Investigation of the 2006 drought and 2007 flood extremes at the Southern Great Plains through an integrative analysis of observations

Abstract

provide a unique opportunity to examine hydrological extremes in the central United States because there are no other examples of two such highly contrasting precipitation extremes occurring in consecutive years at the Southern Great Plains (SGP) in recorded history. The HY06 annual precipitation in the state of Oklahoma, as observed by the Oklahoma Mesonet, is around 61% of the normal (92.84 cm, based on the 1921-2008 climatology), which results in HY06 as the second-driest year in the record. In particular, the total precipitation during the winter of 2005-2006 is only 27% of the normal, and this winter ranks as the driest season. On the other hand, the HY07 annual precipitation amount is 121% of the normal, and HY07 ranks as the seventh-wettest year for the entire state and the wettest year for the central region of the state. Summer 2007 is the second-wettest season for the state. Large-scale dynamics play a key role in these extreme events. During the extreme dry period (11/2005-02/2006), a dipole pattern in the 500 hPa geopotential height anomaly existed where an anomalous high was over the southwestern U.S. region and an anomalous low was over the Great Lakes. This pattern is associated with inhibited moisture transport from the Gulf of Mexico and strong sinking motion over the SGP, both contributing to the extreme dryness. The precipitation deficit over the SGP during the extreme dry period is clearly linked to significantly suppressed cyclonic activity over the southwestern United States, which shows a robust relationship with the western Pacific teleconnection pattern. The precipitation events during the extreme wet period (May-July 2007) were initially generated by active synoptic weather patterns, linked with moisture transport from the Gulf of Mexico by the northward low-level jet, and enhanced the frequency of thunderstorms and their associated latent heat release. Although the drought and pluvial conditions are dominated by large-scale dynamic patterns, we have found two possible positive feedback processes during the extreme dry and wet periods in this study that play key certain roles to maintain and reinforce the length and severity of existing drought and flood events. For example, during the extreme dry period, with less clouds, liquid water path, precipitable water vapor, precipitation, and thinner Cu cloud thickness, more net radiation was absorbed and used to evaporate water from the ground. The evaporated moisture, however, was removed by low-level divergence. Thus, with less precipitation and removed atmospheric moisture, more absorbed incoming solar radiation was used to increase surface temperature and to make the ground drier.

A Remotely Sensed Global Terrestrial Drought Severity Index

“…The DSI results are also consistent with the severe drought in the contiguous United States in 2006 (Fig. 1) and reported by Dong et al (2011).…”

Land surface phenology along urban to rural gradients in the U.S. Great Plains

“…The drought experienced by much of the region in 2006 (Dong et al, 2011) generally resulted in a contraction of the ISA-modulated amplitude response in the western Texas cities, where the rural vegetation signal was relatively indistinguishable from the urban one during periods of drought (Fig. 8).…”

“…Precipitation rates generally decrease along an east to west gradient, from a mean 20th century high of 1180 mm in the east Texas municipalities of Longview, Texarkana, and Tyler, to a low of 315 mm approximately 725 km west, in the town of Odessa, Texas (NOAA NCDC, 2014a). During the time frame of this study, the region experienced area-specific drought conditions in multiple years : 2002: , 2007: (Dong et al, 2011NOAA NCDC, 2014b). The unusually warm spring of 2012 prompted early flowering and budding across much of the region (Ault et al, 2013).…”

Assessing extreme droughts in Spain during 1750–1850 from rogation ceremonies

“…recorded across large regions of western United States, as well as in the Southern Plains (Dong et al, 2011). Since 1997, Southeast Australia has been gripped by the most severe drought in the last 120 years, the so-called "Big Dry" (Murphy and Timbal, 2008).…”