Entity

Time filter

Source Type


Wang C.,CAS Institute of Atmospheric Physics | Wang C.,University of Chinese Academy of Sciences | Gao S.,CAS Institute of Atmospheric Physics | Gao S.,Chinese Academy of Meteorological Sciences | And 3 more authors.
Advances in Atmospheric Sciences | Year: 2015

Terrain characteristics can be accurately represented in spectrum space. Terrain spectra can quantitatively reflect the effect of topographic dynamic forcing on the atmosphere. In wavelength space, topographic spectral energy decreases with decreasing wavelength, in spite of several departures. This relationship is approximated by an exponential function. A power law relationship between the terrain height spectra and wavelength is fitted by the least-squares method, and the fitting slope is associated with grid-size selection for mesoscale models. The monotonicity of grid size is investigated, and it is strictly proved that grid size increases with increasing fitting exponent, indicating that the universal grid size is determined by the minimum fitting exponent. An example of landslide-prone areas in western Sichuan is given, and the universal grid spacing of 4.1 km is shown to be a requirement to resolve 90% of terrain height variance for mesoscale models, without resorting to the parameterization of subgrid-scale terrain variance. Comparison among results of different simulations shows that the simulations estimate the observed precipitation well when using a resolution of 4.1 km or finer. Although the main flow patterns are similar, finer grids produce more complex patterns that show divergence zones, convergence zones and vortices. Horizontal grid size significantly affects the vertical structure of the convective boundary layer. Stronger vertical wind components are simulated for finer grid resolutions. In particular, noticeable sinking airflows over mountains are captured for those model configurations. © 2015, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg. Source


Liang H.,Chinese Academy of Meteorological Sciences | Liang H.,University of Chinese Academy of Sciences | Zhang R.,Chinese Academy of Meteorological Sciences | Liu J.,Chinese Academy of Meteorological Sciences | And 3 more authors.
Advances in Atmospheric Sciences | Year: 2012

In this study, the clear sky hourly global and net solar irradiances at the surface determined using SUNFLUX, a simple parameterization scheme, for three stations (Gaize, Naqu, and Lhasa) on the Tibetan Plateau were evaluated against observation data. Our modeled results agree well with observations. The correlation coefficients between modeled and observed values were > 0. 99 for all three stations. The relative error of modeled results, in average was < 7%, and the root-mean-square variance was < 27 W m -2. The solar irradiances in the radiation model were slightly overestimated compared with observation data; there were at least two likely causes. First, the radiative effects of aerosols were not included in the radiation model. Second, solar irradiances determined by thermopile pyranometers include a thermal offset error that causes solar radiation to be slightly underestimated. The solar radiation absorbed by the ozone and water vapor was estimated. The results show that monthly mean solar radiation absorbed by the ozone is < 2% of the global solar radiation (< 14 W m -2). Solar radiation absorbed by water vapor is stronger in summer than in winter. The maximum amount of monthly mean solar radiation absorbed by water vapor can be up to 13% of the global solar radiation (95 W m -2). This indicates that water vapor measurements with high precision are very important for precise determination of solar radiation. © 2012 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg. Source


Wang C.,CAS Institute of Atmospheric Physics | Wang C.,University of Chinese Academy of Sciences | Gao S.,CAS Institute of Atmospheric Physics | Gao S.,Chinese Academy of Meteorological Sciences | And 5 more authors.
Atmospheric Research | Year: 2014

A rainstorm process that occurred in North China from July 24-25, 2011 was accurately simulated using the Weather Research and Forecasting model, and the multi-scale characteristics of moisture transport were studied based on the simulated results. The results indicated that water vapor was carried to North China mainly by the southwest low-level jet and easterly flow, with the former playing a principal role. The enhancement and northward extension of the southwesterly wind were consistent with the increase of magnitude and northward propulsion of the moisture flux. The variation of the winds mirrored fluctuations in the amount of precipitation. In addition, the water vapor from low latitudes to North China was transported first near the boundary layer over 15°N-21°N and then primarily at 850. hPa over 21°N-30°N, 900. hPa over 30°N-39°N, and 800. hPa over the region north of 39°N. The net budget of water vapor in North China was always positive during the rainstorm process because the zonal deficit was much smaller than the meridional surplus. The contribution of the water vapor advection was larger than that of the water vapor convergence in the prior period of rainfall, and the subsequent moisture aggregation relied on the water vapor convergence. The rainband in North China presented frontal mesoscale characteristics, and the short-term aggregation of moisture was closely related to the genesis and development of the mesoscale convective system that was triggered mainly by the cold air intrusion near the boundary layer. The underlying cold air not only lifted the warm air to trigger the convection, but it also influenced the development of the low pressure system in the lower levels, which further intensified the convergence and benefited the rapid accumulation of moisture to the convective zone near the boundary layer. The moisture transport reached its maximum an hour before the rainstorm occurred. © 2014 Elsevier B.V. Source


Cheng X.-L.,CAS Institute of Atmospheric Physics | Li J.,CAS Institute of Atmospheric Physics | Hu F.,CAS Institute of Atmospheric Physics | Xu J.,CAS Institute of Atmospheric Physics | Zhu R.,Public Weather Service Center
Wind and Structures, An International Journal | Year: 2015

A coupled model system for Wind Resource Assessment (WRA) was studied. Using a mesoscale meteorological model, the Weather Research and Forecasting (WRF) model, global-scale data were downscaled to the inner nested grid scale (typically a few kilometers), and then through the coupling Computational Fluid Dynamics (CFD) mode, FLUENT. High-resolution results (50 m in the horizontal direction; 10 m in the vertical direction below 150 m) of the wind speed distribution data and ultimately refined wind farm information, were obtained. The refined WRF/FLUENT system was then applied to assess the wind resource over complex terrain in the northern Poyang Lake region. The results showed that the approach is viable for the assessment of windenergy. Copyright © 2015 Techno-Press, Ltd. Source


Li C.,Beijing Normal University | Li C.,Henan Polytechnic University | Shen L.,Beijing Normal University | Wang H.-B.,Public Weather Service Center | Lei T.,Beijing Normal University
Proceedings - 2nd IEEE International Conference on Advanced Computer Control, ICACC 2010 | Year: 2010

As an important means of obtaining spatial data, the unmanned aerial vehicle (UAV) remote sensing has such advantages as real-time, flexible, high-resolution, cost-effective etc, and it can gather information in dangerous environments without risk to flight crews. Because UAV remote sensing is a powerful supplement of spaceborne remote sensing and airborne remote sensing, it has enormous potential and bright prospect. In this paper, the compositions and key technologies of UAV remote sensing system are presented, and the applications such as land use, land supervision, flood disasters, meteorology disasters, geological disasters, forest fire disasters as well as surveying and mapping are summarized. In the end, we predict the main direction of studying on UAV remote sensing in the future. © 2010 IEEE. Source

Discover hidden collaborations