Convective suppression before and during the United States Northern Great Plains flash drought of 2017

Abstract

Abstract. Flash droughts tend to be disproportionately destructive because they intensify rapidly and are difficult to prepare for. We demonstrate that the 2017 US Northern Great Plains (NGP) flash drought was preceded by a breakdown of land–atmosphere coupling. Severe drought conditions in the NGP were first identified by drought monitors in late May 2017 and rapidly progressed to exceptional drought in July. The likelihood of convective precipitation in May 2017 in northeastern Montana, however, resembled that of a typical August when rain is unlikely. Based on the lower tropospheric humidity index (HIlow), convective rain was suppressed by the atmosphere on nearly 50 % of days during March in NE Montana and central North Dakota, compared to 30 % during a normal year. Micrometeorological variables, including potential evapotranspiration (ETp), were neither anomalously high nor low before the onset of drought. Incorporating convective likelihood to drought forecasts would have noted that convective precipitation in the NGP was anomalously unlikely during the early growing season of 2017. It may therefore be useful to do so in regions that rely on convective precipitation.

Multicomponent Satellite Assessment of Drought Severity in the Contiguous United States From 2002 to 2017 Using AMSR‐E and AMSR2

“…In contrast to the widespread drought conditions of the region in August, comparatively little drought was reported by the USDM in May 2017 (Figure a). However, anomalous low precipitation and high temperatures were observed for the month (Wang et al, ), while both the PDSI‐Z and ASWI (Figures b and c) detected severe spring drought onset in eastern Montana and North Dakota, which preceded and exacerbated more severe summer drought conditions across the region (Gerken et al, ; Otkin et al, ). The ASWI component influence map also indicated that the major contributions to the drought initially stemmed from anomalously high VPD levels (Figure d), which intensified surface evaporation and soil moisture depletion (Gerken et al, ; Otkin et al, ).…”

“…Qualitative comparisons were made between the ASWI record and the other drought indices for three major drought events occurring within the CONUS domain during the 2002-2017 study period. These severe droughts included (a) the 2012 Great Plains Drought (Hoerling et al, 2014), (b) the 2012-2015 California Drought (Griffin & Anchukaitis, 2014), and (c) the 2017 Northern Plains Drought (Gerken et al, 2018). The respective PDSI-Z, USDM, and ASWI data from August 2012, June 2014, and August 2017 were used for plotting relative drought severity maps and assessing the associated events from each index.…”

“…The 2017 Northern Plains Drought was a severe flash drought that rapidly developed from late May to September 2017 and was associated with anomalously low convective precipitation (Gerken et al, 2018). The drought sparked widespread wildfires and caused approximately $2.6 billion in losses to the agricultural sector alone (Hoell et al, 2019).…”

“…The contiguous United States (CONUS) has experienced severe droughts since 2002, which have caused profound impacts to the environment and economy (Gerken et al, 2018;Griffin & Anchukaitis, 2014;Hoerling et al, 2014;Pielke et al, 2005). Drought is a natural disaster associated with the prolonged shortage of water stored in the lower atmosphere or near surface soil and groundwater (Wilhite & Glantz, 1985).…”

“…Drought is a natural disaster associated with the prolonged shortage of water stored in the lower atmosphere or near surface soil and groundwater (Wilhite & Glantz, 1985). Persistent continental drought is often associated with sea surface temperature anomalies (AghaKouchak et al, 2015;Dai, 2011), while regional flash drought, characterized by a rapid rate of intensification (Otkin et al, 2018) and generally driven by anomalously warm temperatures and low precipitation (Mo & Lettenmaier, 2016), may be exacerbated by local land-atmosphere interactions (Gerken et al, 2018). Climate variability can have cascading impacts on the terrestrial water cycle at local to regional scales, leading to meteorological drought exemplified by a shortage of precipitation or increase of potential evapotranspiration, agricultural drought characterized by below-normal soil moisture, or relatively slower-progressing hydrological drought associated with declining terrestrial water storage (AghaKouchak et al, 2015;Dai, 2011;Dracup et al, 1980;Heim, 2002).…”