Climate Change & Indian Climate Change & Indian

Monsoon Monsoon : Some Key Issues: Some Key Issues

B. N. GoswamiB. N. Goswami(goswami@tropmet.res.in)(goswami@tropmet.res.in)

Indian Institute of Tropical Meteorology, Indian Institute of Tropical Meteorology, PunePune

What is the Indian Summer Monsoon?

A manifestation of seasonal northward migration of the Rain Band or

Tropical Convergence Zone (TCZ)

Long term mean

JJA precipitation and

DJF precipitation

Monsoon ?

Wet- summer

Dry - winter

Characteristic features of summer monsoon circulation

Low level, cross-equatorial flow, south-westerlies, westerly jet in Arabian sea

Upper level easterlies, Monsoon Easterly Jet

Deep Baroclinic vertical

structure

All India Rainfall (AIR)

JJAS Mean

Interannual Variability

AIR Mean : 86 cm

AIR S.D. : 8.6 cm

No increasing trend in Monsoon rainfall past No increasing trend in Monsoon rainfall past 100 yrs.100 yrs.

Global mean temperatures are rising faster with timeGlobal mean temperatures are rising faster with time

150 0.0450.012100 0.0740.018

50 0.1280.026 25 0.1770.052

Warmest 12 years:1998,2005,2003,2002,2004,20

06, 2001,1997,1995,1999,1990,20

00

Period Rate

Years /decade

IPCC

Trend in temp. is similar to global temp. Trend in temp. is similar to global temp. trend. Much faster during past 50 yearstrend. Much faster during past 50 years

Annual Annual mean mean Temp. Temp. over over IndiaIndia

1875-1875-20042004

Indian Ocean Indian Ocean temperature temperature also shows also shows warming warming trend trend

All India Rainfall (AIR)

Interannual Variability

No increasing trend in Monsoon rainfall past No increasing trend in Monsoon rainfall past 100 yrs.100 yrs.

Questions : Questions :

Why is the mean Indian Summer Why is the mean Indian Summer Monsoon rainfall not increasing Monsoon rainfall not increasing with increasing temperature due with increasing temperature due to Climate Change?to Climate Change?

Is there some aspects of the Indian Is there some aspects of the Indian monsoon clearly affected by monsoon clearly affected by Climate Change?Climate Change?

BlueBlue : : 1950-1950-19701970

RedRed : : 1980-1980-20002000

Time series of count over CI

Low & Moderate events

Heavy events (>10cm)

V. Heavy events (>15cm)

Goswami et al. 2006, Goswami et al. 2006, Science, 314, 1442Science, 314, 1442

Why no trend in the seasonal mean ?

Global Warming makes Indian Global Warming makes Indian Monsoon Weather Less Predictable!Monsoon Weather Less Predictable!

Higher level of saturation of errors in the Higher level of saturation of errors in the high frequency events would cascade high frequency events would cascade larger errors to weather scale and could larger errors to weather scale and could decrease the predictability of monsoon decrease the predictability of monsoon weatherweather

Neena Joseph Mani, E. Suhas and B. N. GoswamiNeena Joseph Mani, E. Suhas and B. N. GoswamiGeophys.Res. Letts (2009)Geophys.Res. Letts (2009)

• Used the daily gridded data set prepared by Used the daily gridded data set prepared by Rajeevan et al. 2008, Geophys. Res. Lett. Rajeevan et al. 2008, Geophys. Res. Lett. Between 1901-2004Between 1901-2004

• And calculated the Lyapunov Exponents over And calculated the Lyapunov Exponents over different 26 year periodsdifferent 26 year periods

Error doubling Time for the last two quarters (1953-1978 and 1979-2004)

(18N-27N, 73E -85E)

Long Time series ----combined time series of all the grid points in the 3°× 4° boxes. That is, for each quarter we used a time series of length 57408

• Used the daily gridded Used the daily gridded data set prepared by data set prepared by Rajeevan et al. 2008, Rajeevan et al. 2008, Geophys. Res. Lett. Geophys. Res. Lett. Between 1901-2004Between 1901-2004

• And calculated the And calculated the Lyapunov Exponents Lyapunov Exponents over different 26 year over different 26 year periodsperiods

• Error doubling time Error doubling time averaged over central averaged over central India in four different India in four different quarters (solid) and quarters (solid) and number of extreme rainfall number of extreme rainfall events (>15 cm/dayevents (>15 cm/day))

• Error doubling time Error doubling time averaged over central averaged over central India in 3 different 30-year India in 3 different 30-year periods (solid) and periods (solid) and number of extreme rainfall number of extreme rainfall events (>15 cm/dayevents (>15 cm/day))

• Average CAPE (solid) and Average CAPE (solid) and CINE (dashed) over CINE (dashed) over Central India during the Central India during the period calculated from period calculated from NCEP reanalaysisNCEP reanalaysis

What it meansWhat it means

A lower error doubling time means A lower error doubling time means decrease in the potential predictability of decrease in the potential predictability of monsoon weather. monsoon weather. The monsoon weather The monsoon weather has become almost twice as difficult to has become almost twice as difficult to predict! predict!

Thus, effective predictions would demand a Thus, effective predictions would demand a quantum leap in improvement of quantum leap in improvement of observations and prediction models and observations and prediction models and high computational power.high computational power.

Questions : On Projections of MonsoonQuestions : On Projections of Monsoon

What will happen to the monsoon What will happen to the monsoon hydrological cycle 50-100 years from hydrological cycle 50-100 years from now under different scenarios? In now under different scenarios? In particular, will the quantum of seasonal particular, will the quantum of seasonal mean rainfall increase or decrease and if mean rainfall increase or decrease and if so by how much?so by how much?

What is the uncertainty in these What is the uncertainty in these projections? Can we quantify this projections? Can we quantify this uncertainty?uncertainty?

How can we reduce this uncertainty?How can we reduce this uncertainty?

Future Scenarios Future Scenarios for Summer for Summer Monsoon Rainfall Monsoon Rainfall and Annual and Annual Temperature over Temperature over South Asia under South Asia under A2 Scenario (High A2 Scenario (High Emissions)Emissions)based on IPCC AR4 based on IPCC AR4 Simulations of Simulations of AOGCMsAOGCMs(Anomalies relative to (Anomalies relative to

current period)current period) Model spread-a Model spread-a rough measure of rough measure of uncertaintyuncertainty

South Asia

Kripalani et al. 2007, Theor. Appl. Clmatol. Kripalani et al. 2007, Theor. Appl. Clmatol.

South Asia

Kripalani et al. 2007, Theor. Appl. Clmatol. Kripalani et al. 2007, Theor. Appl. Clmatol.

What is our confidence level that What is our confidence level that Indian monsoon will be stronger with Indian monsoon will be stronger with increasing GHG and global warming?increasing GHG and global warming?

None whatsoever!!None whatsoever!!

In fact, just the opposite may be In fact, just the opposite may be possible, namely monsoon may even possible, namely monsoon may even go to a perpetual drought state!!go to a perpetual drought state!!

Rignot et al. GRL, Rignot et al. GRL, 20082008

Melting of Greenland Ice due to Global

Warming

PersistentWeak

Monsoon

Fresh water addition to North Atlantic

Ocean

Weakening of Atlantic Thermohaline

Circulation

Weak north-southAtmos. Temp. Gradient over Indian Longitudes

Climate on a threshold!

Monsoon may tip to a persistent drought phase!

Back

Mean=5.2 Mean=5.2 mm/daymm/day

S.D. =14.7% S.D. =14.7% meanmean

LTA monsoon rainfall (JJAS) decreases by LTA monsoon rainfall (JJAS) decreases by 20%!20%!

• 100 year simulation with fresh water in NA and 100 year simulation with fresh water in NA and comparison with Control.comparison with Control.

• Monsoon will remain in a perpetual drought state!Monsoon will remain in a perpetual drought state!

Projections of monsoon under climate changeProjections of monsoon under climate change

scenarios by current climate models are not scenarios by current climate models are not reliable!reliable!

Because current climate models are unable to Because current climate models are unable to simulate the present mean monsoon climate simulate the present mean monsoon climate

and its variability with fidelityand its variability with fidelity

Wavenumber-frequency spectra of twice daily OLR in tropics showing Kelvin, Rossby and MRG waves (Wheeler and Kiladis, JAS,1999, vol.56,374pp)

Space-time spectra Space-time spectra of tropical waves of tropical waves from symmetric from symmetric component of component of precipitation precipitation simulated by some simulated by some AR4 models AR4 models

Observations usedObservations used

• GPI- Global Precip GPI- Global Precip Index, 2.5 x 2.5 Index, 2.5 x 2.5 resolution, mostly resolution, mostly based on IR databased on IR data

• 1DD- GPCP daily 1DD- GPCP daily precip at 1 x 1 precip at 1 x 1 resolution based resolution based both IR and both IR and microwave datamicrowave data

Lin et al. 2006, J. Lin et al. 2006, J. ClimateClimate

NICANICAM M

Obs.Obs. (Takayabu et al. 1999)(Takayabu et al. 1999)NICAM (7-km)NICAM (7-km)

Matsuno (AMS, 2007)

Cloud distribution simulated by ECMWF forecast model on a Cloud distribution simulated by ECMWF forecast model on a given daygiven day

Tools required for reliable answer to Regional Tools required for reliable answer to Regional Climate Change Questions: Climate Change Questions:

Atmosphere GCMAtmosphere GCM

With Stratospheric With Stratospheric Chemistry, Chemistry, Aerosol , Aerosol , Dynamic Dynamic vegetation, vegetation, resolve trop. resolve trop. Meososcale Meososcale cloudsclouds

Ocean GCMOcean GCM

With With biogeochemistbiogeochemistry modelry model

Carbon Carbon Cycle Cycle ModelModel

What kind of resolution may be required? What kind of resolution may be required?

Atmosphere Atmosphere GCMGCM

10 km global 10 km global

50 levels in 50 levels in verticalvertical

Ocean GCM 1/3 x Ocean GCM 1/3 x 11OO near equator near equator and 1and 1OO x1 x1OO outside 10outside 10OO

50 levels in 50 levels in verticalvertical

Carbon Carbon Cycle Cycle ModelModel

• Multicentury integration with such a model is Multicentury integration with such a model is requiredrequired

• Computation requirements: dedicated machines Computation requirements: dedicated machines with with PetaflopsPetaflops crunching capabilities!! crunching capabilities!!

What are crucial What are crucial requirements?requirements?

Must simulate the present global Must simulate the present global climate and Indian monsoon well!climate and Indian monsoon well!

The computing requirements The computing requirements mentioned earlier is a pre-requisite, mentioned earlier is a pre-requisite, but does not guarantee that the but does not guarantee that the high resolution coupled model will high resolution coupled model will simulate the present Climate and simulate the present Climate and Indian monsoon wellIndian monsoon well

A lot of intensive research with such A lot of intensive research with such computing facility will be required!computing facility will be required!

In India, Where do we stand In India, Where do we stand today?today?

With the help of MoESWith the help of MoES, c, computer infrastructure omputer infrastructure is improving rapidly. However, it is still sub-is improving rapidly. However, it is still sub-critical. We are talking about 1000 times larger critical. We are talking about 1000 times larger than the best presently available capacity!than the best presently available capacity!

Arrival of NKN is timely and will help. Arrival of NKN is timely and will help.

However, climate modeling community in India However, climate modeling community in India is very small, not quite ready for modeling is very small, not quite ready for modeling required for climate change!required for climate change!

Focused Capacity Building (training) urgently Focused Capacity Building (training) urgently required to create a pool of expert climate required to create a pool of expert climate system modelerssystem modelers

Strategy at CCCR, IITMStrategy at CCCR, IITM On Capacity Building On Capacity Building

Recruit new climate scientists, modelersRecruit new climate scientists, modelersRun a sustained in-house Training ProgramRun a sustained in-house Training ProgramGet some selected young scientists trained at Get some selected young scientists trained at Centres of excellenceCentres of excellence

On Estimation of Uncertainty of Projections of On Estimation of Uncertainty of Projections of MonsoonMonsoon

First, we shall do this using multiple projections with a First, we shall do this using multiple projections with a number of regional models with a number of global number of regional models with a number of global model B.Csmodel B.Cs

On reduction of uncertainty of Projections and On reduction of uncertainty of Projections and Model DevelopmentModel DevelopmentDevelop a global coupled climate model with about Develop a global coupled climate model with about 50 km resolution whose monsoon climate is close to 50 km resolution whose monsoon climate is close to observationsobservationsMake ensemble of projections with such a modelMake ensemble of projections with such a model

Thank Thank You !You !

UnprecedenteUnprecedented fast d fast Variations in Variations in recent pastrecent past

Basic energy spectrum (thick curve) and Basic energy spectrum (thick curve) and error energy spectrum (thin curves)error energy spectrum (thin curves)

Lorenz 1969

Predictability limit in any scale is the time required for the error to propagate “upscale” from very, very small initial scale to that scale and become as large as the variance in that scale.

South Asia

Kripalani et al. 2007, Theor. Appl. Clmatol. Kripalani et al. 2007, Theor. Appl. Clmatol.

Space-time spectra of Space-time spectra of tropical waves from tropical waves from anti-symmetric anti-symmetric component of component of precipitation precipitation simulated by some simulated by some AR4 models AR4 models