oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Weekly cycle in NCAR-NCEP reanalysis surface temperature data
TESOURO, M.;DE LA TORRE, L.;NIETO, R.;GIMENO, L.;RIBERA, P.;GALLEGO, D.;
Atmósfera , 2005,
Abstract: a weekly cycle has been detected in the surface temperature field of the ncar-ncep reanalysis for the north atlantic area. this cycle consists of a minimum in the weekend for most of the studied area and a minimum in the mid-week for areas with important snow or ice cover.
Validation of ECMWF and NCEP--NCAR Reanalysis Data in Antarctica

YU Lejiang,ZHANG Zhanhai,ZHOU Mingyu,Shiyuan ZHONG,Donald LENSCHOW,Hsiaoming HSU,WU Huiding,SUN Bo,

大气科学进展 , 2010,
Abstract: The European Center for Medium-Range Weather Forecast (ECMWF) Re-Analysis (ERA-40) and the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) ECMWF (ERA-40) and NCEP--NCAR reanalysis data were compared with Antarctic station observations, including surface-layer and upper-layer atmospheric observations, on intraseasonal and interannual timescales. At the interannual timescale, atmospheric pressure at different height levels in the ERA-40 data are in better agreement with observed pressure than that in the NCEP--NCAR reanalysis data. ERA-40 reanalysis also outperforms NCEP--NCAR reanalysis in atmospheric temperature, except in the surface layer where the biases are somewhat larger. The wind velocity fields in both datasets do not agree well with surface- and upper-layer atmospheric observations. At intraseasonal timescales, both datasets capture the observed intraseasonal variability in pressure and temperature during austral winter.
Effects of the baroclinic adjustment on the tropopause in the NCEP-NCAR reanalysis  [PDF]
Alessandro Dell'Aquila,Paolo M. Ruti,Alfonso Sutera
Physics , 2005,
Abstract: In this work, we study the mean tropopause structure from the NCEP-NCAR reanalysis in the framework of a theory of baroclinic adjustment, focusing on the impact of baroclinic eddies on the mean tropopause height. In order to measure the effects of such perturbations, we introduce an appropriate global index that selects events of high baroclinic activity and allows us to individuate the phases of growth and decay of baroclinic waves. We then composite the tropopause mean structure before and after a baroclinic event, finding that baroclinic disturbances cause the zonally averaged midlatitude winter tropopause height to rise. Our results suggest that the baroclinic adjustment processes should be taken into account to explain the nature of the midlatitude tropopause.
Reliability of NCEP/NCAR reanalysis data in the Himalayas/Tibetan Plateau

XIE Aihong,REN Jiawen,QIN Xiang,KANG Shichang,

地理学报 , 2007,
Abstract: Due to the difficult logistics in the extreme high elevation regions over the Himala-yas and Tibetan Plateau, the observational meteorological data are very few. In 2003, an automatic weather station was deployed at the northeastern saddle of Mt. Nyainqentanglha (NQ) (30°24′44.3″ N, 90°34′13.1″ E, 5850 m a.s.l.), the southern Tibetan Plateau. In 2005, another station was operated at the East Rongbuk Glacier Col (28°01′0.95″ N, 86°57′48.4″ E, 6523 m a.s.l.) of Mt. Qomolangma. Observational data from the two sites have been com-pared with the reanalysis data from the National Centers for Environmental Predic-tion/National Center for Atmospheric Research (NCEP/NCAR), reliability of NCEP/NCAR reanalysis data has been investigated in the Himalayas/Tibetan Plateau region. The reanaly-sis data can capture much of the synoptic-scale variability in temperature and pressure, al-though the reanalysis values are systematically lower than the observation. Furthermore, most of the variability magnitude is, to some degree, underestimated. In addition, the weather event extracted from the NCEP/NCAR reanalyzed pressure and temperature prominently appears one day ahead of the observational data on Mt. Qomolangma, while on Mt. NQ it occurs basically in the same day.
A Comparison of NCEP/NCAR, ERA-40 Reanalysis and Observational Data of Sensible Heat in Northwest China
比较NCEP/NCAR和ERA-40再分析资料与观测资料计算得到的感热资料的差异

ZHOU Liantong,
周连童

气候与环境研究 , 2009,
Abstract: The sensible heat in Northwest China are compared by using NCEP/NCAR, ERA-40 reanalysis and observational data during 1958-2000. The analyzed results show that the one of most center for sensible heat is in Northwest China by NCEP/NCAR, ERA-40 reanalysis data. The ERA-40 reanalysis data is more close to observational data in interdecadal time scale than that of NCEP/NCAR reanalysis data.
《广雅疏证》以“凡”语说明 “名”、“实”、“义”关系情况浅析  [PDF]
马景仑
安徽大学学报(哲学社会科学版) , 2010,
Abstract: 《广雅疏证》以“凡”语说明“名”、“实”、“义”之间的关系。其中包括两种情况一、以“凡”语说明某些“实”之得“名”缘由和某些“名”所指的“实”的内容范围,指明“名”与“实”之间的关系。二、以“凡”语说明相同、相近、相因之“义”分别用相同之“名”或音同音近之“名”表示,指明“名”与“义”之间的关系。
The Application of NCEP/NCAR Reanalysis Data to the Assessment of the Wind Resource
NCEP/NCAR再分析数据在风能资源评估中的应用研究

FENG Shuanglei,WANG Weisheng,LIU Chun,DAI Huizhu,
冯双磊
,王伟胜,刘纯,戴慧珠

资源科学 , 2009,
Abstract: Measure-Correlate-Predict (MCP) is not only a primary technical method to evaluate the development level of wind resource of a wind farm in plan, but it can also determine the annual energy production. The result of MCP can be influenced by the long term wind reference data, which means that if the long term wind reference data is low in credibility, the result of MCP is also unreliable; and then the wind resource assessment of the wind farm in plan can be false. However, in engineering practice, the long term wind reference data from meteorological stations can be affected by some objective factors, such as the new buildings around the wind masts; small trees around the wind masts can grow up to 20m or even higher, which would also affect the wind data. The NCEP/NCAR reanalysis dataset, which are produced by National Centers for Environmental Prediction (NCEP) and National Center for Atmospheric Research (NCAR), is widely used as an alternative long term wind reference data. The dataset is available from January 1 in 1948 to the present and data samples are recorded every 6 hours. Surface wind data and 10 m wind data are available and are saved on a grid at 2.5 degree resolution at different air pressure levels ranging from 10 hPa to 1000 hPa. This paper studies the application of the NCEP/NCAR reanalysis dataset in the wind resource assessment, because of the low resolution of the NCEP/NCAR reanalysis dataset and the general MCP methods, such as the regression method, the Weibull scale method and the matrix method, are not sufficient any more; therefore, a new MCP method, named as wind index, is presented. For evaluate the feasibility of the dataset and the new MCP method, a case study is carried out. The calculated energy production of the studied wind farm, which is based on the long term wind reference data from meteorological stations and NCEP/NCAR reanalysis dataset are compared. The result shows that the calculated energy production is very close to real energy production, which means that different long term reference wind data and different MCP methods show almost same development level of wind resource. Therefore, it can be concluded that the combination of the NCEP/NCAR reanalysis dataset with wind index MCP method is a very reliable MCP calculation principle and can have a good practical value.
Evaluation of Mid-Depth Currents of NCEP Reanalysis Data in the Tropical Pacific Using ARGO Float Position Information
XIE Jiping,ZHU Jiang,XU Li,GUO Pinwen,
XIE Jiping
,ZHU Jiang,XU Li,GUO Pinwen

大气科学进展 , 2005,
Abstract: The global project of the Array for Real-time Geostrophic Oceanography (ARGO) provides a unique opportunity to observe the absolute velocity in mid-depths of the world oceans. A total of 1597 velocity vectors at 1000 (2000) db in the tropical Pacific derived from the ARGO float position information during the period November 2001 to October 2004 are used to evaluate the intermediate currents of the National Centers for Environmental Prediction reanalysis. To derive reliable velocity information from ARGO float trajectory points, a rigorous quality control scheme is applied, and by virtue of a correction method for reducing the drift error on the surface in obtaining the velocity vectors, their relative errors are less than 25%. Based on the comparisons from the quantitative velocity vectors and from the space-time average currents, some substantial discrepancies are revealed. The first is that the velocities of the reanalysis at mid-depths except near the equator are underestimated relative to the observed velocities by the floats.The average speed difference between NCEP and ARGO values ranges from about -2.3 cms-1 to -1.8cms-1. The second is that the velocity difference between the ocean model and the observations at 2000dB seems smaller than that at 1000 dB. The third is that the zonal flow in the reanalysis is too dominant so that some eddies could not be simulated, such as the cyclonic eddy to the east of 160°E between 20°N and 30°N at 2000 dB. In addition, it is noticeable that many floats parking at 1000 dB cannot acquire credible mid-depth velocities due to the time information of their end of ascent (start of descent) on the surface in the trajectory files. Thus, relying on default times of parking, descent and ascent in the metadata files gravely confines their application to measuring mid-depth currents.
Reliability of NCEP/NCAR Reanalysis Data on Mount Qomolangma and Western Nyainqentanglha Range
NCEP/NCAR 再分析资料在珠穆朗玛峰 —念青唐古拉山脉气象研究中的可信性

XIE Aihong,QIN Dahe,REN Jiawen,QIN Xiang,KANG Shichang,JIANG Youyan,
谢爱红
,秦大河,任贾文,秦翔,康世昌,蒋友严

地理学报 , 2007,
Abstract: Mount Qomolangma, the highest peak on Earth, is often referred to as the third pole of the globe. The Nyainqentanglha is one of the closest remote parts of mountain range north to the Himalayas. As such the two places are relatively inaccessible on the southern Tibetan Plateau and little is known about their meteorology. In 2003, an auto weather station was deployed at the north col of western Nyainqentanglha (WNQ) range (30o24'44.3"N, 90o34'13.1"E, 5850 m a.s.l.). In 2005, the other station was operated at the north col of Mount Qomolangma (28o01'0.95"N, 86o57'48.4"E, 6523 m a.s.l.). We believe that these represent the high elevation at which continuous weather data have never been collected and thus are valuable datasets with which to investigate the meteorology of the high altitude southern Tibetan Plateau. In this paper, we compare the observations with the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis, in order to understand the reliability of NCEP/NCAR reanalysis data on Mount Qomolangma and Nyainqentanglha Range. We find that the reanalysis captures much of the synoptic-scale variability in temperature and pressure, although the reanalysis values are systematically lower than the observations. Furthermore, most of the variability magnitude is, to some extent, underestimated. In addition, the weather event extracted from the NCEP/NCAR reanalyzed pressure and temperature prominently appears one-day lead to that from the observational data on Mount Qomolangma, while on the WNQ range it frequently occurs on the same day and there is no obvious lead or lag. Influenced by the same atmosphere circulation, Mount Qomolangma and the WNQ range have close correlations both in the observational data and reanalyzed data.
Structure and precursors of the 1992 / 93 drought in KwaZulu-Natal, South Africa from NCEP reanalysis data
Lawrence T. Dube,, Mark R. Jury
Water SA , 2003,
Abstract: The historical context and potential causes and structure of the 1992/93 drought in KwaZulu-Natal are analysed using NCEP reanalysis data. The analysis indicates that increased westerly winds with surface marine lows and continental highs prevailed over Southern Africa. Anomalous divergence and subsidence occur over the eastern subcontinent, coupled with reduced tropical moist inflows. Mid-latitude confluence, anticyclonic vorticity and upper level convergence suppressed convection over KwaZulu/Natal. The precipitable water field reflects a SE-NW orientated stationary wave-train pattern over Southern Africa with KwaZulu-Natal anti-phase with the Zambezi valley. A meridional overturning cell is seen as a driving mechanism behind the 1992/93 drought over South Africa. The velocity potential shows a dipole between the Zambezi and the SW Indian Ocean, and it appears that the kinematic structure was more important than the thermodynamic. Impacts include a reduction in crop yield and streamflows, and a slowing of economic activity. (WaterSA: 2003 29(2): 201-208)
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.