Applied climatology: drought

I Introduction By linking climatic variations with the fundamental biological requirement of water availability , drought is a primary topic within applied climatology. Drought acts as a unifying climatological approach that provides valuable information for agricultural, ecological, and hydrological applications. While a lack of water is straightforward to comprehend and appreciate, a wide array of approaches are used in the analysis of drought. However defined, drought can be thought of as an extended period of time where water availability is lower than expected or needed. With growing population and resource pressures, as well as a number of severe and ongoing droughts worldwide, this is an active time for drought research. There has been a wide range of recent developments in drought research that include near real-time monitoring , improved drought reconstructions via proxies, and high-resolution simulations of future drought conditions. Although proxy records of drought continue to play an important role in the characterization of drought conditions, this brief report will focus on three topics within drought research that are most relevant to applied climatology: (1) modern drought monitoring using instrumental products, (2) impacts of recent climatic change on drought variability, and (3) modeling of modern and future drought. In all cases, a selection of the recent literature on precipitation variations and associated drought conditions is reviewed, synthesized, and critiqued. II Modern drought monitoring and analysis Despite a number of well-documented limitations (Guttman et al. Drought Severity Index (PDSI) continues to be a central approach in drought monitoring. The PDSI is useful because it (1) incorporates cumulative anomalies of both moisture supply and demand and (2) has recognized categories of moisture defi cit and surplus, even though the categories themselves are somewhat obscure. Use of the term 'PDSI' also can be somewhat ambiguous, as there are a number of different formulations, including recent contributions that allow spatial comparisons to be more meaningful (Wells et al., 2004) and that improve the identifi cation of drought onset (Rhee and Carbone, 2007). The complexity and limitations of the PDSI – primarily its lack of spatial and temporal stationarity, which make spatial comparisons difficult and change-detection *