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Liu Y.,Chengdu University of Information Technology | Duan Q.,Beijing Normal University | Zhao L.,Public Meteorological Service Center | Ye A.,Beijing Normal University | And 4 more authors.
Hydrological Processes | Year: 2013

The National Center for Environmental Predictions (NCEP) has produced an ensemble meteorological reforecast product by using a fixed version of Global Forecast System (GFS) ensemble prediction system since 1 January 1979. The 15-member ensemble product, with a global coverage at a 2.5°×2.5° spatial resolution and a 14-day lead time, has been used successfully by the River Forecast Centers of the National Weather Service (NWS) to produce basin scale precipitation and temperature ensemble forecasts in the US for several years now. This study evaluates the predictive skill of post-processed ensemble forecasts based on GFS precipitation reforecast in China's Huai river basin. The evaluation is carried out in 15 sub-areas of the Huai river basin and covers the 1/1/1981-31/12/2003 period. The Ensemble Pre-Processing system version 3 (EPP3), developed at NWS, is used to develop joint probability distributions between forecasted ensemble mean precipitation and corresponding observations and to generate individual ensemble members that preserve space-time correlation of the observed precipitation data. Several statistical verification measures are used to quantify the goodness of fit between post-processed (i.e. EPP3 processed) ensemble mean and observation and to assess the ensemble spread. Results indicate that the post-processed forecasts have meaningful predictive skill for the first few days for ensemble daily precipitation forecasts. Predictive skill of ensemble forecasts of cumulative precipitation for lead times up to 14days are significant. The forecast skill is highly dependent on seasonality, with relatively lower skills seen for wet summer season, when convective storm patterns dominate, as compared with other seasons. The predictive skill of the post-processed ensemble precipitation is much better than the raw forecasts and the climatological ensemble forecasts. The results from this study suggest that the NCEP's GFS reforecasts can be a valuable resource for places other than the US. © 2012 John Wiley & Sons, Ltd.

Li L.,Harbin Institute of Technology | Kareem A.,University of Notre Dame | Hunt J.,University College London | Xiao Y.,Harbin Institute of Technology | And 2 more authors.
Boundary-Layer Meteorology | Year: 2014

A conceptual model is proposed for the characteristic sub-ranges in the velocity and temperature spectra in the boundary layer of tropical cyclones (hurricanes or typhoons). The model is based on observations and computation of radial and vertical profiles of the mean flow and turbulence, and on the interpretation of eddy mechanisms determined by shear (namely roll and streak structures near the surface), convection, rotation, blocking and sheltering effects at the ground/sea surface and in internal shear layers. The significant sub-ranges, as the frequency increases, are associated with larger energy containing eddies, shear and blocking, inertial transfer between large and small scales, and intense small-scale eddies generated near the surface caused by waves, coastal roughness change, and the buoyancy force associated with the evaporation of spray droplets. These sub-ranges vary with the locations at which the spectra are measured, i.e. the level z in relation to the height zmax of the peak mean velocity and the depth h of the boundary layer, and the radius r in relation to the eyewall radius Rew and the outer-vortex radius Rov. For two tropical cyclones (Nuri and Hagupit), experimental data were analyzed. Spectra were measured where r is near to Rew and Rov using four 1-h long datasets at coastal towers, at 10- and 60-m heights for tropical cyclone Nuri, and at 60-m height for tropical cyclone Hagupit at the south China coast. The field measurements of spectra within the boundary layer show significant sub-ranges of self-similar energy spectra (lying between the length scale 1,000 m and the smallest scales less than 40 m) that are consistent with the above conceptual model of the surface layer. However, with very high wind speeds near the eyewall, the energy of the independently generated intense surface eddy motions, associated with surface waves and water droplets in the airflow, greatly exceeds the energies of the small scales in the inertial sub-range of the boundary layer, over scales less than about 3–40 m depending on the height z and the radius r. This rise in the small-scale frequency weighted spectra (nSu (n), where n is natural frequency, and Su (n) is the energy spectrum of the longitudinal wind component) is consistent with the hypothesis that these processes are only weakly correlated with the main boundary-layer turbulence. © 2014, Springer Science+Business Media Dordrecht.

Li L.,Harbin Institute of Technology | Li L.,University of Notre Dame | Xiao Y.,Harbin Institute of Technology | Kareem A.,University of Notre Dame | And 2 more authors.
Journal of Wind Engineering and Industrial Aerodynamics | Year: 2012

This study focuses on enhancing our understanding of the spectral features of typhoon winds with critical implications on the mitigation of disproportionate damage experienced in typhoons-prone coastal regions. Examination of data suggests that generally used empirical models of wind power spectrum for extratropical storms may not adequately represent the tropical cyclone winds. In this paper, a data-driven model is proposed for wind power spectrum in tropical cyclone winds over the sea surface. Rather than fitting data to a universal spectral description, first the physical meaning of parameters in such a model is carefully examined and the contribution of each parameter is delineated. With these backgrounds, field measurements in typhoon Hagupit are used to model these spectral parameters in terms of the Monin-Obukhov length, mean wind speed and roughness length. Finally, the proposed spectral model is validated using arbitrarily selected four hours of data in different sectors of typhoon Hagupit wind field. The model shows a good agreement with the measurements. © 2012 Elsevier Ltd.

Wang L.,Capital Normal University | Gong H.,Capital Normal University | Liao W.,Sun Yat Sen University | Wang Z.,Public Meteorological Service Center
Science of the Total Environment | Year: 2015

Plants can effectively remove airborne particles from ambient air and consequently improve air quality and human health. The accumulation of particles on the leaf surfaces of three plant species with different epicuticular wax ultrastructures, such as thin films, platelets and tubules, was investigated during leaf expansion in Beijing under extremely high particulate matter (PM) concentration. The accumulation of particles on the leaf surfaces after bud break rapidly reached a high amount within 4-7days. Rainfall occasionally resulted in a considerable increase in the accumulation of particles on the leaf surfaces at a high PM concentration, which resulted from the wet deposition of PM, and balanced the amount of PM on the leaf surfaces over a longer period. The equilibrium value of the particle cover area on the adaxial leaf surface of the three test species in this study was 10%-50% compared with 3%-35% on the abaxial leaf surface. The epicuticular wax ultrastructures contributed significantly to the PM adsorption of the leaves. The capability of these ultrastructures to capture PM decreased in the following order: thin films, platelets and tubules. The ridges (at a scale of 1-2μm) on the leaf surfaces were more efficient at accumulating PM, particularly PM2.5, compared with the roughness (P-V distance) at a 5-20-μm scale. © 2015 Elsevier B.V.

Bao H.,Public Meteorological Service Center | Bao H.,National Meteorological Center | Zhao L.,Public Meteorological Service Center | Zhao L.,National Meteorological Center
Acta Meteorologica Sinica | Year: 2012

A coupled atmospheric-hydrologic-hydraulic ensemble flood forecasting model, driven by The Observing System Research and Predictability Experiment (THORPEX) Interactive Grand Global Ensemble (TIGGE) data, has been developed for flood forecasting over the Huaihe River. The incorporation of numerical weather prediction (NWP) information into flood forecasting systems may increase forecast lead time from a few hours to a few days. A single NWP model forecast from a single forecast center, however, is insufficient as it involves considerable non-predictable uncertainties and leads to a high number of false alarms. The availability of global ensemble NWP systems through TIGGE offers a new opportunity for flood forecast. The Xinanjiang model used for hydrological rainfall-runoff modeling and the one-dimensional unsteady flow model applied to channel flood routing are coupled with ensemble weather predictions based on the TIGGE data from the Canadian Meteorological Centre (CMC), the European Centre for Medium-Range Weather Forecasts (ECMWF), the UK Met Office (UKMO), and the US National Centers for Environmental Prediction (NCEP). The developed ensemble flood forecasting model is applied to flood forecasting of the 2007 flood season as a test case. The test case is chosen over the upper reaches of the Huaihe River above Lutaizi station with flood diversion and retarding areas. The input flood discharge hydrograph from the main channel to the flood diversion area is estimated with the fixed split ratio of the main channel discharge. The flood flow inside the flood retarding area is calculated as a reservoir with the water balance method. The Muskingum method is used for flood routing in the flood diversion area. A probabilistic discharge and flood inundation forecast is provided as the end product to study the potential benefits of using the TIGGE ensemble forecasts. The results demonstrate satisfactory flood forecasting with clear signals of probability of floods up to a few days in advance, and show that TIGGE ensemble forecast data are a promising tool for forecasting of flood inundation, comparable with that driven by raingauge observations. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2012.

Zhang Y.,CAS Institute of Atmospheric Physics | Zhang Y.,University of Chinese Academy of Sciences | Shen Y.,Public Meteorological Service Center | Shi G.,CAS Institute of Atmospheric Physics
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2016

Along with the rapid development of solar energy industry, more and more solar energy is integrated into electricity grid in the form of concentrating solar power (CSP). Forecasting direct normal irradiance (DNI) accurately several days ahead has become the foundation for solar energy integration as well as operation and maintenance of a CSP power plant. Treated in the paper are the definition of DNI, the electric power industry standards in China, methodology of short-term DNI forecasting, influence factors of forecast accuracy, approaches to accuracy improvement, and most recent advances of research in the nation. Meanwhile, problems in current researches are presented and future research and trends are envisioned for reference by the development of CSP in the “13th five-year plan” period. © 2016 Automation of Electric Power Systems Press.

Feng L.,CAS Institute of Atmospheric Physics | Feng L.,Public Meteorological Service Center | Zhou T.,CAS Institute of Atmospheric Physics
Journal of Geophysical Research: Atmospheres | Year: 2012

The atmospheric water vapor transport for summer precipitation over the southeastern Tibetan Plateau (hereafter TP) during 1979-2002 is examined by using five precipitation data sets and three reanalysis data sets. The multidata ensemble mean shows that under climate mean conditions, TP is a moisture sink in summer, having a net moisture convergence of 4 mm/day. The climatological water vapor transport from the southern boundary, which originates from the Indian Ocean and the Bay of Bengal, dominates the summer precipitation over the southeastern TP. It is estimated that the water vapor from the western boundary along the southern edge of the TP is about 32% of that from the southern boundary. The summer precipitation over the southeastern TP exhibits strong interannual variability, with a standard deviation of 1.3 mm/day, but no significant long-term trend. The water vapor transport for the interannual variability of summer rainfall over the southeastern TP mainly comes from the western boundary of the TP, which is originally from lower latitudes. An excessive rainfall anomaly of 1 mm/day over the southeastern TP is associated with an anomalous water vapor input of 138 (104) kg/m/s from the western (southern) boundary. It is worth noting that the quantitative analysis in this study is determined by the setting of the domain. The interannual variability of summer precipitation over the southeastern TP is dominated by an anomalous anticyclone over the northern Indian subcontinent and the Bay of Bengal, which intensifies the water vapor transport along the southern edge of the TP and leads to more water vapor convergence over the southeastern TP, thus the excessive rainfall in the area. © 2012. American Geophysical Union. All Rights Reserved.

Wang B.,Public Meteorological Service Center | Song L.,Public Meteorological Service Center | Chen W.,Guangdong Climate Center
Advances in Meteorology | Year: 2013

Using data from wind towers during typhoons Hagupit and Nuri, drag coefficient was estimated. The relationship between drag coefficient and atmospheric stability was examined. The results indicate that the drag coefficient decreased when atmosphere stability changed from weakly stable or unstable to neutral. Relationship between drag coefficient and wind speed was also examined, and the results indicate that the relationships between drag coefficient and wind speed were similar to other researchers' result, but the wind thresholds were different due to different observation sites. Quantitative expressions between drag coefficient and wind speed were derived. © 2013 Binglan Wang et al.

Tang Q.,Public Meteorological Service Center | Xie L.,North Carolina State University | Lackmann G.M.,North Carolina State University | Liu B.,North Carolina State University
Advances in Meteorology | Year: 2013

The contribution of the large-scale atmospheric environment to precipitation and flooding during Hurricane Floyd was investigated in this study. Through the vortex removal technique in the Weather Research and Forecasting (WRF) model, the vortex associated with Hurricane Floyd (1999) was mostly removed in the model initial conditions and subsequent integration. Results show that the environment-induced precipitation can account for as much as 22% of total precipitation in the innermost model domain covering North Carolina coastal area and 7% in the focused hydrological study area. The high-resolution precipitation data from the WRF model was then used for input in a hydrological model to simulate river runoff. Hydrological simulation results demonstrate that without the tropical systems and their interactions with the large-scale synoptic environment the synoptic environment would only contribute 10% to the total discharge at the Tarboro gauge station. This suggests that Hurricane Floyd and Hurricane Dennis preceding it, along with the interactions between these tropical systems and the large-scale environment, have contributed to the bulk (90%) of the record amount of flood water in the Tar-Pamlico River Basin. © 2013 Qianhong Tang et al.

Shen Y.-B.,Center for Wind and Solar Energy Resources Assessment | Shen Y.-B.,Public Meteorological Service Center | Wang B.,CAS Institute of Atmospheric Physics
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2011

Most of Earth's surface energy is from solar, and the change of surface solar radiation will profoundly affect the global climate. In this paper, the synchronous observational data of global radiation and temperature from 14 stations in South-East China was used to analyse the probable influence of surface solar radiation change on temperature change from 1961 to 2008. During 1961 - 1989, surface solar radiation in South-East China was significantly weakened, resulting in a slight decrease of average temperature. During 1993-2008, surface solar radiation in South-East China was increased, which was superposed on the other warming effects and accelerated the increase of temperature. In a word, the surface solar radiation change plays an essential role in the climate change in South-East China during these 50 years.

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