm) 1986 (780 mm)1986 (780 mm) 1987 (739 mm)1987 (739 mm) 2002 (715 mm)2002 (715 mm) 2009 (698 mm)2009 (698 mm)

Mean 1041mm Mean 739 mm


IPCC 2007: Global temperature declined between 1945-77, presentWarming since 1980 to 2005


Summer Monsoon Variability:Summer Monsoon Variability:1951-1975 vs 1981-20051951-1975 vs 1981-2005

1951-1975 1951-1975 4 floods, 3 droughts4 floods, 3 droughts Mean rainfall:917 mmMean rainfall:917 mm Only 8 years below Only 8 years below

normalnormal

1981-20051981-2005 2 floods, 4 droughts 2 floods, 4 droughts Mean rainfall:888 mmMean rainfall:888 mm 12 years below normal 12 years below normal 2 years close to 2 years close to

normalnormal

Summer monsoon was stronger during 1951-75, weaker in recent years in a warming climate


IOD Indian Ocean DipolePositive phase

IOD Indian Ocean DipoleNegative phase

Drought

Flood


Severe Drought


Floods in Pakistan and NW India


Summary & ConclusionsSummary & Conclusions Indian Monsoon is a robust system and its inter-annual variability is governed Indian Monsoon is a robust system and its inter-annual variability is governed

by large-scale atmosphere-ocean patterns.by large-scale atmosphere-ocean patterns.

Droughts/floods have occurred irregularly throughout a 200-year long Droughts/floods have occurred irregularly throughout a 200-year long dataset.dataset.

Indian Monsoon appears to exhibit a decadal variability with approximately Indian Monsoon appears to exhibit a decadal variability with approximately 30-year period of above/below rainfall. 30-year period of above/below rainfall.

Indian (and by extension Asian) monsoon is NOT impacted at this time by the Indian (and by extension Asian) monsoon is NOT impacted at this time by the modest warming of the earth’s climate. Indian and global monsoon modest warming of the earth’s climate. Indian and global monsoon circulations have weakened, in general, in the last 30 years or so. circulations have weakened, in general, in the last 30 years or so.

A conceptual drought/flood model of Indian Monsoon based on selected A conceptual drought/flood model of Indian Monsoon based on selected large-scale indices can help predict future droughts and floods with a lead large-scale indices can help predict future droughts and floods with a lead time of few weekstime of few weeks

heartland conference on climate change chicago may 21-23 2012 indian monsoon variability &...

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