Transcript Powerpoint slides here

Indian Monsoon Variability &
Climate Change
Madhav Khandekar, CANADA
Expert Reviewer IPCC 2007 Climate Change
September 15, 2015
1
GWPF UK Presentation
Short Abstract
An analysis of Indian Summer Monsoon
Rainfall (ISMR) reveals that droughts and
floods have occurred irregularly throughout
a 200-year long excellent dataset with NO
Link to “global warming OR climate change”
at this point in time.
GWPF UK Presentation
2
September 15, 2015
Monsoon: General Notes
Indian/Asian monsoon is the largest seasonal abnormality in the global
climate system
Indian/Asian monsoon affects about 4 billion people of south Asia.
Timely arrival and well distributed rainfall during the summer season
(May-October) is critical for agriculturally dominated countries of south
Asia.
Climate models have achieved only a limited success so far in
simulating many features of global and regional monsoon. Most climate
models project monsoon circulation to intensify in a warmer future
climate. In reality, Monsoon circulation has weakened in the last fifty
years.
GWPF UK Presentation
3
September 15, 2015
Basic Facts on Indian Summer
Monsoon
1.
2.
3.
4.
5.
Summer (June-September) rains most important for whole of
India for agriculture & water supply
Mean rainfall ~90 cm; On west coast ( Mumbai-Goa-Kerala
Coast)~ 150-200 cm; central India ~100-125 cm; northwest India
~50 cm
Monsoon onset on west coast tip of India ~June 7th
Despite year-to-year variability, this onset date is robust: Over
Bay of Bengal & northeast, monsoon arrival ~1-12 June
By 25 June, monsoon spreads over most of India
GWPF UK Presentation
4
September 15, 2015
Cherapunji
September 15, 2015
5
GWPF UK Presentation
Highest/Lowest Rainfall
Highest One Year Rainfall: Cherrapunji 2646 cm
Aug 1860- July 1861
Highest One Month Rainfall: Cherrapunji 930 cm
July 1861
Highest 2-day Rainfall: 41 in ( ~105 cm) Mumbai
July 2005
Lowest seasonal Rainfall: 33mm (1918), 49mm (1899) in West Rajasthan: Both
the years ( 1899 &1918 ) were severe drought years over whole of India
GWPF UK Presentation
6
September 15, 2015
Seasonal Forecasting
Historical Notes
Sir Gilbert Walker’s pioneering research on correlation
with worldwide weather elements led to first operational
forecast issued in 1906.
Walker’s work was extended to include various regional
and worldwide land/ocean parameters. Present seasonal
forecasting algorithm includes five or more such
parameters.
Walker’s work was analyzed by Jacob Bjerknes, who
envisaged an east-west circulation in the equatorial
vertical plane and named it as “Walker’s Circulation”
in
GWPF
UK
Presentation
7
September 15, 2015
1969.
Regional controls of Monsoon
Depressions traveling along Monsoon trough
September 15, 2015
8
GWPF UK Presentation
Large-scale controls of Indian
Monsoon
ENSO phase in the equatorial Pacific (El Nino linked to drought)
Eurasian snow cover, previous winter (Heavy snow cover weakens
monsoon)
Equatorial stratospheric wind oscillation (QBO: quasi-biennial
oscillation)
Indian Ocean Dipole (IOD)
These large-scale controls and their various phases, produce major
droughts/floods in summer monsoon
GWPF UK Presentation
9
September 15, 2015
September 15, 2015
10
GWPF UK Presentation
The 1997/98 El Nino structure at about Sep 1997
September 15, 2015
11
GWPF UK Presentation
Eurasian winter snow cover
Blanford (1884) first identified adverse impact of heavy
winter snow cover on subsequent monsoon rains
Sir Gilbert Walker used snow cover as one of the important
parameters
Barnett et al (1989) simulated snow/monsoon adverse
relationship using climate models
In general, heavier snow cover produces weaker monsoon
and vice-versa
GWPF UK Presentation
12
September 15, 2015
A schematic of Indian Ocean Dipole (IOD)
Positive phase: warmer SSTs in west equatorial ocean
Negative phase: warmer SSTs in east equatorial ocean
September 15, 2015
13
GWPF UK Presentation
Quasi-Biennial Oscillation (QBO) at Equatorial Stratosphere
September 15, 2015
14
GWPF UK Presentation
This jet (peak winds ~100 knots at 15 km level) is due to reversal
of north-south temperature gradient. The jet disappears by October.
September 15, 2015
15
GWPF UK Presentation
Decadal and longer-scale variability in Monsoon
September 15, 2015
16
GWPF UK Presentation
Indian Monsoon Rainfall standardized values 1871-2001 (Top)
Cramer’s t-statistic for 11-year running mean depicting decadal
variability and epochs (Bottom)
Indian monsoon exhibits decadal variability
and is not influenced by Global Warming at
this time
September 15, 2015
17
GWPF UK Presentation
20y running average of summer monsoon showing ~ 60y cycles
September 15, 2015
solar cycles ?18
GWPF UK Presentation
Major Flood Years 1892, 1917, 1933, 1961, 1970, 1975
Major drought years 1868, 1877, 1899, 1918, 1951, 1972, 1987
September 15, 2015
19
GWPF UK Presentation
Conceptual flow model for drought and flood
Drought
IOD Indian Ocean Dipole
Negative phase
Flood
Indian Ocean Dipole
September 15,IOD
2015
Positive phase
20
GWPF UK Presentation
Recent summer Monsoon performance
During Years, 2009, 2010, 2015
September 15, 2015
21
GWPF UK Presentation
Major Drought
September 15, 2015
22
GWPF UK Presentation
2010 surplus with flooding in Pakistan
September 15, 2015
23
GWPF UK Presentation
Monsoon 2015
Most climate models had projected a major drought by
mid-May 2015.
So far, Monsoon 2015 is below normal BUT NOT A
MAJOR DROUGHT
Heavy rains in third week of June and later end of July
produced localized flooding
In Mumbai and in northern States and also in nearby
Bangladesh and Myanmar/Burma.
Once again, Monsoon has defied model projections
GWPF UK Presentation
September 15, 2015
24
September 15, 2015
25
GWPF UK Presentation
Mumbai Suburban Scene June 23-24 2015
September 15, 2015
26
GWPF UK Presentation
Satellite map after cyclone Komen over Bangladesh
September 15, 2015
27
GWPF UK Presentation
Flooding in North India
First Week of August 2015
September 15, 2015
28
GWPF UK Presentation
September 15, 2015
29
GWPF UK Presentation
Summary & Conclusions
Indian Monsoon is a robust system and its inter-annual variability is governed
by large-scale atmosphere-ocean patterns.
Droughts/floods have occurred irregularly throughout a 200-year long dataset.
Indian Monsoon appears to exhibit a decadal variability with approximately 30year period of above/below rainfall. Also a 60-year cycle is identified
suggesting a possible SOLAR LINK.
Indian monsoon is NOT impacted by ‘Global Warming’ or climate change.
Indian and global monsoon circulations have weakened in the last 30 to 50
years.
A conceptual flow model of Indian Monsoon based on selected large-scale
indices can help predict Monsoon droughts and floods with a lead time of few
weeks or longer.
GWPF UK Presentation
30
September 15, 2015