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.

A review on irrigation parameterizations in Earth system models

“…Enhanced dataset together with uncertainty estimates can help to better integrate irrigation as a human activity in Earth system approaches an reanalyzes especially with respect to an enhanced representation of the terrestrial water cycle. Two field campaigns in the recent years have addressed the impact of irrigation on the climate system employing intensive observational periods (IOPs), namely GRAINEX (Phillips et al, 2022) and LIAISE . LIASE field campaign data and review has not been published yet, as it was undergoing in 2021.…”

“…Irrigation water volumes used during GRAINEX were not available due to policy issues in Nebraska (Christopher Phillips, personal communication). However, the GrainEX IOPs provide a fair good knowledge of the timing and the field locations through indirect observations (Phillips et al, 2022), e.g., soil moisture peaks in absence of precipitation. This concept has also been previously used by Brocca et al (2014) for the SM2RAIN algorithm, which combines soil moisture satellite products with rainfall estimations to quantify the missing precipitation.…”

Irrigation strongly influences near‐surface conditions and induces breeze circulation: Observational and model‐based evidence

“…This change is primarily due to changes in the surface turbulent fluxes of heat and water vapour, also called sensible and latent heat fluxes respectively. Irrigation modifies the partitioning of available surface energy between sensible and latent heat fluxes to the benefit of the latter (Phillips et al, 2022; Segal & Arritt, 1992; Sorooshian et al, 2011). Lobell et al (2008) ran a global climate model from 1978 to 1999 to quantify the influence of irrigation on the surface energy balance (SEB) and temperatures in several irrigated areas across the world.…”

“…The change in turbulent fluxes and near‐surface temperature and humidity then influences the atmosphere above. By reducing the sensible heat flux at the surface, irrigation also inhibits convection, thereby stabilizing the atmospheric boundary layer (ABL) and reducing its thickness (Lawston et al, 2020; Phillips et al, 2022; Qian et al, 2020; Sridhar, 2013; Valmassoi et al, 2020; Yang et al, 2017). Valmassoi et al (2020) mentions, for example, a decrease in the average height of the ABL from 1.5 to 1 km over the months of June and July 2015 in the Po Valley, Italy.…”

Where does the irrigated water in the Tarim Basin go? A hydrological analysis of water budgets and atmospheric transport

“…Meanwhile, irrigation is demonstrated to remarkably influence hydro-climate by altering surface energy balance (SEB) and hydrological cycle (McPherson 2007, Biggs et al 2008, Sridhar 2013, Yang et al 2019: enhanced evaporation can alter SEB by reducing sensible heat fluxes and increasing latent heat fluxes and lead to reduced surface temperature and diurnal temperature range, at both global and regional scales (Haddeland et al 2006, Mahmood et al 2006, Sacks et al 2009, Ozdogan et al 2010, Puma and Cook 2010, Sorooshian et al 2011, Kueppers and Snyder 2012, Han and Yang 2013, Jiang et al 2014, Chen and Dirmeyer 2019; irrigation modifies the hydrological cycle by increasing soil moisture and surface moisture fluxes, resulting in the increase of the amount of atmospheric water which may indirectly enhance cloud cover and precipitation (Zheng and Eltahir 1998, Boucher et al 2004, Gordon et al 2005, Mahmood et al 2008, Lo and Famiglietti 2013, Tuinenburg et al 2014, Lo et al 2021. And such influences in precipitation by irrigation are found at both local and regional scales (Segal et al 1998, Im et al 2013, Phillips et al 2022 but through different pathways.…”