Were the 2010 Pakistan floods predictable?
P. J. Webster, V. E. Toma, and H.‐M. Kim
GEOPHYSICAL RESEARCH LETTERS, VOL. 38, L04806, doi:10.1029/2010GL046346, 2011
http://www.agu.org/pubs/crossref/2011/2010GL046346.shtml
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During July 2010, a series of monsoonal deluges over northern Pakistan resulted in catastrophic flooding, loss of life and property and an agricultural crisis that may last for years. Was the rainfall abnormal compared to previous years? Furthermore, could a high probability of flooding have been predicted? To address these questions, regional precipitation is analyzed using three dataset sets covering the 1981–2010 time period. It is concluded that the 2010 average May to August (MJJA) rainfall for year 2010 is somewhat greater in magnitude than previous years. However, the rainfall rate of the July deluges, especially in North Pakistan was exceptionally rare as deduced from limited data. The location of the deluges over the mountainous northern part of the country lead to the devastating floods. The European Centre for Medium Range Weather Forecasts (ECMWF) 15-day Ensemble Prediction System (EPS) is used to assess whether the rainfall over the flood affected region was predictable. A multi-year analysis shows that Pakistan rainfall is highly predictable out to 6–8 days including rainfall in the summer of 2010. We conclude that if these extended quantitative precipitation forecasts had been available in Pakistan, the high risk of flooding could have been foreseen. If these rainfall forecasts had been coupled to a hydrological model then the high risk of extensive and prolonged flooding could have anticipated and actions taken to mitigate their impact.
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多大な被害をもたらした2010年のパキスタンの大洪水。
その異常性と予測可能性を議論した論文。
TRMMとCMORPHの観測データ、ECMWFのアンサンブル予測
などから丁寧に議論している。
とりわけ、ECMWFのアンサンブル予報、
リードタイムでいうと15日前からの予測雨量が
どのように変化していったかを見ている
Figure 3が興味深い。
けっこうきちんと当たっているのですね。
あと、災害にあわせてレターを出したという雰囲気ではなくて、
普段から同様の分野を専門としている人による
「専門家の分析」なのだなぁ、と引用文献リストを見て実感。
自分が使いこなせる理論とデータを持っていることは重要だな。
あと、現実を把握する手段としてのデータ同化は
現場を対象とするモデルを専門とするなら、
やはり避けては通れない道ですね。