ORCID Profile
0000-0002-9055-2583
Current Organisations
University of California, Irvine
,
UC Irvine
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Publisher: Copernicus GmbH
Date: 21-11-2022
Abstract: Abstract. Deep learning (DL) models are popular but computationally expensive, machine learning (ML) models are old-fashioned but more efficient. Their differences in hydrological probabilistic post-processing are not clear at the moment. This study conducts a systematic model comparison between the quantile regression forest (QRF) model and probabilistic long short-term memory (PLSTM) model as hydrological probabilistic post-processors. Specifically, we compare these two models to deal with the biased streamflow simulation driven by three kinds of satellite precipitation products in 522 sub-basins of Yalong River basin of China. Model performance is comprehensively assessed by a series of scoring metrics from the probabilistic and deterministic perspectives, respectively. In general, the QRF model and the PLSTM model are comparable in terms of probabilistic prediction. Their performance is closely related to the flow accumulation area of the sub-basin. For sub-basins with flow accumulation area less than 60,000 km2, the QRF model outperforms the PLSTM model in most of the sub-basins. For sub-basins with flow accumulation area larger than 60,000 km2, the PLSTM model has an undebatable advantage. In terms of deterministic predictions, the PLSTM model should be more preferred than the QRF model, especially when the raw streamflow is poorly simulated and used as an input. But if we put aside the model performance, the QRF model is more efficient in all cases, saving half the time than the PLSTM model. This study can deepen our understanding of ML and DL models in hydrological post-processing and enable more appropriate model selection in practice.
Publisher: American Geophysical Union (AGU)
Date: 03-09-2021
DOI: 10.1029/2021GL094092
Abstract: It is very important to quantify errors of precipitation estimation products. However, the existing methods do not describe all error components and are therefore not comprehensive enough. In this study, we propose a four‐component error decomposition method (4CED) that decomposes the total errors of precipitation products into four independent parts: hit positive bias, hit negative bias, false bias, and missed bias. And we use it to evaluate the performance of the three latest satellite precipitation products in the eastern monsoon region of China. Our study reveals 4CED has apparent improvements compared with the previous method. Results also provide new insights for tracking error sources and quantifying the error magnitudes of precipitation products. Moreover, the proposed 4CED can be extended to different spatial and temporal scales. Our new method will not only contribute to product upgrades, but also provide guidance for potential applications.
Publisher: MDPI AG
Date: 04-08-2021
DOI: 10.3390/RS13163061
Abstract: Satellite precipitation estimates (SPEs) are promising alternatives to gauge observations for hydrological applications (e.g., streamflow simulation), especially in remote areas with sparse observation networks. However, the existing SPEs products are still biased due to imperfections in retrieval algorithms, data sources and post-processing, which makes the effective use of SPEs a challenge, especially at different spatial and temporal scales. In this study, we used a distributed hydrological model to evaluate the simulated discharge from eight quasi-global SPEs at different spatial scales and explored their potential scale effects of SPEs on a cascade of basins ranging from approximately 100 to 130,000 km2. The results indicate that, regardless of the difference in the accuracy of various SPEs, there is indeed a scale effect in their application in discharge simulation. Specifically, when the catchment area is larger than 20,000 km2, the overall performance of discharge simulation emerges an ascending trend with the increase of catchment area due to the river routing and spatial averaging. Whereas below 20,000 km2, the discharge simulation capability of the SPEs is more randomized and relies heavily on local precipitation accuracy. Our study also highlights the need to evaluate SPEs or other precipitation products (e.g., merge product or reanalysis data) not only at the limited station scale, but also at a finer scale depending on the practical application requirements. Here we have verified that the existing SPEs are scale-dependent in hydrological simulation, and they are not enough to be directly used in very fine scale distributed hydrological simulations (e.g., flash flood). More advanced retrieval algorithms, data sources and bias correction methods are needed to further improve the overall quality of SPEs.
Publisher: Copernicus GmbH
Date: 21-11-2022
No related grants have been discovered for Phu Nguyen.