tailieunhanh - Drought and Water Cruises: Science, Technology, and Management Issues - Chapter 2

Kiểm tra các hồ sơ khí hậu dài hạn ở một số vùng trên toàn thế giới cho thấy xu hướng kéo dài và thời gian của Lượng mưa trung bình dưới kéo dài trong nhiều năm cho một thập kỷ hoặc hơn, trong khi các khu vực khác hiện nhiều tập, hạn hán ngắn hơn. Do đó nó rất hữu ích để xem xét các dự báo hạn hán theo mùa để khoảng thời gian interannual và, một cách riêng biệt, còn tuần mười ngày khoảng thời gian | Part II Drought and Water Management The Role of Science and Technology Copyright 2005 by Taylor Francis Group 2 The Challenge of Climate Prediction in Mitigating Drought Impacts NEVILLE NICHOLLS MICHAEL J. COUGHLAN AND KARL MONNiK CONTENTS I. Forecasting Drought. 34 A. Introduction. 34 B. Seasonal to Interannual Prediction. 34 1. Forecasts Based on Empirical Analysis of the Climate Record . 33 2. Explicit Computer Model Predictions. 36 C. Can We Forecast Droughts on Even Longer Time Scales . 38 II. Climate Prediction and Drought Early Warning Systems. 39 III. Impediments to Using Climate Predictions for Drought Mitigation . 44 IV. Climate Change and Drought Mitigation. 46 References. 47 33 Copyright 2005 by Taylor Francis Group 34 Nicholls et al. I. FORECASTING DROUGHT A. Introduction Examination of the long-term climate records in some regions around the globe reveals persistent trends and periods of below-average rainfall extending over years to a decade or more while other regions exhibit episodic shorter droughts. Hence it is useful to consider the prediction of droughts on seasonal to interannual timescales and separately on longer decadal timescales. B. Seasonal to Interannual Prediction Our theoretical ability to make an explicit reliable prediction of an individual weather event reduces to very low levels by about 10-15 days this is called the weather predictability barrier so forecasts with lead times longer than this should be couched in probabilistic terms. Consequently a forecast with a lead time of a month or more requires a statistical basis for arriving at a set of probability estimates for the ensuing seasonal to interannual conditions. Two approaches allow us to derive these estimates. The first is based on statistical analyses of the climatic record and assumptions about the degree to which the statistics of the future record will differ from the past record. The second and more recent approach is based on the generation of statistics from .