城市化对天气事件(如:降雨、温度、UHI)影响的研究现在处于什么阶段?世界各地已经进行了大量观测和模拟研究，发现(在我的理解中)城市化导致了城市化地区强降雨频率和强度的增加，温度升高，热岛，边界层变化等，主要是由于陆地表面的变化。那么，这一研究领域存在哪些挑战和可能性呢?< / p >

我在大学期间完成了对城市周围湿度变化的观测。这是一个有趣的领域，尽管考虑到令人难以置信的空间和时间可变性，描绘和解释变化似乎相当具有挑战性。所以这绝对是其中一个挑战。另一个是目前的观测密度，因为微网设置很少，卫星分辨率可能无助于诊断小时间/距离尺度上的变化。但是，虽然它肯定不像气候模型本身那样受到关注(或金钱)，但至少有一些聪明的人在这个领域工作。从我的经验来看，我曾涉猎过这个话题，但对过去十年的研究并不完全熟悉，理论微尺度建模似乎是最有成效的研究方向。计算能力和模型不断提升，还有更好的实验空间。但是，要证明这些理想化的模拟与现实相符，以及将变化与理论/原因明确联系起来，仍然是非常困难的。< / p >

Indeed, if somehow sharp links can be made that are powerfully convincing, then work could be directed into reshaping urban planning to address such changes.

城市区域与自然区域最大的差异是地表反照率和热容。深色表面的建筑物和道路反照率较低，吸收更多的阳光和热量。建筑材料特别是混凝土的比热容比天然植被低，夜间容易升温，使周围环境变暖，产生热岛效应。城市中心的高层建筑也在近地表大气上形成了一个城市边界层，这改变了风速，从而影响了蒸散和热扩散。因此，它还会捕获空气污染物，造成光化学烟雾。城市地区的交通和工厂产生高浓度的气溶胶，氮氧化物，CH4，并通过二次污染产生臭氧。对流层的臭氧气体对生物是极其危险的，它可以引发哮喘，减少植物的光合作用。灰尘和PM2.5颗粒也可能导致更高的降水，因为它们是雨滴形成的吸湿核。城区通常建有高效的排水系统以避免洪水泛滥。但这减少了降雨事件的蒸发和蒸腾作用，导致相对湿度降低。

城市区域的这些属性被纳入了地表模型。 One of the model that did this is the Joint UK Land Environment Simulator (JULES). It has a land tile that is specifically dedicated to urban area [Young, 2014, presentation]. It can be used to test the urban canyon effect, heat island effect and the impact of building green roofs and sky garden etc.

More detail about the model can be found here: http://jules.jchmr.org/content/about#overview

Now that urban effects on regional weather can be observed, modeled, and to a large degree verified, all that remains on the science side is improving forecast resolution.

Serious work, however, is being done on the policy side given these new cause and effect scenarios, although how seriously this effort is being taken is largely nation-dependent: China's response to Beijing's consequences of creating its UHI is a lot different than how the US responds to Atlanta's.

To give you another example, consider how basic mortality data for a heat wave is tabulated for Paris versus New York City. For similar events, Paris records heat-related deaths that are orders of magnitude higher than in NYC, for the simple reason that in NYC, according to city records, the elderly die of "natural causes" regardless of weather. By contrast, in Paris, if a spike in deaths is concurrent with a weather event, the weather event is held accountable.