Validation of the WRF regional climate model over the subregions of Southeast Asia: climatology and interannual variability

This study investigates the capability of a regional climate model in simulating the climate variability over Southeast Asia (SE Asia). The present-day climate, covering the period 1991 to 2015, was dynamically downscaled using the Weather Research and Forecasting (WRF) model with a horizontal resolution of 27 km. The initial and boundary conditions for the WRF model is provided with the European Centre for medium-range weather forecasting (ECMWF) reanalysis (ERA-Interim) data. The model reproduced the mean precipitation climatology as well as the annual cycle. Nevertheless, the model overestimated the boreal summer precipitation over the SE Asian mainland, and underestimated the boreal winter precipitation over the Indonesian region. Model biases are associated with the bias in simulating the vertically integrated moisture fluxes. At an interannual scale, the model shows good performance over the SE Asian mainland and the Philippines in all seasons except for the boreal summer. The influence of El Niño/Southern Oscillation (ENSO) on rainfall over mainland SE Asia and the Philippines during JJA is weak, and the model successfully simulated the weak relationship realistically. In contrast, model interannual variability over the Indonesia region is good only in boreal summer and autumn seasons. This is because the model successfully simulated the significant negative correlation between rainfall and ENSO. The influence of the Indian Ocean Dipole (IOD) is seen only in the boreal autumn over the Indonesian region, and the model reproduced it reasonably well. The improvement in the representation of precipitation anomaly associated with ENSO/IOD is due to reasonably accurate simulation of large-scale circulation over SE Asia

Heatwave impact on mortality and morbidity and associated vulnerable factors : a systematic review protocol

Heatwave can increase the risk for heat-related illnesses and mortality. Many studies showed certain population are vulnerable to heatwave such as elderly, children and low-income households. However, the findings were inconsistent. This study aims to identify the effect of heatwave on the mortality and morbidity and associated vulnerability factors. Five electronic databases (Pubmed, Ebsco Host, WOS, OVID Medline and Scopus) will be the primary searching tools to retrieve relevant literatures. An additional searching tool (Google Scholar) will be used to seek for grey literatures. Selection of literature will be based on the inclusion criteria (empirical full-text article, English language and published between 2010-2021). Two authors will be assigned in each step of the process, starting from screening of the title, abstract and full text based on the inclusion criteria, data extraction and quality appraisal. Mixed-Method Appraisal Tool (MMAT) will be utilized to assess the quality of selected articles. Meta-analysis, thematic analysis and narrative approach will be the option used to describe the findings. This study protocol is registered under PROSPERO (CRD42021232847). This study presents a reliable and valid systematic review process that identifies a comprehensive evidence-based information on impacts of heatwave on human health especially upon the vulnerable groups

A baseline study of tropical phytoplankton abundance and its relationships to the environmental variables in the Terengganu river estuary, Malaysia

Phytoplankton is a vital and important organism as a producer of the primary food supply of the marine and freshwater food webs. This study is conducted to investigate the variability of phytoplankton abundance related to environmental variables in the Terengganu River Estuary, by using statistical analysis. Total of ten water samples were collected, of which three stations were in the estuary and seven stations were in the coastal water. A total of 124 taxa of 55 genera, belonging to six taxonomic classes were observed at the study area. The order of phytoplankton abundance was diatoms > blue-green algae > golden-brown algae > dinofalgellates > green algae > euglenoids. The phytoplankton abundance was higher in the coastal area compared to the estuary, with the maximum density 764.10 cells mL-1 and 157.40 cells mL-1 respectively. It was recorded that 10.96% of the total abundance from the data collection was registered in the estuary, while the remaining 89.04% were logged in the coastal region. The freshwater phytoplankton was dominated by golden-brown algae (Chrysophyceae), while marine phytoplankton was governed by diatoms and blue-green algae. It was observed that the water temperature and salinity were positively correlated with marine phytoplankton but negatively related to freshwater phytoplankton. High levels of water temperature and hypersalinity at the coastal region was observed to enhance the production rate in the coastal region. In contrast, the nutrients were positively related to freshwater phytoplankton, but negatively correlated to the marine phytoplankton, which results in low concentrations of nutrients in the coastal region that could be caused by intensive uptake by the abundance of marine phytoplankton. This study revealed that environmental variables are an important element in determining the phytoplankton community compositions in the tropical region

Drought variability and characteristics in the Muda river basin of Malaysia from 1985 to 2019

This study aimed to analyze the spatiotemporal changes of historical droughts over the Muda River basin (MRB), Malaysia, from 1985 to 2019 using the Standardized Precipitation Index (SPI) and the Standardized Streamflow Index (SSI). The Mann–Kendall test and Sens’ slope were used to evaluate the trends and magnitude changes in the droughts, respectively, while Spearman’s rho was applied to understand the relationships of the droughts with large-scale atmospheric circulations, such as the El Niño Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and the Madden– Julian Oscillation (MJO). The results show that the intense droughts in the MRB mostly occurred in 1991–1992, 1995, 1998, 2002–2003, 2005–2006, 2008, 2012–2013, and 2016. In addition, a declining SPI trend was found from May to December at most of the stations. About 80% of the stations experienced about 10 severely dry droughts, while almost all stations experienced at least 5 extremely dry events. Moreover, a higher response rate of the SSI than the SPI was found during low-rainfall months from January to May. Lastly, ENSO had a larger impact on the drought formations over the MRB compared to the IOD and MJO, especially during the dry period

Improvement of the ESA CCI land cover maps for water balance analysis in tropical regions: A case study in the Muda River Basin, Malaysia

Study region: The Muda River Basin (MRB), Malaysia. Study Focus: This study proposed a framework to improve the European Space Agency Climate Change Initiative Land Cover (ESA CCI LC) products through the integration with the Annual Oil Palm Dataset (AOPD). The improved land use land cover (LULC) maps were then used to produce five LULC scenarios as input maps into the Soil and Water Assessment Tool (SWAT) model for analyzing the impact of LULC changes on water balance in the MRB. New hydrological insights for the region: The improved LULC maps have good performance in representing rubber and oil palm, with an overall accuracy up to 81 %. In addition, SWAT simulated monthly streamflow well for the MRB, with the highest R2 and NSE values of 0.84 and 0.86, respectively. During the 2001–2016 period, the MRB experienced an expansion of oil palm from 7.10%–17.36 %, a reduction of rubber from 34.93 % to 26.38 % and a slight decrease in forest from 54.23%–52.80 %. The urban expansion scenario showed significant increment in surface runoff, while the reforestation scenario helped to reduce surface runoff, while increase lateral flow and groundwater. Oil palm expansion led to a higher reduction in lateral flow and groundwater than rubber trees due to the higher soil water absorption rate. The proposed framework can be duplicated and applied in other tropical basins, particularly in Indonesia and Malaysia

Global exposure of population and land‐use to meteorological droughts under different warming levels and SSPs: a CORDEX‐based study

Global warming is likely to cause a progressive drought increase in some regions, but how population and natural resources will be affected is still underexplored. This study focuses on global population, forests, croplands and pastures exposure to meteorological drought hazard in the 21st century, expressed as frequency and severity of drought events. As input, we use a large ensemble of climate simulations from the Coordinated Regional Climate Downscaling Experiment (CORDEX), population projections from the NASA-SEDAC dataset and land-use projections from the Land-Use Harmonization 2 project for 1981–2100. The exposure to drought hazard is presented for five Shared Socioeconomic Pathways (SSP1-SSP5) at four Global Warming Levels (GWLs: 1.5°C to 4°C). Results show that considering only Standardized Precipitation Index (SPI; based on precipitation), the SSP3 at GWL4 projects the largest fraction of the global population (14%) to experience an increase in drought frequency and severity (versus 1981–2010), with this value increasing to 60% if temperature is considered (indirectly included in the Standardized Precipitation-Evapotranspiration Index, SPEI). With SPEI, considering the highest GWL for each SSP, 8 (for SSP2, SSP4, SSP5) and 11 (SSP3) billion people, that is, more than 90%, will be affected by at least one unprecedented drought. For SSP5 at GWL4, approximately 2 × 10$^{6}$ km$^{2}$ of forests and croplands (respectively, 6% and 11%) and 1.5 × 10$^{6}$ km$^{2}$ of pastures (19%) will be exposed to increased drought frequency and severity according to SPI, but for SPEI this extent will rise to 17 × 10$^{6}$ km$^{2}$ of forests (49%), 6 × 10$^{6}$ km$^{2}$ of pastures (78%) and 12 × 10$^{6}$ km$^{2}$ of croplands (67%), being mid-latitudes the most affected. The projected likely increase of drought frequency and severity significantly increases population and land-use exposure to drought, even at low GWLs, thus extensive mitigation and adaptation efforts are needed to avoid the most severe impacts of climate change

Future changes in annual precipitation extremes over Southeast Asia under global warming of 2°C

THIS ARTICLE PROVIDES detailed information on projected changes in annual precipitation extremes over Southeast Asia under global warming of 2°C based on the multi-model simulations of the Southeast Asia Regional Climate Downscaling/Coordinated Regional Climate Downscaling Experiment Southeast Asia (SEACLID/CORDEX-SEA). Four indices of extreme precipitation are considered: annual total precipitation (PRCPTOT), consecutive dry days (CDD), frequency of rainfall exceeding 50 mm/day (R50mm), and intensity of extreme precipitation (RX1day). The ensemble mean of 10 simulations showed reasonable performance in simulating observed characteristics of extreme precipitation during the historical period of 1986–2005. The year 2041 was taken as the year when global mean temperature reaches 2°C above pre-industrial levels under unmitigated climate change scenario based on Karmalkar and Bradley (2017). Results indicate that the most prominent changes during the period of 2031–2051 were largely significant. Robust increases in CDD imply impending drier conditions over Indonesia, while increases in RX1day suggest more intense rainfall events over most of Indochina under 2°C global warming scenario. Furthermore, northern Myanmar is projected to experience increases in CDD, R50mm and RX1day, suggesting that the area may face more serious repercussions than other areas in Southeast Asia

The worldwide C3S CORDEX grand ensemble: A major contribution to assess regional climate change in the IPCC AR6 Atlas

peer reviewedAbstract The collaboration between the Coordinated Regional Climate Downscaling Experiment (CORDEX) and the Earth System Grid Federation (ESGF) provides open access to an unprecedented ensemble of Regional Climate Model (RCM) simulations, across the 14 CORDEX continental-scale domains, with global coverage. These simulations have been used as a new line of evidence to assess regional climate projections in the latest contribution of the Working Group I (WGI) to the IPCC Sixth Assessment Report (AR6), particularly in the regional chapters and the Atlas. Here, we present the work done in the framework of the Copernicus Climate Change Service (C3S) to assemble a consistent worldwide CORDEX grand ensemble, aligned with the deadlines and activities of IPCC AR6. This work addressed the uneven and heterogeneous availability of CORDEX ESGF data by supporting publication in CORDEX domains with few archived simulations and performing quality control. It also addressed the lack of comprehensive documentation by compiling information from all contributing regional models, allowing for an informed use of data. In addition to presenting the worldwide CORDEX dataset, we assess here its consistency for precipitation and temperature by comparing climate change signals in regions with overlapping CORDEX domains, obtaining overall coincident regional climate change signals. The C3S CORDEX dataset has been used for the assessment of regional climate change in the IPCC AR6 (and for the interactive Atlas) and is available through the Copernicus Climate Data Store (CDS)