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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. | 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 Drought is undoubtedly one of the worst natural hazards 1 . This phenomenon is a normal feature of climate with inevitable occurrence appears 2 . Drought can appear in any place causing significant damage both in natural environment and in human lives. It may start at any time last indefinitely and may attain many degrees of severity 3 . Therefore it has been classified into different types such as meteorological hydrological economic or agricultural drought 4 . Palmer 1965 defined drought as a prolonged and abnormal moisture deficiency. A drought period is an interval of time generally of the order of months or years Corresponding author. Tel. 84-4-38584943. E-mail hangvt@vnu.edu.vn when the moisture supply of a region consistently falls short of the climatically expected or climatically appropriate moisture supply 5 . Investigations of drought are carried out all over the world. However because of the complexity of this natural phenomenon a common methodology for drought studies has not yet been developed .