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- Title
Effects of irrigation: A study with new parameterizations within the WRF-ARW model, the case of the Po Valley (Italy).
- Authors
Valmassoi, Arianna; Dudhia, Jimy; Sabatino, Silvana Di; Pilla, Francesco
- Abstract
Local climate and agriculture production are strongly intertwined. Agriculture strongly relieson irrigation to increase the yield, both in arid region and not. However, the impact ofirrigation on the local climate is not well understood. The majority of the studies found that ithas a local cooling effect with a different magnitude depending on the representation, regionand model used. For some specific regions, such as Southern Europe and India, the responseis less clear as some studies obtained local warming. The common method to representirrigation processes in the literature study is by saturating the whole soil column. This leadsto a water request that is almost a hundred times more of what is available, whichis unrealistic and it could cause an overestimation of the irrigation impact. Themethods developed in this paper allow the model to account for the human decisioncomponent of the process: water amount and start, frequency and length of irrigation aredecided a priori. In particular, this study focuses on three new surface irrigationmethods, within the limited area model Weather Research Forecast (WRF-ARW 3.8.1),which summarize the most common ones: channel, drip, and sprinkler. The channeland drip methods apply the water to the surface, but the latter has leaf and canopyinterception. For the sprinkler, the water used for irrigation is sprayed in the lowest modellevel and interact with the microphysics. These methods allow a more realisticrepresentation of surface irrigation with respect to the commonly used saturationone.The test case for this study is the Po valley (northern Italy) during the heat wave of July2015, at the convection-permitting scale as well as the convection parameterizedone.Irrigation parameterizations improve the results due to a reduction in the biases of potentialevapotranspiration (MODIS), the monthly mean and maximum temperature (stations’ data).It is found that both soil moisture and surface atmospheric variables are more influenced bythe scheme itself rather than the a priori assumptions of timing. The cooling effect has a cleardaily cycle up to 1.2 K averaging over the irrigated land, with the maximum effect during themiddle of the day. The magnitude of the cooling effect agrees with the previous studies.Irrigation affects the surface fluxes by reducing the sensible heat and increasing the upwardmoisture flux. Interestingly, precipitation is affected by irrigation at both the convectionpermitting and parameterized scale. The monthly precipitation accumulated, in theirrigated area of the Po Valley, is increased by 9.5% for the high-resolution run.
- Subjects
ITALY; IRRIGATION; METEOROLOGICAL research; MICROIRRIGATION; IRRIGATION water; HUMIDITY; WEATHER forecasting; SPRINKLER irrigation; HEAT waves (Meteorology)
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article