Monsoon variability over South and East Asia: statistical downscaling from CMIP5 models AMITA PRABHU* Jaiho OH, P. Bhaskar, R.H. Kripalani Indian Institute of Tropical Meteorology Pune 411008, India *Presenter: Current Affiliation: Pukyong National University, Busan, South Korea Jeju, S. Korea, 03-09 Dec. 2016 1
CLIMATOLOGY: SUMMER MONSOON RAINFALL JUN-SEP BASED ON CRU DATA 1901-2014 (mm/day) Large Amounts Of Rainfall - West Coast of India - Central India - NE India - Myanmar Coast - Southeast Asia - SE China - Korea-Japan Peninsula Similar Pattern for Variability (SD) 2
Inter-annual and multi-decadal summer monsoon rainfall variations 3
Linear trends in Asian summer monsoon rainfall (mm/day/45 years) Data period: 1970-2014 CRU data Statistical Significance at 95% CI shown as dot marks South Asia (i) NE India (76-85 E, 22-34 N + 85-95 E, 22-28 N) (ii) WCI (68-76 E, 15-25 N) East Asia (i) Korea-Japan (125-132 E, 30-38 N) (ii) South China (110-120 E, 21-28 N) 4
Possible Factors for the Observed Trends Many authors report a south flood north drought trend in the EASM since the 1970s (Gong and Ho 2002; Ding et al. 2008) and have attributed to anthropogenic influence or natural variability (Song et al. 2014; Lei et al. 2014) Increased Aerosols and decrease in Land-Ocean Temperature contrast have been attributed to declining trend in ISMR (Bollasina et al. 2011; Lau and Kim 2015) Significant land-use land-cover changes and increased greenhouse gas emissions have also been cited (e.g. Krishnan et al. 2105) But, we need to examine the trends and teleconnections for following factors of monsoon variability Monsoon Trough Over South Asia North Pacific Sub-Tropical High over East Asia South Asian / Tibetan High Mascarene High
C/45 years Linear Trends Warming Trend over most Indo-Pacific region hpa/45 years Monsoon Trough westward shift by about 2-3 longitudes Weakening: less moisture over India m/s/45 years NPSH westward shift about 5-7 longitudes Strengthening: more moisture towards East Asia Entire Lower Tropospheric Circulation appears to have shifted westwards 6
MSLP (hpa/45 years) Linear Trends Slight Westward Extension Strong Southerly Flow Intensification of Findlater Jet GPH at 200 hpa (m/45 years) Intensification and Expansion of the South Asian High 7
Inferences Trends in rainfall over South and East Asia appear to be consistent with the surface as well as lower tropospheric circulation trends However, we need to find out how the monsoon rainfall variations over the identified South and East Asian regions are linked to the variations in largescale forcing 8
Tele-connection with Rainfall over South Asian Monsoon Blocks North East India West Central India 9
Tele-connection with Rainfall over East Asian Monsoon Blocks Korea-Japan South China 10
Role of Indo-Pacific SST forcing in modulating Asian Monsoons Relation with Rainfall Significant positive relation over Southern peninsular India, NE India up to Korea with SSTs over WPO Negative relation over northern parts of India and North China, which means Drying trends over northern India and North China may be related with SSTs over WIO 11
Relation with MSLP Comparison with earlier pattern confirms influence of WPO on South Asia Comparison with above Panel: area of positive relation over WPO increasing and intensifying 12
Relation with 850 hpa winds Cyclonic circulation over southern India Weakening Monsoon circulation over South Asia 13
Schematic representation of Monson Flow Cross-diagonal Effect 14
Inferences Monsoon Flow including the Monsoon Trough over South Asia and NPSH over East Asia shifted westwards Westward shift and weakening of monsoon trough: less moisture supply from Bay of Bengal over Northern parts of India Westward shift and strengthening of NPSH: more moisture supply from West Pacific towards East Asia SSTs over WPO and WIO are the most important components driving the trends of South and East Asian monsoon CMIP5 model outputs are examined for projections of monsoon rainfall trends and teleconnections 15
Scatter Plot: CMIP5 Models to satisfy following two conditions for Summer Monsoon Rainfall over India (1) Positive relation with rainfall over North China (2) Negative relation with rainfall over Korea-Japan sector Models in Quadrant I (III) satisfy first (second) condition Models in Quadrant II (IV) satisfy both (none) conditions
List of the nine CMIP5 climate models selected for analysis: Here Results for ACCESS1.0 Model only presented Sr. No. Model Name Institution 1 ACCESS1.0 Australian Community Climate and Earth System Simulator, Commonwealth Scientific and Industrial Research Organization (CSIRO) and Bureau of Meteorology (BOM), Australia 2 CSIRO Mk3 6.0 Commonwealth Scientific and Industrial Research Organisation in collaboration with the Queensland Climate Change Centre of Excellence, Australia 3 FIO-ESM The First Institute of Oceanography, SOA, China 4 GISS-E2-H-CC NASA Goddard Institute for Space Studies 5 GISS-E2-H NASA Goddard Institute for Space Studies 6 GISS-E2-R NASA Goddard Institute for Space Studies 7 INMCM4 Institute for Numerical Mathematics, Russia 8 IPSL-CM5A-LR Institut Pierre-Simon Laplace, France 9 IPSL-CM5A-MR Institut Pierre-Simon Laplace, France
SIMULATED MULTI-DECADAL VARIABILITY MATCHES WITH OBSERVATIONS CRU- based OBS ACCESS1.0 MODEL OBSERVED PATTERNS
Monsoon Trough Eastern edge: 1975-2005 90 E 2020-2050 82 E 2070-2100 88 E Zonal Oscillatory behavior NPSH Western Edge: 1975-2005 163 E 2020-2050 157 E 2070-2100 160 E Zonal Oscillatory behavior ACCESS1-0 model simulation (1975-2005; black contours) and Projections: near future (2020-2050; green contours) and far future (2070-2100; red contours) for (a) Monsoon Trough (b) South Asian High (c) Mascarene High (d) North Pacific Sub-tropical High
Summary Monsoon Flow including the Monsoon Trough over South Asia and NPSH over East Asia shifted westwards Projections with ACCESS1.0 Model indicate oscillatory behavior of Monsoon Trough and NPSH in the 21 st century Alternate decades with monsoon rainfall more over South than East Asia and vice versa Hence, recent trends may be a part of natural multi-decadal variability South Asian Monsoon need not collapse It could revive in the near future 20
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