Strong Trends in the Skill of the ERA-40 and NCEP–NCAR Reanalyses in the High and Midlatitudes of the Southern Hemisphere, 1958–2001*

2004 ◽  
Vol 17 (23) ◽  
pp. 4603-4619 ◽  
Author(s):  
David H. Bromwich ◽  
Ryan L. Fogt
Keyword(s):  
Satellite Data ◽  
Austral Winter ◽  
Weather Forecasts ◽  
Atmospheric Research ◽  
June July August ◽  
Medium Range ◽  
Height Fields ◽  
Environmental Prediction ◽  
June July ◽  
High Level

Abstract The European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) and the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis (NCEP1) data are compared with Antarctic and other mid- to high-latitude station observations for the complete years of overlap, 1958–2001. Overall, it appears that ERA-40 more closely follows the observations; however, a more detailed look at the presatellite era reveals many shortcomings in ERA-40, particularly in the austral winter. By calculating statistics in 5-yr moving windows for June–July–August (JJA), it is shown that ERA-40 correlations with observed MSLP and surface (2 m) temperatures are low and even negative during the mid-1960s. A significant trend in skill in ERA-40 is observed in conjunction with the assimilation of satellite data during winter, eventually reaching a high level of skill after 1978 that is superior to NCEP1. NCEP1 shows consistency in its correlation with observations throughout time in this season; however, the biases in the NCEP1 MSLP fields decrease significantly with time. Similar problems are also found in the 500-hPa geopotential height fields above the direct influences of the mountainous topography. The height differences between ERA-40 and NCEP1 over the South Pacific are substantial before the modern satellite era throughout the depth of the troposphere. The ability for ERA-40 to be more strongly constrained by the satellite data compared to NCEP1, which is largely constrained by the station observational network, suggests that the differing assimilation schemes between ERA-40 and NCEP1 lead to the large discrepancies seen here. Thus, both reanalyses must be used with caution over high southern latitudes during the nonsummer months prior to the assimilation of satellite sounding data.

scholarly journals Validation of the Aura High Resolution Dynamics Limb Sounder geopotential heights

2014 ◽  
Vol 7 (2) ◽  
pp. 1001-1025
Author(s):  
L. L. Smith ◽  
J. C. Gille
Keyword(s):  
High Resolution ◽  
System Model ◽  
Weather Forecasts ◽  
Atmospheric Research ◽  
Earth Observing System ◽  
Medium Range ◽  
High Bias ◽  
Environmental Prediction ◽  
The Tropics ◽  
Data Screening

Abstract. Global satellite observations from the EOS Aura spacecraft's High Resolution Dynamics Limb Sounder (HIRDLS) of temperature and geopotential height (GPH) are discussed. The accuracy, resolution and precision of the HIRDLS version 7 algorithms are assessed and data screening recommendations are made. Comparisons with GPH from observations, reanalyses and models including European Center for Medium-Range Weather Forecasts Interim Reanalysis (ERA-Interim), National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis, Goddard Earth Observing System Model (GEOS) version 5, and EOS Aura Microwave Limb Sounder (MLS) illustrate the HIRDLS GPH have a precision ranging from 2 m to 30 m and an accuracy of ±100 m. Comparisons indicate HIRDLS GPH may have a slight low bias in the tropics and a slight high bias at high latitudes. Geostrophic winds computed with HIRDLS GPH qualitatively agree with winds from other data sources including ERA-Interim, NCEP and GEOS-5.

scholarly journals Validation of the Aura High Resolution Dynamics Limb Sounder geopotential heights

2014 ◽  
Vol 7 (8) ◽  
pp. 2775-2785 ◽  
Author(s):  
L. L. Smith ◽  
J. C. Gille
Keyword(s):  
High Resolution ◽  
High Latitudes ◽  
Weather Forecasts ◽  
Atmospheric Research ◽  
Earth Observing System ◽  
Medium Range ◽  
High Bias ◽  
Environmental Prediction ◽  
The Tropics ◽  
Data Screening

Abstract. The geopotential height (GPH) product created from global observations by the High Resolution Dynamics Limb Sounder (HIRDLS) instrument on NASA's Earth Observing System (EOS) Aura spacecraft is discussed. The accuracy, resolution and precision of the HIRDLS version 7 algorithms are assessed and data screening recommendations are made. Comparisons with GPH from observations, reanalyses and models including European Centre for Medium-Range Weather Forecasts Interim Reanalysis (ERA-Interim), and National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis illustrate the HIRDLS GPHs have a precision ranging from 2 to 30 m and an accuracy of ±100 m up to 1 hPa. Comparisons indicate HIRDLS GPH may have a slight low bias in the tropics and a slight high bias at high latitudes. Geostrophic winds computed with HIRDLS GPH qualitatively agree with winds from other data sources including ERA-Interim.

scholarly journals Evento de Precipitação Intensa Associado às Perturbações Ondulatórias dos Alísios Sobre o Estado de Alagoas.

2020 ◽  
Vol 13 (07) ◽  
pp. 3195
Author(s):  
Matheus José Arruda Lyra ◽  
Ismael Guidson Farias Freitas ◽  
Dimas De Barros Santiago
Keyword(s):  
Reanalysis Data ◽  
Wave Disturbance ◽  
Precipitation Event ◽  
Trade Winds ◽  
Climatological Data ◽  
Weather Forecasts ◽  
Global Era ◽  
Medium Range ◽  
Strong Convection ◽  
High Level

O estudo teve como objetivo analisar a forte convecção provocada por uma Perturbação Ondulatória dos Alísios (POA) sobre o estado de Alagoas no dia 27 de maio de 2017. A análise e previsão de sistemas dessa magnitude desperta interesse devido os fenômenos adversos provocados e consequências à população. Foram utilizados dados de reanálise global ERA Interim fornecidos pelo European Centre for Medium-Range Weather Forecasts (ECMWF) com resolução espacial de 0,75º de latitude x 0,75º de longitude. Estes dados foram utilizados no software OpenGrADS para plotagem dos campos meteorológicos para a análise sinótica. Os dados referentes à precipitação acumulada foram fornecidos pela Secretaria de Estado do Meio Ambiente e dos Recursos Hídricos (SEMARH) a partir de 25 estações meteorológicas espalhadas por Alagoas. A perturbação se desenvolveu após a passagem de um sistema frontal que atingiu o Nordeste do Brasil alguns dias antes. O sistema sinótico pôde ser observado no campo de pressão à nível do mar e através das linhas de correntes em baixos níveis (925 e 850hPa) entre os dias 26 e 27, onde o eixo do cavado se concentrou sobre o estado de Alagoas. Os campos do fluxo de umidade integrado na vertical indicaram valores bastante elevados provenientes do Atlântico, adentrando Alagoas entre os dias 25 e 27. Através da análise da série de dados climatológica, maio de 2017 registrou o terceiro maior pico de pluviometria (692mm/24h), onde somente no dia 27 foram registrados 173mm/24h, o que correspondeu à cerca de 25% da média histórica. Intense Precipitation Event Provoked by the Wave Disturbance of Trade Winds Over the Alagoas State A B S T R A C TThe main objective of this study was to analyze the Wave Disturbance of Trade Winds (WDTW) dynamics that provoked strong rainfall over the Alagoas state on May 27 of 2017. The analysis and systems forecasting of this magnitude arouses interest due to the adverse phenomena caused and consequences to the population. Global ERA Interim reanalysis data was provided by the European Center for Medium-Range Weather Forecasts (ECMWF) with spatial resolution of 0.75º latitude x 0.75º longitude. This dataset was used in conjunction with OpenGrADS software to the meteorological fields plot for synoptic analysis. Precipitation dataset were collected from 25 meteorological stations spread across the Alagoas state provided by the State Secretary for the Environment and Water Resources (SEMARH). The disturbance developed after a frontal system passage that reached BNE a few days earlier. The synoptic system could be observed in the pressure at sea level field and through the streamlines at low levels (925 and 850hPa) between 26 and 27 of May, where the Trough axis was concentrated over Alagoas. The strong convection was also driven by a high-level Trough, lasted from 30ºS. The vertical integrated moisture flow fields indicated very high values from the Atlantic Ocean, reaching Alagoas between 25th and 27 of May. Through the analysis of climatological data, in May 2017 was registered the third highest peak of rainfall (692 mm/24h), where only on the 27th 173 mm/24h was recorded, which corresponded to the fence 25% of the historical average.Keywords: WDTW; Adverse Phenomena, Alagoas.

Climatology of Anticyclonic and Cyclonic Rossby Wave Breaking on the Dynamical Tropopause in the Southern Hemisphere

2011 ◽  
Vol 24 (4) ◽  
pp. 1239-1251 ◽  
Author(s):  
Jie Song ◽  
Chongyin Li ◽  
Jing Pan ◽  
Wen Zhou
Keyword(s):  
Southern Hemisphere ◽  
Rossby Wave ◽  
Zonal Wind ◽  
Potential Vorticity ◽  
Wave Breaking ◽  
Austral Summer ◽  
Austral Winter ◽  
Rossby Wave Breaking ◽  
Weather Forecasts ◽  
Medium Range

Abstract The characteristics of the climatological distribution of the anticyclonic (LC1) and cyclonic (LC2) Rossby wave breaking (RWB) in the Southern Hemisphere (SH) are investigated by calculating the occurrence frequency of the LC1- and LC2-like stratospheric potential vorticity (PV) streamers in the SH during the austral summer [December–February (DJF)] and wintertime [June–August (JJA)] on several isentropic surfaces by using the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) daily dataset. The results show that 1) on the equatorward flank of the climatological midlatitude jet (MLJ), the LC1-like PV streamers are frequently found over the central oceanic regions, whereas the LC2-like PV streamers are almost absent. On the poleward flank of the climatological MLJ, both types of PV streamers are frequently observed and the LC2-like PV streamers predominate; 2) the regions where the occurrences of the PV streamers are frequent overlap the weak zonal wind regions; and 3) in austral winter, a “double-jet” setting is evident in two regions of the SH [the double-jet upstream (DU) and the spilt jet region]. In the double-jet setting regions, the LC1-like PV streamers are frequently found both in the DU and the split-jet regions, while the occurrence of the LC2-like PV streamers is frequent in the split-jet region but is rather infrequent in the DU region.

What Is the Source of the Stratospheric Gravity Wave Belt in Austral Winter?

2014 ◽  
Vol 71 (5) ◽  
pp. 1583-1592 ◽  
Author(s):  
Eric A. Hendricks ◽  
James D. Doyle ◽  
Stephen D. Eckermann ◽  
Qingfang Jiang ◽  
P. Alex Reinecke
Keyword(s):  
Wave Field ◽  
Gravity Wave ◽  
Storm Tracks ◽  
Austral Winter ◽  
S Wave ◽  
Winter Storm ◽  
Weather Forecasts ◽  
The Andes ◽  
Geographical Variations ◽  
Medium Range

Abstract During austral winter, and away from orographic maxima or “hot spots,” stratospheric gravity waves in both satellite observations and Interim European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim) data reveal enhanced amplitudes in a broad midlatitude belt extending across the Southern Ocean from east of the Andes to south of New Zealand. The peak latitude of this feature slowly migrates poleward from 50° to 60°S. Wave amplitudes are much weaker across the midlatitude Pacific Ocean. These features of the wave field are in striking agreement with diagnostics of baroclinic growth rates in the troposphere associated with midlatitude winter storm tracks and the climatology of the midlatitude jet. This correlation suggests that these features of the stratospheric gravity wave field are controlled by geographical variations of tropospheric nonorographic gravity wave sources in winter storm tracks: spontaneous adjustment emission from the midlatitude winter jet, frontogenesis, and convection.

Improvement of Medium-Range Forecasts Using the Analog-Dynamical Method

2014 ◽  
Vol 142 (4) ◽  
pp. 1570-1587 ◽  
Author(s):  
Haipeng Yu ◽  
Jianping Huang ◽  
Jifan Chou
Keyword(s):  
Lead Time ◽  
Forecast Skill ◽  
Forecast Errors ◽  
Weather Forecasts ◽  
Planetary Scale ◽  
Anomaly Correlation Coefficient ◽  
Systematic Correction ◽  
Medium Range ◽  
Dynamical Method ◽  
Height Fields

Abstract This study further develops the analog-dynamical method and applies it to medium-range weather forecasts. By regarding the forecast field as a small disturbance superimposed on historical analog fields, historical analog errors can be used to estimate and correct forecast errors. This method is applied to 10-day forecasts from the Global and Regional Assimilation and Prediction System (GRAPES). Both the distribution of atmospheric circulation and the pattern of sea surface temperature (SST) are considered in choosing the analog samples from a historical dataset for 2001–10 based on NCEP Final (FNL) data. The results demonstrate that the analog-dynamical method greatly reduces forecast errors and extends the period of validity of the global 500-hPa height field by 0.8 days, which is superior to results obtained using systematic correction. The correction effect at 500 hPa is increasingly significant when the lead time increases. Although the analogs are selected using 500-hPa height fields, the forecast skill at all vertical levels is improved. The average increase of the anomaly correlation coefficient (ACC) is 0.07, and the root-mean-square error (RMSE) is decreased by 10 gpm on average at a lead time of 10 days. The magnitude of errors for most forecast fields, such as height, temperature, and kinetic energy is decreased considerably by inverse correction. The model improvement is primarily a result of improvement for planetary-scale waves, while the correction for synoptic-scale waves does not affect model forecast skill. As this method is easy to operate and transport to other sophisticated models, it could be appropriate for operational use.

scholarly journals The Impact of Analysis Error on Medium-Range Weather Forecasts

2008 ◽  
Vol 136 (9) ◽  
pp. 3425-3431 ◽  
Author(s):  
Kyle L. Swanson ◽  
Paul J. Roebber
Keyword(s):  
North Pacific Ocean ◽  
Forecast Skill ◽  
Ensemble Spread ◽  
Weather Forecasts ◽  
The North ◽  
Medium Range ◽  
Difference Fields ◽  
Height Fields ◽  
Analysis Error ◽  
The Impact

Abstract All meteorological analyzed fields contain errors, the magnitude of which ultimately determines the point at which a given forecast will fail. Here, the authors explore the extent to which analysis difference fields capture certain aspects of the actual but unknowable flow-dependent analysis error. The analysis difference fields considered here are obtained by subtracting the NCEP and ECMWF reanalysis 500-hPa height fields. It is shown that the magnitude of this 500-hPa analysis difference averaged over the North Pacific Ocean has a statistically significant impact on forecast skill over the continental United States well into the medium range (5 days). Further, it is shown that the impact of this analysis difference on forecast skill is similar to that of ensemble spread well into the medium range, a measure of forecast uncertainty currently used in the operational setting. Finally, the analysis difference and ensemble spread are shown to be independent; hence, the impact of these two quantities upon forecast skill is additive.

scholarly journals Evaluation of the Perspective of ERA-Interim and ERA5 Reanalyses for Calculation of Drought Indicators for Uzbekistan

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 527
Author(s):  
Natella Rakhmatova ◽  
Mikhail Arushanov ◽  
Lyudmila Shardakova ◽  
Bakhriddin Nishonov ◽  
Raisa Taryannikova ◽  
...  
Keyword(s):  
High Spatial Resolution ◽  
Limited Data ◽  
Near Surface ◽  
Weather Forecasts ◽  
Mountain Ranges ◽  
Medium Range ◽  
Drought Indicators ◽  
High Level ◽  
Level Of Agreement ◽  
Arid And Semiarid

The arid and semiarid regions of Uzbekistan are sensitive and vulnerable to climate change. However, the sparse and very unevenly distributed meteorological stations within the region provide limited data for studying the region’s climate variation. The aim of this work was to evaluate the performance of the European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA)-Interim and ERA5 products for the fields of near-surface temperature, humidity, and precipitation over Uzbekistan from 1981 to 2018 using observations from 74 meteorological stations. Major results suggested that the reanalysis datasets match well with most of the observed climate records, especially in the plain areas. While ERA5, with a high spatial resolution of 0.1°, is able more accurately reproduce mountain ranges and valleys. Compared to ERA-Interim, the climatological biases in temperature, humidity, and total precipitation from ERA5 are clearly reduced, and the representation of inter-annual variability is improved over most regions of Uzbekistan. Both reanalyses show a high level of agreement with observations on the standardized precipitation evaporation index (SPEI) with a correlation coefficient of 0.7–0.8.Although both of these ECMWF products can be successfully implemented for the calculation of atmospheric drought indicators for Uzbekistan and adjacent regions of Central Asia, the newer and advanced ERA5 is preferred.

An Assessment of ECMWF and NCEP–NCAR Reanalyses in the Southern Hemisphere at the End of the Presatellite Era: Results from the EOLE Experiment (1971–72)

2006 ◽  
Vol 134 (11) ◽  
pp. 3367-3383 ◽  
Author(s):  
Albert Hertzog ◽  
Claude Basdevant ◽  
François Vial
Keyword(s):  
Southern Hemisphere ◽  
Storm Track ◽  
Upper Troposphere ◽  
Weather Forecasts ◽  
Subtropical Jet ◽  
Observation Network ◽  
Medium Range ◽  
Standard Deviations ◽  
Environmental Prediction

Abstract This article estimates the biases and standard deviations of the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) and the 50-yr National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) Reanalysis (NN50) in the upper troposphere and lower stratosphere in 1971–72. These estimates are obtained by comparing the reanalyzed temperatures and winds with EOLE observations, a dataset collected during 480 superpressure-ballon flights in the Southern Hemisphere (SH). Dedicated algorithms have been developped to control the quality of this dataset and a stringent selection has been performed on the observations. None of the atmospheric centers has assimilated the EOLE dataset, which is therefore fully independent from the reanalyses. It is furthermore argued that the statistics obtained in this study at the end of the presatellite era may be representative of the reanalysis accuracy since 1957. The results of these comparisons indicate that NN50 tends to be a few degrees colder than the observations in the SH subpolar latitudes, while ERA-40 is less hit by this cold-pole issue. Both reanalyses, on the other hand, are found to be warmer than the observations by about 1 K in the subtropics. In contrast, the wind comparisons only exhibit nonsignificant or small reanalysis biases, even though the reanalyzed subtropical jet is slightly displaced equatorward with respect to the observations. The ability of reanalyses to capture the atmospheric synoptic-scale variability in the upper troposphere is assessed by computing the standard deviations of the reanalysis minus observation differences. The ERA-40 and NN50 standard deviations show a maximum (i.e., a poorer reanalysis accuracy) in the SH storm track. However, ERA-40 standard deviations are found to be much larger than NN50 standard deviations. The standard deviations also exhibit a marked decrease above the continents, stressing the heterogeneity of the atmospheric observation network during the presatellite era. Finally, in contrast with previous studies, the reanalysis accuracy does not appear to be better during summer than during winter.

OBEST: An Observation-Based Ensemble Subsetting Technique for Tropical Cyclone Track Prediction

2016 ◽  
Vol 31 (1) ◽  
pp. 57-70 ◽  
Author(s):  
Lin Dong ◽  
Fuqing Zhang
Keyword(s):  
Tropical Cyclone ◽  
Lead Times ◽  
Track Forecast ◽  
Forecast Errors ◽  
Cyclone Track ◽  
Tropical Cyclone Track ◽  
Weather Forecasts ◽  
Ensemble Mean ◽  
Medium Range ◽  
Environmental Prediction

Abstract An observation-based ensemble subsetting technique (OBEST) is developed for tropical cyclone track prediction in which a subset of members from either a single- or multimodel ensemble is selected based on the distance from the latest best-track position. The performance of OBEST is examined using both the 2-yr hindcasts for 2010–11 and the 2-yr operational predictions during 2012–13. It is found that OBEST outperforms both the simple ensemble mean (without subsetting) and the corresponding deterministic high-resolution control forecast for most forecast lead times up to 5 days. Applying OBEST to a superensemble of global ensembles from both the European Centre for Medium-Range Weather Forecasts and the National Centers for Environmental Prediction yielded a further reduction in track forecast errors by 5%–10% for lead times of 24–120 h.

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