Understanding the Sensitivity of Different Drought Metrics to the Drivers of Drought under Increased Atmospheric CO2
Understanding the Sensitivity of Different Drought Metrics to the Drivers of Drought under Increased Atmospheric CO2
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DOI：
10.1175/2011jhm1386.1
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发表时间：
2011-12-01
影响因子：
3.8
通讯作者：
Burke, Eleanor J.
中科院分区：
文献类型：
--
作者：
Burke, Eleanor J.
一个扰动物理学哈德利中心气候模式集合被用来研究干旱对大气CO2加倍的影响。分析的干旱指标是基于1）降水异常，2）土壤水分异常。（3）帕尔默干旱严重度指数（PDSI）。在单一CO2条件下，干旱发生率为17%。在CO2加倍时，一般来说，PDSI干旱比土壤水分干旱发生得更频繁，土壤水分干旱比降水干旱发生得更频繁。本文探讨了每个干旱指标对干旱主要驱动因素（即降水和可用能量）变化的相对敏感性。当平均降水量减少、平均可利用能量增加、降水量标准差增加、可利用能量标准差减少时，干旱有增加的趋势。简单的线性近似表明，干旱的敏感性，平均降水量的变化是相似的三个不同的指标。然而，干旱对平均可用能量变化的敏感性（预计在大气CO2增加的情况下会增加）高度依赖于度量：PDSI干旱最敏感，土壤湿度不太敏感，降水独立于可用能量。干旱指标对驱动因素变异性的变化只有轻微的敏感性。干旱的另一个驱动因素是植物对二氧化碳增加的反应。这一过程减少了蒸散量，增加了土壤湿度，通常会导致土壤湿度减少干旱。相反，可用能量的相关增加通常会导致PDSI干旱的增加。在制定适应战略时，需要考虑到这些不同的敏感性。
A perturbed physics Hadley Centre climate model ensemble was used to study changes in drought on doubling atmospheric CO2. The drought metrics analyzed were based on 1) precipitation anomalies, 2) soil moisture anomalies. and 3) the Palmer drought severity index (PDSI). Drought was assumed to occur 17% of the time under single CO2. On doubling CO2, in general, PDSI drought occurs more often than soil moisture drought, which occurs more often than precipitation drought. This paper explores the relative sensitivity of each drought metric to changes in the main drivers of drought, namely precipitation and available energy. Drought tends to increase when the mean precipitation decreases, the mean available energy increases, the standard deviation of precipitation increases, and the standard deviation of available energy decreases. Simple linear approximations show that the sensitivity of drought to changes in mean precipitation is similar for the three different metrics. However, the sensitivity of drought to changes in the mean available energy (which is projected to increase under increased atmospheric CO2) is highly dependent on metric: with PDSI drought the most sensitive, soil moisture less sensitive, and precipitation independent of available energy. Drought metrics are only slightly sensitive to changes in the variability of the drivers. An additional driver of drought is the response of plants to increased CO2. This process reduces evapotranspiration and increases soil moisture, and generally causes less soil moisture drought. In contrast, the associated increase in available energy generally causes an increase in PDSI drought. These differing sensitivities need to be taken into consideration when developing adaptation strategies.