THIS RESEARCH DISCUSSES THE EFFECT OF CLIMATE CHANGE ON EXTREME RAINFALL IN WEST JAVA USING THE RCP 4.5 AND RCP 8.5 SCENARIOS BY COMPARING DAILY RAINFALL DATA WITH MODEL ACCESS-1, CSIROMK3.6 MODEL, MIROC-5 FROM NASA EARTH EXCHANGE GLOBAL DAILY DOWNSCALED PROJECTION (NEX-GDDP) AND THE ENSEMBLE OF THREE MODELS EACH SEASON WITH EXTREME DEPENDENCY SCORE (EDS) METHOD. THIS STUDY PROJECTS AN EXTREME RAINFALL INDEX OF 30 YEARS (2011-2040). THE THREE EXTREME RAINFALL INDICES ISSUED BY THE EXPERT DETECTION TEAM AND THE CLIMATE CHANGE INDEX (ETCCDI) CONSISTED OF RX1DAY, R50MM, AND R95P USED IN THIS STUDY. THE RESULTS SHOWED THAT THE PROJECTION PERIOD (2011-2040) USED RCP 8.5 WHICH HAD A TREND OF INCREASING EXTREME RAIN INDEX THAT WAS GREATER THAN RCP 4.5. FOR RCP 8.5 THE MAXIMUM RAINFALL WILL INCREASE IN INDRAMAYU, MAJALENGKA, PURWAKARTA, SUKABUMI AND CIAMIS AREAS. INCREASED RAINY DAYS OCCURRED IN BOGOR, BEKASI, KARAWANG, PURWAKARTA, BANDUNG, SUMEDANG, MAJALENGKA, CIREBON, INDRAMAYU. EXTREME RAINFALL WILL INCREASE IN BEKASI, KARAWANG AND BOGOR REGIONS.

RESEARCH ON MESOSCALE CONVECTIVE SYSTEMS (MCS) IN INDONESIA HAS BEEN STUDIED TO IDENTIFY THE CHARACTERISTICS AND DISTRIBUTION OF MCS. PERSISTENT ELONGATED CONVECTIVE SYSTEM (PECS) IS ONE OF THE MCS TYPES THAT CAN CAUSE EXTREME WEATHER. HOWEVER, THE PECS EVENT AND ITS CHARACTERISTICS IN INDONESIA HAVE NOT BEEN STUDIED FURTHER TO IDENTIFY THE SPATIAL AND TEMPORAL VARIATIONS OF PECS IN THE INDONESIAN. THIS STUDY EXAMINES THE PERSISTENT ELONGATED CONVECTIVE SYSTEM (PECS) IN THE MARITIME CONTINENT FROM 2010-2014.

MERG DATASET WITH BRIGHTNESS TEMPERATURE IS USED TO IDENTIFY PECS AND AS AN INPUT GRAB ‘EM TAG ‘EM GRAPH ‘EM (GTG) TRACKING ALGORITHM TO GAIN A BETTER UNDERSTANDING OF SPATIOTEMPORAL VARIATION IN INDONESIA. FLOOD DATA FROM BNPB IN INDONESIA IS USED TO FIND OUT THE CORRELATION BETWEEN FLOOD AND PECS EVENTS IN INDONESIA.

TOTALLY, PECS EVENTS IN 2010-2014 IS 5.574 EVENTS WHICH THE TRANSITIONAL PERIOD (MAM AND SON) HAS MOST PECS EVENTS AND LONGEST DURATION OF LIFE. THE PECS SPREAD IN THE EARLY MORNING ON LAND AND SEA, WHILE ON DAY AND NIGHT TIME, IT IS CONCENTRATED ON LAND FOR THE AREA OF JAVA, PAPUA, AND SOUTHERN KALIMANTAN. JAVA AND PAPUA HAVE THE LARGEST CONCENTRATED PECS EVENTS. THE LIFE PHASE OF THE PECS HAS TWO PEAKS OR SEMIDIURNAL CYCLE, IN THE MORNING AND NIGHT TIME. THERE ARE DIFFERENCES IN PEAK TIMES FOR EACH PHASE OF THE PECS ON LAND AND SEA. IN INDONESIA, PECS HAS THE SMALLEST AVERAGE MAXIMUM AREA THAN IN THE USA AND CHINA BUT HAS THE LONGEST DURATION AND LARGEST ECCENTRICITY. BASED ON FLOOD DATA FROM BNPB, DURING 2010-2014, JAVA HAS THE MOST FLOOD. ACCORDING TO FLOOD DATA AND PECS EVENTS IN JAVA, THERE IS 8,6% OF FLOOD COINCIDED WITH THE OCCURRENCE OF PECS EVENTS DURING THE PERIOD.

THIS STUDY EXAMINED THE CAUSE OF A RECORD TORRENTIAL RAIN EVENT THAT OCCURRED OVER THE WESTERN COAST OF SUMATRA ISLAND IN MARCH 2016. THE INFLUENCE OF ATMOSPHERIC EQUATORIAL WAVES (EWS) AND THE CHARACTERISTICS OF THE EWS WERE INVESTIGATED. ANALYSIS OF THE JAPANESE 55-YEAR REANALYSIS DATA (JRA-55) AND PRECIPITATION DATA FROM THE GLOBAL PRECIPITATION MEASUREMENT (GPM) SATELLITE SHOWED THAT THE EVENT WAS CAUSED BY THE COMBINED EFFECTS OF KELVIN WAVES, EQUATORIAL ROSSBY WAVES, AND WESTWARD INERTIO-GRAVITY (WIG) WAVES. AN EXAMINATION OF THE CHARACTERISTICS OF THE EWS REVEALED THAT THE KELVIN WAVES HAD LONGITUDINAL SCALES OF ~6,000 KM, WITH A PERIOD OF ~6 DAYS AND PHASE SPEED OF ~12 M S^-1, WHICH WAS TYPICAL OF THE CONVECTIVELY COUPLED KELVIN WAVES IN THIS REGION. THE WIG WAVES HAD A SCALE OF ~2,500 KM, WITH A PERIOD OF 2.5 DAYS AND A RELATIVELY FAST PHASE SPEED OF 12~13 M S^-1. HEAVY PRECIPITATION OCCURRED WHEN AN EASTWARD KELVIN WAVE FROM THE INDIAN OCEAN ENCOUNTERED A WIG WAVE FROM WESTERN KALIMANTAN ISLAND OVER SUMATRA ISLAND. IT WAS CONCLUDED THAT ALONG WITH THE KELVIN AND ROSSBY WAVES, THE WIG WAVES MAY HAVE PLAYED A KEY ROLE IN THE FORMATION OF THE EXTREME PRECIPITATION EVENT.

IN THIS STUDY, MERIDIONAL MIGRATION CHARACTERISTIC OF DIURNAL EXTREME RAINFALL (DER) OVER JAVA AND SURROUNDING WATERS AND ITS RELATION TO MADDEN JULIAN OSCILLATION (MJO) WAS INVESTIGATED. THE RAINFALL DATA WAS THE CLIMATE PREDICTION CENTRE MORPHING (CMORPH) V1.0 FOR THE PERIOD OF 1998-2019. THE THRESHOLD OF EXTREME RAINFALL WAS BASED ON THE 95% PERCENTILE OF DAILY RAINFALL AREA AVERAGE OF MOUNTAINOUS AREA (MA), NORTHERN PLAIN AREA (NPA), NORTHERN WATERS (NW),  SOUTHERN PLAIN AREA (SPA), AND SOUTHERN WATERS (SW) THAT WERE BASED ON GLOBAL LAND ONE-KILOMETER BASE ELEVATION (GLOBE) DIGITAL ELEVATION MODEL. WE ANALYZED MERIDIONAL MIGRATION OF DER THROUGH HOVMOLLER DIAGRAM AND OVERLAY CONTOUR MAPS. TO GET MJO SIGNAL, WE USED THE WHEELER-KILADIS WAVENUMBER-FREQUENCY DOMAIN TO FILTER OUTGOING LONGWAVE RADIATION (OLR). THE RESULTS SHOWED THAT DER OF MA DID NOT MIGRATE OR WAS STATIONARY AT 11-23 LOCAL TIME (LT), DER OF NPA (SPA) WAS FORMED OVER NORTHERN (SOUTHERN) MOUNTAINOUS AT 14-22 LT AND MIGRATED TO THE JAVA SEA (THE INDIAN OCEAN) WITH A LOWER INTENSITY AT 23-07LT, AND DER OF NW (SW) OCCURRED AT 21-15 LT WAS FORMED FROM RAINFALL MIGRATION OF THE JAVA ISLAND AT 13-03 LT AND STATIONARY RAINFALL OVER THE JAVA SEA (INDIAN OCEAN). BASED ON A COMPARISON OF MJO-OLR IN THE DER PERIOD OF MA, NPA, SPA, NW, AND SW, IT SEEMS THAT MJO HAD A STRONGER IMPACT ON THE DER OF NW AND SW THAN THE OTHERS.

THE MARITIME CONTINENT (MC) IS A REGION SUBJECTED TO EXTREME AND DAMAGING PRECIPITATION EVENTS WHICH ARE STILL POORLY PREDICTED BY NUMERICAL WEATHER PREDICTION (NWP) MODELS. TO IMPROVE PREDICTABILITY OF SUCH EVENTS, NWP NEED TO BE EVALUATED AGAINST ACCURATE MEASURES OF EXTREME PRECIPITATION ACROSS THE WHOLE MC. WITH THE BENEFIT OF ITS HIGH SPATIAL COVERAGE AT HIGH SPATIO-TEMPORAL RESOLUTION, THE NEW VERSION 06B OF THE INTEGRATED MULTI-SATELLITE RETRIEVAL FOR GLOBAL PRECIPITATION MEASUREMENTS (IMERG) PRODUCT APPEARS TO BE A GOOD CANDIDATE FOR NWP EVALUATION OF EXTREME PRECIPITATION IN THE MC. THE ABILITY OF IMERG TO ACCURATELY DETECT EXTREME PRECIPITATION IN THE MC REMAINS TO BE CHECKED PRIOR TO ITS UTILIZATION IN NWP VALIDATION. PREVIOUS STUDIES IN THE MC CONCLUDED THAT IMERG TENDS TO UNDERESTIMATE PRECIPITATION EXTREMES BUT DID NOT ACCOUNT FOR SPATIAL SAMPLING ERROR. IN THIS CONTEXT, IMERG IS EVALUATED AGAINST STATION DATA FROM THE GLOBAL HISTORICAL CLIMATOLOGY NETWORK (GHCN) AND RADAR DATA IN MALAYSIA AND IN THE PHILIPPINES. IT IS FOUND THAT THE HIGH INTRA-GRID SPATIAL VARIABILITY OF PRECIPITATION EXTREMES RESULTS IN LARGE SPATIAL SAMPLING ERRORS WHEN EACH GPM IMERG GRIDBOX IS COMPARED TO ONLY ONE LOCAL PRECIPITATION MEASUREMENT INSIDE THE GRIDBOX. THIS SPATIAL SAMPLING ERROR LIKELY EXPLAINS MOST OF THE ROOT MEAN SQUARE ERROR BETWEEN IMERG AND GHCN, AS WELL AS THOSE FOUND IN EARLIER STUDIES IN THE MC. THE USE OF RADAR DATA MAKES IT POSSIBLE TO MITIGATE THE SAMPLING ERROR. OVERALL, GPM IMERG DAILY PRECIPITATION IS SIMILAR TO LOCAL PRECIPITATION BETWEEN THE 85TH AND 95TH, BUT TENDS TO OVERESTIMATE ABOVE THE 95TH PERCENTILE. THIS IMPLIES THAT GPM IMERG CAN BE USED FOR NWP EVALUATION OF EXTREME DAILY PRECIPITATION UP TO THE 95TH PERCENTILE. IMERG DATA WERE ALSO COMPARED WITH RADAR DATA IN WESTERN PENINSULAR MALAYSIA FOR SUB-DAILY TIMESCALES. ALLOWING FOR UNCERTAINTIES IN RADAR DATA DUE TO TEMPORAL INTERPOLATION, THE CHOICE OF THE Z--R RELATIONSHIP, AND POTENTIAL HAIL CONTAMINATION, THE ANALYSIS SUGGESTS THAT THE 95TH PERCENTILE COULD STILL BE USED FOR NWP EVALUATION OF EXTREME SUB-DAILY PRECIPITATION, WITH A TENDENCY FOR UNDERESTIMATION ABOVE THE 95TH PERCENTILE FOR THE SHORTEST ACCUMULATION TIMES.  

MESOSCALE CONVECTIVE SYSTEM (MCS) IS A SYSTEM CONSISTING OF GROUPS OF CONVECTIVE CELLS IN THE MESO SCALE. ONE OF THE LARGEST TYPES OF MCS SUBCLASS IS MESOSCALE CONVECTIVE COMPLEX (MCC) OCCURRED IN THE EASTERN PART OF THE MAKASSAR STRAIT NEAR THE MADJENE AND POLEWALI MANDAR REGIONS ON DECEMBER 9, 2014 MORNING TO EVENING (09.00 - 15.00 WITA). USING MTSAT-2 SATELLITE IMAGERY DATA, REANALYSIS OF ECMWF INTERIM ERA, GSMAP RAINFALL, SEA SURFACE TEMPERATURE, SURFACE AIR OBSERVATION AND UPPER AIR OBSERVATION, THE AUTHOR WILL EXAMINE THE EXISTENCE OF MCC IN THE MAKASSAR STRAIT IN TERMS OF ATMOSPHERIC CONDITIONS WHEN MCC ENTERS THE INITIAL UNTIL EXTINCT AND THE ACCOMPANYING EFFECTS OF PRECIPITATION. THE RESULT SHOWS THAT IN GENERAL, MCC FORMED IN THE WATERS OF THE MAKASSAR STRAIT IN THE MORNING AND THEN IT MOVED WESTWARD. THE MECHANISM OF ITS FORMATION WAS THROUGH A PROCESS OF CONVERGENCE OF THE LOWER LAYERS IN THE WATERS OF THE MAKASSAR STRAIT AND ITS SURROUNDINGS SO AS TO TRIGGER THE PROCESS OF CLOUD FORMATION. WARM THERMAL CONDITIONS ALSO GAVE A BIG INFLUENCE TO THE LOWER LAYERS TO THE TOP AND ACTIVATE CONVECTIVE IN THE STUDY AREA. MEANWHILE, IN THE MCC OCCURRENCE REGION ALSO HAS HIGH RELATIVE HUMIDITY, NEGATIVE DIVERGENCE VALUES, AND MAXIMUM VORTICITY VALUES. THE IMPACT OF THE EMERGENCE OF MCC ON THAT DATE RESULTED IN AREAS WITH VERY LARGE HUMIDITY AND CLOUD FORMATION AND PRODUCED RAIN IN THE SURROUNDING AREA, IN THIS CASE USING RAINFALL DATA FROM STAMET HASANUDDIN, MAKASSAR, SOUTH SULAWESI. WITH A DURATION OF UP TO SEVEN HOURS EXTINCT, MCC IN THE MAKASSAR STRAIT PRODUCES HEAVY RAINFALL IN THE MAKASSAR STRAIT WATERS.

 

DROUGHT IS A NATURAL HAZARD THAT RESULTS FROM A DEFICIENCY OF PRECIPITATION, LEADING TO LOW SOIL MOISTURE AND RIVER FLOWS, REDUCED STORAGE IN RESERVOIRS AND LESS GROUNDWATER RECHARGE. THIS STUDY INVESTIGATES THE VARIATIONS IN DROUGHT CHARACTERISTICS (DROUGHT EVENT FREQUENCY, DURATION, SEVERITY, AND INTENSITY). THIS STUDY USING THE STANDARDIZED PRECIPITATION INDEX (SPI) ANALYZE THE DROUGHT CHARACTERISTICS ON THE AGRICULTURAL AREAS IN CENTRA JAVA DURING 1990-2010. ANALYSIS OF DROUGHT CHARACTERISTIC BY SPI DURING 1990 TO 2010 SHOWS THE LONGEST DROUGHT EVENT IS 4 MONTHS, THE HIGHEST AVERAGE SEVERITY IS 6.06 AND THE HIGHEST INTENSITY IS 2.02. EL NINO YEAR’S PROBABILITY DROUGHT OCCURRENCE REACHED 100% IN AUGUST FOR MODERATE DROUGHT, SEVERE DROUGHT AND EXTREME DROUGHT CATEGORY, WHEREAS THE PROBABILITY DROUGHT OCCURRENCES IN THE NORMAL AND LA NINA YEAR RANGE 0-70% FOR MODERATE DROUGHT, 0-50% FOR SEVERE DROUGHT CATEGORY AND 0-40% FOR EXTREME DROUGHT CATEGORY. THE RESULTS OF THIS STUDY MAY HELP INFORM RESEARCHERS AND LOCAL POLICYMAKERS TO DEVELOP STRATEGIES FOR MANAGING DROUGHT.

KEYWORD: DROUGHT INDEX, SPI, DROUGHT CHARACTERISTICS

 

 

FLOOD IS ONE OF THE MOST FREQUENT HYDRO-METEOROLOGICAL DISASTERS IN KETAPANG REGENCY, WEST KALIMANTAN. ALMOST ALL FLOOD RECORDS THAT OCCURRED IN KETAPANG SHOW THAT FLOODING IN THE AREA IS CLOSELY RELATED TO THE INCIDENCE OF HIGH RAINFALL. HOWEVER, THERE HAS BEEN NO IN-DEPTH METEOROLOGICAL STUDY TO REVIEW THE RECORDS OF METEOROLOGICAL ANALYSIS ON FLOOD EVENTS IN KETAPANG. THIS STUDY AIMS TO STUDY THE CHARACTERISTICS OF ATMOSPHERIC DYNAMICS PATTERNS RELATED TO FLOOD EVENTS IN KETAPANG DURING 2015-2020. THE OBSERVATIONAL DATA USED  IN THIS STUDY ARE THE OBSERVATION DATA OF RAIN POSTS IN KETAPANG, AS WELL AS WEATHER OBSERVATION DATA AT RAHADI USMAN KETAPANG METEOROLOGICAL STATION. IN ADDITION TO OBSERVATIONAL DATA, MJO RECORD DATA, HIMAWARI 8 SATELLITE IMAGE, AND ECMWF 0.125 DEGREE REANALYSIS DATA WERE ALSO UTILIZED TO ANALYZE UPPER-AIR PATTERNS IN EACH CASE. THE RESULTS SHOW THAT ALMOST ALL INCIDENTS OF HEAVY RAIN THAT CAUSE FLOODING IN KETAPANG ARE CLOSELY RELATED TO THE VORTEX PATTERN IN THE KALIMANTAN AREA THE INTER-TROPICAL CONVERGENCE ZONE (ITCZ) PATTERN WHICH FORMS THE MOISTURE CONVERGENCE BELT OVER THE KETAPANG AREA. THE WET RELATIVE HUMIDITY VALUES IN THE 850 MB, 700 MB, AND 500 MB LAYERS WAS ALSO CONSISTENT BECOMES THE SIGNATURE OF FLOOD EVENTS. IT IS EMPIRICALLY OBTAINED THAT THE GEOGRAPHICAL AREA OF KETAPANG WHICH IS AN AREA OF WIND BENDS ORIGINATING FROM THE SOUTH CHINA SEA WHEN THE WESTERLY WINDS SEASON MAKE THE KETAPANG VERY VULNERABLE TO MOISTURE ACCUMULATION DUE TO THE VORTEX FORMED IN THE KALIMANTAN AREA, THE KETAPANG LOCATION WHICH IS IN THE CONVERGENCE AREA BETWEEN THE AIR MASSES FROM NORTHERN HEMISPHERE AND SOUTHERN HEMISPHERE ON THE ITCZ PATTERN OCCURRENCE ALSO RESULTED IN LARGE SCALE MOISTURE ACCUMULATIONS WHICH RESULTED IN THE FORMATION OF RAIN CLOUDS WHICH INCREASED THE FLOODING POTENTIAL IN KETAPANG.