the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
An urban module coupled with the Variable Infiltration Capacity model to improve hydrothermal simulations in urban systems
Abstract. Global urban expansion has altered surface aerodynamics and hydrothermal dynamics, aggravating environmental challenges such as urban heat/dry islands. To identify such environmental responses, various physical models, including urban canyon models (UCMs) and land surface models (LSMs), have been developed to represent surface hydrothermal processes. However, UCMs often treat a city as a unified entity and overlook subcity heterogeneity. LSMs are generally designed for natural land covers and lack the capability to capture urban characteristics. To address these limitations, the aim of this study is to couple an urban module with a sophisticated LSM, i.e., the Variable Infiltration Capacity (VIC) model. This coupled model, i.e., the VIC-urban model, is characterized by its ability to coordinate certain critical urban features, including the urban geometry, radiative interactions, and human impacts. Adopting Beijing as an evaluation site, the VIC-urban model shows higher performance than the original version, with excellent accuracy in simulating sensible heat, latent heat, runoff, and land surface temperature (LST). The absolute error is smaller than 25 % for the sensible heat and latent heat, and smaller than 12 % and 30 % for the LST and runoff, respectively, which indicates that VIC-urban can effectively simulate hydrological and thermal fluxes in urban systems. Sensitivity analysis reveals that the roof emissivity and interception capacity exert the greatest impact on the roof temperature and evaporation, and the height-width ratio exerts the greatest influence on the canyon. Our work introduces a reliable option for large-scale land surface simulations that accounts for urban environments, and is among the first attempts to establish a systematic urban modelling framework of the VIC model. The VIC-urban model enables the analysis of urbanization-induced environmental changes and quantification of environmental variations among different urban configurations. The proposed model can thus offer invaluable insights for urban planners and landscape designers.
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Status: final response (author comments only)
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RC1: 'Comment on gmd-2023-232', Anonymous Referee #1, 30 Mar 2024
The authors show an excellent job of coupling an urban model to the VIC model to improve the capability of this global land surface model. The manuscript is well organized, with concrete results demonstrating the advantages of the VIC-urban model. I think it should be accepted after considering the following minor issues.
1. The authors are suggested to give more information about the base map and urban maps. Did the authors update different urban maps during the study period? Because the study period was a time of high urbanization, the urban maps should have changed significantly over time.
2. More details about the Beijing simulation are needed.  What is the simulation resolution of the VIC model? The resolution of the various data used in the model is inconsistent, what methodology did the authors use to standardize the resolution.
3. It is better to show more details about the urban parameters, for example,  the spatial distribution maps of the parameters of the urban model of Beijing.
4.For figure 6 and talbe 3, can the authors show the results in daily scale?Â
Citation: https://doi.org/10.5194/gmd-2023-232-RC1 -
AC1: 'Reply on RC1', Xianhong Xie, 23 Apr 2024
Dear Reviewer,
Many thanks for the positive comments and suggestions. Please find attached document containing point-by-point responses. We hope that the responses provided will be helpful in addressing any concerns raised. We sincerely appreciate your time and effort in providing feedback and look forward to any further suggestions you may have.
King regards,
Xianhong Xie
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AC1: 'Reply on RC1', Xianhong Xie, 23 Apr 2024
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RC2: 'Comment on gmd-2023-232', Anonymous Referee #2, 07 Apr 2024
This is a nice manuscript with a good attempt to include urban characteristics in VIC to make VIC usable for urban regions. I have a few comments, which the authors may address:
1. Urban models should have a strong human component characterized by human behavior and it is difficult to consider the same in VIC. THis is my major concern. The data requitement for development such module is also huge. The authors need to consider this very seriously.
2. For urban heat balance, the anthropogenic heat plays a major role, and I am not sure how do the authors consider them. There are weekly variations in energy budget, like in weekends the office areas will have low energy requirements. The transportation component have a strong sub-daily variations. These are very important and I am a bit curious how to consider them in VIC.
3. The same point is applicable for water use as well.
4. There are existing models like SUEWS, how is the proposed model bettter than SUEWS frameowrk.
I recommend major revision and request the authors to address the above mentioned points.Â
Citation: https://doi.org/10.5194/gmd-2023-232-RC2 - AC2: 'Reply on RC2', Xianhong Xie, 23 Apr 2024
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