Assessing the convective environment over irrigated and non-irrigated land use with land-atmosphere coupling metrics: Results from grainex

Authors: WHITESEL, DANIEL - University Of Nebraska; MAHMOOD, REZAUL - University Of Nebraska; PHILLIPS, CHRISTOPHER - University Of Alabama; ROUNDY, JOSHUA - University Of Kansas; RAPPIN, ERIC - Western Kentucky University; Flanagan, Paul; SANTANELLO, JOSEPH - National Aeronautics And Space Administration (NASA); NAIR, UDAYSANKAR - University Of Alabama; PIELKE SR, ROGER - University Of Colorado

Submitted to: Journal of Hydrometeorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2024
Publication Date: 7/1/2024
Citation: Whitesel, D., Mahmood, R., Phillips, C., Roundy, J., Rappin, E., Flanagan, P.X., Santanello, J., Nair, U., Pielke Sr, R. 2024. Assessing the convective environment over irrigated and non-irrigated land use with land-atmosphere coupling metrics: Results from grainex. Journal of Hydrometeorology. 25(7):1061-1080. https://doi.org/10.1175/JHM-D-23-0187.1.
DOI: https://doi.org/10.1175/JHM-D-23-0187.1

Interpretive Summary: The impact of the land surface on the atmosphere is widely studied, but gaps still exist. In this study, the knowledge gap between irrigation and its impact on the development of the lower atmosphere is investigated. Using data from a field campaign in Nebraska, this study computes several metrics developed to investigate the relationship between the land surface and the evolution of the daily low-level atmospheric environment. The results of this study show that the lower atmospheric environment becomes more favorable for supporting intense thunderstorms across irrigated areas, compared to non-irrigated areas, during the latter part of the growing season when irrigation is more widespread. Earlier in the growing season, prior to the start of widespread irrigation, deep convection was favored over non-irrigated crop fields compared to the other sites investigated. Overall, the results of this work show the impact of irrigation on the evolution of the daily convective environment, and how that impact changes depending on the time of year and intensity of irrigation practices. USDA is an equal opportunity provider and employer.

Technical Abstract: Land use land cover change affects weather and climate. This paper quantifies land-atmosphere interactions over irrigated and non-irrigated land uses during the Great Plains Irrigation Experiment (GRAINEX). Three coupling metrics were used to quantify some land-atmosphere interactions as it relates to convection. They include: the Convective Triggering Potential (CTP) and the Low-Level Humidity Index (HIlow), and the Lifting Condensation Level (LCL) Deficit. These metrics’ were calculated from the rawinsonde data obtained from the Integrated Sounding Systems (ISS) for Rogers Farm and York Airport along with soundings launched from the Doppler on Wheels (DOW) sites. Each metric was categorized by Intensive Observation Period (IOP), cloud cover, and the time of day. The results show that with higher CTP, lower HIlow, and lower LCL Deficit, conditions were more favorable for convective development over irrigated land use. When metrics were grouped and analyzed by IOP, compared to non-irrigated land use, HIlow was found to be lower for irrigated land use suggesting favorable conditions for convective development. Furthermore, when metrics were grouped and analyzed by clear and non-clear days, CTP values were higher over irrigated cropland compared to non-irrigated land use. In addition, compared to non-irrigated land use, LCL Deficit during the peak growing season was lower over irrigated land use, suggesting favorable condition for convection. It is found that with the transition from the early summer to the mid/peak summer and increased irrigation, the environment became more favorable for convective development over irrigated land use. Finally, it was found that regardless of background atmospheric conditions, irrigated land use provided favorable environment for convective development. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. USDA is an equal opportunity provider and employer.