Abstract Irrigation is crucial in sustaining food production and it is found to have a cooling effect. Changes at the surface affect both the circulation and the precipitation. The magnitude depends on the model used, the irrigation description and the water amount, as well as the region. The study focuses on northern Italy (the Po Valley) due to its vulnerability to heatwaves and dependency on local water sources. This study is performed with the Weather Research and Forecasting (WRF) model and newly developed irrigation parameterizations defined by different evaporative processes. The model runs at a 3 km convection-permitting resolution, starting in May 2015 and analyzing July. An irrigation amount of 5.7 mm is applied daily at 5 UTC for 3 h, starting from May 15. A set of convection-parameterized sensitivity simulations is used to investigate the results' dependency on timing. Using a convection-parameterized set of experiments, it is assessed that irrigation increases the precipitation accumulated over the region. While irrigation modifies the air mass properties, convection-permitting runs show that afternoon events are inhibited due to an increase in convection inhibition and decrease in boundary layer height. This happens despite the increase in the convective available potential energy (CAPE) and a decrease in both the lifting condensation level and level of free convection. For the nighttime event, irrigation increases significantly both boundary layer moisture and CAPE, increasing the precipitation. All cases are compared against the national radar composite accumulated over two hours, finding that the irrigated runs perform better than the control.

中文翻译：

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使用 WRF-ARW 的热浪事件期间灌溉对降水的影响：2015 年夏季波谷案例

摘要 灌溉对于维持粮食生产至关重要，并且被发现具有降温作用。地表的变化既影响环流又影响降水。大小取决于使用的模型、灌溉描述和水量，以及区域。该研究侧重于意大利北部（波谷），因为该地区易受热浪影响且依赖当地水源。这项研究是使用天气研究和预测 (WRF) 模型以及由不同蒸发过程定义的新开发的灌溉参数化进行的。该模型以 3 公里允许对流分辨率运行，从 2015 年 5 月开始并分析 7 月。从 5 月 15 日开始，每天在世界标准时间 5 点应用 5.7 毫米的灌溉量，持续 3 小时。一组对流参数化灵敏度模拟用于研究结果对时间的依赖性。使用一组对流参数化的实验，评估灌溉增加了该地区累积的降水。虽然灌溉会改变空气质量，但允许对流的运行表明，由于对流抑制的增加和边界层高度的降低，下午的事件受到抑制。尽管对流可用势能 (CAPE) 增加并且提升凝结水平和自由对流水平都降低，但这种情况还是会发生。对于夜间事件，灌溉显着增加了边界层水分和 CAPE，从而增加了降水。所有案例都与超过两个小时累积的国家雷达合成进行比较，