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Abstract This paper analyzed observations from the Great Plains Irrigation Experiment (GRAINEX) to better understand L-A interactions and PBL evolution. This study is focused on a day when the largest forcing on the boundary layer originated from the land surface/land use. To examine these impacts, we also applied the Weather Research and Forecasting (WRF) model. Results from the observations show that compared to non-irrigated areas, air temperature, wind speed, and PBL height were lower while dew point temperature and latent heat flux were higher over irrigated areas. Findings suggest that entrainment layer drying and differences in energy partitioning over irrigated and non-irrigated areas played an important role in PBL evolution. In the final hours of the day, the PBL collapsed faster over non-irrigated areas compared to irrigated. The WRF model simulations agree with these observations. They also show that the extent of irrigation (expressed as irrigation fraction or IF) in an area impacts L-A response. Under ∼60% IF, the latent heat flux and mixing ratio reach their highest value while temperature and PBLH are at their lowest, and sensible heat flux is near its lowest value. Results are reversed for ∼2% IF. It is concluded that irrigation notably impacts L-A interactions and PBL evolution.
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Influence of Irrigation on Diurnal Mesoscale Circulations: Results From GRAINEX
Abstract In order to understand the impact of irrigation on weather and climate, the 2018 Great Plains Irrigation Experiment collected comprehensive observations straddling irrigated and non‐irrigated regions in southeast Nebraska. Using these observations, we examine how irrigation affects diurnal terrain‐generated slope circulations, specifically the slope wind. We find that irrigation applied to upslope regions of gently sloping terrain reduces terrain‐induced baroclinicity and the associated pressure gradient force by up to two‐thirds. This leads to the reduction in the afternoon and evening upslope wind and is supported through comparisons to the High‐Resolution Rapid Refresh operational model, which does not explicitly account for irrigation. Additionally, the presence of irrigation decreases daytime sensible heat flux (Bowen ratio reduced 40% compared to non‐irrigated regions), weakening turbulent transport of momentum. Modifications to the terrain‐forced circulation by irrigation has the potential to affect moisture transport and thus cloud and precipitation formation over the Great Plains.
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- Award ID(s):
- 1720477
- PAR ID:
- 10381072
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 49
- Issue:
- 7
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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