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Hong S.-Y.,Yonsei University | Kim H.M.,Yonsei University | Kim J.-E.,Yonsei University | Hwang S.-O.,Yonsei University | Park H.,Numerical Weather Prediction Center
Terrestrial, Atmospheric and Oceanic Sciences

The impact of model uncertainties on analyzed data is investigated using a global data assimilation system. This issue is explored in a 3D-Var system based on the National Centers for Environmental Prediction (NCEP)/Department of Energy (DOE) system using two convective parameterization schemes, the Simplified Arakawa scheme and the Community Climate Model (CCM) scheme. Two sets of six-hourly analysis data are generated for the summer of 2004. The difference between the resulting analyses using different convective parameterization schemes is found to be significantly greater than that between two well-known analyzed data sets, the NCEP/National Center for Atmospheric Research (NCAR) reanalysis (RAl) and the NCEP/DOE reanalysis (RA2). This dependency is more pronounced in data-sparse areas like the East Asian region than in data-rich areas like the North American region. Our study indicates that predictabilities for short- to medium-range forecasts in the global forecast system are indirectly influenced by forecast model accuracy via the quality of the initial conditions. Source

In this paper, we discuss the applications of random balance design Fourier amplitude sensitivity test (RBD-FAST) and extended Fourier amplitude sensitivity test (EFAST) in the parameter sensitivity analysis of land surface process model. We use the common land model and data of Tongyu station, which is a reference site of CEOP in the semi-arid regions, use five model outputs (sensible heat flux, latent heat flux, surface temperature, temperature of air at 2 m over surface, moisture of air at 2 m over surface) as focus output, and use 11 model parameter (soil depth, the soil proportion of 1-5 layers of soil, the porosity of soil, the max dew depth, the roughness of the air between surface and the canopy, and the drag coefficient under the canopy) as the parameters to be analyzed. After the 10 RBD-FAST experiments, we obtain the first-order sensitivity results, and we gain not only first-order sensitivity but also the total sensitivity after the EFAST experiment. The first-order results of two methods show their consistency. The RBD-FAST takes less computing time and is easy to implemente, while the EFAST also has a more comprehensive and reasonable total sensitivity result. All results above illustrate the applications of both RBD-FAST and EFAST in the parameter sensitivity analysis of land surface model. Researchers can choose the suitable one to solve the different problems. © 2015 Chinese Physical Society. Source

Wannawong W.,Numerical Weather Prediction Center | Humphries U.W.,King Mongkuts University of Technology Thonburi | Wongwises P.,King Mongkuts University of Technology Thonburi | Vongvisessomjai S.,Regional Environmental Management Center
International Journal of Computational and Mathematical Sciences

The three steps of the standard one-way nested grid for a regional scale of the third generation WAve Model Cycle 4 (WAMC4) is scrutinized. The model application is enabled to solve the energy balance equation on a coarse resolution grid in order to produce boundary conditions for a smaller area by the nested grid technique. In the present study, the model takes a full advantage of the fine resolution of wind fields in space and time produced by the available U.S. Navy Global Atmospheric Prediction System (NOGAPS) model with 1 degree resolution. The nested grid application of the model is developed in order to gradually increase the resolution from the open ocean towards the South China Sea (SCS) and the Gulf of Thailand (GoT) respectively. The model results were compared with buoy observations at Ko Chang, Rayong and Huahin locations which were obtained from the Seawatch project. In addition, the results were also compared with Satun based weather station which was provided from Department of Meteorology, Thailand. The data collected from this station presented the significant wave height (Hs) reached 12.85 m. The results indicated that the tendency of the Hs from the model in the spherical coordinate propagation with deep water condition in the fine grid domain agreed well with the Hs from the observations. Source

Liu Y.,Numerical Weather Prediction Center | Xu T.,PLA University of Science and Technology | Liu J.,Guangxi University
Advances in Space Research

Using the Global Navigation Satellite System (GNSS) radio occultation observations from Formosa Satellite mission-3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC) from 2007 to 2012, the climatological characteristics of the global tropopause was studied, with the following features identified. The overall results generally agree with previous studies. The tropopause has an obvious zonal structure, with more zonal characteristics in the Southern Hemisphere than the Northern Hemisphere. The vertical shape of the tropopause is sharp in the tropics and broad in the sub-tropical latitudes, with the sharpest latitudinal gradient in the mid-latitudes of both hemispheres. The global tropopause exists in a large range between 8 km and 17 km (or between 100 hPa and 340 hPa). The highest tropopause is over the South Asian monsoon regions for the entire year. The spatial structure of the tropopause in the polar region is of concentric structure, with an altitude between 7.5 km and 10 km. It is more symmetric in the Antarctic than the Arctic. Differing from other places, the height of the tropopause in the Antarctic is higher in winter as opposed to summer. The tropopause has distinct seasonal variability, especially in polar regions. © 2014 COSPAR. Published by Elsevier Ltd. All rights reserved. Source

Liu Y.,Numerical Weather Prediction Center | Liu Y.,National Meteorological Center | Xue J.,Chinese Academy of Meteorological Sciences
Atmospheric Measurement Techniques

This paper reviews the development of the global navigation satellite system (GNSS) radio occultation (RO) observations assimilation in the Global/Regional Assimilation and PrEdiction System (GRAPES) of China Meteorological Administration, including the choice of data to assimilate, the data quality control, the observation operator, the tuning of observation error, and the results of the observation impact experiments. The results indicate that RO data have a significantly positive effect on analysis and forecast at all ranges in GRAPES, not only in the Southern Hemisphere where conventional observations are lacking but also in the Northern Hemisphere where data are rich. It is noted that a relatively simple assimilation and forecast system in which only the conventional and RO observation are assimilated still has analysis and forecast skill even after nine months integration, and the analysis difference between both hemispheres is gradually reduced with height when compared with NCEP (National Centers for Environmental Prediction) analyses. Finally, as a result of the new on-board payload of the Chinese FengYun-3 (FY-3) satellites, the research status of the RO of FY-3 satellites is also presented. © Author(s) 2014. Source

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