A retro-prospective cohort study by Weihong Chen and colleagues provides new estimates for the risk of total and cause-specific mortality due to long-term silica dust exposure among Chinese workers.

a b s t r a c tThis paper describes an advanced multi-scale weather modeling system, WRF-RTFDDA-LES, designed to simulate synoptic scale ( $ 2000 km) to small-and micro-scale ($ 100 m) circulations of real weather in wind farms on simultaneous nested grids. This modeling system is built upon the National Center for Atmospheric Research (NCAR) community Weather Research and Forecasting (WRF) model. WRF has been enhanced with the NCAR Real-Time Four-Dimensional Data Assimilation (RTFDDA) capability. FDDA is an effective data assimilation algorithm, which is capable of assimilating diverse weather measurements on model grids and seamlessly providing realistic mesoscale weather forcing to drive a large eddy simulation (LES) model within the WRF framework. The WRF based RTFDDA LES modeling capability is referred to as WRF-RTFDDA-LES. In this study, WRF-RTFDDA-LES is employed to simulate real weather in a major wind farm located in northern Colorado with six nested domains. The grid sizes of the nested domains are 30, 10, 3.3, 1.1, 0.370 and 0.123 km, respectively. The model results are compared with wind-farm anemometer measurements and are found to capture many intra-farm wind features and microscale flows. Additional experiments are conducted to investigate the impacts of subgrid scale (SGS) mixing parameters and nesting approaches. This study demonstrates that the WRF-RTFDDA-LES system is a valuable tool for simulating real world microscale weather flows and for development of future real-time forecasting system, although further LES modeling refinements, such as adaptive SGS mixing parameterization and wall-effect modeling, are highly desired.

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To investigate the mechanisms for the record‐breaking rainfall in the coastal metropolitan city of Guangzhou, China during 6–7 May 2017, budget analyses of advection and source/sink terms of the water vapor, potential temperature, and vertical momentum equations were conducted using the model output of a nested very large eddy simulation with the Weather Research and Forecasting model. Results show that the warm and moist air flows from the south and east onshore in the lower troposphere provided the main moisture source for the heavy rainfall. The structure of vertical velocity and hydrometeors (low‐echo centroid structure), in which the heavy rainfall was separated from the low‐level updraft, was favorable for the formation and maintenance of a heavy precipitation rate. The removal of the heat due to the advection (cooling tendency) in the upper troposphere increased the convective available potential energy of parcels rising from the lower troposphere, maintaining the development of updrafts. Although the total buoyancy forcing was the main contribution term for maintaining the updrafts, total dynamic acceleration played an important role in the vertical acceleration below the maximum vertical velocity core. In particular, the nonlinear dynamic perturbation pressure gradient force in the lower troposphere induced by the rotations aloft maintained the strong updrafts.

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