the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Introduction of Prognostic Graupel Density in Weather Research and Forecasting (WRF) Double-Moment 6-Class (WDM6) Microphysics and Evaluation of the Modified Scheme During the ICE-POP Field Campaign
Abstract. The Weather Research and Forecasting (WRF) Double-Moment 6-class (WDM6) scheme was modified by incorporating prognostic graupel density. Explicitly prognosed graupel density, in turn, modifies graupel characteristics such as the fall velocity–diameter and mass–diameter relationships of graupel. The modified WDM6 has been evaluated based on a two-dimensional (2D) idealized squall line simulation and winter snowfall events that occurred during the International Collaborative Experiment for Pyeongchang Olympics and Paralympics (ICE-POP 2018) field campaign over the Korean Peninsula. From the 2D simulation, we confirmed that the modified WDM6 can simulate varying graupel density, ranging from low values in an anvil clouds region to high values in the convective region at the mature stage of a squall line. Simulations with the modified WDM6 increase graupel amounts at the surface and decreased graupel aloft because of the faster sedimentation of graupel for two winter snowfall cases during the ICE-POP 2018 campaign, as simulated in the 2D idealized model. The altered graupel sedimentation in the modified WDM6 influenced the magnitude of the major microphysical processes of graupel and snow, subsequently reducing the surface snow amount and precipitation over the mountainous region. The reduced surface precipitation over the mountainous region mitigates the surface precipitation bias observed in the original WDM6, resulting in better statistical skill scores for the root mean square errors. Notably, the modified WDM6 reasonably captures the relationship between graupel density and its fall velocity, as retrieved from 2D video disdrometer measurements, thus emphasizing the necessity of including prognostic graupel density to realistically represent the microphysical properties of graupel in models.
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Status: final response (author comments only)
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RC1: 'Comment on gmd-2023-241', Anonymous Referee #1, 25 Apr 2024
The comment was uploaded in the form of a supplement: https://gmd.copernicus.org/preprints/gmd-2023-241/gmd-2023-241-RC1-supplement.pdf
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AC1: 'Reply on RC1', Kyo-Sun Lim, 18 Jun 2024
Thank you for your valuable review and constructive feedback. Our manuscript has been revised including a more detailed description of the WDM6 microphysics scheme to offer better understanding of results. Additionally, we focused more closely on the observation-model comparisons by highlighting the verification of model results with 2DVD. We are confident that these changes make our study more accessible and informative for readers, better focusing the importance and effectiveness of the new predicted graupel density implementation in the WDM6 microphysics scheme. Please find the attached file for the detailed responses.
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AC1: 'Reply on RC1', Kyo-Sun Lim, 18 Jun 2024
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RC2: 'Comment on gmd-2023-241', Anonymous Referee #2, 02 May 2024
The comment was uploaded in the form of a supplement: https://gmd.copernicus.org/preprints/gmd-2023-241/gmd-2023-241-RC2-supplement.pdf
- AC2: 'Reply on RC2', Kyo-Sun Lim, 18 Jun 2024
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RC3: 'Comment on gmd-2023-241', Minghui Diao, 03 May 2024
This manuscript is focused on the development of a new prognostic parameter that controls graupel density and fall terminal speed in the WDM6 microphysics scheme. The 2-D idealized simulation of a squall line scenario was compared with observations from the ICE-POP 2018 field campaign during the Winter Olympics in Pyeongchang, Korea. Overall, the manuscript is well written and easy to follow. The reviewer has 3 main comments related to the impacts on cloud microphysical processes, the relationship with thermodynamic conditions specifically relative humidity, and the evaluation against more measurements. Reviewer recommends the manuscript being revised by addressing the following comments.Below are the main comments.1. Figure 6 shows the evolution of graupel density and mixing ratio as well as the key source and sink terms. This figure is very helpful for understanding the formation of graupel. Can the authors also provide this figure for the WDM6_FD simulation? In addition, the reviewer suggests more discussion about the impacts and differences related to cloud microphysical processes. The authors can consider adding supplemental figures showing this type of cross sections in an evolutionary view for other variables, including cloud liquid, cloud ice, snow, and relative humidity with respect to ice.2. Table 4 provides a critical assessment of the performance of the new scheme. However, there is not much description of this table. The review only found this sentence on line 310, stating that the RMSE for all CL cases is much improved. Is this a comparison of the graupel mass collected at surface? There are other measured properties that the authors mentioned in section 3.2, and line 220, which are the 2DVD measured diameter, fall velocity, and geometry of each hydrometeor falling. However, the reviewer didn’t find comparisons on these three properties, or maybe they were mentioned only in the text but not in any figures and tables. Can the authors provide additional comparison on these properties?In addition to surface measurements, are there other types of observations available? What about radiosonde measurements of temperature, humidity and wind speed, and satellite observations of cloud properties?3. Another main comment is about the relationship with thermodynamic conditions, especially with RHice. In previous studies evaluating other double moment microphysics schemes against in situ aircraft observations, the results showed large sensitivities of the cloud microphysical properties (I.e., ice crystal mass and number concentrations) to the ice nucleation thresholds in terms of RHice threshold. For example, the Morrison 2 moment scheme uses a default 108% RHice, and the Thompson 2 moment scheme uses a default 125% RHice for initiating ice nucleation at lower temperatures, which may lead to transition from clear sky ice supersaturation to ice crystals too early (D’Alessandro et al., 2017). And this RHice threshold was found to be more realistic if it is set at 125-130% in an idealized squall line scenario when compared with the NSF DC3 field campaign (Diao et al., 2017). The reviewer wonders what is the current ice nucleation threshold used in the WDM scheme, and if that parameter has a very large impact on the simulated graupel density and fall speed. If a similar RHice threshold is adopted in WDM scheme around 108% similar to the Morrison 2 moment scheme, then the reviewer recommends testing increasing that threshold to 125% or 130%.Minor comment.Some figures seem to have the dimension compressed, such as Figure 4, which seems to be compressed vertically (too narrow in vertical).References mentioned above.Diao, M., G.H. Bryan, H. Morrison, and J.B. Jensen, Ice nucleation parameterization and relative humidity distribution in idealized squall line simulations, Journal of the Atmospheric Sciences, 74, 2761–2787, https://doi.org/10.1175/JAS-D-16-0356.1, 2017.D'Alessandro, J., M. Diao, C. Wu, X. Liu, M. Chen, H. Morrison, T. Eidhammer, J.B. Jensen, A. Bansemer, M.A. Zondlo, J.P. DiGangi. Dynamical conditions of ice supersaturation and ice nucleation in convective systems: a comparative analysis between in-situ aircraft observations and WRF simulations, Journal of Geophysical Research: Atmosphere, 122, doi:10.1002/2016JD025994, 2017.Citation: https://doi.org/
10.5194/gmd-2023-241-RC3 - AC3: 'Reply on RC3', Kyo-Sun Lim, 19 Jun 2024
- AC4: 'Comment on gmd-2023-241', Kyo-Sun Lim, 19 Jun 2024
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