Spatial and temporal patterns of drought in Oklahoma (1901–2014)

Abstract

This study uses the Standardized Precipitation Evapotranspiration Index (SPEI) at a 6‐month timescale to document the spatial and temporal patterns of drought in Oklahoma from 1901 to 2014. A principal component analysis (PCA) with a VARIMAX rotation was used to divide Oklahoma into four spatially contiguous regions with similar drought patterns that are located in northwestern, northeastern, southwestern and southeastern regions of the state. Droughts tend to occur more frequently in northwestern Oklahoma, but all four regions show that droughts in Oklahoma have substantial variability at decadal timescales. A Mann–Kendall trend test demonstrates that there has been a statistically significant increase in the SPEI in Oklahoma since 1901. This indicates that conditions are generally getting wetter in Oklahoma. However, there is substantial variability in moisture conditions that is evident at shorter timescales. Prolonged periods of drier than normal conditions occurred in the 1910s, 1930s, 1950s, 1970s and 1980s, while conditions from the 1980s to the 2000s have been wetter than normal. Recently, the SPEI has decreased, which suggests that Oklahoma may be at the beginning of another dry cycle. In addition, while most droughts during the study period were caused by decreases in precipitation, recent droughts, such as the severe drought in 2011, were caused by both decreases in precipitation and increases in potential evapotranspiration. This may be indicative of future drought conditions in Oklahoma.

Spatial–Temporal Evolution of Drought Characteristics Over Hungary Between 1961 and 2010

“…As many scholars (e.g. Tan et al 2015;Tian and Quiring 2019) indicate results of an MK test may be affected by autocorrelations of the time series. Thus, pre-whitening was applied before conducting the MK test to reduce the effects of the autocorrelation on the trend detection.…”

“…In order to produce more localized spatial regions, the Varimax orthogonal rotation method was applied to the ''loadings'' (the correlation matrix between the SPI time series at single stations and the corresponding PCA); because it simplifies the structure of the patterns by forcing the value of the loading coefficients towards zero or ± 1 (Hannachi et al 2007;Raziei et al 2009;Tian and Quiring 2019). In the next step, the loadings scores were illustrated using ArcGIS software as a thematic map (i.e.…”

Exploring the Evolution of Drought Characteristics in Balochistan, Pakistan

“…Various thresholds have been used in the literature for identifying droughts. Tian and Quiring [20] used the objective SPEI drought threshold in Oklahoma, which was −0.7. Liu et al [18] and Jamro et al [26] used −0.5 as their chosen thresholds.…”

“…Therefore, SPEI reflects the effects of temperature on droughts, and so is more suitable for drought monitoring in a changing climate. There have been various studies conducted that show the efficiency of SPEI as an index to monitor and characterize droughts [14][15][16][17][18][19][20][21][22]. SPEI has also been documented to be a suitable indicator for monitoring droughts in Pakistan [14,23].…”

Spatio-Temporal Variability of Drought in Pakistan Using Standardized Precipitation Evapotranspiration Index

“…The arithmetical mean of drought duration, severity, intensity, and peak is used to compare different zones. Several studies have used the run theory for the identification and characterization of droughts [18,19,21,23,41].…”