Diverse Explorations of Rainfall Nowcasting with TrajGRU
Mitigating Smoothness and Fading Out Challenges for Longer Lead Times
Y. Zou (TU Delft - Civil Engineering & Geosciences)
Marc Schleiss – Mentor (TU Delft - Atmospheric Remote Sensing)
Francesco Fioranelli – Graduation committee member (TU Delft - Microwave Sensing, Signals & Systems)
R. Taormina – Graduation committee member (TU Delft - Sanitary Engineering)
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All visual prediction results in this thesis project (include images and animation)
https://doi.org/10.4121/12437ba3-4cf4-47c4-928b-94dc9bdec663.v1Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Abstract
Machine learning models offer promising potential in precipitation nowcasting. However, a common issue faced by many of these models is the tendency to produce blurry precipitation nowcasts, which are unrealistic. Previous research on the deep learning model - TrajGRU (Shi et al., 2017) indicated that data imbalance in radar images and the double-penalty effect of pixel-wise loss functions are underlying causes for this blurriness.
In this thesis, we continue to explore various approaches to improve the predictive performance of TrajGRU. Our research has first investigated spatially and temporally enhanced loss functions to address the two remaining issues: data imbalance and double penalty. The second part of our research focuses on manifold optimizations within the model network, such as incorporating additional model inputs or increasing batch size, to understand the model’s limitations.
Our results reveal that enhanced loss functions did not lead to predictive improvements and even resulted in undesired checkerboard patterns. Changes to the model network make a difference in the image sharpness and predictive rain evolution. Our visual analysis indicates that a larger batch size generates sharper rain field edges; predictions by using multiple parameter groups exhibit more rain dynamics. The incorporation with other transformed datasets introduces finer structures within rain fields. Although the blurriness has not been completely resolved, our study recommended future work can continue exploring the optimization in the TrajGRU network.