城市洪水是世界性的重大问题，造成巨大的经济损失，严重威胁公共安全。减轻其影响的一种有希望的方法是开发实时洪水风险管理系统；然而，由于缺乏高时空降雨数据，构建这样一个系统通常具有挑战性。虽然一些方法（即地面降雨站或雷达和卫星技术）可用于测量和（或）预测降雨强度，但使用这些方法很难获得具有理想时空分辨率的准确降雨数据。本文提出了一种基于图像的深度学习模型来估计具有高时空分辨率的城市降雨强度。进一步来说，一种称为基于图像的降雨卷积神经网络（image-based rainfall convolutional neural network, irCNN）模型是使用从现有密集传感器（即智能手机或交通摄像头）收集的降雨图像及其相应的测量降雨强度值开发的。随后使用经过训练的irCNN 模型根据传感器的降雨图像有效地估计降雨强度。分别利用合成降雨数据和真实降雨图像来探索irCNN 在理论和实际模拟降雨强度方面的准确性。结果表明，irCNN 模型提供的降雨量估计值的平均绝对百分比误差在13.5%~21.9%之间，超过了文献中其他最先进的建模技术的性能。更重要的是，所提出的irCNN 的主要特点是它在有效获取高时空城市降雨数据方面成本较低。irCNN 模型为估算城市降雨强度提供了一种有前景的替代方案，可以极大地促进城市实时洪水风险管理的发展。

Urban flooding is a major issue worldwide, causing huge economic losses and serious threats to public safety. One promising way to mitigate its impacts is to develop a real-time flood risk management system; however, building such a system is often challenging due to the lack of high spatiotemporal rainfall data. While some approaches (i.e., ground rainfall stations or radar and satellite techniques) are available to measure and/or predict rainfall intensity, it is difficult to obtain accurate rainfall data with a desirable spatiotemporal resolution using these methods. This paper proposes an image-based deep learning model to estimate urban rainfall intensity with high spatial and temporal resolution. More specifically, a convolutional neural network (CNN) model called the image-based rainfall CNN (irCNN) model is developed using rainfall images collected from existing dense sensors (i.e., smart phones or transportation cameras) and their corresponding measured rainfall intensity values. The trained irCNN model is subsequently employed to efficiently estimate rainfall intensity based on the sensors' rainfall images. Synthetic rainfall data and real rainfall images are respectively utilized to explore the irCNN's accuracy in theoretically and practically simulating rainfall intensity. The results show that the irCNN model provides rainfall estimates with a mean absolute percentage error ranging between 13.5% and 21.9%, which exceeds the performance of other state-of-the-art modeling techniques in the literature. More importantly, the main feature of the proposed irCNN is its low cost in efficiently acquiring high spatiotemporal urban rainfall data. The irCNN model provides a promising alternative for estimating urban rainfall intensity, which can greatly facilitate the development of urban flood risk management in a real-time manner.