ACG06-01

Room:101A

Time:May 26 11:00-11:20

Quick water cycle over the Indonesian maritime continent: An ”AM radio” hypothesis
YAMANAKA, Manabu D.1∗
1

DCOP, JAMSTEC / DP-GSS, Kobe U

High-resolution observations with radars and other hydrometeorological instruments have been installed and operated since
JEPP-HARIMAU (FY2005-09) and SATREPS-MCCOE (FY2009-13) projects by Japan-Indonesia collaborations.
The most important result is that over the Indonesian maritime continent (IMC) all of landward (sea wind) water-vapor transport, rainfall and seaward (river) water transport have diurnal cycles, which suggest a very quick hydrologic cycle. In other words
the water budget is almost balanced and reset every day, and is probably closed locally almost within a river basin, although thecycling (e.g. rainfall) amount is changed each day/area dependent on the diurnal-cycle (sea-land breeze circulation) amplitudecontrolled directly by sea-land heat/water contrast (affected by longer/larger scale climate such as cold surges and ENSO/IOD).
This situation is just like an AM radio, in which an input signal modifies the output amplitude but generates no interactions/modifications in the carrier wave frequency itself. Therefore, the concept/strategy of hydrometeorological observations/predictions over IMC must be somewhat different from those in mid-latitudes where synoptic-scale space-time continuity ismost important. Namely, over the IMC, observations arranged in each area/basin and predictions restarted each day (with many
recalculations analyzed statistically) would be more effective than in mid-latitudes.
Keywords: Indonesian maritime continent, cloud convection, water cycle, diurnal cycle, HARIMAU, MCCOE

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ACG06-02

Room:101A

Time:May 26 11:20-11:35

MJO role on Intraseasonal variation of stable isotope of Precipitation in Indonesia Maritime Continent
BELGAMAN, Halda aditya1∗ ; ICHIYANAGI, Kimpei1 ; TANOUE, Masahiro2 ; SUWARMAN, Rusmawan3 ;YOSHIMURA, Kei4 ; MORI, Shuichi5 ; KURITA, Naoyuki61GSST Kumamoto Univ., 2 School of Engineering, The University of Tokyo, 3 Bandung Institute of Technology, 4 AORI, The
Univ. of Tokyo, 5 JAMSTEC, Japan, 6 Nagoya Univ.
MJO (Madden-Julian Oscillation) is one of the disturbances for Asian Monsoon in the Maritime Continent Area. Intraseasonalvariability of precipitation in the Indonesia Maritime Continent (IMC) is mainly due to The Madden-Julian Oscillation (MJO),
cold surge, or other synoptic scale disturbance. This study examined the relationship between MJO and stable isotope in precipitation over the IMC. Observation and simulation model data from isotope circulation model was used. From 2001 - 2009, 10main MJO events were detected and 6 of the event occurred at Boreal Winter season (Asian Monsoon). Temporal and spatial
analysis from simulated stable isotopes model reveals that isotopic variation is correlated to MJO event in different phase fordifferent stations. Generally, δ 18 O in precipitation became lighter in most observation station at phase 3, 4 and 5 at western partof IMC, and phase 4, 5, and 6 at north east part of IMC. Spatial distribution of δ 18 O in precipitation for each MJO phase showthat mainly MJO governed δ 18 O variability in intraseasonal timescale for IMC area. Further investigation showed clear signalof MJO in δ 18 O was observed at Bukit Tinggi (GAW) station only; it is confirmed with result from Isotope Circulation Model(ICM). When MJO is in active phase (enhanced) precipitation in western part of IMC, precipitable water was came from IndianOcean and South IMC Ocean.
Keywords: asian monsoon disturbance, stable isotope, Madden Julian Oscillation, moisture transport analysis

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Room:101A

Time:May 26 11:35-11:50

Relative role of the ocean for interannual and decadal variations in summer monsoon
onset over the South China Sea
IMAKAWA, Shin2∗ ; HIGUCHI, Atsushi1
1Center for Environmental Remote Sensing (CEReS), Chiba University, 2 Graduate School of Science, Chiba University

In this study, we reveal a difference of mechanisms with interannual variation a 15-years variation in the South China Sea
Summer Monsoon (SCSSM) onset. The SCSSM onset occurs in active convections over the South China Sea (SCS), whenconvections are active over the Philippine Sea (PS). Variations in the SCSSM onset are affect by the variations in the convective
activities over SCS and PS. The increase in the sea surface temperature (SST) over the Western Pacific in recent years causes
the more active convection over the PS, therefore the SCSSM onset is advanced in 15-years variation as already pointed out byKajikawa and Wang (2012).
Moreover, we elucidate the relation between the SCSSM onset date anomaly and aggregated SST over the SCS from Januaryto March. The correlation is good between the SCSSM onset date anomaly and the aggregated SST over SCS, while a poor
relation founds between the 15-years variation oriented signal in onset date and the SST in SCS. When SCSSM onset date isdelayed, the aggregated SST in SCS has tend to high temperature. On the other hand, the correlation is good between the 15-years
variation in the SCSSM onset date and the aggregated SST over the PS. The SST anomalies over the SCS are influenced by thefrequencies and strength of cold surges during boreal winter. Strong and longer cold surges bring the lower SST over the SCS.
The cold surges are brought about the anticyclone over the Eastern Eurasian continent. An arctic sea-ice decline instigates thehigh-pressure deviation over the Eurasian Continent. Then relatively lower land surface temperature in middle latitude, and bringthe cold surge over the SCS.

Keywords: summer monsoon, onset, South China Sea

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ACG06-04

Room:101A

Time:May 26 11:50-12:05

Climatological seasonal changes of rainfall and circulation in the Philippines
MATSUMOTO, Jun1∗ ; NGUYEN-LE, Dzung1 ; VILLAFUERTE, Marcelino ii2
1

Department of Geogreaphy, Tokyo Metropolitan University, 2 PAGASA, Philippines

Climatological seasonal changes of rainfall and lower tropospheric circulation in the Philippines were analyzed by utilizing
5-day mean TRMM 3B-42 and station rainfall data provided by PAGASA, and ERA-Interim wind data for the period 1998-2013.
In particular, climatological onset and withdrawal processes of the southwest monsoon were investigated.
It was found that the onset of southwest monsoon occurred abruptly in mid-May. It started from the north in the Philippines
both in rainfall and wind, which showed a peculiar feature in this region. After the onset, anti-cyclonic flow from the Pacific highwas predominant, and it changed into cyclonic flow in mid-June. Easterlies still remained in the south until early July, afterwards
SW monsoon covered the whole country and enhanced from late July.
Southwest monsoon began to retreat from the north in mid- September, and fully retreated from the southern tip of the Philippines in late October.
Acknowledgment: Part of this study was supported by The JSPS KAKENHI, The GRENE program of the MEXT, and the
Asian Human Resource Fund of the Tokyo Metropolitan Government.
Keywords: monsoon, seasonal changes, monsoon onset, monsoon withdrawal, rainy season

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ACG06-05

Room:101A

Time:May 26 12:05-12:25

Long-term Regional Precipitation Disparity in Northwestern China and Its Driving Forces
LEE, Harry F.1∗
1

Department of Geography, The University of Hong Kong

Precipitation in Northwestern China (NW China) is characterized by salient regional differences. Yet, the long-term regional
precipitation disparity in NW China still remains insufficiently-explored. In the present study, we base on historical documentation to derive the fine-grained precipitation indices of two macro regions in NW China between AD580 and 1979 to (1)determine the multi-decadal to centennial regional precipitation disparity in NW China; and (2) find the major driving forces
behind it. Wavelet analysis is applied. Our results show that there is significant regional discrepancy of precipitation changein NW China over extended period. Besides, the association between the regional precipitation disparity in NW China andvarious modes of atmospheric circulation (Asian Summer Monsoon, Arctic Oscillation, Pacific Decadal Oscillation, and North
Atlantic Oscillation) is significant and characterized by a regime shift during the transition from the warm episode to the Little
Ice Age in the 14th century. Most importantly, the ∼180 to 240 year cycle of the El Niño-Southern Oscillation is found to be themost prominent pacemaker of regional precipitation disparity in NW China at the long-term temporal scales. Our findings helpto demonstrate which atmospheric circulation is primarily responsible for the long-term regional precipitation disparity in NW
China, which may have important implications for water resource management there.
Keywords: precipitation, moisture, atmospheric circulations, Asian Summer Monsoon, El Nino-Southern Oscillation, Northwestern China

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ACG06-P01

Room:Convention HallTime:May 26 18:15-19:30

Future Projection of Himalayan Monsoon Season Precipitation by CMIP5 Models underWarming Climates
KADEL, Indira1∗ ; YAMAZAKI, Takeshi11Department of Geophysics, Tohoku UniversityI. Introduction: Livelihood of the Himalayan people depends largely upon precipitation. Any variability on its regular patternexacts profound social and economical costs.
In response to increasing anthropogenic forcing, the global monsoon precipitation is expected to amplify over most of theglobal region [1]. However, the response varies from region to region owing to various factors such as topography, forcing etc.
[2]. Recent studies found that monsoon precipitation over India is likely to increase under the global warming scenario with enhanced variability [3, 4]. Similarly, it has also been found that precipitation over the Himalaya particularly over Nepal is poorly
comparable with all India rainfall [5]. Since, study on precipitation over the world’s unique geographical region, Himalaya underwarming scenario is very limited, this study is aimed to investigate the future precipitation change over the Himalaya.
II. Models, Data and Methodology: We employed 26 general circulation models (GCMs) participating in Coupled Model
Intercomparison Project Phase 5 (CMIP5) to evaluate their skill in simulating present monsoon season (June-September) precipitation (MSP) climatology (1979-2005) over Himalaya (20-35 0 N latitude and 75-94 0 E longitude). The skill of the models was
judged based on their ability to represent annual cycle, spatial pattern and variability using Taylor diagram. Global Precipitation
Climatology Project Version 2.2 monthly data was used for the model evaluation. The best model was selected whenever normalized standard deviation (STD) lies in 0.8-1.2, correlation coefficient (CC) >0.5 and centered root mean square (RMS) difference<1. To assess the future change, simulations from Representative Concentration Pathway 2.6 (RCP2.6), 4.5 (RCP4.5) and 8.5(RCP8.5) of selected best models of 2070-2099 were compared with the historical runs of 1970-1999. Monthly precipitation ofeach model from one ensemble (r1i1p1) run was used.
III. Results and Discussions: All the models reproduced annual cycle of mean precipitation over the Himalaya more or lessaccurately with CC is greater than 0.7. Among them, only 13 models met the criteria mentioned in section II for reproducing
annual cycle. We found that simulating the spatial pattern over the complex terrain became a major challenge for the models. Outof the 26 GCMs, only nine of them were comparatively better than others to reproduce spatial pattern with high CC, less variability and error. Likewise, simulation of the STD of MSP was also found to be a problematic one. Taylor diagram of MSP indicatedthat only nine models performed relatively well. Our analysis revealed that neither of the models performed equally to simulate
all three matrices used in this study. Thus, only five models; HadGEM2-ES, MPI-ESM-LR, MPI-ESM-MR, NorESM1-M andNorESM1-ME were selected based on their skill to simulate all three matrices. Ensemble projections of the best models under
RCP8.5 scenario indicated that MSP might be increased by 11 % compared to present climatology with amplified variability overheavy rainfall zone. Multi-model mean annual cycle of monthly precipitation showed the enhancement of monthly precipitation
during monsoon season.
IV. Conclusion: Precipitation over the Himalaya simulated by 26 GCMs was evaluated. No model was found to simulate
all aspects of MSP equally. Relatively, high resolution earth system models performed better than the low resolution models.
Ensemble mean of five reliable models projected that the MSP will increase over the Himalaya in future warmer climate withenhanced variability over the heavy precipitation zones.
References:[1] Lee, J.-Y. and B. Wang, 2014, Clim. Dyn. , 42, 101-119[2] Turner, A. G. and H. Annamalai, 2012, Nat. Clim. Chang. ., 2, 587-595[3] Menon et al., 2013, Earth Syst. Dyn. , 4, 287-300[4] Sharmila et al., 2015, Glob. Planet. Chang. , 124, 62-78[5] Shrestha et al., 2000, Int. J. Climatol. , 20, 317-327

Keywords: Monsoon precipitation, Future projection, CMIP5, Himalaya

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