Systematic daytime increases in atmospheric biases linked to dry soils in irrigated areas in Indian operational forecasts

Barton, Emma J.; Taylor, Christopher M.; Mitra, Ashis K.; Jayakumar, A.

doi:10.1002/asl.1172

Cited by 4 publications

(1 citation statement)

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“…The Coupled Model Intercomparison Project (Phase 6) (CMIP6) climate models, for example, include a basic representation of land‐use and land‐cover change, but very few include irrigation. This can give rise to systematic warm‐and‐dry simulation biases (Barton et al, 2023). Studies have shown that the cooling effects of irrigation may be underestimated by global climate models due to their coarse spatial resolutions (Chen & Dirmeyer, 2020; Sorooshian et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Irrigation contrasts through the morning transition

Brooke,

Best,

Lock

et al. 2023

Quart J Royal Meteoro Soc

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The Land surface Interactions with the Atmosphere over the Iberian Semi‐arid Environment (LIAISE) campaign was conducted in July 2021 primarily to investigate the role of irrigation in modulating the boundary layer evolution in the Catalan region of northeastern Spain. Contrasts in near‐surface meteorological parameters and boundary layer thermodynamic profiles at an irrigated and rainfed (arid) site were established during the morning transition. Evapotranspriation dominated the flux partitioning at the irrigated site (Bowen ratio of 0.07–1.1), whilst sensible heat flux dominated at the rainfed (arid) site (Bowen ratio greater than 10.0). The cumulative evapotranspiration during July 2021 was a factor of 10 greater at the irrigated site than at the rainfed (arid) site. The presence of irrigation was shown to modulate the vertical gradients of turbulence, temperature, and moisture. Irrigation is shown to have a significant effect on the development of the boundary layer including during the morning transition. The morning transition mean buoyancy flux was 2.8 times smaller at the irrigated site (1.1 m2 s−2) compared with the rainfed (arid) site (3.1 m2 s−2), with a resultant delay in the near‐surface buoyancy‐flux crossover time (30‐min to 90‐min) at the irrigated site. At the start of the morning transition (sunrise), the average screen‐level (50 m) temperature was ‐1.2 K (‐1.9 K) colder at the irrigated site relative to the rainfed (arid) site. The colder temperatures at sunrise at the irrigated site are predominately the result of colder boundary layer thermodynamic profile from the previous day. At the end of the morning transition (convective onset), temperature differences between the two sites extend through much of the boundary layer and increased in magnitude. The average screen‐level (50 m) temperature difference was ‐3.6 K (‐2.4 K) colder at the irrigated site relative to the rainfed (arid) site. There was considerable day‐to‐day variability in temperature contrasts at a regional level (‐2.4 to ‐6.0 K).This article is protected by copyright. All rights reserved.

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Section: Introductionmentioning

confidence: 99%

Irrigation contrasts through the morning transition

Brooke,

Best,

Lock

et al. 2023

Quart J Royal Meteoro Soc

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Irrigation impact on boundary layer and precipitation characteristics in Weather Research and Forecasting model simulations during LIAISE‐2021

Udina,

Peinó,

Polls

et al. 2024

Quart J Royal Meteoro Soc

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The Land Surface Interactions with the Atmosphere over the Iberian Semi‐arid Environment (LIAISE) campaign examined the impact of anthropization on the water cycle in terms of land–atmosphere–hydrology interactions. The objective of this study is to assess the effects of irrigation on the atmosphere and on precipitation in Weather Research and Forecasting model simulations during the LIAISE special observation period in July 2021. Comparisons between simulations and observations show better verification scores for air temperature, humidity, and wind speed and direction when the model included the irrigation parametrization, improving the model warm and dry bias at 2 m over irrigated areas. Other changes found are the weakening of the sea breeze circulation and a more realistic surface energy partitioning representation. The boundary‐layer height is lowered in the vicinity of irrigated areas, causing a decrease in the lifting condensation level and the level of free convection, which induce increases in convective available potential energy and convective inhibition. Precipitation differences between simulations become relevant for smaller areas, close to the irrigated land. When convection is parametrized, simulations including irrigation tend to produce a decrease in rainfall (negative feedback), whereas convection‐permitting simulations produce an increase (positive feedback), although the latter underestimates substantially the observed precipitation field. In addition, irrigation activation decreases the areas exceeding moderate hourly precipitation intensities in all simulations. There is a local impact of irrigated land on model‐resolved precipitation accumulations and intensities, although including the irrigation parametrization did not improve the representation of the observed precipitation field, as probably the precipitation systems during the LIAISE special observation period in July 2021 were mostly driven by larger scale perturbations or mesoscale systems, more than by local processes. Results reported here not only contribute to enhance our understanding of irrigation effects upon precipitation but also demonstrate the need to include irrigation parametrizations in numerical forecasts to overcome the biases found.

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