Building on almost 10 years of expertise and operational application of the Combined Drought Indicator (CDI), which is implemented within the European Commission's European Drought Observatory (EDO) for the purposes of early warning and monitoring of agricultural droughts in Europe, this paper proposes a revised version of the index. The CDI conceptualizes drought as a cascade process, where a precipitation shortage (WATCH stage) develops into a soil water deficit (WARNING stage), which in turn leads to stress for vegetation (ALERT stage). The main goal of the revised CDI proposed here is to improve the indicator's performance for those events that are currently not reliably represented, without altering either the modelling conceptual framework or the required input datasets. This is achieved by means of two main modifications: (a) use of the previously occurring CDI value to improve the temporal consistency of the time series and (b) introduction of two temporary classes – namely TEMPORARY RECOVERY for soil moisture and vegetation greenness, respectively – to avoid brief discontinuities in a stage. The efficacy of the modifications is tested by comparing the performances of the revised and currently implemented versions of the indicator for actual drought events in Europe during the last 20 years. The revised CDI reliably reproduces the evolution of major droughts, outperforming the current version of the indicator, especially for long-lasting events, and reducing the overall temporal inconsistencies in stage sequencing of about 70 %. Since the revised CDI does not need supplementary input datasets, it is suitable for operational implementation within the EDO drought monitoring system.

中文翻译：

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欧洲干旱天文台（EDO）使用的综合干旱指标（CDI）的修订版

基于近十年的综合干旱指标（CDI）的专业知识和操作应用，该指标在欧洲委员会的欧洲干旱观测站（EDO）内实施，目的是对欧洲的农业干旱进行早期预警和监测。索引的修订版。CDI将干旱概念化为一个级联过程，其中降水不足（WATCH阶段）发展为土壤缺水（WARNING阶段），进而导致植被压力（ALERT阶段）。此处提出的修订的CDI的主要目标是在不更改建模概念框架或所需输入数据集的情况下，针对那些当前无法可靠表示的事件提高指标的绩效。这是通过两个主要修改来实现的：（a）使用先前出现的CDI值来改善时间序列的时间一致性，以及（b）引入两个临时类-分别是土壤水分和植被绿色度的临时恢复-以避免阶段中的短暂中断。通过比较过去20年中欧洲实际干旱事件指标的修订版和当前实施版的性能，测试了修改的有效性。修订后的CDI可靠地重现了主要干旱的演变，胜过了当前版本的指标，尤其是对于持续时间较长的指标，并减少了约70％的阶段排序总体时间不一致。由于修订后的CDI不需要补充输入数据集，