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The influence of double-moment representation of warm-rain and ice hydrometeors on the numerical simulations of a mesoscale convective system (MCS) over the US Southern Great Plains has been evaluated. The Weather Research and Forecasting (WRF) model is used to simulate the MCS with three different microphysical schemes, including the WRF single-moment 6-class (WSM6), WRF double-moment 6-class (WDM6), and Morrison double-moment (MORR) schemes. It is found that the double-moment schemes outperform the single-moment schemes in terms of the simulated structure, life cycle, cloud coverage, precipitation, and microphysical properties of the MCS. However, compared with UND-Citation observations, collected during the Midlatitude Continental Convective Clouds Experiment (MC3E), the WRF simulated ice hydrometeors with all three schemes do not agree well with the observations. Overall results from this study suggest that uncertainty in microphysical schemes could still be a productive area of future research from perspective of both model improvements and observations.

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Basic wind speed is a very essential parameter used for conversion into wind loads on building structures. In Cambodia, the information on basic wind speed remains uncertain due to insufficient fundamental studies on the wind characteristics associated with regional climatic conditions. The aim of this paper is to assess and discuss the basic wind speeds for structural wind-resistant design in Cambodia by using statistical and probabilistic approaches. The datasets have been collected from National Centers for Environmental Information datasets, National Oceanic and Atmospheric Administration under World Meteorological Organization, and Mekong River Commission in forms of hourly wind speeds. The hourly wind speeds were then statically converted to 3-second gusts speeds using Gaussian Distribution Transformation. The extreme value distributions namely, Gumbel and Gringorten were used to analyze the extreme speed in accordance with a return period. The results showed that with a return period of 10 to 1000 years, the basic wind speed varies from a minimum of 22m/s to a maximum of 53m/s, respectively. These results provided a new aspect over traditionally uncertain basic wind speed selection and can be an alternative for the estimation of wind loads for the design of building structures in Cambodia.

This study investigates the effects of the total solar eclipse of 22 July 2009 on surface ozone and other photo-oxidants over central China using the WRF-Chem model. Chemical and meteorological observation data were used to validate the model, and results suggest that the WRF-Chem model can capture the effects of the total solar eclipse well. The maximum impacts of the eclipse occur over the area of totality, with a decrease in surface temperature of 1.5 °C and decrease in wind speed of 1 m s⁻¹. In contrast, the maximum impacts on atmospheric pollutants occur over parts of north and east China where emissions are greater, with an increase of 5 ppbv in NO₂ and 25 ppbv in CO and a decrease of 10 ppbv in O₃ and 3 ppbv in NO. This study also shows the effects of the solar eclipse on surface photo-oxidants in different parts of China. Although the sun was obscured to a smaller extent in polluted areas than in clean areas, the impacts of the eclipse in polluted areas are greater and last longer than they do in clean areas. The change in radical concentrations during the eclipse reveals that nighttime chemistry dominates in both polluted and clean areas. In contrast to the effects on atmospheric pollutants, the change in radical concentrations (OH, HO₂ and NO₃ in clean areas is much larger than in polluted areas mainly because of the limited sources of radicals in these areas. In addition, since solar eclipse does provide a natural opportunity to test our understanding more thoroughly on atmospheric chemistry, especially on photolysis-related chemistry, a comprehensive experimental campaign is highly recommended during solar eclipses in future