Analysis of climatic trends in climate divisions of Oklahoma, U.S.

Authors: SINGH, ASEEM - Oklahoma State University; TAGHVAEIAN, SALEH - Oklahoma State University; MIRCHI, ALI - Oklahoma State University; MANSARAY, ABU - Oklahoma State University; ALDERMAN, PHIL - Oklahoma State University; Moriasi, Daniel

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2023
Publication Date: 1/1/2023
Citation: Singh, A., Taghvaeian, S., Mirchi, A., Mansaray, A., Alderman, P.D., Moriasi, D.N. 2023. Analysis of climatic trends in climate divisions of Oklahoma, U.S. Applied Engineering in Agriculture. 39(2):167-177.

Interpretive Summary: Current and past climate change research indicate increasing global temperatures and precipitation changes. Increased number of dry periods and intensity of precipitation can affect water availability and evapotranspiration, which have important implications for agricultural water management. This study investigated long-term annual and seasonal trends of maximum, average, and minimum air temperature (Tmax, Tavg, and Tmin, respectively), precipitation (P), and reference evapotranspiration (ETo) in the nine climate divisions of Oklahoma, USA, using 70 years of climatological datasets from the National Oceanic and Atmospheric Administration to identify priority areas for agricultural water resources planning and adaptive management. The results show increasing temperature gradients from south to north and increasing P gradients from west to east of the state. Increasing trends were observed in annual Tmin in all climate divisions over time. Increasing trends were also observed in seasonal Tmin and Tavg across different climate divisions whereas decreasing trends were observed in summer Tmax. Winter P showed increasing trends across Oklahoma, while ETo showed decreasing trends only in the south central climate division on an annual basis, and in central and eastern parts of the state during summers. It is important to incorporate the observed trends into planning and management of water resources and agricultural infrastructure in the face of recurring severe droughts.

Technical Abstract: We used monthly climatological datasets from the NOAA U.S. Climate Divisional Database to detect long-term trends (1951-2021) in the nine climate divisions of Oklahoma, U.S. We applied Hargreaves-Samani method to calculate reference evapotranspiration (ETo) and used 12-month standardized precipitation index to characterize meteorological droughts. Modified Mann-Kendall and Sen’s slope non-parametric trend tests were performed to identify significant (p < 0.05) positive and negative trends in maximum, average, and minimum air temperature (Tmax, Tavg, Tmin, respectively), precipitation (P), and ETo on annual and seasonal time scales. Innovative trend analysis and least square regression were used to further support the results. Statistically significant positive trends were observed in annual Tmin in all climate divisions. Statistically significant increasing trends were also observed in Tmin and Tavg on a seasonal scale across different climate divisions whereas significant decreasing trends were observed in summer Tmax. Winter P showed statistically significant increasing trends across Oklahoma. ETo only showed significant decreasing trends in the south central climate division on an annual basis, and in central and eastern parts of the state during summers. The rate of change in temperature ranged from -0.010 °C/yr. to 0.020 °C/yr. The rate of change in P ranged from -0.16 mm/yr. to 3.16 mm/yr. while ETo ranged from -0.44 mm/yr. to 0.42 mm/yr. These trends have critical implications for agricultural management to cope with potential long-term climate impacts on agricultural production, pests and invasive species, water resources, and soil moisture.