Beijing Aviation Meteorological Institute

Beijing, China

Beijing Aviation Meteorological Institute

Beijing, China

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Zheng J.,Tsinghua University | Zheng J.,Beijing Aviation Meteorological Institute | He H.,Beijing Aviation Meteorological Institute | Zhang T.,Beijing Aviation Meteorological Institute | Zhu J.,Tsinghua University
Qinghua Daxue Xuebao/Journal of Tsinghua University | Year: 2015

There are many digital terrain reconstructing methods based on divide and conquer. This study analyzes all possible cases of the merging of two subnet convex hulls. A subnet merging algorithm is then developed to overcome the limitations and drawbacks of traditional algorithms. The public support line and support points are found from the projection position of the vertices of the convex hulls. Then, the convex hull vertices between the support points are linked to generate new triangles so that no two triangles are intersect. Tests show that the algorithm is stable and reliable and that any two subnet convex hulls can be successfully merged. ©, 2015, Press of Tsinghua University. All right reserved.


Zheng J.,Tsinghua University | Zheng J.,Beijing Aviation Meteorological Institute | Zhang T.,Beijing Aviation Meteorological Institute
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2015

Filtering is the key to acquire digital terrain model from airborne LiDAR point cloud. In this paper, a new LiDAR point cloud filtering method is proposed. First, the scanning lines formed with point sequence are obtained throuth scanning the point cloud along the same direction. Then a circle with the variable radius rolling over the bottom of these scanning lines, the purpose is to acquire the points on the ground surface and delete the points on the objects at the same time. The next step is interval sampling from the scanning lines. On this basis, after fitting terrain surface with uniform B-spline surface, every point is projected to the fitting surface and calculate its height. According to compare the real height and its projection height to judge every point is on the terrain surface or not. The experiments show that filtering precision of the algorithm proposed in this paper is improved 1 to 5 times of the traditional methods, it can be used for the city, mountains and forest, and the time complexity of the algorithm is O(n). © 2015, Surveying and Mapping Press. All right reserved.


Hu L.,CAS Institute of Atmospheric Physics | Hu L.,University of Chinese Academy of Sciences | Yang S.,I-Systems | Li Y.,CAS Institute of Atmospheric Physics | And 2 more authors.
Advances in Atmospheric Sciences | Year: 2010

The diurnal variability of precipitation depth over the Tibetan Plateau and its surrounding regions is investigated using nine years of Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) measurements. The Tibetan Plateau, the plains area, and the East China Sea are selected as the focus regions in this study. The average precipitation depths (PD) are about 4.6 km, 5.8 km, and 5.6 km, while convective (stratiform) PDs are about 6.6 (4.5) km, 7.5 (5.7) km, and 6.0 (5.6) km over the plateau, the plains, and the ocean region, respectively. Results demonstrate a prominent PD diurnal cycle, and its diurnal phase is generally a few hours behind the surface precipitation. The spatial variation of the PD diurnal magnitude is weaker near the coastal areas than that of surface precipitation. The height of the PD diurnal peak is around 6-7 km for convective systems and 5-6 km for stratifrom systems. The dominant afternoon diurnal peak for convective PD and the flat diurnal peak for stratiform PD over the Tibetan Plateau indicate that solar diurnal forcing is the key mechanism of the PD diurnal cycle over land. In addition, the diurnal variation is obvious for shallow and deep convective systems, but not for shallow and deep stratiform systems. © Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer Berlin Heidelberg 2010.


Hu L.,National Satellite Meteorological Center | Hu L.,CAS Institute of Atmospheric Physics | Li Y.,CAS Institute of Atmospheric Physics | Li Y.,Beijing Aviation Meteorological Institute | Deng D.,CAS Institute of Atmospheric Physics
Advances in Atmospheric Sciences | Year: 2013

The relationship between surface rain rate and depth of rain system (rain depth) over Southeast Asia is examined using 10-yr Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) measurements. Results show that, in general, a large surface rain rate is associated with a deep precipitating system, but a deep rain system may not always correspond with a large surface rain rate. This feature has a regional characteristic. Convective rain develops more frequently over land than over the ocean, while stratiform rain can extend to higher altitudes over the ocean than over land. A light surface rain rate has the largest probability to occur, regardless of rain depth. A convective rain system is more likely associated with a stronger surface rain rate than a stratiform rain system. Results show that precipitation systems involve complex microphysical processes. Rain depth is just one characteristic of precipitation. A linear relationship between surface rain rate and rain depth does not exist. Both deep convective and stratiform rain systems have reflectivity profiles that can be divided into three sections. The main difference in their profiles is at higher levels, from 4.5 km up to 19 km. For shallow stratiform rain systems, a two-section reflectivity profile mainly exists, while for convective systems a three-section profile is more common. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg.


Shi X.K.,Beijing Aviation Meteorological Institute | Liu J.W.,Beijing Aviation Meteorological Institute | Li Y.D.,Beijing Aviation Meteorological Institute | Tian H.,Chinese Academy of Sciences | Liu X.P.,PLA University of Science and Technology
Science China Earth Sciences | Year: 2014

The regional verification of soil moisture is a vital step in evaluating and improving numerical model performance and utilizing forecast results. Currently, even with improved spatial and temporal resolutions of numerical model, verification methods for soil moisture data still rely on the traditional intensity verification parameters, such as mean error (ME) and root-mean-squared error (RMSE). Those methods provide only incomplete and sometimes inaccurate messages and thus hinder a proper evaluation of a forecast model. The SAL method is an object-based regional verification method with respect to precipitation forecasts. Based on the SAL method, a novel object-based method (SAL-DN) is proposed here, which can be used to test regional soil moisture. Both the ideal experiment and real experiment show that the SAL-DN method can reveal the differences between the observed and forecast soil moisture in three aspects: structure, amplitude, and location, and the results can reflect the actual situation. Furthermore, compared with the SAL method, the SAL-DN method is also capable of verifying physical quantities with high-value and low-value centers like temperature. Therefore, the SAL-DN method enhances verification accuracy and can be applied widely. © 2014, Science China Press and Springer-Verlag Berlin Heidelberg.


Zhuhua Z.,Beijing Aviation Meteorological Institute | Yuling L.,Beijing Aviation Meteorological Institute | Wenjun Z.,Beijing Aviation Meteorological Institute | Rong F.,Beijing Institute of Applied Meteorology
AIP Conference Proceedings | Year: 2013

Satellites provide an opportunity of obtaining spatially continuous visibility data. This paper develops an algorithm that retrieves visibility from the Medium Resolution Spectral Imager (MERSI) onboard the FY-3A satellite. The visibility retrieval algorithm consists of two basic steps. First, aerosol optical depth (AOD) is retrieved with MERSI observations at the 2.1 μm, 0.47 μm, and 0.65 μm channels based on look-up-table approach. Second, visibility is calculated with the relationship between visibility and aerosol optical thickness and aerosol scale height, which can be derived from the Koschmieder equation. Two sets of aerosol scale heights are tested, one based on climatic statistics and the other on mixing layer height forecasts. Results show that the distribution pattern and the high and low centers of retrieved visibility match well with that of the surface observations. Compared to the results derived based on climatologically aerosol scale heights, the ones based on mixing layer heights deviate less from surface observations. © 2013 AIP Publishing LLC.


Shi X.-K.,Beijing Aviation Meteorological Institute | Liu J.-W.,Beijing Aviation Meteorological Institute | Li Y.-D.,Beijing Aviation Meteorological Institute | Huang B.,Beijing Aviation Meteorological Institute | Tan Y.-Q.,Beijing Aviation Meteorological Institute
Natural Hazards | Year: 2015

Forecasting aircraft turbulence accurately is of vital importance for route optimization and flight safety. The common methods including TI index and L-P are usually used to predict aircraft turbulence by diagnosing the strength of atmospheric turbulence, not taking into account the impact of aircraft itself and other elements, and can only be applied to the products with low horizontal resolutions. By considering factors that affect the aircraft lift, a new diagnostic index method, S Index (SI) method, is designed in this paper for aircraft turbulence, which can be applicable to high-resolution NWP products or analysis products. SI method mainly focuses on the factors that impact aircraft turbulence such as flight speed, wing loading, vertical velocity of air flow, horizontal wind speed, air density. The paper also provides a method of determining parameters based on the existing experience and mathematical techniques which are combined with aircraft reports and high-resolution NWP results. In addition, pointing to the level flight and takeoff/landing stages, SI analysis and calculation are carried out, respectively. To validate the application scope of the accuracy of SI method objectively, the physical quantity of turbulence area ratio (TAR), which is a statistical parameter to describe the ratio of turbulence area and the overall diagnostic region, is defined. In the case that the horizontal and vertical resolutions of weather research and forecasting (WRF) forecasts are 9 km and 300 m, respectively, the diagnostic results of SI show that for the stage of level flight, when the TAR ratio is 41 %, the overall forecast accuracy of aircraft turbulence can reach 74 %, of which the accuracy of moderate turbulence forecast is 60 % and the severe 27 %. For the stage with 20° elevation during the process of takeoff and landing, when the TAR ratio is 40 %, the overall forecast accuracy can get to 63 %, of which the accuracies of moderate and severe turbulence are 41 and 14 %, respectively. © 2015, Springer Science+Business Media Dordrecht.


Shi X.K.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Shi X.K.,Beijing Aviation Meteorological Institute | Wen J.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Liu J.W.,Beijing Aviation Meteorological Institute | And 3 more authors.
Science China Earth Sciences | Year: 2010

Accurate assignment of model and observation errors is crucial for the successful application of land surface data assimilation algorithms. Poorly-specified model and observation errors can significantly degrade assimilation results. In 2008, Reichle et al. developed an operational procedure to adaptively tune model and observation errors. In this paper, we modified and applied Reichle's procedure in the Noah land surface model to assimilate observed surface soil moisture data. Numerical simulations showed that: (1) the best estimate of model and observation errors appears when the empirical factor β equals 1.02; (2) the Reichle procedure can be deployed to adaptively tune errors if their true values change slowly; and (3) convergence of the Reichle procedure was improved using better initial errors achieved by iterative computations. © Science China Press and Springer-Verlag Berlin Heidelberg 2010.


Hu L.,National Satellite Meteorological Center | Hu L.,CAS Institute of Atmospheric Physics | Li Y.D.,CAS Institute of Atmospheric Physics | Li Y.D.,Beijing Aviation Meteorological Institute | And 2 more authors.
Science China Earth Sciences | Year: 2011

Seasonal variations in tropical and subtropical convective and stratiform precipitation of the East Asian monsoon are analyzed using 10-year (1998-2007) Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) rain products (2A25). Datasets from the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) 24 general circulation models (GCMs) are evaluated using TRMM PR rain products in terms of their ability to simulate convective and stratiform precipitation and their deficiencies. The results show that Asian monsoon convective and stratiform precipitation increases significantly after onset of the summer monsoon, but the percentage of convective precipitation clearly decreases over tropical areas while it increases in subtropical regions. The GCMs simulate well the seasonal variation in the contribution of Asian monsoon subtropical convective precipitation to the total rainfall; however, the simulated convective precipitation amount is high while the simulated stratiform precipitation amount is low relative to TRMM measurements, especially over the Asian monsoon tropical region. There is simultaneous TRMM-observed convective and stratiform precipitation in space and time, but GCMs cannot simulate this relationship between convective and stratiform precipitation, resulting in the deficiency of stratiform precipitation simulations. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg.


Xi S.,National Satellite Meteorological Center | Dong P.-M.,Beijing Aviation Meteorological Institute | Zhang P.,National Satellite Meteorological Center | Ma G.,National Satellite Meteorological Center | Qin D.-Y.,National Satellite Meteorological Center
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

This study introduces constructions of the satellite observation cycling assimilation system in National Satellite Meteorological Center (NSMC)/China Meteorological Administration (CMA). A typhoon (1209 Saola) is chosen as a test case to check performance of the cycling assimilation system at low resolution. Three experiments are designed: control, ATOVS microwave observation assimilation and forecasting with cold start, assimilation and forecasting with warm start. Compared with the cold start forecasting, the cycling forecasting scheme (with warm restart and assimilation every 6 hours) showed advantages in describing Tropical Cyclones (TC) in details. As for track and intensity predictions, the two assimilation experiments were superior to the control experiment. Especially, the cycling experiment (with warm restart) is better than the cold start experiment for the first day, third day, and day before its landfall, but does not perform well during TC's mature stage, which may suggest that this model could not present the typhoon Saola well during TC mature stage with a low resolution. Results also demonstrate that this scheme is fine during TC's slow intensification period. © 2014 SPIE.

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