High temperatures in summer can prevent people from using urban green spaces. Irrigating urban green spaces is a promising strategy to reduce temperatures. In this study, we aimed to a) identify the proportional contribution of different irrigation cooling mechanisms and b) quantify the impacts of different irrigation amounts (from 2 to 30 mm d) on the cooling effect of irrigating turfgrass in Melbourne, Australia. We first used a field experiment in Melbourne to provide empirical data to calibrate and verify the performance of an urban ecohydrological model, UT&C. Then, we used UT&C to predict the impacts of irrigating turfgrass on evapotranspiration, the energy balance and microclimate. UT&C predicted that irrigating turfgrass 4 mm d would increase the evaporation from grass canopy and soil surface by 0.2 and 0.6 mm d, respectively, whereas it would reduce transpiration by 0.6 mm d due to intercepted water covering part of the grass canopy following the irrigation. UT&C predicted that daytime (10:00–16:59) mean air temperature reductions would increase from 0.2 to 0.4 °C when the irrigation amount increased from 2 to 4 mm d. However, increasing the irrigation amount beyond 4 mm d would not increase the cooling benefits.

中文翻译：

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确定灌溉在夏季为城市绿地降温的机制

夏季高温会阻碍人们使用城市绿地。灌溉城市绿地是一种很有前途的降低气温的策略。在本研究中，我们的目的是 a) 确定不同灌溉冷却机制的比例贡献，b) 量化不同灌溉量（2 至 30 mm d）对澳大利亚墨尔本灌溉草坪冷却效果的影响。我们首先在墨尔本进行了现场实验，提供经验数据来校准和验证城市生态水文模型 UT&C 的性能。然后，我们使用 UT&C 来预测灌溉草坪对蒸散量、能量平衡和小气候的影响。 UT&C 预测，对草坪进行 4 毫米·天的灌溉将使草冠层和土壤表面的蒸发量分别增加 0.2 和 0.6 毫米·天，而由于灌溉后截获的水覆盖了部分草冠层，蒸腾量将减少 0.6 毫米·天。 UT&C 预测，当灌溉量从 2 毫米/天增加到 4 毫米/天时，白天（10:00–16:59）平均气温下降幅度将从 0.2 °C 增加到 0.4 °C。然而，将灌溉量增加到超过 4 mm·d 并不会增加冷却效益。