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 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.

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.

Statistical Characterization of Zonal and Meridional Ocean Wind Stress

2005 ◽  
Vol 22 (9) ◽  
pp. 1353-1372 ◽  
Author(s):  
Sarah T. Gille
Keyword(s):  
Wind Stress ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
Statistical Characterization ◽  
Weather Forecasts ◽  
The Pacific ◽  
Meridional Winds ◽  
Wind Events ◽  
Environmental Prediction ◽  
The Tropics

Abstract Four years of ocean vector wind data are used to evaluate statistics of wind stress over the ocean. Raw swath wind stresses derived from the Quick Scatterometer (QuikSCAT) are compared with five different global gridded wind products, including products based on scatterometer observations, meteorological analysis winds from the European Centre for Medium-Range Weather Forecasts, and reanalysis winds from the National Centers for Environmental Prediction. Buoy winds from a limited number of sites in the Pacific Ocean are also considered. Probability density functions (PDFs) computed for latitudinal bands show that mean wind stresses for the six global products are largely in agreement, while variances differ substantially, by a factor of 2 or more, with swath wind stresses indicating highest variances for meridional winds and for zonal winds outside the Tropics. Higher moments of the PDFs also differ. Kurtoses are large for all wind products, implying that PDFs are not Gaussian. None of the available gridded products fully captures the range of extreme wind events seen in the raw swath data. Frequency spectra for the five gridded products agree with frequency spectra from swath data at low frequencies, but spectral slopes differ at higher frequencies, particularly for frequencies greater than 100 cycles per year (cpy), which are poorly resolved by a single scatterometer. In the frequency range between 10 and 90 cpy that is resolved by the scatterometer, spectra derived from swath data are flatter than spectra from gridded products and are judged to be flatter than ω−2/3 at all latitudes.

scholarly journals Statistics of locally coupled ocean and atmosphere intraseasonal anomalies in Reanalysis and AMIP data

2003 ◽  
Vol 10 (3) ◽  
pp. 245-251 ◽  
Author(s):  
M. Peña ◽  
E. Kalnay ◽  
M. Cai
Keyword(s):  
Phase Relationship ◽  
Reanalysis Data ◽  
Sea Surface ◽  
Strong Reduction ◽  
Atmospheric Research ◽  
Ocean Atmosphere ◽  
Using Data ◽  
The One ◽  
Environmental Prediction ◽  
The Tropics

Abstract. We apply a simple dynamical rule to determine the dominant forcing direction in locally coupled ocean-atmosphere anomalies in the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/ NCAR) reanalysis data. The rule takes into account the phase relationship between the low-level vorticity anomalies and the Sea Surface Temperature (SST) anomalies. Analysis of the frequency of persistent coupled anomalies for five-day average data shows that, in general, the ocean tends to force the atmosphere in the tropics while the atmosphere tends to force the ocean in the extratropics. The results agree well with those obtained independently using lagged correlations between atmospheric and oceanic variables, suggesting that the dynamical rule is generally valid. A similar procedure carried out using data from the NCEP global model run with prescribed SST (in which the coupling is one-way, with the ocean always forcing the atmosphere) produces fewer coupled anomalies in the extratropics. They indicate, not surprisingly, an increase in ocean-driving anomalies in the model. In addition, and very importantly, there is a strong reduction of persistent atmosphere-driving anomalies, indicating that the one-way interaction of the ocean in the model run may provide a spurious negative feedback that damps atmospheric anomalies faster than observed.

scholarly journals An update on global atmospheric ice estimates from satellite observations and reanalyses

2018 ◽  
Author(s):  
David Ian Duncan ◽  
Patrick Eriksson
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Principal Component ◽  
Diurnal Variability ◽  
Weather Forecasts ◽  
Earth Observing System ◽  
Current State ◽  
Medium Range ◽  
Ice Water ◽  
Modern Era

Abstract. This study assesses the global distribution of mean atmospheric ice mass from current state-of-the-art estimates and its variability on daily and seasonal timescales. Ice water path (IWP) retrievals from active and passive satellite platforms are compared and analysed against estimates from two reanalysis datasets, ERA5 (European Centre for Medium-range Weather Forecasts Reanalysis 5) and MERRA-2 (Modern-era Retrospective Reanalysis for Research and Applications 2). Large discrepancies in IWP exist between the satellite datasets themselves, making validation of the model results problematic and indicating that progress towards consensus on the distribution of atmospheric ice has been limited. Comparing the datasets, zonal means of IWP exhibit similar shapes but differing magnitudes. Diurnal analysis centred on A-Train overpasses shows homologous structures in some regions, but the degree and sign of the variability varies widely; the reanalyses exhibit noisier and higher amplitude diurnal variability than borne out by the satellite estimates. Spatial structures governed by the atmospheric general circulation are fairly consistent across the datasets, as principal component analysis shows that the patterns of seasonal variability line up well between the datasets but disagree in severity. These results underscore the limitations of the current Earth observing system with respect to atmospheric ice, as the level of consensus between observations is mixed. The large-scale variability of IWP is relatively consistent, whereas disagreements on diurnal variability and global means point to varying microphysical assumptions in retrievals and models alike that seem to underlie the biggest differences.

scholarly journals Global characteristics of the westward-propagating quasi-16-day wave with zonal wavenumber 1 and the connection with the 2012/2013 SSW revealed by ERA-Interim

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Wei Li ◽  
Chunming Huang ◽  
Shaodong Zhang
Keyword(s):  
Baroclinic Instability ◽  
Polar Vortex ◽  
Meridional Wind ◽  
Local Source ◽  
High Latitudes ◽  
Stratospheric Sudden Warming ◽  
Weather Forecasts ◽  
Zonal Wavenumber ◽  
Medium Range ◽  
One Year

AbstractWe analyze global characteristics of the westward-propagating quasi-16-day wave (Q16DW) with zonal wavenumber 1 (W1) in the troposphere and stratosphere using zonal wind, meridional wind, vertical velocity, temperature, geopotential, and potential vorticity data from the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis during one year from December 2012 to November 2013. The amplitudes of the W1 Q16DW are larger in the stratosphere than in the troposphere, and remarkable amplitudes are found at middle and high latitudes in the Northern Hemisphere (NH). More detailed analyses on the temporal variation in the W1 Q16DW show that this wave is significantly enhanced during the 2012/2013 Stratospheric Sudden Warming (SSW) event, and the strong wave most likely provides additional forcing on the splitting of the displaced polar vortex. Analysis of the Eliassen–Palm flux (EP flux) and its divergence of the interaction between W1 Q16DW and quasi-stationary planetary waves with wavenumber 1 during the 2012/2013 SSW event reveals that it causes an upward heat flux and exerts a westward acceleration on the background winds, indicating that this interaction plays an important role in the eastward stratospheric jet reversal. Moreover, the wave is amplified in the occurrence region of barotropic and/or baroclinic instability, suggesting a local source of the growing W1 Q16DW during this SSW event.

scholarly journals HOAPS and ERA-Interim precipitation over sea: Validation against shipboard in-situ measurements

2016 ◽  
Author(s):  
Karl Bumke ◽  
Gert König-Langlo ◽  
Julian Kinzel ◽  
Marc Schröder
Keyword(s):  
Reanalysis Data ◽  
Data Sets ◽  
Weather Forecasts ◽  
Rain Gauges ◽  
Medium Range ◽  
Temporal And Spatial ◽  
The Tropics ◽  
Along Track ◽  
Spatial Threshold

Abstract. The satellite derived HOAPS (Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite data) and ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-Interim reanalysis data sets have been validated against in-situ precipitation measurements from ship rain gauges and optical disdrometers over the open-ocean by applying a statistical analysis for binary forecasts. For this purpose collocated pairs of data were merged within a certain temporal and spatial threshold into single events, according to the satellites' overpass, the observation and the forecast times. HOAPS detects the frequency of precipitation well, while ERA-Interim strongly overestimates it, especially in the tropics and subtropics. Although precipitation rates are difficult to compare because along-track point measurements are collocated with areal estimates and the numbers of available data are limited, we find that HOAPS underestimates precipitation rates, while ERA-Interim's Atlantic-wide average precipitation rate is close to measurements. However, regionally averaged over latitudinal belts, there are deviations between the observed mean precipitation rates and ERA-Interim. The most obvious ERA-Interim feature is an overestimation of precipitation in the area of the intertropical convergence zone and the southern sub-tropics over the Atlantic Ocean. For a limited number of snow measurements by optical disdrometers it can be concluded that both HOAPS and ERA-Interim are suitable to detect the occurrence of solid precipitation.

scholarly journals HOAPS and ERA-Interim precipitation over the sea: validation against shipboard in situ measurements

2016 ◽  
Vol 9 (5) ◽  
pp. 2409-2423 ◽  
Author(s):  
Karl Bumke ◽  
Gert König-Langlo ◽  
Julian Kinzel ◽  
Marc Schröder
Keyword(s):  
Reanalysis Data ◽  
Data Sets ◽  
Weather Forecasts ◽  
Rain Gauges ◽  
Medium Range ◽  
Temporal And Spatial ◽  
The Tropics ◽  
Along Track ◽  
Spatial Threshold

Abstract. The satellite-derived HOAPS (Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data) and ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-Interim reanalysis data sets have been validated against in situ precipitation measurements from ship rain gauges and optical disdrometers over the open ocean by applying a statistical analysis for binary estimates. For this purpose collocated pairs of data were merged within a certain temporal and spatial threshold into single events, according to the satellites' overpass, the observation and the ERA-Interim times. HOAPS detects the frequency of precipitation well, while ERA-Interim strongly overestimates it, especially in the tropics and subtropics. Although precipitation rates are difficult to compare because along-track point measurements are collocated with areal estimates and the number of available data are limited, we find that HOAPS underestimates precipitation rates, while ERA-Interim's Atlantic-wide average precipitation rate is close to measurements. However, when regionally averaged over latitudinal belts, deviations between the observed mean precipitation rates and ERA-Interim exist. The most obvious ERA-Interim feature is an overestimation of precipitation in the area of the intertropical convergence zone and the southern subtropics over the Atlantic Ocean. For a limited number of snow measurements by optical disdrometers, it can be concluded that both HOAPS and ERA-Interim are suitable for detecting the occurrence of solid precipitation.

scholarly journals Origins of Dry Air in the Tropics and Subtropics

2007 ◽  
Vol 20 (12) ◽  
pp. 2745-2759 ◽  
Author(s):  
Piero Cau ◽  
John Methven ◽  
Brian Hoskins
Keyword(s):  
Potential Temperature ◽  
Lower Troposphere ◽  
Transport Processes ◽  
Air Masses ◽  
Weather Forecasts ◽  
Dry Air ◽  
Medium Range ◽  
Net Pressure ◽  
The Tropics ◽  
The Relationship

Abstract The humidity in the dry regions of the tropical and subtropical troposphere has a major impact on the ability of the atmosphere to radiate heat to space. The water vapor content in these regions is determined by their “origins,” here defined as the last condensation event following air masses. Trajectory simulations are used to investigate such origins using the 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40) data for January 1993. It is shown that 96% of air parcels experience condensation within 24 days and most of the remaining 4% originate in the stratosphere. Dry air masses are shown to experience a net pressure increase since last condensation, which is uniform with latitude, while the median time taken for descent is 5 days into the subtropics but exceeds 16 days into the equatorial lower troposphere. The associated rate of decrease in potential temperature is consistent with radiative cooling. The relationship between the drier regions in the Tropics and subtropics and the geographical localization of their origin is investigated. Four transport processes are identified to explain these relationships.

scholarly journals Comparing forecast systems with multiple correlation decomposition based on partial correlation

2020 ◽  
Vol 6 (2) ◽  
pp. 103-113
Author(s):  
Rita Glowienka-Hense ◽  
Andreas Hense ◽  
Sebastian Brune ◽  
Johanna Baehr
Keyword(s):  
Added Value ◽  
Source Information ◽  
Multiple Correlation ◽  
Weather Forecasts ◽  
Medium Range ◽  
Shared Information ◽  
Directed Information ◽  
Explained Variance ◽  
The Tropics ◽  
Persistence Model

Abstract. The multiple correlation and/or regression information that two competing forecast systems have on the same observations is decomposed into four components, adapting the method of multivariate information decomposition of Williams and Beer (2010), Wibral et al. (2015), and Lizier et al. (2018). Their concept is to divide source information about a target into total, (target) redundant or shared, and unique information from each source. It is applied here to the comparison of forecast systems using classic regression. Additionally, non-target redundant or shared information is newly defined that resumes the redundant information of the forecasts which is not observed. This provides views that go beyond classic correlation differences. These five terms share the same units and can be directly compared to put prediction results into perspective. The redundance terms in particular provide a new view. All components are given as maps of explained variance on the observations and for the non-target redundance on the models, respectively. Exerting this concept to lagged damped persistence is shown to be related to directed information entropy. To emphasize the benefit of the toolkit on all timescales, two analysis examples are provided. Firstly, two forecast systems of the German decadal prediction system of “Mittelfristige Klimaprognose”, namely the pre-operational version and a special version using ensemble Kalman filter for the ocean initialization, are compared. The analyses reveal the clear added value of the latter and provide an as yet unseen map of their non-target redundance. Secondly, 4 d lead forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) are compared to a simple autoregressive and/or damped persistence model. The analysis of the information partition on this timescale shows that interannual changes in damped persistence, seen as target redundance changes between forecasts and damped persistence models, are balanced by associated changes in the added value of the dynamic forecasts in the extratropics but not in the tropics.

Sign in / Sign up

Export Citation Format

Share Document