Time filter

Source Type

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.


Bao H.-J.,Public Weather Service Center | Bao H.-J.,National Meteorological Center | Zhao L.-N.,Public Weather Service Center | Zhao L.-N.,National Meteorological Center | And 8 more authors.
Advances in Geosciences | Year: 2011

The incorporation of numerical weather predictions (NWP) into a flood forecasting system can increase forecast lead times from a few hours to a few days. A single NWP forecast from a single forecast centre, however, is insufficient as it involves considerable non-predictable uncertainties and lead to a high number of false alarms. The availability of global ensemble numerical weather prediction systems through the THORPEX Interactive Grand Global Ensemble' (TIGGE) offers a new opportunity for flood forecast. The Grid-Xinanjiang distributed hydrological model, which is based on the Xinanjiang model theory and the topographical information of each grid cell extracted from the Digital Elevation Model (DEM), is coupled with ensemble weather predictions based on the TIGGE database (CMC, CMA, ECWMF, UKMO, NCEP) for flood forecast. This paper presents a case study using the coupled flood forecasting model on the Xixian catchment (a drainage area of 8826 km2) located in Henan province, China. A probabilistic discharge is provided as the end product of flood forecast. Results show that the association of the Grid-Xinanjiang model and the TIGGE database gives a promising tool for an early warning of flood events several days ahead. © 2011 Author(s).


Liu J.,CAS Institute of Atmospheric Physics | Liu J.,Public Weather Service Center | Liu J.,Nanjing University of Information Science and Technology | Xia X.,CAS Institute of Atmospheric Physics | And 12 more authors.
Tellus, Series B: Chemical and Physical Meteorology | Year: 2010

Based on AErosol RObotic NETwork and Chinese Sun Hazemeter Network data, the Multi-angle Imaging SpectroRadiometer (MISR) level 2 aerosol optical depth (AOD) products are evaluated in China. The MISR retrievals depict well the temporal aerosol trend in China with correlation coefficients exceeding 0.8 except for stations located in northeast China and at the Lanzhou site. In general, the MISR AOD retrievals agree well with ground-based observations for AOD < 0.5. The retrievals are systematically underestimated for AOD > 0.5 in the east, southwest and northeast regions of China. Concerning surface types, the greatest underestimations occur in farmland and forest ecosystems. The largest and smallest biases are seen in spring and in summer, respectively. The systematic underestimation seems to stem from the use of too high single scattering albedos ∼0.96 which is significantly higher than those estimated from ground-based observations. Further improvements to the MISR aerosol algorithm, especially in the aerosol model, are recommended. © 2010 The Authors Journal compilation © 2010 Blackwell Munksgaard.


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.


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.


Bao H.,Public Weather Service Center | Bao H.,National Meteorological Center | Zhao L.,Public Weather Service Center | Zhao L.,National Meteorological Center
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2012

This paper develops a flood routing model of plain rivers with a real-time roughness coefficient updating technique based on the Kalman filter theory. With the cross sections of long river simplified into rectangle, triangle and parabola shapes, the roughness coefficient can be updated step by step in routing calculation. Based on the relationship between Froude number and inertia terms of Saint-Venant equations, a relationship between roughness coefficient and water depth was obtained. In a case study of Wangjiaba-Lutaizi reach of Huaihe river, this new model was verified by comparing its real-time forecasts with the ones by a traditional hydraulic model. Results show that the river stages forecasted six hours in advance by both models are in good agreement with the observations and that the new model shows better performances than the traditional model. © right.


Zhao L.-N.,Public Weather Service Center | Zhao L.-N.,National Meteorological Center | Tian F.-Y.,National Meteorological Center | Wu H.,Public Weather Service Center | And 6 more authors.
Advances in Geosciences | Year: 2011

The precipitation forecasts of three ensemble prediction systems (EPS) and two multi-model ensemble prediction systems (MM EPS) were assessed by comparing with observations from 19 rain gauge stations located in the Dapoling-Wangjiaba sub-catchment of Huaihe Basin for the period from 1 July to 6 August 2008. The sample Probabilistic Distribution Functions (PDF) of gamma distribution, the Relative Operating Characteristic (ROC) diagrams, the percentile precipitation and a heavy rainfall event are analyzed to evaluate the performances of the single and multi-model ensemble prediction system (EPS). The three EPS were from the China Meteorological Administration (CMA); the United States National Centre for Environment Predictions (NCEP); and the European Centre for Medium-Range Weather Forecasts (ECMWF), all were obtained from the TIGGE-CMA archiving centre (THORPEX Interactive Grand Global Ensemble, TIGGE). The MM EPS were created using the equal weighting method for every ensemble member over the test area, the first ( MM-1) consisted of all three EPS, the second (MM-2) consisted of the ECMWF and NCEP EPS. The results demonstrate the level of correspondence between deterioration in predictive skill and extended lead time. Compared with observations and with a lead time of one day, ECMWF performs a little better than other centre's. With over five days in advance, all the three EPS and the two MM EPS don't give reliable probabilistic precipitation forecasts. Both MM EPS can outperform CMA and NCEP for most of the forecasted days, but still perform a little worse than ECMWF. Though variation of daily percentile precipitation and ROC areas show MM-2 outperforms MM-1, gamma distribution indicates much similar performances for all 10-day forecast, and neither is superior to ECMWF. © 2011 Author(s).


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.


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.


Cheng X.,CAS Institute of Atmospheric Physics | Wu L.,CAS Institute of Atmospheric Physics | Song L.,Public Weather Service Center | Wang B.,Public Weather Service Center | Zeng Q.,CAS Institute of Atmospheric Physics
Journal of Meteorological Research | Year: 2014

The structures and characteristics of the marine-atmospheric boundary layer over the South China Sea during the passage of strong Typhoon Hagupit are analyzed in detail in this paper. The typhoon was generated in the western Pacific Ocean, and it passed across the South China Sea, finally landfalling in the west of Guangdong Province. The shortest distance between the typhoon center and the observation station on Zhizi Island (10 m in height) is 8.5 km. The observation data capture the whole of processes that occurred in the regions of the typhoon eye, two squall regions of the eye wall, and weak wind regions, before and after the typhoon's passage. The results show that: (a) during the strong wind (average velocity ū ≥ 10 m s-1) is almost independent of height, and vertical velocity w̄ is greater than 0, increasing with ū and reaching 2-4 m s-1 in the squall regions; (b) the turbulent fluctuations (frequency > 1/60 Hz) and gusty disturbances (frequency between 1/600 and 1/60 Hz) are both strong and anisotropic, but the anisotropy of the turbulent fluctuations is less strong; (c) ū can be used as the basic parameter to parameterize all the characteristics of fluctuations; and (d) the vertical flux of horizontal momentum contributed by the average flow (ū·w̄) is one order of magnitude larger than those contributed by fluctuation fluxes (Formula presented.), implying that strong wind may have seriously disturbed the sea surface through drag force and downward transport of eddy momentum and generated large breaking waves, leading to formation of a strongly coupled marine-atmospheric boundary layer. This results in w̄ ≥ 0 in the atmosphere, and some portion of the momentum in the sea may be fed back again to the atmosphere due to ū · w̄ ≥ 0. © 2014 The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg.

Loading Public Weather Service Center collaborators
Loading Public Weather Service Center collaborators