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- II. -Easterly wind forecasting
- Where
- III. - Cursory about predicting the salinity and water are surged by easterly wind
IN THE MEKONG DELTAI. - BackgroundAgricultural production is one of the main food and food-staff programs of the National economy of Vietnam. That is why one of the most important tasks of the Hydrometeorological Service is to serve Agricultural production in the province. The Mekong River delta constitutes the most important food production area of Vietnam. With regard to the Mekong River delta, the problem of making the best use of fresh water resources is necessary and urgent for agricultural production. The Mekong River delta has high basic temperature with monthly mean temperature ranging from 25o to 29oC and solar radiation; duration and sunshine are plentiful. The total amount of solar radiation fluctuates from 370 to 400 cal/cm2 per day and 145 to 155 kcal/cm2 per years. Average balance of solar radiation is about 6 to 11 kcal/cm2 per day and 85 to 95 kcal/cm2 per years. The rainfall regime changes considerably with irregular distribution. The rainfall amount is about 1400 to 2000 mm per year. There are two seasons in a year: dry season (from December of previous year to April of present year) and wet season (from May to November). The rainfall amount in wet season occupies 90% out of yearly rainfall volumes. These create unfavorable conditions for agricultural production causing inundation in wet season and draught in dry season. The Mekong river delta, being situated along coastal area of East Sea, with developed river and canal systems and river density of about 25 to 30m/ha is greatly influenced by tidal regime. Tide is really useful for agricultural production especially in dry season. The farmers know how to take advantages of tide raising to get fresh water for their cultivation. Although tide create favourable conditions for agricultural production it also brings about salt water intrusion which affect or kill crops growing in vast area. At present, 40% out of the total cultivated area of the Mekong river delta is intruded by salt water causing great difficulties for agricultural production in the Mekong river delta (about 1.7 million hectares of total 4 million). Salinity intrusion into the Mekong river system is a result of integration of three major factors: salinity propagation from the sea under effect of tides and wind induced water surge; water balance of the entire river system; geographical, topographic and hydrodynamic structure of system. Salinity water comes from the sea, so its effect on salinity regime is the most important factor from the above-described ones, especially during dry season with the north-easterly monsoons prevailing on the South Vietnam shelf. It should be noted that the sea effect presents in two forms: tide and sea is surged by wind. Tide changes harmoniously and it is not difficult to obtain rules of its activities by analysing relatively sufficient series of observed data on water level. Concerning easterly wind forecast for computed water river level and salinity surge has d II. -Easterly wind forecastingDuring the actual operation of the salinity forecasting in the Mekong River delta of Vietnam, it is noticed that one of specific factors perceptibly related to the accuracy of forecasts is a local easterly wind (locally called GIO CHUONG). This wind is under the atmospheric circulation of the north-easterly monsoon in the South East Asia and is evident in geophysical conditions along the coastline covered Mekong River delta of Vietnam. The Southern Region Hydro-Meteorological Centre (SRHMC) with its experienced staff is technically capable of resolving the problem of improving the understanding and applicability of the local easterly wind in order to match the specific local characteristics and to increase the forecast accuracy. 1. Data collection Daily 4-observation data during easterly wind seasons will be collected. 1.1 Wind data Wind speed and direction at boundary stations (Vung Tau, Con Dao, Truong Sa), at stations in the hinterland (Tan An, Vinh Long, Cang Long, Can Tho, Soc Trang, Ba Tri, Vung Tau) and ship data obtained from synoptic charts of corresponding period of time. 1.2 Air pressure As air pressure is directly related with easterly wind formation and movement, it is necessary to collect air pressure at selected stations as follow: Station code: 492 – in China. 820 – Hanoi. 839 – Bachlongvi. 855 – Danang. 918 – Condao. 2. Statistically analysing and classifying synoptic systems associated with easterly wind at synoptic charts. 3. Analysing meteorological factors and the above mentioned atmospheric processes to: a. Establish weather models corresponded to easterly wind surges in order to improve the knowledge of its formation reasons and its movement laws. b C = a * p . Determine an experimental formula for calculating wind speed as follows: 
Where:A is an experimental coefficient implying complicated factor unexplained by the theory of wind calculation in the sub-equatorial zone. p is different of air pressures at station 492 and 820 respectively (in case of 5-day to 10-day in advance forecast), 839 and 918, 855 and 918 respectively (in case of 24-hour to 48-hour in advance forecast). III. - Cursory about predicting the salinity and water are surged by easterly windIV. – Conclusion and recommendationThe Mekong River delta constitutes the most important food production area of Vietnam. One of the most serious problems in the Mekong River delta is salinity intrusion in dry season. Salinity affects nearly half of delta lands in Vietnam. Studies on problem of the salinity intrusion have undertaken by the SRHMC and Mekong River Commission. The hydrodynamic model in general simulates very well the actual situation of salinity intrusion into entire estuary system. However, the some problem of the salinity forecasts with some large errors, the following points can be noted: - But when the salinity forecasts were given we did not forecasted the meteorological conditions, such as: * However, that strong east wind caused suddenly rise of maximum salinity and river water level all stations can not be forecasted correctly. * The local rainfall which could affect very close with salinity. It is obvious that salinity reduces when the local rainy. In order to forecast salinity intrusion successfully, it is necessary to improve forecasting quality easterlies wind based on all obtain results as well as other works and studies RELATIONSHIP BETWEEN SUMMER MONSOON OF INDIA AND EAST ASIA Leâ Thò Xuaân Lan Southern Regional Hydrometeorological Centre
Каталог: haiphong haiphong -> Xác định đóng góp của khoa học và công nghệ vào Năng suất yếu tố tổng hợp (tfp) haiphong -> CỘng hòa xã HỘi chủ nghĩa việt nam độc lập – Tự do – Hạnh phúc haiphong -> CỘng hòa xã HỘi chủ nghĩa việt nam độc lập – Tự do – Hạnh phúc haiphong -> Mẫu số 10 Ban hành kèm theo Thông tư số 38/2010/tt-blđtbxh ngày 24 tháng 12 năm 2010 của Bộ Lao động-Thương binh và Xã hội CƠ quan có thẩm quyền công ty haiphong -> CỤc thống kê tp hải phòng cộng hoà XÃ HỘi chủ nghĩa việt nam haiphong -> CỤc thống kê tp hải phòng cộng hoà XÃ HỘi chủ nghĩa việt nam haiphong -> Nghị định của Chính phủ số 107/2004/NĐ-cp ngày 01 tháng 4 năm 2004 quy định số lượng Phó Chủ tịch và cơ cấu thành viên Uỷ ban nhân dân các cấp haiphong -> BỘ XÂy dựng haiphong -> Nghị ĐỊnh của chính phủ SỐ 75/2006/NĐ-cp ngàY 02 tháng 8 NĂM 2006 quy đỊnh chi tiết và HƯỚng dẫn thi hành một số ĐIỀu của luật giáo dụC haiphong -> BỘ TÀi chính tải về 1.08 Mb. Chia sẻ với bạn bè của bạn:
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