1 / 20

GRL Seminar Dec 11, 2013

GRL Seminar Dec 11, 2013 . Advanced Asian summer monsoon onset in recent decades Yoshiyuki Kajikawa ( ykaji@riken.jp ) RIKEN, Advanced Institute for Computational Science .

millie
Download Presentation

GRL Seminar Dec 11, 2013

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. GRL Seminar Dec 11, 2013 Advanced Asian summer monsoon onset in recent decades Yoshiyuki Kajikawa (ykaji@riken.jp) RIKEN, Advanced Institute for Computational Science Kajikawa, Y., T. Yasunari, S. Yoshida, and H. Fujinami, 2012: Advanced Asian monsoon onset in recent decades. Geophys. Res. Lett. Kajikawa, Y., and B. Wang, 2012: Interdecadal change of the South China Sea summer monsoon onset. J. Climate., 25, 3207-3218

  2. Issues and used data sets [Q] How, and to what extent has Asian monsoon changed since the late 20th century? [Q] How are its regionality and seasonality? We analyze the trends (1979-2008) on a monthly mean basis • Rainfall • (1) CMAP, (2) GPCP, (3) APHRODITE, • (4) University of Delaware (http://www.esrl.noaa.gov/psd/) • Water vapor flux • NCEP DOE reanalysis II (Kanamitsu et al., 2002) • Hadley Center SST dataset (Rayner, 2003) (Kajikawa et al., 2012)

  3. Trend of rainfall in May and June May Jun-May Jun • Increasing trend in May along 10N • Decreasing trend in June • Rainfall pattern in May during recent decades is become closer to that in June during previous. (Kajikawa et al., 2012)

  4. Inter-comparison of the rainfall trend in May CMAP GPCP APHRODITE Delaware (Kajikawa et al., 2012)

  5. Trend of rainfall along 10-15N w/ climatology (Kajikawa et al., 2012) 10-15N, 60-140E

  6. Trend of seasonal mean rainfall JJA MJJAS (Kajikawa et al., 2012) Jun The trend of boreal summer mean rainfall changes significantly depending upon whether it includes rainfall in May.

  7. Stepwise Asian summer monsoon onset (climatology) The Julian pentad in which the relative CPM rainfall rate exceeds 5 mm day is defined as the onset pentad. (Wang and LinHo, 2002)

  8. Asian summer monsoon onset difference Onset pentad [1994-2008] – Onset Pentad [1979-1993] Earlier Later Earlier Earlier Later (Kajikawa et al., 2012)

  9. Trend of atmospheric thickness (200-500hPa) 30N-5N SST(5N) 30N Warming trend over the continent in May (Right: 30N) has induced earlier seasonal overturning of land-sea heat contrast (Left: 30N-5N). (Kajikawa et al., 2012)

  10. Advanced Indian summer monsoon onset was affected by earlier seasonal overturning of land-sea heat contrast. [Q] is it also primary factor for the advanced western Pacific monsoon onset? We’ll Focus on the South China Sea summer monsoon onset change in detail …

  11. Focus on the South China Sea summer monsoon onset SCSSM index= U850 (5-15N, 110-120E) - (Wang et al.2004) 1979-1993 Westerly 1994-2008 Wind Significant Easterly • Decadal change of the SCSSM is clear only in May and June. • The SCSSM starts earlier in 1994-2008. (Kajikawa and Wang, 2012)

  12. Previous study (Kajikawa and Wang 2012) 1979-1993 1994-2008 • the SCSSM onset date is shifted 2 weeks around 1993/1994. 5/30 5/14 (Kajikawa and Wang, 2012)

  13. SCSSM onset evolution (OLR and U850) 1979-1993 The SCSSM onset is primarily associated with northward seasonal march of the ITCZ (Kajikawa and Wang, 2012) Mean onset date is early June

  14. SCSSM onset evolution (OLR and U850) 1994-2008 The SCSSM onset is affected by enhanced northwestward moving TC from the Eq WP (Kajikawa and Wang, 2012) Mean onset date is mid-May

  15. Possible mechanism of SCSSM onset change • Factors responsible for the SCSSM onset variability around 1993/1994 Abrupt convection enhancement for the monsoon onset Shifted two weeks Thermal condition Convective instability Tropical disturbances as triggers for monsoon onset no significant change Possibly changed … • Tropical Cyclone genesis • Intraseasonal variability (Kajikawa and Wang, 2012)

  16. Possible mechanism of SCSSM onset change 1979-1993 #7 1994-2008 #13 GPI diff SST diff Difference between 1979-1993 and 1994-2008 (Kajikawa and Wang, 2012)

  17. Previous study (Kajikawa and Wang 2012) Difference of the intraseasonal variation activities during 4/15-5/15 between 1994-2008 and 1979-1993 10-25-day ISV 30-70-day ISV Enhanced ISV activity over the western Pacific in the latter epoch 1994-2008 significantly.

  18. Summary We have elucidated the significant seasonality in long-term trends in the Asian monsoon. Increasing rainfall trend in May along 10N correspond to the advanced monsoon onset. Rainfall trends in July and August showed less significant. The advanced monsoon onset (continental monsoon region) was most likely due to the heat contrast between land and Ocean. The heating trend over the Asian landmass primarily contributed . One plausible factor for the warming trend would be dust aerosol loading along the Himalaya-Tibetan Plateau. The enhancements of the ISV and tropical cyclone activity, which are attributed to significant SST warming over the western Pacific, could be also a stronger trigger of the advanced monsoon onset over the South China Sea and western Pacific.

  19. Decadal change of seasonal cycle (precipitation) 1979-1993 (110E-120E) China Northward moving of Mei-Yu front is sharp and abrupt in 1994-2007. Rainfall in June over China in 1994-2007 is stronger than 1979-1993. Double peak of convection over the SCS is clear in 1979-1993. SCS 1994-2007 China SCS SCSSM may be key area for Mei-yu front variability…

  20. 감사합니다

More Related