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Regional climate simulations from the Southeast Asia Regional Climate Downscaling/Coordinated Regional Climate Downscaling Experiment – Southeast Asia (SEA) indicated model biases in temperature and rainfall over SEA. Given the influence of sea surface temperature (SST) variability on SEA climate, this study examines SST representation in climate models to investigate its potential contribution to the resulting model biases over the Philippines. Observed SST over SEA is first characterized by its spatial patterns and temporal variability. An analysis of the SST representation over SEA and its potential influence on modelled climate over the Philippines in Coupled Model Intercomparison Project Phase 5 (CMIP5) global climate models (GCMs) is then conducted, followed by an assessment of the potential influence of SST representation in CMIP5 GCMs on downscaled regional climate output. Our results show that GCMs with well represented SSTs (i.e., low bias, well captured variability, and pattern) can produce climate simulations well over the Philippines. Whether or not the GCMs with poor SST representation can perform well is inconclusive. During boreal winter (summer), climate variables with high (low) spatial correlation with model SST get poor (better) spatial correlation with observed climate. Over west of the Philippines, where model SST seasonal variability is captured well, models also adequately simulate climate variables. Results suggest that the negative temperature biases, and positive precipitation and wind speed biases, in both GCMs and downscaled simulations, are associated with negative model SST biases. These findings give a better understanding on how SST potentially influences modelled climatology over the Philippines. [ABSTRACT FROM AUTHOR]

This study uses six regional climate model (RCM) experiments from the Coordinated Regional Climate Downscaling Experiment—Southeast Asia (CORDEX‐SEA) and their driving global climate models (GCM) to investigate the model performance and the time of emergence (ToE) of temperature and precipitation over Vietnam and its seven sub‐climatic regions. A simple delta (multiplicative) bias correction (BC) method has been applied to the model temperature (precipitation). Results show clear added values of the BC downscaled products compared to their driving GCMs, particularly for temperature. The projected trends of RCM temperature during 2006–2100 under two representative concentration pathway (RCP) RCP4.5 and RCP8.5 scenarios are similar to those of their driving GCMs. Consequently, the RCM‐based ToE and GCM‐based ToE are generally consistent for temperature, occurring in the beginning of the 21st century. The earliest and latest ToE occur in summer and winter, respectively. The seasonal differentiation for temperature‐ToEs is stronger in the northern areas compared to the southern areas of Vietnam. The ToE difference between two RCPs increases from the south to the north. As for precipitation, ToE occurs quite late, in the latter half of the 21st century at the earliest. Results from ToE estimations also indicate an opposite precipitation trend between the GCMs and RCMs. The largest difference is in summer over the southern region of Vietnam. The opposite trend between the GCM and RCM precipitation under a similar increasing temperature implies the uncertainty in assessing the impact of warming on hydrological cycles in Vietnam. [ABSTRACT FROM AUTHOR]

This study identified the analogue locations of five big cities and the future appearance of novel climate in Southeast Asia (SEA) at the end of the 21st century under the Representative Concentration Pathways 8.5 (RCP8.5) and 4.5 (RCP4.5) scenarios. A modified version of an existing formulation to estimate climate distance is introduced, using the monthly means of temperature and precipitation from six regional climate experiments and from six global climate models (GCMs). Results showed that regional downscaling allowed a more accurate representation of temperature but displayed a higher variability in rainfall over SEA compared to the GCM performance. The ensemble mean (ENS) experiment had a relatively better performance compared to each individual experiment in representing the monthly time series of temperature and precipitation. The common tendency of climatic relocation towards warmer regions for the five big cities in SEA (Hanoi, Bangkok, Manila, Kuala Lumpur and Jakarta) was prominent with the regional ENS experiment. At the end of the 21st century, the ratio of novel climate areas over SEA, mainly located in low elevation, coastal, equatorial regions, and islands, was less than 2% under RCP4.5, but increased to 24 and 21% under RCP8.5 for the ensemble regional and global experiments, respectively. [ABSTRACT FROM AUTHOR]

This study used a multi‐model ensemble (MME) simulation to project changes in extreme precipitation (EP) over the next century based on four relevant indexes (R95P, FRE, total precipitation [PRCPTOT] and PPER) during the monsoon period (May–September) over eastern Asia. The ensemble model was built from three global climate models from the Coupled Model Inter‐comparison Project Phase 5. The results indicate that the MME results can reproduce observations of the spatial distribution characteristics of EP indexes in eastern Asia. Compared with the reference period of 1986–2005, the EP (R95P), PRCPTOT and the ratio of EP to PRCPTOT (PPER) in eastern Asia will increase during the monsoon period under the three emission scenarios in three durations (the early period: 2020–2039, middle period: 2050–2069 and late period: 2080–2099) throughout the 21st century. This feature is especially strong in southeast China and the Malay Islands. Meanwhile, the variation in the frequency of EP events (FRE) has prominent regional differences, including a decrease in the Yellow River Basin and the Indochina Peninsula and an increase in southeast China. All projected increasing were most significant under high emissions (RCP8.5). This study also suggests that EP would not generally increase in frequency but rather in intensity. With an increase in emissions concentration, the temperature threshold at which EP occurs is likely to rise, so the EP might need triggered by the higher temperatures. [ABSTRACT FROM AUTHOR]

This paper highlights detailed projected changes in rainfall over Thailand for the early (2011–2040), middle (2041–2070) and late (2071–2099) periods of the 21st century under the representative concentration pathways (RCP) 4.5 and RCP 8.5 using the high‐resolution multi‐model simulations of the Coordinated Regional Climate Downscaling Experiment (CORDEX) Southeast Asia. The ensemble mean is calculated based on seven members consisting of six general circulation models (GCMs) and three regional climate models (RCMs). Generally, the ensemble mean precipitation agrees reasonably well with observations, best represented by the Global Precipitation Climatology Center (GPCC) data, over Thailand during the historical period (1976–2005). However, inter‐model variations can be large among ensemble members especially during dry months (December to March) for northern‐central‐eastern parts, and throughout the year for the southern parts of Thailand. Similarly for future projection periods, inter‐model variations in the sign and magnitude of changes exist. The ensemble means of projected changes in rainfall for both RCPs during dry months show distinct contrast between the northern‐central‐eastern parts and the southern parts of Thailand with generally wetter and drier conditions, respectively. The magnitude of change can be as high as 15% of the historical period, which varies depending on the sub‐region, season, projection period, and RCP scenario. In contrast, generally drier conditions are projected during the wet season (June to September) throughout the country for both RCPs where the rainfall reduction can be as high as 10% in some areas. However, the magnitude of projected rainfall changes of some individual models can be much larger than the ensemble means, exceeding 40% in some cases. These projected changes are related to the changes in regional circulations associated with the winter and summer monsoons, which are projected to weaken. The drier (wetter) condition is associated with the enhanced subsidence (rising motion). [ABSTRACT FROM AUTHOR]

Frequently occurring extreme precipitation events have caused severe disasters over the years, especially in monsoon regions such as Southeast Asia and East China (SAEC). Understanding the characteristics of extreme precipitation in SAEC on annual and monthly scales is essential for improving predictions extreme precipitation events. In this study, the temporal and spatial distribution characteristics of extreme precipitation events in the summer half‐year (May to September) are analysed from 1986 to 2015 over SAEC, based on the threshold of extreme precipitation defined with a percentile method and the daily precipitation data from 190 meteorological stations. The results indicate that the precipitation in annual and summer half‐year over the SAEC are mainly attributed to extreme precipitation events. The frequency and amount of extreme precipitation are significant in South China and Southeast Asia, the Yangtze River region, and North China; specifically, the duration of high extreme precipitation events are longer in South China and Southeast Asia compared to those in other areas. The frequency and amount of extreme precipitation increased in South China, Southeast Asia and North China while have a decreasing trend in Yangtze River basin. Further investigation of the possible relationship between summer extreme precipitation events and the activity of the Asian summer monsoon (ASM) indicate that, the movements of extreme precipitation are consistent with the northward advance and southward withdrawal of summer monsoon and are commonly located in the vicinity of the front of the ASM. This phenomenon suggests that summer extreme precipitation events over SAEC are closely connected with ASM activity and may be the products of ASM. The spatial distribution of (a) mean annual extreme precipitation (R95P), (b) mean annual extreme precipitation frequency, (c) annual total precipitation (PRCPTOT) and (d) the proportion of annual extreme precipitation to annual precipitation (PPER) over Southeast Asia and East China during 1986–2015. The black dots denote geographic distribution of 190 stations in Southeast Asia and East China. [ABSTRACT FROM AUTHOR]

The Quantile Mapping (QM) bias correction (BC) technique was applied for the first time to address biases in the simulated precipitation over Vietnam from the Regional Climate Model (RegCM) driven by five Coupled Model Intercomparison Project Phase 5 (CMIP5) Global Climate Model (GCM) products. The QM process was implemented for the period 1986-2005, and subsequently applied to the mid-future period 2046-2065 under both Representative Concentration Pathway (RCP) 4.5 and RCP 8.5. Comparison with the original model outputs during the independent validation period shows a large bias reduction from 45% to 3% over Vietnam and significant improvements in representing precipitation indices (PI) after applying the QM technique. Moreover, the ensemble average of the BC products generally performed better than an individual BC member in capturing the spatial distribution of the PIs. A drier condition with a longer rainfall break, and shorter consecutive rainfall events are anticipated over Northern and Central Vietnam during their respective wet seasons in the mid-future. Furthermore, this study showed that the QM method minimally modified the future changes in PIs over most of Vietnam; thus, these corrected projections could be used in climate impacts and adaptation studies. [ABSTRACT FROM AUTHOR]

ABSTRACT In this study, simulations over Southeast Asia (15°S-40°N, 80°-145°E) at 36 km resolution were conducted for the period 1989-2007 using the Regional Climate Model version 4.3 ( RegCM4.3) under the framework of the Southeast Asia Regional Climate Downscaling/Coordinated Regional Climate Downscaling Experiment - Southeast Asia (or SEACLID/ CORDEX- SEA) project. Forced by the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis (ERA-Interim), 18 experiments were carried out using different combinations of cumulus parameterization and ocean flux schemes. Twelve extreme indices for both rainfall and temperature were estimated from the model output. A statistical omega index was used to measure the degree of similarity among the 18 experiments in phase and shape. The results showed relatively high similarities among the experiments over mainland Asia compared to those over the Maritime Continent for both seasonal and inter-annual variability. The extreme rainfall indices had a lower omega compared to that of temperature. Observed daily rainfall and temperature data at 52 meteorological stations over the SEA region were used to validate the simulated extreme indices. The results showed that extreme temperature indices were generally underestimated across the region. Systematic biases for each simulated rainfall index were also identified. A score ranking system was established to compare the relative performance of the 18 experiments over the 52 selected stations objectively. It was shown that the experiments with the Massachusetts Institute of Technology ( MIT)-Emanuel scheme performed relatively better than the other convective schemes. The combination of the MIT-Emanuel convective scheme with the Biosphere-Atmosphere Transfer scheme ( BATS1e) ocean flux scheme produced the best performance. [ABSTRACT FROM AUTHOR]

ABSTRACT Meteorological droughts in Malaysia have significantly impacted critical sectors such as agriculture, water resources, health, the environment, tourism and various socio‐economic sectors, affecting the population's livelihood and well‐being. This study analyses drought characteristics over a 39‐year period, from 1982 to 2021, using the Standardised Precipitation Index (SPI) derived from 5‐km resolution Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS). The droughts were assessed on 3‐, 6‐, 9‐ and 12‐month timescales to investigate spatio‐temporal variations in characteristics such as frequency, duration, peak, severity and intensity. The study also provides an in‐depth analysis of large‐scale drought modulation, particularly associated with the El Niño phenomenon and its teleconnection in the Maritime Continent. Depending on the location and timescale, the number of meteorological drought occurrences varied from 10 to 22 for the 3‐month timescale and 4 to 14 for the 12‐month timescale. Generally, as the timescale of a drought increases, the peak intensity decreases, while the duration and severity increase. Additionally, drought intensity decreases over longer timescales. These characteristics show significant spatial variations. Results indicate that meteorological droughts in Malaysia were almost entirely modulated by the El Niño phenomenon through its induced teleconnection over the Maritime Continent. Drought characteristics exhibit a strong seasonality linked to changes in the Walker circulation and the strengthening and weakening of anticyclonic circulations associated with Rossby waves induced by heating in the Pacific Ocean. Very strong El Niño events had the most significant influence on the droughts. The positive Indian Ocean Dipole (pIOD) strengthened the effects of El Niño but it itself had no significant influence on the droughts. In most regions, there were no significant trends in the characteristics of meteorological droughts. However, in northeast Peninsular Malaysia and some scattered areas along the west coast of the peninsula, significant trends are observed in peak, duration and severity. [ABSTRACT FROM AUTHOR]

This study examines the projected precipitation extremes for the end of 21st century (2081–2100) over Southeast Asia (SEA) using the output of the Southeast Asia Regional Climate Downscaling/Coordinated Regional Climate Downscaling Experiment – Southeast Asia (SEACLID/CORDEX-SEA). Eight ensemble members, representing a subset of archived CORDEX-SEA simulations at 25 km spatial resolution, were examined for emission scenarios of RCP4.5 and RCP8.5. The study utilised four different indicators of rainfall extreme, i.e. the annual/seasonal rainfall total (PRCPTOT), consecutive dry days (CDD), frequency of extremely heavy rainfall (R50mm) and annual/seasonal maximum of daily rainfall (RX1day). In general, changes in extreme indices are more pronounced and covering wider area under RCP8.5 than RCP4.5. The decrease in annual PRCPTOT is projected over most of SEA region, except for Myanmar and Northern Thailand, with magnitude as much as 20% (30%) under RCP4.5 (RCP8.5) scenario. The most significant and robust changes were noted in CDD, which is projected to increase by as much as 30% under RCP4.5 and 60% under RCP8.5, particularly over Maritime Continent (MC). The projected decrease in PRCPTOT over MC is significant and robust during June to August (JJA) and September to November (SON). During March to May (MAM) under RCP8.5, significant and robust PRCPTOT decreases are also projected over Indochina. The CDD changes during JJA and SON over MC are even higher, more robust and significant compared to the annual changes. At the same time, a wetting tendency is also projected over Indochina. The R50mm and RX1day are projected to increase, during all seasons with significant and robust signal of RX1day during JJA and SON. • Future changes of Southeast Asia precipitation extremes were examined. • The result was derived from the CORDEX-SEA simulations experiments. • The dry tendency is projected over the maritime continent. • Increasing extreme rainfall frequency and intensity over the mainland Indo-China. • Significant and robust change signals during JJA and SON. [ABSTRACT FROM AUTHOR]