Climatic Drought Conditions in US and India during the Past Century

Abstract:

The public and governments have a serious concern on increasing drought threats, particularly whether those are caused by climate change. Literature shows inconsistent assessments of drought conditions in the past century. The most recent assessment of the IPCC (Fifth Assessment Report, AR5) concludes that there is not enough evidence available in favor of or against any global trend in drought with high confidence, and admits that the global increasing trend in drought suggested by the IPCC AR4 was probably overestimated. On the other hand, droughts are expected to intensify in the future at regional level. This study joins many such efforts to assess drought conditions in the US and India during the past century using Palmer Drought Severity Index (PDSI) from two latest datasets (Dai 2011 and 2013; Sheffield et al. 2012). Besides the trend analyses of PDSI based on mean global or regional PDSI time series, we conduct frequency analysis by calculating the return period of drought with a particular intensity and duration. The following results will be presented: 1) the trend and abrupt changes of regional drought represented by historical PDSI, and 2) the change of the frequency, intensity and duration of drought events during the past century, in the continental states of the US and northern India. Preliminary results show that drought variables are highly correlated, and thus Copulas joint distribution is used to enable the calculation of multivariate return periods. Implications for drought risk management in places in US and India will be discussed.

Dai, A., 2011a: Characteristics and trends in various forms of the Palmer Drought Severity Index (PDSI) during 1900-2008. J. Geophys. Res., 116, D12115, doi:10.1029/2010JD015541.

Dai, A., 2013: Increasing drought under global warming in observations and models. . Nature Climate Change, 3, 52-58. DOI: 10.1038/nclimate1633.

Sheffield, J., E. F. Wood, and M. L. Roderick, 2012: Little change in global drought over the past 60 years. Nature, 491, 435–438. doi:10.1038/nature11575.