the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Estimation of 1 km downwelling shortwave radiation over the Tibetan Plateau under all-sky conditions
Peizhen Li
Yaoming Ma
Yunfei Fu
Meilin Cheng
Xian Wang
Yuting Qi
Zixin Wang
Abstract. Downwelling shortwave radiation (DSR) is the basic driving force for the energy and water cycles of the Earth’s climate system. As called the Third Pole of the Earth, the Tibetan Plateau (TP) absorbs a large amount of shortwave radiation and exert important impacts on global weather and climate change. However, due to coarse spatial resolution and insufficient consideration of factors influencing radiative transfer processes, DSR parameterization schemes are still need to be improved when applied to the TP. Based on satellite datasets and meteorological forcing data, all-sky DSR over the TP at a spatial resolution of 1 km was derived using an improved parameterization scheme. The influence of topography and different radiative attenuations were comprehensively taken into account. Specifically, the introduction of cloud multiscattering and topography factors further improves the DSR estimation accuracy. The validation results indicated that the developed parameterization scheme showed reasonable accuracy. By comparing with current widely used DSR products based on the same in situ observations, the derived DSR performed much better on different spatial and temporal scales. On instantaneous, ten-day, and monthly timescales, the root-mean-square errors (RMSEs) of the derived DSR are 132.8–158.2 W m−2, 70.8–76.5 W m−2, and 61.3–67.5 W m−2, respectively, which are much smaller than those of current DSR products. The derived DSR not only captured the temporal variation characteristics that are more consistent with the in situ measurements, but also provided reasonable spatial patterns. Meanwhile, the proposed parameterization scheme demonstrated its superiority in characterizing more details and high dynamics of the spatial pattern of DSR due to its terrain correction and high resolution. Moreover, this parameterization scheme does not need any local correction in advance and it has the potential to be extended to other regions in the world.
Peizhen Li et al.
Status: open (until 05 Apr 2023)
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RC1: 'Comment on acp-2022-773', Anonymous Referee #3, 03 Mar 2023
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Please see the supplement for detailed comments.
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RC2: 'Comment on acp-2022-773', Anonymous Referee #1, 05 Mar 2023
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Reliable downwelling shortwave radiation (DSR) estimation over the Tibetan Plateau (TP) is still a challenging scientific issue. This manuscript developed an improved parameterization scheme to obtain all-sky DSR based on satellite data and meteorological forcing data. The topic of the paper is interesting and it’s a good fit for the scope of ACP. The whole paper is well organized with clear logic and robust results. The description of the method is clear. Numbers of work are integrated into this paper, and abundant discussions are presented as well. However, there are still some rooms for the improvement.
Major issues:
- The spatial resolution of DSR estimated in this paper is 1 km. The spatial resolution of DSR products for comparison is coarser than 10 km. While the scale of the stations normally represents a scale of about less than 1 km. The authors should give some explanation about their scale mismatch problem.
- As far as I know, three atmospheric conditions (clear-sky, completely cloud-covered and partially cloud-covered) were distinguished based on cloud fraction data in previous study. In this paper, the author used MOD06 cloud product to distinguish cloud sky and clear sky conditions. Will this cause some uncertainties?
- The derived DSR was compared with current widely used DSR products in this paper. That’s convincing. To our best knowledge, Letu et al. (2022) generated surface radiation products under all-sky conditions from the Himawari-8/AHI Next-Generation Geostationary Satellite. If the derived DSR can be compared with the latest DSR product, this paper may be more appealing. The reference is as follows,
Letu et al., A New Benchmark for Surface Radiation Products over the East Asia–Pacific Region Retrieved from the Himawari-8/AHI Next-Generation Geostationary Satellite, Bulletin of the American Meteorological Society, 103, E873-E888, 10.1175/bams-d-20-0148.1, 2022
Minor issues:
- Figure 1: the caption is too brief. The same problems exist in other figures. Please check and modify.
- Page 4, L116: The references cited here are too old. Are there any updated references on relevant studies?
- L 46: “It plays a decisive role” => “It plays an important role”
- L 55: “and other major rivers in Asia originate from the TP” => “and most major rivers in Asia originate from the TP”
- L 57: “an important research object of global and regional energy” => “an important research object for global and regional energy”
Citation: https://doi.org/10.5194/acp-2022-773-RC2 -
RC3: 'Comment on acp-2022-773', Anonymous Referee #2, 09 Mar 2023
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A smart DSR retrieval scheme was developed and applied over the Tibetan Plateau. The effect of complex terrain in this region was investigated. The research looks interesting and the results look robust. My major concerns are as follows,
1. It is not clear how to derive water vapor content, whether it is derived from meteorological observations of temperature or relative humidity or directly from MODIS product.
2. It is not clear how to estimate turbidity from AOD at 550nm, my understanding is that Angstrom wavelength exponent over land is not good enough for the extrapolation.
3. It was stated by the authors the accuracy of the retrieval algorithm is highly dependent on the quality of input data, so it seems very necessary to do some sensitivity analysis on the uncertainty produced by potential errors of input products.
4. It is necessary to validate retrievals under clear and cloudy conditions, which is helpful for understanding of the uncertainty sources.
5. Measurements of DSR, especially the maintenance, data quality control, etc, should be introduced.Citation: https://doi.org/10.5194/acp-2022-773-RC3
Peizhen Li et al.
Peizhen Li et al.
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