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ARS Home » Plains Area » Bushland, Texas » Conservation and Production Research Laboratory » Soil and Water Management Research » Research » Publications at this Location » Publication #366415
Research Project: Precipitation and Irrigation Management to Optimize Profits from Crop Production

Location: Soil and Water Management Research

Title: Irrigation impacts on minimum and maximum surface moist enthalpy in the Central Great Plains of the USA

Author
item ZHANG, TIANYI - Kansas State University
item MAHMOOD, REZAUL - University Of Nebraska
item LIN, XIAOMAO - Kansas State University
item PIELKE SR, ROGER - University Of Colorado

Submitted to: Weather and Climate Extremes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2019
Publication Date: 1/18/2019
Citation: Zhang, T., Mahmood, R., Lin, X., Pielke Sr., R.A. 2019. Irrigation impacts on minimum and maximum surface moist enthalpy in the Central Great Plains of the USA. Weather and Climate Extremes. 23:100197. https://doi.org/10.1016/j.wace.2019.100197.
DOI: https://doi.org/10.1016/j.wace.2019.100197

Interpretive Summary: Agricultural activities alter near-surface heat content. However, past research primarily focused on dry bulb temperature without considering the role of relative humidity on surface air heat content. Therefore, scientists from Kansas State University in the ARS-led Ogallala Aquifer Program examined minimum and maximum surface relative humidity and temperature to investigate the potential impacts of irrigation. During the growing season, maximum surface averages were significantly higher in irrigated cropland sites compared to grassland sites. This can be explained by increased transpiration linked to irrigation. Such results are of interest to plant physiologists to better understand parameters that affect crop canopy temperatures.

Technical Abstract: Agricultural activities notably alter weather and climate including near-surface heat content. However, past research primarily focused on dry bulb temperature without considering the role of water vapor (dew point temperature) on surface air heat content. When using dry bulb temperature trends to assess these changes, for example, not including concurrent trends in absolute humidity can lead to errors in the actual rate of warming or cooling. Here we examined minimum and maximum surface moist enthalpy, which can be expressed as “equivalent temperature.” Using hourly climate data in the Central Great Plains (Nebraska and Kansas) from 1990 to 2014, the averages and trends of minimum and maximum equivalent temperature (TE_min; TE_max) were analyzed to investigate the potential impacts of irrigation. During the growing season, TE_max averages were significantly higher in irrigated cropland sites compared to grassland sites. This can be explained by increased transpiration linked to irrigation. In addition, TE_max exhibits a decreasing trend in most sites over the growing season. However, the difference of the trends under irrigated croplands and grasslands is not statistically significant. A longer time series and additional surface energy flux experiments are still needed to better understand the relationships among temperature, energy, and land cover.