A multiscale modeling study of a real case has been conducted to explore the capability of WRF-LES over the Xiaohaituo Mountain (a game zone for the Beijing-2022-Winter-Olympic-Games). Comparing WRF-LES results with observations collected during the MOUNTAOM (MOUNtain Terrain Atmospheric Observations and Modeling) field campaign, it is found that at 37 m resolution with LES settings, the model can reasonably capture both large-scale events and microscale atmospheric circulation characteristics. Employing SRTM1 (≈30 m) high resolution topographic dataset instead of traditional USGS_30s (≈900 m) dataset effectively improves the model capability for reproducing fluctuations and turbulent features of surface winds. Five sensitivity experiments are conducted to investigate the impact of different PBL treatments, including YSU/SH PBL schemes and LES with 1.5TKE, SMAG, NBA subgrid-scale (SGS) stress models. In this case, at gray zone scales, differences between YSU and SH are negligible. LES outperform two PBL schemes which generate smaller turbulence kinetic energy, and increase the model errors for mean wind speed, energy spectra and probability density function of velocity. Another key finding is that wind field features in the boundary layer over complex terrain are more sensitive to the choice of SGS models than above the boundary layer. With the increase of model resolution, the effects of SGS model become more significant, especially for the statistical characteristics of turbulence. Among these three SGS models, NBA has the best performance. Overall, this study demonstrates that WRF-LES is a promising tool for simulating real weather flows over complex terrain.

Vegetation constitutes one of the fundamental types of land use on Earth. The presence of trees in urban areas can decrease local winds and exchange sensible and latent heat with the surrounding environments, thus exerting notable influences on the urban microenvironment. A better understanding of the turbulent transfer of momentum and scalars around vegetation canopy could significantly contribute to improvement of the urban environment. This work develops a large-eddy simulation (LES) method that is applicable to model the flow and scalar transport over the forest canopy. We study the atmospheric flow over complex forested areas under typical weather conditions by coupling LES to the mesoscale model. Models of radiation and energy balance have been developed with explicit treatment of the vegetation canopy. By examining the flow over a forest canopy under a range of stability conditions, we found that buoyancy enhances or suppresses turbulent mixing in unstable or stable atmosphere respectively, with decreasing or increasing wind shear, respectively. From the multiscale modeling of the Beijing Olympic Forest Park, the present coupling scheme proves to better resolve the diurnal variations in wind speed, temperature, and relative humidity over complex urban terrains. The coupling scheme is superior to the traditional mesoscale model in terms of wind field simulation. This is mainly because the coupling scheme not only takes the influences of external mesoscale flow into consideration, but also resolves the heterogeneous urban surface at a fine scale by downscaling, thus better reproducing the complex flow and turbulent transport in the urban roughness sublayer.

The important roles played by branched polyubiquitin chains were recently uncovered in proteasomal protein degradation, mitotic regulation, and NF-κB signaling. With the new realization of a wide presence of branched ubiquitin chains in mammalian cells, there is an urgent need of identifying the reader and eraser proteins of the various branched ubiquitin chains. In this work, we report the generation of noncleavable branched triubiquitin probes with combinations of K11-, K48-, and K63linkages. Through a pulldown approach using the branched triUb probes, we identified human proteins that recognize branched triubiquitin structures including ubiquitin-binding proteins and deubiquitinases (DUBs). Proteomics analysis of the identified proteins enriched by the branched triubiquitin probes points to possible roles of branched ubiquitin chains in cellular processes including DNA damage response, autophagy, and receptor endocytosis. In vitro characterization of several identified UIM-containing proteins demonstrated their binding to branch triubiquitin chains with moderate to high affinities. Availability of this new class of branched triubiquitin probes will enable future investigation into the roles of branched polyubiquitin chains through identification of specific reader and eraser proteins, and the modes of branched ubiquitin chain recognition and processing using biochemical and biophysical methods.

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