2006-2015 Mega-drought in the Western USA from NOAA Operational Satellites

During 2014 and early 2015, scientific and online publications strongly focused on the multi-year drought over western USA showing its dramatic consequences for the USA economy, environment and society. Considering such an extraordinary drought, many questions related to its beginning, duration, dynamics, intensity, genesis, extend and frequency became unanswered and/or sometimes even controversial. How different is this current event from the extraordinary US drought of the 1930s and other intensive droughts? Is this drought can be classified as a mega-drought? This paper attempts to answer most of these questions by applying NOAA global operational satellite system estimating vegetation health. It is shown that the latest western USA drought started in 2006 and has continued for nine full years. Since the vegetation stress is still continuing in the first few months of 2015 (when this paper is written) coming into the 10th year, this drought was classified as “mega-drought.” In 2006, when the drought began, vegetation was stressed over 61% western USA and during 2012 and 2013 (strongest drought intensification) this area increased to 71% and 67%, respectively. All 17 states of the western two third of the USA were affected by this drought, especially South Dakota, Nebraska, Oklahoma, Texas, Montana and Wyoming with up to 100% of a state area with severe vegetation stress during 2012-2014. Compared to other catastrophic droughts of the past 100 years, the current drought in the worst year (2012) affected 71.3% western USA, which is comparable with the drought area in 1934 (71.6%) and much higher than in 1956 (49%) and 1988 (31%). In terms of number of drought years, the other droughts in the western USA (1985-1986, 1988-1992, 1995-1996, and 2001-2003) were shorter and less intensive. Among western states, California was the most severely drought-affected, especially in 2014, when areas of stronger than moderate vegetation stress reached 70 percent.