A Comparison study of convective precipitation by using RegCM4 over Indonesia Region

1. A Comparison study of convective precipitation by using RegCM4 over Indonesia Region BY Kadarsah,Dodo Gunawan, Jose Rizal Research and Devepment Centre THE INDONESIA AGENCY FOR METEOROLOGY CLIMATOLOGY AND GEOPHYSICS

2. 3 3 3 Outline Introduction 1 Model Description :RegCM4 2 Desain Model 3 Results and Discussion 4 Conclusion 5

3. Introduction Convective activity over the Maritime Continentregion is generally more active than over othertropical regions, and latent heat released into theatmosphere in the region is one of the major energysources driving global atmospheric circulations (Ramage 1968; Neale and Slingo 2003). This region is characterized by its low latitudelocation and complex land/ocean geography.The complicatedtopography and its induced circulations cansignificantly affect the formation and distributionof convection in the region. Convection over large islands exhibits alate afternoon and evening maximum. Over seaareas in the vicinity of large islands, maximumconvective activity generally occurs in the morning(Murakami 1983; Nitta and Sekine 1994; Ohsawa et al. 2001) Convective rainfall predominates in the afternoon to evening over the land area, whereascompound stratiform and convective rain is predominantin the morning over the surrounding sea region (Mori et al. 2004).

4. The afternoon and evening maximum of convectionand rainfall typically observed over tropical islandsresults from development of the mixed layerand diurnal changes in boundary-layer flow drivenby diurnal heating associated with the strong solarirradiance at low latitudes (Oki and Mushiake 1994; Mapes et al. 2003a; Wu et al. 2003). Indonesia is a large area of land–sea complex consistingof more than ten thousand islands surrounded by ocean.Many islands of this region are mountainous and located in the equatorial area where the convectiveactivity is the highest. The tropical deep convection isthe engine that drives atmospheric circulation through theuptake and release of significant amount of latent heat of vaporisation.

5. Objective The purpose of this study isto compare the convective activityover Indonesia region and to gain improved understandingof the formation convection over the sea and land throughanalysis results from surface meteorological observationsand numerical experiments with a non-hydrostatic model (RegCM4) . www.themegallery.com

6. Model Description: RegCM4 Nellie Elguindi, dkk:2010

7. Nellie Elguindi, dkk:2010

8. DESAIN MODEL 1996: Normal year 1997: El Nino year 1998: La Nina year centre

9. RegCM4 (Regional Climate Model version 4) SKEMA FISIS RegCM4 Nellie Elguindi, dkk:2010

10. EVOLUSI REGCM Nellie Elguindi, dkk:2010

11. Validation : TRMM vs convective sheceme September 2006 precipitation around topography/land area :underestimateand sea area :overestimate Over coastal seas bordering land areas with significant topography, topographically-induced local circulation may have an effect on convectiveactivity. wind–terrain interactions produce more rainfall on the windward side of mountains (Chang et al.2005)

12. Precipitation of TRMM-scheme of precipitaion Skema Zeng/Grell is the best option Didah project data is very important to analysisoutput from RegCM4. Precipitation data cover bothland and ocean, which is important for analyzing rainfallpattern across the Indonesia region. The coarse resolution datasets may miss local-scale details, which may be of critical concern for local users of climate riskmanagement. Next research, we use a high-resolutionregional climate model and rain gauge (DIDAH project ) and satellite observations to study this problem. positif negatif Overestimate Underestimate

13. Verification Data from DIDAH project ---to support validation RegCM4 Ekuatorial local Monsoonal

14. Total precipitation vs Convective precipitation Total precipitation/tpr TPR September 2006,BATS-KUO,30 km Total Precipitation = Convective Precipitation + Large Scale Precipitation RegCM4 output Convective precipitation/prcv 30 Km

15. Scenario 1996/normal year Convective precipitation is concentrated along the centre of Maritime Continent Indonesia Total Precipitation = Convective Precipitation + Large Scale Precipitation Persen convective precipitation contribute= convective precipitation (prcv)/total precipitation (tpr) x 100 %

16. Scenario 1997/El Nino year Convective precipitation is concentrated along the centre of Maritime Continent Indonesia. Scenario 1997 smaller than scenario 1996

17. Scenario 1998/La nina year Scenario 1998 Larger than scenario 1996

18. Conclusion Understanding the formation of theconvection over the Maritime Continentregion is essential for improved predictability ofrainfall in weather forecasts and improved globalclimate predictions. RegCM4 could, in general, reproduce the spatial pattern of monthly over sea areas but underestimated the rainfall over land. In convective precipitation area, scenario 1997 smaller than 1996 but scenario 1998 larger than scenario 1996. Superiority of RegCM4 over the sea is due to surface flux and the coupling to an ocean model seems to be needed. The formation mechanism of convection/rainfall in tropical regions isunclear, since observational data are often unavailable,especially over the vast tropical ocean and rain forest areas.-Data from DIDAH Project is important for analyzing rainfallpattern across the Indonesia region.

19. Reference • Aldrian, E., and R. D. Susanto, 2003: Identification of three dominant rainfall regions within Indonesia and their relationship to sea surface temperature. Int. J. Climatol., 23, 1435–1452. • Chang, C. P., Z. Wang, J. McBride, and C.-H. Liu, 2005: Annual cycle of Southeast Asia–Maritime Continent rainfall and asymmetric monsoon transition. J. Climate, 18, 287–301. • Mapes, B.E., T.T. Warner, and M. Xu, 2003b: Diurnal patterns of rainfall in northwestern south America.Part III: Diurnal gravity waves and nocturnalconvection offshore. Mon. Wea. Rev., 131, 830−44. • Mori, S., J.-I. Hamada, Y.I. Tauhid, M.D. Yamanaka, N.Okamoto, F. Murata, N. Sakurai, H. Hashiguchi,and T. Sribimawati, 2004: Diurnal land-sea rainfallpeak migration over Sumatera Island, Indonesianmaritime continent observed by TRMM satellite and intensive rawinsonde soundings. Mon. Wea. Rev., 132, 2021−2039. • Murakami, M., 1983: Analysis of the deep convective activity overthe western Pacific and southwest Asia. Part I: Diurnal variation.J. Meteor. Soc. Japan, 61, 60–76. • Neale, R., and J. Slingo, 2003: The Maritime Continent and its rolein the global climate: A GCM study. J. Climate, 16, 834–848 • Nellie Elguindi, Xunqiang Bi, Filippo Giorgi, Badrinath Nagarajan,Jeremy Pal, Fabien Solmon, Sara Rauscher, and Ashraf Zakey,2010:RegCM Version 4.0 User’s Guide,Trieste, Italy, ICTP • Nitta, T., and S. Sekine, 1994: Diurnal variation of convective activityover the tropical western Pacific. J. Meteor. Soc. Japan, 72, 627–641. • Ohsawa, T., H. Ueda, T. Hayashi, A. Watanabe, and J. Matsumoto, 2001: Diurnal variations of convective activity and rainfall in tropical Asia. J. Meteor. Soc. Japan, 79, 333–352 • Oki, T. and K. Mushiake, 1994: Seasonal change ofthe diurnal cycle of precipitation over Japan andMalaysia. J. Appl. Meteor., 33, 1445−1463. • Qian, J.-H., 2008: Why precipitation is mostly concentrated over islands in theMaritime Continent. J.Atmos. Sci., 65, 1428–1441 • Ramage, C. S., 1968: Role of a tropical ‘‘maritime continent’’ in theatmospheric circulation. Mon. Wea. Rev., 96, 365–370. • Wu, P., J.-I. Hamada, S. Mori, Y. I. Tauhid, M. D. Yamanaka, and F.Kimura, 2003: Diurnal variation of precipitable water over amountainous area of Sumatra Island. J. Appl. Meteor., 42, 1107–1115.

20. Thank You!