Analyzing Past and Predicting Future Droughts with Comprehensive Drought Indices for Arkansas-Red River Basin
This study intends to examine the past and predict future drought scenarios for Arkansas-Red River Basin with comprehensive drought indices in areas of study including meteorology, hydrometeorology, and hydrology. In this proceeding, we present some early results and analysis with the Standardized Precipitation Index (SPI) and the Palmer Drought Severity Index (PDSI). Historical climate data of 1900-2009 were archived to derive the drought indices calculation as well as projected A2 and A1B climate data from 16 statistically downscaled Global Climate Models (GCM). These datasets were applied in drought occurrence frequency and affected area prediction. The results from SPI and PDSI show that widespread drought took place in the 1910s, 1930s, 1950s and 1960s, which agrees with the historical climate record. Both SPI and PDSI indicate more frequent droughts in the second part of the 21st century, but predictions from the two indices were carried out under different scenarios. Figure 1. Arkansas-Red River Basin (ABRFC) 1. Past and Future Climate •The temperature in the ABRFC displayed an upward trend after 2010 and it is projected to increase by 4-5 degrees by the end of the century. Precipitation however does not show a discernible trend overall, although the A2 scenario shows a slight decreasing trend after 2050. •The two indicators both capture the major droughts in the 1950s and the 1960s. SPI and PDSI agree quite well from 1950 to 1999 but not for the future period. •According to the SPI, ABRFC is under wet conditions for the first half of the 21st century, but precipitation becomes less abundant after 2060 which leads to a severe drought in the mid to late 2060s followed by another severe drought in the late 2070s. This indicates a possible drought cycle of 110 years looking back at the drought occurrence throughout 20th and 21st century. •According to PDSI, it appears that overall this region is going to get drier and the western portions of the ABRFC region will experience a more severe drought than the eastern portions during the next 90 years. The simulation does however indicate that a wetter period will occur from 2010 - 2039. SPI Values 2.0+ extremely wet 1.5 to 1.99 very wet 1.0 to 1.49 moderately wet -.99 to .99 near normal -1.0 to -1.49 moderately dry -1.5 to -1.99 severely dry -2 and less extremely dry Palmer Classifications 4.0+ extremely wet 3.0 to 3.99 very wet 2.0 to 2.99 moderately wet 1.0 to 1.99 slightly wet 0.5 to 0.99 incipient wet spell 0.49 to -0.49 near normal -0.5 to -0.99 incipient dry spell -1.0 to -1.99 mild drought -2.0 to -2.99 moderate drought -3.0 to -3.99 severe drought -4.0 and less extreme drought Table 3. SPI classification Table 4. PDSI classification Figure 2. Drought classification Drought index Inputs Indicator for SPI (Standardized Precipitation Index) Precipitation Meteorological drought PDSI (Palmar Drought Severity Index) Precipitation Temperature Meteorological drought Table 2. Drought indices information 2. Past and Future Drought Variables taken into account Complexity Cons SPI Precipitation Easier 1.Doesn’t consider evapotranspiration 2.Simple, not necessarily indicate drought 3.Requires quite a long period of precipitation record PDSI Precipitation and temperature More difficult 1.Sensitive to soil type 2.All precipitation is treated as rain 3.Underestimation of runoff 4.Potential evapotranspiration is estimated from Thornthwaite model 3. Comparison Data Source Data Parameters Resolution Time Period Data Type WCRP CMIP3 Precipitation Temperature 1/8 degree (~15 km) 1950-1999 (simulation) 2000-2099 (projection) Gridded monthly data PRISM Precipitation 4 km 1900-2000 (simulation) Gridded monthly data Table 1. Data used in research The two indices describe future drought from a temporal and a spatial perspective. Future SPI indicates there might be 110 years of drought cycles occurring in the Arkansas-Red River Basin under A2, and future PDSI shows more severe droughts in the western portions of the Arkansas-Red River Basin under A1B.
Red River Basin, historical climate record, Standard Percipitation Index, Palmer Drought severity Index, drought prediction
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