Báo cáo nghiên cứu khoa học An analysis of drought conditions in Central Vietnam during 1961-2007

Dữ liệu lượng mưa hàng tháng được đưa ra bởi các quan sát khí tượng bề mặt trong thời gian 1961-2007 ở miền Trung Việt Nam được sử dụng để tính toán các chỉ số hạn hán. Kết quả cho thấy rằng các điều kiện hạn hán hơi tăng ở Bắc Trung Bộ Việt Nam nhưng lại giảm ở Nam Trung Bộ và Tây Nguyên Việt Nam. Đáng kể thời gian hạn hán thường xảy ra từ tháng một-Tháng ba. Tỷ lệ phần trăm của những năm khô hạn trong thời gian 1961-2007 là lớn hơn trong giai đoạn tham...
Nội dung trích xuất từ tài liệu:
Báo cáo nghiên cứu khoa học " An analysis of drought conditions in Central Vietnam during 1961-2007 "VNU Journal of Science, Earth Sciences 26 (2010) 75-81 An analysis of drought conditions in Central Vietnam during 1961-2007 Vu Thanh Hang*, Nguyen Thi Trang Faculty of Hydro-Meteorology and Oceanography, Hanoi University of Science, VNU, 334 Nguyen Trai, Hanoi, Vietnam Received 05 September 2010; received in revised form 24 September 2010 Abstract. Monthly rainfall data given by surface meteorological observations during the period 1961-2007 in Central Vietnam is used to calculate drought indices. Results show that drought conditions slightly increase in North Central Vietnam but decrease in South Central and Highland Central Vietnam. Significant drought periods often occur from January to March. The percentage of dry years during the period 1961-2007 is larger than that in the reference period of 1961-1990 in North Central while smaller in South Central and almost similar to that in Highland Central Vietnam. Keywords: Drought, trend, Central Vietnam.1. Introduction when the moisture supply of a region consistently falls short of the climatically Drought is undoubtedly one of the worst expected or climatically appropriate moisturenatural hazards [1]. This phenomenon is a supply [5].normal feature of climate with inevitable Investigations of drought are carried out alloccurrence appears [2]. Drought can appear in over the world. However, because of theany place causing significant damage both in complexity of this natural phenomenon, anatural environment and in human lives. It may common methodology for drought studies hasstart at any time, last indefinitely and may attain not yet been developed, althought some indicesmany degrees of severity [3]. Therefore, it has of drought are widely used [6]. Drought indicesbeen classified into different types such as are normally continuous functions of rainfallmeteorological, hydrological, economic, or and/or temperature, river discharge or otheragricultural drought [4]. Palmer (1965) defined measurable hydrometeorological variable.drought as a prolonged and abnormal moisture Many indices have been devised for differentdeficiency. A drought period is an interval of types of drought, including the Rainfalltime, generally of the order of months or years, Anomaly index, the Palmer Drought index_______ (PDI), the Bhalme-Mooley index, the Corresponding author. Tel.: 84-4-38584943. Standardized Anomaly index, etc [5,7-9]. The E-mail: hangvt@vnu.edu.vn 7576 V.T. Hang, N.T. Trang / VNU Journal of Science, Earth Sciences 26 (2010) 75-81 where the symbol j = 1, ... , N denotes years, xi ismost well known and the widely used of the the total annual precipitation in the ith station, xidrought index is PDI. The index has been usedin various studies to illustrate the areal extent is the averaged annual precipitation for the stationand severity of drought in the northeastern ith, and n is number of stations. Values of P > 1United States during the early to mid-1960s and indicate wet conditions, values of P < 1 indicateacross the United States during the hot, dry drought conditions, and P = 1 is normalsummer of 1980 [10,11]. condition. An analysis of moisture extremes over The frequency distribution of annualEurope shows strong decadal-scale variability pre ...