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Downscaling ERA-Interim temperature data in complex terrain
L. Gao,M. Bernhardt,K. Schulz
Hydrology and Earth System Sciences Discussions , 2012, DOI: 10.5194/hessd-9-5931-2012
Abstract: Air temperature controls a large variety of environmental processes, and is an essential input parameter for land surface models e.g. in hydrology, ecology and climatology. However, meteorological networks, which can provide the necessary information, are commonly sparse in complex terrains, especially in high mountainous regions. In order to provide temperature data in an adequate temporal and spatial resolution for local scale applications, we have developed a new downscaling method able to scale 3-hourly ERA-Interim temperature data. The scheme is based on model internal vertical lapse rates derived from different ERA-Interim pressure levels. The results are validated for three meteorological stations, located within the same ERA-Interim grid element: Zugspitze, Garmisch-Partenkirchen and Zugspitzplatt, in the German Alps; they are also compared with two other statistical, lapse rate based downscaling approaches. The results indicate that the use of model internal ERA-Interim lapse rates can significantly improve the downscaling performance when compared to the standard procedure of using fixed lapse rates.
Verification of the new ECMWF ERA-Interim reanalysis over France
C. Szczypta, J.-C. Calvet, C. Albergel, G. Balsamo, S. Boussetta, D. Carrer, S. Lafont,C. Meurey
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2011,
Abstract: An evaluation of the global ECMWF atmospheric reanalysis ERA-Interim (with a 0.5° grid) is performed over France, based on the high resolution (8 km) SAFRAN atmospheric reanalysis. The ERA-Interim precipitation, Incoming Solar Radiation (ISR), air temperature, air humidity, and wind speed, are compared with their SAFRAN counterparts. Also, interpolated in situ ISR observations are used in order to consolidate the evaluation of this variable. The daily precipitation estimates produced by ERA-Interim over France correlate very well with SAFRAN. However, the values are underestimated by 27%. A GPCP-corrected version of ERA-Interim is less biased (13%). The ERA-Interim estimates of ISR correlate very well with SAFRAN and with in situ observations on a daily basis. Whereas SAFRAN underestimates the ISR by 6 Wm 2, ERA-Interim overestimates the ISR by 10 Wm 2. In order to assess the impact of the ERA-Interim errors, simulations of the ISBA-A-gs land surface model are performed over the SMOSREX grassland site in southwestern France using ERA-Interim (with and without GPCP rescaling) and SAFRAN. Latent and sensible heat fluxes are simulated, together with carbon dioxide fluxes. The rescaled ERA-Interim performs better than the original ERA-Interim and permits to achieve flux scores similar to those obtained with SAFRAN.
Verification of the new ECMWF ERA-Interim reanalysis over France  [PDF]
C. Szczypta,J.-C. Calvet,C. Albergel,G. Balsamo
Hydrology and Earth System Sciences Discussions , 2010, DOI: 10.5194/hessd-7-7151-2010
Abstract: An evaluation of the global ECMWF atmospheric reanalysis ERA-Interim (with a 0.5° grid) is performed over France, based on the high resolution (8 km) SAFRAN atmospheric reanalysis. The ERA-Interim precipitation, Incoming Solar Radiation (ISR), air temperature, air humidity, and wind speed, are compared with their SAFRAN counterparts. Also, interpolated in situ ISR observations are used in order to consolidate the evaluation of this variable. The daily precipitation estimates produced by ERA-Interim over France correlate very well with SAFRAN. However, the values are underestimated by 26%. A GPCP-corrected version of ERA-Interim is less biased (10–15%). The ERA-Interim estimates of ISR correlate very well with SAFRAN and with in situ observations on a daily basis. Whereas SAFRAN underestimates the ISR by 6–8 W m 2, ERA-Interim overestimates the ISR by 9–10 W m 2. In order to assess the impact of the ERA-Interim errors, simulations of the ISBA-A-gs land surface model are performed over the SMOSREX grassland site in southwestern France using ERA-Interim (with and without GPCP rescaling) and SAFRAN. Latent and sensible heat fluxes are simulated, together with carbon dioxide fluxes. The rescaled ERA-Interim performs better than the original ERA-Interim and permits to achieve flux scores similar to those obtained with SAFRAN.
Age of stratospheric air in the ERA-Interim
M. Diallo,B. Legras,A. Chédin
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2012, DOI: 10.5194/acp-12-12133-2012
Abstract: The Brewer-Dobson mean circulation and its variability are investigated in the ERA-Interim over the period 1989-2010 by using an off-line Lagrangian transport model driven by analysed winds and heating rates. At low and mid-latitudes, the mean age of air in the lower stratosphere is in good agreement with ages derived from aircraft, high altitude balloon and satellite observations of long-lived tracers. At high latitude and in the upper stratosphere, we find, however that the ERA-Interim ages exhibit an old bias, typically of one to two years. The age spectrum exhibits a long tail except in the low tropical stratosphere which is modulated by the annual cycle of the tropical upwelling. The distribution of ages and its variability is consistent with the existence of two separate branches, shallow and deep, of the Brewer-Dobson circulation. Both branches are modulated by the tropical upwelling and the shallow branch is also modulated by the subtropical barrier. The variability of the mean age is analysed through a decomposition in terms of annual cycle, QBO, ENSO and trend. The annual modulation is the dominating signal in the lower stratosphere and is maximum at latitudes greater than 50° in both hemispheres with oldest ages at the end of the winter. The phase of the annual modulation is also reversed between below and above 25 km. The maximum amplitude of the QBO modulation is of about 0.5 yr and is mostly concentrated within the tropics between 25 and 35 km. It lags the QBO wind at 30 unit{hPa} by about 8 months. The ENSO signal is small and limited to the lower northen stratosphere. The age trend over the 1989–2010 period, according to this ERA-Interim dataset, is significant and negative, of the order of 0.3 to 0.5 yr dec 1, within the lower stratosphere in the Southern Hemisphere and south of 40° N in the Northern Hemisphere below 25 km. The age trend is positive (of the order of 0.3 yr dec 1) in the mid stratosphere but there is no region of consistent significance. This suggests that the shallow and deep Brewer-Dobson circulations may evolve in opposite directions. Finally, we find that the long lasting influence of the Pinatubo eruption can be seen on the age of air from June 1991 until the end of 1993 and can bias the statistics encompassing this period.
Dobson, Brewer, ERA-40 and ERA-Interim original and merged total ozone data sets – evaluation of differences: a case study, Hradec Králové (Czech), 1961–2010
K. Vaní ek, L. Metelka, P. Sk ivánková,M. Staněk
Earth System Science Data (ESSD) & Discussions (ESSDD) , 2012, DOI: 10.5194/essd-4-91-2012
Abstract: Homogenized data series of total ozone measurements taken by the regularly and well calibrated Dobson and Brewer spectrophotometers at Hradec Králové (Czech) and the data from the re-analyses ERA-40 and ERA-Interim were merged and compared to investigate differences between the particular data sets originated in Central Europe, the Northern Hemisphere (NH) mid-latitudes. The Dobson-to-Brewer transfer function and the algorithm for approximation of the data from the re-analyses were developed, tested and applied for creation of instrumentally consistent and completed total ozone data series of the 50-yr period 1961–2010 of observations. This correction has reduced the well-known seasonal differences between Dobson and Brewer data below the 1% calibration limit of the spectrophotometers. Incorporation of the ERA-40 and ERA-Interim total ozone data on days with missing measurements significantly improved completeness and reliability of the data series mainly in the first two decades of the period concerned. Consistent behaviour of the original and corrected/merged data sets was found in the pre-ozone-hole period (1961–1985). In the post-Pinatubo (1994–2010) era the data series show seasonal differences that can introduce uncertainty in estimation of ozone recovery mainly in the winter-spring season when the effect of the Montreal Protocol and its Amendments is expected. All the data sets confirm substantial depletion of ozone also in the summer months that gives rise to the question about its origin. The merged and completed data series of total ozone will be further analyzed to quantify chemical ozone losses and contribution of natural atmospheric processes to the ozone depletion over the region. This case study points out the importance of selection and evaluation of the quality and consistency of the input data sets used in estimation of long-term ozone changes including recovery of the ozone layer over the selected areas. Data are available from the PANGAEA database at doi:10.1594/PANGAEA.779819.
КОРЕКЦ Я РАД ОЛОКАЦ ЙНОГО СИГНАЛУ ЗА КУТОМ М СЦЯ ПРОМЕНЯ ПОЛЯРИМЕТРИЧНОГО МЕТЕОРОЛОГ ЧНОГО РАД ОЛОКАТОРА Correction of radar signal for elevation beam polarimetric weather radar Коррекция радиолокационного сигнала по углу места луча поляриметрического метеорологического радиолокатора  [cached]
Ю.А. Авер’янова,A.А. Аверьянов
Proceedings of National Aviation University , 2008,
Abstract: Пор вняно розрахунки за анал тичним виразом залежност коеф ц нта корекц рад олокац йного сигналу за кутом м сця з в домими експериментальними даними. Показано розроблену структурну схему автоматично корекц та видалення грав тац йно складово п д час оц нювання нтенсивност турбулентност . The analytical calculations of radar signal correction coefficient on elevation angle is compared with known experimental data. The developed structural diagram of automatic correction and gravitational component separation when turbulence intensity estimate is shown. Сравнительно расчеты по аналитическим выражением зависимости коэффициента коррекции радиолокационного сигнала по углу места с известными экспериментальными данными. Показано разработанную структурную схему автоматической коррекции и удаления гравитационной составляющей при оценке интенсивности турбулентности.
Arctic Clouds and Surface Radiation – a critical comparison of satellite retrievals and the ERA-Interim reanalysis
M. Zygmuntowska, T. Mauritsen, J. Quaas,L. Kaleschke
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2012,
Abstract: Clouds regulate the Earth's radiation budget, both by reflecting part of the incoming sunlight leading to cooling and by absorbing and emitting infrared radiation which tends to have a warming effect. Globally averaged, at the top of the atmosphere the cloud radiative effect is to cool the climate, while at the Arctic surface, clouds are thought to be warming. Here we compare a passive instrument, the AVHRR-based retrieval from CM-SAF, with recently launched active instruments onboard CloudSat and CALIPSO and the widely used ERA-Interim reanalysis. We find that in particular in winter months the three data sets differ significantly. While passive satellite instruments have serious difficulties, detecting only half the cloudiness of the modeled clouds in the reanalysis, the active instruments are in between. In summer, the two satellite products agree having monthly means of 70–80 percent, but the reanalysis are approximately ten percent higher. The monthly mean long- and shortwave components of the surface cloud radiative effect obtained from the ERA-Interim reanalysis are about twice that calculated on the basis of CloudSat's radar-only retrievals, while ground based measurements from SHEBA are in between. We discuss these differences in terms of instrument-, retrieval- and reanalysis characteristics, which differ substantially between the analyzed datasets.
基于era-interim再分析资料的中国极端气温分析  [PDF]
高路,KarstenSchulz,陈兴伟,林广发
南水北调与水利科技 , 2014,
Abstract: 采用中国陆域1989年-2009年3小时0.71°格点的era-interim地表2m气温预报数据,运用累积分布函数与分位数对研究区的极端低温和极端高温进行分析。结果表明:东北、青藏高原及西北地区为极端低温的集聚区,极端低温逐步沿西北-东南方向递增;青藏高原为全国极端高温中的唯一冷中心,西北盆地为最热中心;era-interim再分析资料能够较好地反映中国极端低温和极端高温空间分布规律,整体上具有较好的可信度。结合分位数方法定量分析了极端气温的持续时间,为极端气候事件的定量研究提供了方法借鉴。
era-interim应用于中国地区地基gps/pwv计算的精度评估  [PDF]
赵静旸,宋淑丽,朱文耀
武汉大学学报(信息科学版) , 2014,
Abstract: ?目的由于中国绝大多数地基gps网观测时未作气象观测,致使已积累的大量gps观测数据无法在气象领域发挥作用。针对这一情况,研究和分析了利用era-interim再分析产品获取中国地区气象资料和计算gps/pwv的方法。以全国分布的24个气象观测站2006、2007年的气压、温度和相对湿度的实测资料为标准,评估了中国地区era-interim再分析资料提取这三个参数和计算gps/pwv所能达到的精度,并进行了精度评估。
ERA-Interim 再分析数据在中国沿海的质量评估  [PDF]
高志刚,骆敬新,刘克修,张庆河,范文静,武双全,李响
海洋科学 , 2015, DOI: 10.11759/hykx20140522001
Abstract: 本文采用1979~2012年的中国沿海台站观测数据对ERA-Interim(简称“ERA-I”)的气温、气压和海温数据进行质量评估。结果表明:(1)从常年平均来看,ERA-I气温、气压和海温多年月平均变化与观测数据吻合较好,可以反映气候态的季节变化特征。与台站观测数据相比,ERA-I气温平均偏高0.19℃,气压平均偏低0.17hPa,海温平均偏高0.70℃。(2)从年际变化情况来看,ERA-I和台站观测的气温、气压和海温变化趋势一致,气温和海温呈上升趋势,气压呈下降趋势。但在海南岛附近使用ERA-I气温做年际变化分析和在东海台湾海峡至北部湾沿岸使用ERA-I海温做年际变化趋势分析时要谨慎。(3)从月均变化分析来看,ERA-I月均气温、气压和海温数据与台站实测数据具有很好的一致性。从误差空间分布来看,ERA-I气温在黄海沿岸平均误差最小,ERA-I气压在渤海沿岸平均误差最小,ERA-I海温在南海沿岸平均误差最小。需要特别指出的是,ERA-I月均海温在渤海和台湾海峡附近沿岸平均误差较大(部分站均方根误差超过2.5℃),在上述区域使用ERA-I海温数据时应考虑其产品偏差。
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