MỐI QUAN HỆ GIỮA ĐỘNG VẬT ĐÁY CÓ GIÁ TRỊ KINH TẾ CHỦ YẾU VỚI ĐẶC TRƯNG SINH THÁI CỦA ĐẦM THỊ NẠI, VIỆT NAM

Relations between economic zoobenthos species and ecological characteristics of Thi Nai lagoon were reported as results of three surveys carried out during 2014–2015. The results have pointed out 11 zoobenthos species that have primarily economic value at the Thi Nai lagoon (5 bivalve species, 5 crustacea species and 1 gastropoda species). Bivalve group possesses 91% of the entire commercial yield of benthic animal (7,456.9 tons/year), in which Glauconome chinensis and Gari elongata possess dominatingly (possess 90% of the entire commercial yield of bivalves: 6,817 tons/year). Bivalve and gastropoda groups were found in correlation with sandy sediment and mangroves but crustacea group was found in correlation with muddy sand sediments and seagrass. The results of this study will conntribute the scientific basis for further studies on the trophic relationship, food web and data for planning, zoning and appropriate exploitation of fisheries resources.Mối quan hệ giữa động vật đáy (ĐVĐ) có giá trị kinh tế chủ yếu với đặc trưng sinh thái của đầm Thị Nại được xác định thông qua 3 đợt điều tra khảo sát từ năm 2014-2015. Kết quả đã xác định được 11 loài ĐVĐ (5 loài Bivalvia, 5 loài Crustacea và 1 loài Gastropoda) có giá trị kinh tế chủ yếu trong đầm Thị Nại, trong đó nhóm hai mảnh vỏ chiếm trên 91% tổng sản lượng thương phẩm ĐVĐ (7.456,9 tấn) và tập trung chủ yếu vào hai loài Glauconome chinensis và Gari elongata (chiếm trên 90% tổng sản lượng hai mảnh vỏ: 6.817 tấn/năm). Nhóm hai mảnh vỏ và chân bụng có quan hệ chặt chẽ với trầm tích đáy cát và RNM, nhưng nhóm giáp xác có quan hệ chặt chẽ với ở trầm tích đáy cát bùn và TCB. Kết quả nghiên cứu này cung cấp cơ sở khoa học cho việc nghiên cứu về chuỗi thức ăn và cung cấp dữ liệu cho phục hồi, bảo tồn sinh cư; quy hoạch, phân vùng và khai thác thủy sản hợp lý

ĐẶC TRƯNG KHAI THÁC NGUỒN LỢI ĐỘNG VẬT ĐÁY CÓ GIÁ TRỊ KINH TẾ CHỦ YẾU Ở THỦY VỰC NHA PHU, KHÁNH HÒA

The exploitation characteristics of zoobenthos resources with economic value at the Nha Phu waters were determined by five field trips carried out from 2011 - 2016. The results shows that Nha Phu waters have had great exploitation pressure, with high density of boats (11.9 motorboats/100 ha, 7.7 boats/100 ha and 16.2 people/100 ha), average days of fishery exploitation being high (185 days/fishery/year) and concentrating mainly in the dry season (70% of total average days of fishery/year), specially the destructive artisanal fisheries, (56% of total time of fishery). The average yeild of fishery was dominant in the dry season (73% of total commercial yield and 93% of total number of benthic animal seeds), in which the destructive artisanal fisheries possess 73% of the entire yield of benthic animal. Yields of zoobenthos have decreased seriously, specially for crustaceans (17%). It may be due to greater pressure of fishery exploitation, especially the destructive artisanal fisheries. The results of this study will contribute the scientific basis and data to planning for effective exploitation and management of fisheries resources.Đặc trưng khai thác nguồn lợi động vật đáy có giá trị kinh tế chủ yếu ở thủy vực Nha Phu, Việt Nam được xác định thông qua 5 chuyến điều tra khảo sát từ năm 2011 - 2016. Kết quả nghiên cứu cho thấy, thủy vực Nha Phu có áp lực khai thác lớn, với mật độ phương tiện (11,9 ghe/100 ha, 7,7 sỏng/100 ha và 16,2 người/100 ha), số nghề (13 nghề) và thời gian khai thác trung bình nghề khá cao (185 ngày/nghề/năm) và tập trung chủ yếu vào mùa khô (chiếm gần 70% tổng thời gian hoạt động trung bình nghề/năm), đặc biệt nghề khai thác hủy diệt tận thu như xiết điện, lưới lồng, cào máy, giã cào (chiếm trên 56% tổng thời gian năm). Sản lượng của các nghề khai thác chiếm ưu thế vào mùa khô (chiếm trên 73% tổng sản lượng khai thác thương phẩm (423,9 tấn/năm) và trên 93% tổng con giống (161.000 con giống/năm) động vật đáy cả năm), trong đó các nghề hủy diệt, tận thu chiếm chiếm trên 73% tổng sản lượng động vật đáy. Thành phần và sản lượng nguồn lợi động vật đáy có chiều hướng suy giảm nghiêm trọng, đặc biệt nguồn lợi giáp xác (giảm 17%). Nguyên nhân có thể do thời gian hoạt động trung bình/năm và doanh thu của các loại nghề khá cao, đặc biệt nghề khai thác mang tính hủy diệt, tận thu. Kết quả nghiên cứu này cung cấp cơ sở khoa học và dữ liệu cho quy hoạch khai thác và quản lý nguồn lợi thủy sản hợp lý

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

Sensitivity of Southeast Asia rainfall simulations to cumulus and air-sea flux parameterizations in RegCM4

We investigated the performance of RegCM4 in simulating rainfall over Southeast Asia with different combinations of deep-convection and air-sea flux parameterization schemes. Four different gridded rainfall datasets were used for the model assessment. In general, the simulations produced dry biases over the equatorial region and slightly wet biases over mainland Indo-China, except those experiments with the MIT Emanuel cumulus schemes, in which large positive rainfall biases were simulated. However, simulations with the MIT schemes were generally better at reproducing annual rainfall variations. The simulations were not sensitive to the treatment of air-sea fluxes. While the simulations generally produced the rainfall climatology well, all simulations showed stronger inter-annual variability compared to observations. Nevertheless, the time evolution of the inter-annual variations was well reproduced, particularly over the eastern Maritime Continent. Over mainland Southeast Asia, all simulations produced unrealistic rainfall anomaly responses to surface temperature. The lack of summer air-sea interactions in the model resulted in enhanced oceanic forcing over the regions, leading to positive rainfall anomalies during years with warm ocean temperature anomalies. This shortcoming in turn caused much stronger atmospheric forcing on the land surface processes compared to that of the observation. A robust score-ranking system was designed to rank the simulations according to their performance in reproducing different aspects of rainfall characteristics. The results suggest that the simulation with the MIT Emanuel convective scheme and the BATS1e air-sea flux scheme performs better overall compared to the rest of the simulations

Projected Future Changes in Mean Precipitation Over Thailand Based on Multi-Model Regional Climate Simulations of CORDEX Southeast Asia

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)

Projected future changes in mean precipitation over Thailand based on multi‐model regional climate simulations of CORDEX Southeast Asia

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)

Projected Future Changes in Rainfall in Southeast Asia Based on CORDEX–SEA Multi-Model Simulations

This paper examines the projected changes in rainfall in Southeast Asia (SEA) in the twenty-first century based on the multi-model simulations of the Southeast Asia Regional Climate Downscaling/Coordinated Regional Climate Downscaling Experiment–Southeast Asia (SEACLID/CORDEX–SEA). A total of 11 General Circulation Models (GCMs) have been downscaled using 7 Regional Climate Models (RCMs) to a resolution of 25 km × 25 km over the SEA domain (89.5° E–146.5° E, 14.8° S–27.0° N) for two different representative concentration pathways (RCP) scenarios, RCP4.5 and RCP8.5. The 1976–2005 period is considered as the historical period for evaluating the changes in seasonal precipitation of December–January–February (DJF) and June–July–August (JJA) over future periods of the early (2011–2040), mid (2041–2070) and late twenty-first century (2071–2099). The ensemble mean shows a good reproduction of the SEA climatological mean spatial precipitation pattern with systematic wet biases, which originated largely from simulations using the RegCM4 model. Increases in mean rainfall (10–20%) are projected throughout the twenty-first century over Indochina and eastern Philippines during DJF while a drying tendency prevails over the Maritime Continent. For JJA, projections of both RCPs indicate reductions in mean rainfall (10–30%) over the Maritime Continent, particularly over the Indonesian region by mid and late twenty-first century. However, examination of individual member responses shows prominent inter-model variations, reflecting uncertainty in the projections