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Promises and Prospects for Predicting the South Asian Monsoon
Jim Kinter
COLAGeorge Mason University
Special Symposium on the South Asia MonsoonAmerican Meteorological Society Annual Meeting
Phoenix, Arizona :: 8 January 2015
Many Thanks To: Rodrigo Bombardi, Paul Dirmeyer, Mike Fennessy, Bohua Huang,
Subhadeep Halder, Ed Schneider, J. Shukla, Chul-Su Shin, Bohar Singh
Figure credit: National Geographic © 2002
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
South Asian Monsoon
– One of largest variations of seasonal to interannual climate observed on Earth
– Affects lives, property and (largely agrarian) economies
of countries inhabited by nearly 25% of human population …
– Current state of the science• Rudimentary understanding of monsoon dynamics• Extremely limited ability to predict monsoon variations
South Asian Monsoon
– One of largest variations seasonal to interannual climate observed on Earth
– Rudimentary understanding of the monsoon remains
– Extremely limited ability to predict monsoon variations
– Affects lives, property and (largely agrarian) economies of countries inhabited by nearly 20% of human population
… either by monsoon flood …
…or by monsoon drought
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
South Asian Monsoon
– One of largest variations seasonal to interannual climate observed on Earth
– Affects lives, property and (largely agrarian) economies
of countries inhabited by nearly 25% of human population
– Current state of the science• Rudimentary understanding of monsoon dynamics• Demonstrable predictability of monsoon seasonal rainfall• Limited ability to actually predict monsoon variations
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
F-values for JJAS precip. based on DEMETER data. Gray color indicates not statistically significant at 95% confidence interval (F < 1.4).
Thanks to J. Shukla & M. Fennessy
F as a Measure of Predictability in DEMETER
(5 CGCMs, 9 members, 46 years)
Monsoon Rainfall is Predictable
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
CFSv2 Reforecasts of JJAS EIMR Precip
February IC:
Ensemble Mean (24)Bias = -1.48 mm/dACC = 0.52RMSE = 0.33 mm/d
May IC:
Ensemble Mean (24)Bias = -0.78 mm/dACC = 0.62RMSE = 0.30 mm/d
Monsoon Rainfall Prediction: Only Moderate Skill
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
National Monsoon Mission of India and COLA Joint Research to Enhance Monsoon Prediction
Ocean-Land-Atmosphere Coupling and Initialization Strategies to Improve CFSv2 and Monsoon Prediction– Sponsored by Ministry of Earth Sciences, Government of India– Improve the coupled ocean-land-atmosphere model (CFSv2)
performance.– Improve initialization of ocean and land states in the pre-
monsoon season to improve forecasts of onset, monsoon season precipitation.
– Improve representation of land-atmosphere feedback in monsoon-dominated regions
– Focus on CFSv2 as baseline model
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
Climate Forecast System version 2 (CFSv2)
• Global coupled model: Atmosphere, Ocean, Land Surface, Sea Ice
• Atmosphere: based on the NCEP Global Forecast System (GFS) used for global numerical weather prediction– spectral discretization at T126 resolution (about 100 km grid spacing)– 64 levels in the vertical
• Ocean: Geophysical Fluid Dynamics Laboratory (GFDL) Modular Ocean Model version 4 (MOM4) – 1/2° horizontal grid spacing; 1/4° meridional grid spacing in the tropics– 40 vertical levels
• Land Surface: Noah (GFS grid)
• Sea Ice: a modified version of the GFDL Sea Ice Simulator (MOM4 grid)
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
ROLE OF ATMOSPHERIC CONVECTION
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
Convective Cloud Parameterization:The Simplified Arakawa-Schubert (SAS) Scheme
Deep ConvectionTrigger Mechanism:
Level of free convection (LFC) [for parcel with no sub-cloud level entrainment] being within 150-hPa of convection starting pointSource: MetEd
http://www.meted.ucar.edu/nwp/pcu2/avncp1.htm
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
Evap Sensible
Heated Condensation Framework (HCF)
• Quantifies how close atmosphere is to moist convection• Does not require parcel selection
• Uses typically measured quantities (needs only q and θ profiles)
• Is “conserved” diurnally• Can be used any time of year or any time of day and interpretation
stays the same
(Tawfik and Dirmeyer 2014 GRL)
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
Evap Sensible
Threshold Variables:
BCL = Buoyant Condensation Level [m]θBM = Buoyant mixing temperature [K]
Heated Condensation Framework
(Tawfik and Dirmeyer 2014 GRL)
Convection is initiated when:PBL intersects BCL
θ2m reaches θBM
New trigger mechanism for deep convection
Original SAS criterion (150-hPa pressure difference).OR.
Condensation due to mixing (HCF)
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
Experiments:
• Seasonal hindcasts
• Four member per year (1998 – 2010)
• From April to October starting on April 1,2,3, and 4
• With (HCF) and without (CTRL) the new trigger
Thanks to Rodrigo BombardiMonthly Accumulated Precip. (mm)
OBS
CTL
Thanks to Rodrigo Bombardi
JJASPrecipitation
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
JJAS Seasonal Precipitation
Thanks to Rodrigo Bombardi
Mean StDev
Improvement of seasonal variability
Small but significant improvementof seasonal total
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
Rainy Season
Improved seasonal cycle of precipitation
Improved rainy season onset dates.
Thanks to Rodrigo Bombardi
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
Mechanisms
The new trigger is an alternative condition
• Better representation of the background state of convection
• SAS triggers more frequently
Small improvement in the right direction
Central India: 16.5-26.5oN, 74.5-86.5oE Thanks to Rodrigo Bombardi
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
OCEAN INITIALIZATION
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
Multiple Ocean Initial Conditions (OICs) for CFSv2
1. Four different ocean data sets• ECMWF Combine-NV (NEMO)
• NCEP CFSR (Climate Forecast System Reanalysis)
• ECMWF ORA-S3 (Ocean Reanalysis System3)
• NCEP GODAS (Global Ocean data Assimilation System)
2. Variables • Monthly mean potential temperature[°C], salinity[g/kg], u[m/s], v[m/s]
3. Pre-Processing• Filling up (extrapolation) the land mass to make up potential gaps due to
different land-sea masks between each ocean analysis and MOM4 (Note that zonal mean of each variable is initially assigned to grids over the land as an initial guess.)
4. Period: 1979-2009 (Jan. – May)
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
OICs
Initial monthNEMO
(4mem*30yrs)CFSR
(4mem*31yrs)ORA-S3
(4mem*31yrs)GODAS
(4mem*31yrs)
May(5-month lead)
April(6-month lead)
March(7-month lead)
February(8-month lead)
January(9-month lead)
* 4 members : 1st 4 days (00Z) of each month using the atmosphere/land surface conditions from CFSR
600 runs completed
620 runscompleted
620 runscompleted
620 runs completed
CFSv2 Retrospective Forecasts with 4 OICs
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
NEMOCFSR
ORA-S3GODAS
ES_MEAN
JAN ICs FEB ICs MAR ICs
CFSv2 Prediction Skill of NINO3.4 (1982-2008) vs. OISST
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
NEMOCFSR
ORA-S3GODAS
ES_MEAN
APR ICs MAY ICs
CFSv2 Prediction Skill of NINO3.4 (1982-2008) vs. OISST
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
Multiple Ocean Analyses Ensemble Mean
CFSv2 Prediction Skill of NINO3.4 (1982-2008) vs. OISST
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
corresponds to ENSO onset years
corresponds to ENSO decay years
(1979 – 2008; linear trend removed)
2 Dominant Modes of JJAS mean Precip
CFSv2
CMAP
1st EOF Mode
Correlation (1979-2008)
lead month
NEMOCFSR
ORA-S3GODAS
ES_MEAN
CFSv2
CMAP
2nd EOF Mode
Correlation (1979-2008)
lead month
NEMOCFSR
ORA-S3GODAS
ES_MEAN
Special Symposium on the South Asia Monsoon :: AMS :: Phoenix, AZ :: January 2015
Conclusions• ROLE OF CONVECTION
– HCF - alternative condition to whether or not deep convection should be initiated - was implemented into the Simplified Arakawa-Schubert scheme in the CFSv2.
• Better representation of background state of convection• Increased frequency at which convective scheme is activated
– HCF improves representation of monsoon in CFSv2:• Better daily and seasonal precipitation, mean & variability• Better seasonal cycle of precipitation, including onset dates
• ROLE OF OCEAN ICs• Substantial dependence on ocean ICs of skill of monsoon rainfall forecasts• Multi-analysis initialization results in superior prediction, on average• Two main modes of monsoon variability, associated with onset and decay
phases of ENSO, are well reproduced and predicted in CFSv2 with most ocean IC data sets
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