Simulating Regional Climate Changes Over Maritime Continent

BMKG

SIMULATING REGIONAL CLIMATE CHANGES OVER MARITIME-CONTINENT MARITIME CONTINENT USING REGIONAL CLIMATE MODEL Siswanto Graduate School of Climate Sciences, Universityy of Bern, Switzerland National Agency for Meteorology Meteorology, Climatology and Geophysics (BMKG), (BMKG) Jakarta, Jakarta Indonesia

Abstract This study investigates how future climate changes over maritime-continent maritime continent particularly t temperature t and d precipitation i it ti change h ffor 21th century based b d on the h IPCC SRES A1B emission i i scenario relative to the present-day climate using a regional climate model (RegCM3) simulation. Compared p to ppresent-day y climate, this scenario experiment p exhibited an increase in temperature p generally ge e a y 1.8 .8oC, both bot over ove land a d and a d seas, except e cept for mountainous area. An extreme change was found over south-east south east area of Indonesia where temperature increased 0oC-4 C 4 oC, C the future projections for precipitation showed seasonal rainfall i f ll changes h are mostt noticeable ti bl increase i d i the during th rainy i season andd are generally ll d decrease dduring i the h ddry season. These h i increase were variously over the region. Extremely increases were found in Java Island, some part of Sumatera,, Central Sulawesi and Papua p where it could reach more over 16 mm per p dayy for February rather than present-day present day with exceptional condition depicted in some areas of Borneo Borneo, Sulawesi and Papua where precipitation seemed to decrease decrease. This increases is expected due to increasing evaporation loss from both land and sea exceeding di iincreased d precipitation i it ti over th these region. i Th The result l suggest that h maritime-continent ii i might undergo large changes under future climate change, leading to potentially devastating consequences q for other related aspects. p

B kg Background d Global warming and global climate change h may llead d tto changes h in i regional g climate, like changes g in precipitation (amount of heavy rainfall) and in climate extremes such us number b off hot h t days, d and d number b off long g dry y spells. p Concerning to Indonesia region region, within th period the i d 2003-2005, 2003 2005 th there were about 1.429 disasters incidences. About 53.3 percent were hydro hydrometeorological disasters disasters. It is likely that global l b l ttemperature t increases i will ill lead l d to g greater extremes of drying y g and heavy rainfall which will in turn lead to higher risk of climate hazards (IPCC (IPCC, 2007) 2007). Projection of climate changes at the regional scale are of fundamental i importance t ffor an assessmentt off the th impacts p of climate change g on human and natural systems.

Objectives

A2

B1

Commitment

Result Fig 4. Projected pattern of seasonal pprecipitation p in the 21th century in comparison with the 20thh century.

Fig. 1 Calculated changes (1960-2100) Fig (1960 2100) in global-mean global mean (top) and Indonesia (bottom) annual surface air temperature for IPCC SRES scenarios ((Hulme et.al,1999). , ) The observed changes to 1998 in both cases are shown by bars and the bold black curves. A1B scenario for Indonesia shows increase in temperature generally 1.8oC. Seasonal Pattern of Precipitation 2000

2.a

• Seasonal rainfall changes g are most noticeable increase during the rainy season and are generally decrease during the dry season. season • The air temperature in most of part of Indonesia will generally increase as annually seasonally and monthly. annually, monthly Seasonal changes in dry season (JJA) will greater than in rainy season (DJF). Seasonally changes is in rate 1,5 15 – 2 0oC, 2.0 C while monthly changes up to 4.0oC. • Changes will occur variously over the region and more intensify in the south and eastern p part of Indonesia.

2b 2.b

Fig 2. 2 (a) Indonesian seasonal rainfall distribution (in mm/day) of reference year and (b) global precipitation changes g ((in %)) ffor the pperiod 2090–2099 relative to 1980 – 1999 based on the SRES A1B scenario (IPCC,2007). White areas are where less than 66% change and stippled areas are where more 90% change. Drying in much of the subtropics, more rain in higher latitudes, continuing the broad pattern of rainfall i f ll changes h already l d observed. b d

Model : Experimental p Design g The model regional g domain covers 24ox50o area,70 area 70 km horizontal grid spacing 18 layers spacing,18 layers. Grell cumulus convective ti scheme h is i used d to t simulate i l t precipitation. p p Rough g calculation of changes is approximated by projection year minus reference year. year Data model input p : ERA40 for year y : 1950-1990 1950 1990,2000; 2000; EH50M : 2050 2050, 2100 based on A1B Scenario Scenario. Observation d t was ttaken data k ffrom CRU and d CMAP for yyear : 2000,1999. , A1B is a typical yp “business business as usual” usual (2090-2099) (2090 2099) scenario: Global mean warming 2 2.8 8oC. C (Changing in seasonal rainfall amount 1951 – 2000)

Fig 5. Monthly temperature and precipitation projection for February 2100 (top) and projected changes relative to reference f year (bottom). (b )

Summary Future climate change g projection j based on A1B scenario resulting from Regional Climate Model (RegCM3) experiment suggest that climate of the most part of Maritime-Continent Indonesia will be warmer in all seasons and wetter in the wet season and drier in the dry season relative to current conditions

References 1.Working Group I IPCC, “Climate Change 2007, The Physical Science Basis”. Intergovernmental Panel on Cli t Ch Climate Change, 2007 2007. 2.Hulme, M. and Sheard,N., “Climate Change Scenarios for Indonesia” Climate Research Unit, Unit 1999. 1999

Acknowledgement (no change) (decrease)

ƒ Provide regional g further information due to climate change in Indonesia using regional climate model

A1B

(increase)

Fig.33 Observed trend changes in seasonal rainfall during Fig 1951-2000 1951 2000 based on rain gauge data in Java Island shows that changes g is not uniform f across the island.

This work Thi k was supported t db by 4th Workshop W k h on Regional R i l Cli t Model Climate M d l 2008 in i The Th Abd Abdus S Salam l IInternational t ti l Centre for Theoretical Physics (ICTP), (ICTP) Trieste, Trieste Italy Italy.

Contact e-mail : [email protected] http://unibe.academia.edu/SiswantoSiswanto/