Quantitative Analysis and Statistics of Land-atmosphere Interactions at Oklahoma Mesonet Sites during Drought Periods

Land-atmosphere interactions play an important role in influencing weather and climate on both local and regional scales. Quantifying the variability of evapotranspiration (ET), which is a critical link to land-atmosphere interactions, would contribute to a better understanding of drought development and alleviation during dry periods. This study estimated ET at Oklahoma Mesonet sites across Oklahoma from 2000 to 2013 by combining in situ data and normalized difference vegetation index (NDVI) values from MODIS sensors from Terra and Aqua satellites via the Mesonet Evapotranspiration Model (MEMo). Climatological analyses of ET as well as the anomaly analyses were conducted for each of the 9 climate divisions of Oklahoma and for the whole state at temporal periods spanning months, seasons and the annual cycle. Statistical methodologies were utilized to acquire the spatial and temporal correlation, lag analysis and coupling strength between ET, soil moisture, vegetation, and atmospheric demand. Results and plots from the analysis demonstrated a 14-year climate of ET across Oklahoma and the statistical relationship between the key variables in the land-atmosphere interactions during drought periods in the studied years. Additionally, specific cases picked from this 14-year period were studied to have an insightful view of significant droughts and flash droughts.