Effects of urbanization on extreme rainfall in an arid/semiarid region,Atmospheric Science Letters

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Effects of urbanization on extreme rainfall in an arid/semiarid region
Atmospheric Science Letters ( IF 2.0 ) Pub Date : 2020-03-09 , DOI: 10.1002/asl.966
Jialun Li ₁ , Alex Mahalov _{1,

2} , Peter Hyde ₃

Affiliation

In this study, an extreme rainfall event that occurred mainly on October 2, 2018, in the Phoenix metropolitan area, southwestern United States, is simulated with the Weather Research and Forecasting (WRF) model, version 4.0, with multiple microphysics and boundary layer schemes. Paired simulations are conducted by running the model first using a realistic land cover and land‐use dataset (URB run), and second, by replacing the urban land cover with open shrubland cover (called NOURB run). The model simulations are first evaluated against radar Stage IV (hereafter Stage IV) data and multiple radar and multiple sensors (MRMS) rainfall to validate the structure, amplitude, and location (SAL) of the rainfall field for both URB runs and NOURB runs. These evaluation results indicate that the model performance varies considerably depending on the physics schemes employed. Based on SAL values, the average of model simulations captures the main features (values of S, A, and L are less than 0.1) both for URB runs and for NOURB runs. Comparisons of hourly rainfall rates show that modeled rainfall maximums occurred about 1 hr earlier than both Stage IV and MRMS data over the Phoenix metro area, while the maximum rainfall amounts from the model are close to MRMS data but lower than Stage IV data. The differences of rainfall and other meteorological variables between URB runs and NOURB runs are analyzed. The differences of rainfall between URB and NOURB vary depending on the physics scheme employed. Our study also indicates that urbanization‐induced rainfall changes are small within the urban area but are significant at some locations outside of it; an explanation for this pattern needs further investigation. This result implies that using a single physics scheme to address the effects of urbanization on extreme rainfall events may result in inappropriate conclusions.

中文翻译：

城市化对干旱/半干旱地区极端降雨的影响

在本研究中，使用天气研究和预报（WRF）模型（版本4.0），具有多个微物理学和边界层方案，模拟了一次主要发生在2018年10月2日在美国西南部凤凰城地区的极端降雨事件。。配对模拟是通过首先使用实际的土地覆盖和土地利用数据集（URB运行）运行模型，然后使用开放的灌木林覆盖代替城市土地覆盖（称为NOURB运行）来进行模型的。首先针对雷达IV级（以下简称IV级）数据以及多雷达和多传感器（MRMS）降雨对模型仿真进行评估，以验证URB和NOURB降雨场的结构，幅度和位置（SAL）。这些评估结果表明，模型性能根据所采用的物理方案而有很大差异。基于SAL值，模型模拟的平均值捕获了URB运行和NOURB运行的主要特征（S，A和L的值小于0.1）。每小时降雨率的比较显示，在凤凰城大都市地区，模拟降雨最大值比IV和MRMS数据早约1小时，而模型的最大降雨量接近MRMS数据，但低于IV数据。分析了URB运行和NOURB运行之间的降雨和其他气象变量的差异。URB和NOURB之间的降雨量差异取决于所采用的物理方案。我们的研究还表明，城市化引起的降雨变化在市区范围内很小，但在市区以外的某些地方却很明显。对这种模式的解释需要进一步研究。该结果表明，使用单一的物理方案来解决城市化对极端降雨事件的影响可能会得出不适当的结论。

更新日期：2020-03-09

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