Comparison of large-scale dynamical variability in the extratropical stratosphere among the JRA-55 family data sets

Reanalysis Data ◽

Family Data ◽

Data Sets ◽

Polar Night ◽

Standard Product ◽

Northern Winter

Abstract. This study compares large-scale dynamical variability in the extratropical stratosphere, such as major stratospheric sudden warmings (MSSWs), among the Japanese 55-year Reanalysis (JRA-55) family data sets. The JRA-55 family consists of three products: a standard product of the JRA-55 reanalysis data, and two sub-products of JRA-55C and JRA-55AMIP. JRA-55C assimilates only conventional observations, whereas JRA-55AMIP runs the same numerical weather prediction model without assimilation of observational data. A comparison of the occurrence of MSSWs in Northern winter shows that compared to the standard product, JRA-55C delays several MSSWs by one to four days and also misses a few MSSWs. JRA-55C also misses the Southern Hemisphere MSSW in September 2002. JRA-55AMIP shows much fewer MSSWs in Northern winter, and especially lacks MSSWs of high aspect ratio of the polar vortex. A further examination of daily geopotential height differences between JRA-55 and JRA-55C reveals occasional peaks in both hemispheres. The delayed and missed MSSW cases have smaller height differences in magnitude than such peaks. The differences include large contributions from the zonal component, which are consistent with underestimations in the weakening of the zonal mean polar night jet in JRA-55C. We also explore strong planetary wave forcings and associated polar vortex weakenings for JRA-55 and JRA-55AMIP. It shows a lower frequency of strong wave forcings and weaker vortex responses to such wave forcings in JRA-55AMIP, consistent with the lower MSSW frequency.

Comparison of large-scale dynamical variability in the extratropical stratosphere among the JRA-55 family data sets: impacts of assimilation of observational data in JRA-55 reanalysis data

10.5194/acp-17-11193-2017 ◽

2017 ◽

Vol 17 (18) ◽

pp. 11193-11207 ◽

Cited By ~ 3

Author(s):

Masakazu Taguchi

Keyword(s):

Observational Data ◽

Northern Hemisphere ◽

Large Scale ◽

Weather Prediction ◽

Polar Vortex ◽

Reanalysis Data ◽

Family Data ◽

Data Sets ◽

Hemisphere Winter

Abstract. This study compares large-scale dynamical variability in the extratropical stratosphere, such as major stratospheric sudden warmings (MSSWs), among the Japanese 55-year Reanalysis (JRA-55) family data sets. The JRA-55 family consists of three products: a standard product (STDD) of the JRA-55 reanalysis data and two sub-products of JRA-55C (CONV) and JRA-55AMIP (AMIP). CONV assimilates only conventional surface and upper-air observations without assimilation of satellite observations, whereas AMIP runs the same numerical weather prediction model without assimilation of observational data. A comparison of the occurrence of MSSWs in Northern Hemisphere (NH) winter shows that, compared to STDD, CONV delays several MSSWs by 1 to 4 days and also misses a few MSSWs. CONV also misses the Southern Hemisphere (SH) MSSW in September 2002. AMIP shows significantly fewer MSSWs in Northern Hemisphere winter and especially lacks MSSWs of the high aspect ratio of the polar vortex in which the vortex is highly stretched or split. A further examination of daily geopotential height differences between STDD and CONV reveals occasional peaks in both hemispheres that are separated from MSSWs. The delayed and missed MSSW cases have smaller height differences in magnitude than such peaks. The height differences for those MSSWs include large contributions from the zonal component, which reflects underestimations in the weakening of the zonal mean polar night jet in CONV. We also explore strong planetary wave forcings and associated polar vortex weakenings for STDD and AMIP. We find a lower frequency of strong wave forcings and weaker vortex responses to such wave forcings in AMIP, consistent with the lower MSSW frequency.

Comparisons of polar processing diagnostics from 34 years of the ERA-Interim and MERRA reanalyses

10.5194/acp-15-3873-2015 ◽

2015 ◽

Vol 15 (7) ◽

pp. 3873-3892 ◽

Cited By ~ 23

Author(s):

Z. D. Lawrence ◽

G. L. Manney ◽

K. Minschwaner ◽

M. L. Santee ◽

A. Lambert

Keyword(s):

Meteorological Data ◽

Polar Vortex ◽

Reanalysis Data ◽

Cloud Formation ◽

Data Sets ◽

Weather Forecasts ◽

Stratospheric Temperature ◽

Vortex Size ◽

Comprehensive Comparison ◽

Modern Era

Abstract. We present a comprehensive comparison of polar processing diagnostics derived from the National Aeronautics and Space Administration (NASA) Modern Era Retrospective-analysis for Research and Applications (MERRA) and the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis (ERA-Interim). We use diagnostics that focus on meteorological conditions related to stratospheric chemical ozone loss based on temperatures, polar vortex dynamics, and air parcel trajectories to evaluate the effects these reanalyses might have on polar processing studies. Our results show that the agreement between MERRA and ERA-Interim changes significantly over the 34 years from 1979 to 2013 in both hemispheres and in many cases improves. By comparing our diagnostics during five time periods when an increasing number of higher-quality observations were brought into these reanalyses, we show how changes in the data assimilation systems (DAS) of MERRA and ERA-Interim affected their meteorological data. Many of our stratospheric temperature diagnostics show a convergence toward significantly better agreement, in both hemispheres, after 2001 when Aqua and GOES (Geostationary Operational Environmental Satellite) radiances were introduced into the DAS. Other diagnostics, such as the winter mean volume of air with temperatures below polar stratospheric cloud formation thresholds (VPSC) and some diagnostics of polar vortex size and strength, do not show improved agreement between the two reanalyses in recent years when data inputs into the DAS were more comprehensive. The polar processing diagnostics calculated from MERRA and ERA-Interim agree much better than those calculated from earlier reanalysis data sets. We still, however, see fairly large differences in many of the diagnostics in years prior to 2002, raising the possibility that the choice of one reanalysis over another could significantly influence the results of polar processing studies. After 2002, we see overall good agreement among the diagnostics, which demonstrates that the ERA-Interim and MERRA reanalyses are equally appropriate choices for polar processing studies of recent Arctic and Antarctic winters.

Chemistry-climate model SOCOL: a validation of the present-day climatology

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-5-509-2005 ◽

2005 ◽

Vol 5 (1) ◽

pp. 509-555 ◽

Cited By ~ 3

Author(s):

T. Egorova ◽

E. Rozanov ◽

V. Zubov ◽

E. Manzini ◽

W. Schmutz ◽

...

Keyword(s):

Climate Model ◽

Middle Atmosphere ◽

Polar Vortex ◽

Data Sets ◽

Radiation Heating ◽

Polar Night ◽

Temperature Bias ◽

Significant Temperature ◽

Higher Temperature ◽

The Tropics

Abstract. In this paper we document ''SOCOL'', a new chemistry-climate model, which has been ported for regular PCs and shows good wall-clock performance. An extensive validation of the model results against present-day climate obtained from observations and assimilation data sets shows that the model describes the climatological state of the atmosphere for the late 1990s with reasonable accuracy. The model has a significant temperature bias only in the upper stratosphere and near the tropopause in the tropics and high latitudes. The latter is the result of the rather low vertical resolution of the model near the tropopause. The former can be attributed to a crude representation of the radiation heating in the middle atmosphere. A comparison of the simulated and observed link between the tropical stratospheric structure and the strength of the polar vortex shows that in general, both observations and simulations reveal a higher temperature and ozone mixing ratio in the lower tropical stratosphere for the case with stronger Polar night jet (PNJ) as predicted by theoretical studies.

Chemistry-climate model SOCOL: a validation of the present-day climatology

10.5194/acp-5-1557-2005 ◽

2005 ◽

Vol 5 (6) ◽

pp. 1557-1576 ◽

Cited By ~ 81

Author(s):

T. Egorova ◽

E. Rozanov ◽

V. Zubov ◽

E. Manzini ◽

W. Schmutz ◽

...

Keyword(s):

Climate Model ◽

Middle Atmosphere ◽

Polar Vortex ◽

Data Sets ◽

Climate Data ◽

Radiation Heating ◽

Polar Night ◽

Temperature Bias ◽

Significant Temperature ◽

Higher Temperature

Abstract. In this paper we document "SOCOL", a new chemistry-climate model, which has been ported for regular PCs and shows good wall-clock performance. An extensive validation of the model results against present-day climate data obtained from observations and assimilation data sets shows that the model describes the climatological state of the atmosphere for the late 1990s with reasonable accuracy. The model has a significant temperature bias only in the upper stratosphere and near the tropopause at high latitudes. The latter is the result of the rather low vertical resolution of the model near the tropopause. The former can be attributed to a crude representation of radiation heating in the middle atmosphere. A comparison of the simulated and observed link between the tropical stratospheric structure and the strength of the polar vortex shows that in general, both observations and simulations reveal a higher temperature and ozone mixing ratio in the lower tropical stratosphere for the case with stronger Polar night jet (PNJ) and slower Brewer-Dobson circulation as predicted by theoretical studies.

Gravity wave activity during the southern hemispheric sudden stratospheric warming 2019

10.5194/egusphere-egu2020-13569 ◽

2020 ◽

Author(s):

Andreas Dörnbrack ◽

Tyler Mixa ◽

Bernd Kaifler ◽

Markus Rapp

Keyword(s):

Weather Prediction ◽

Polar Vortex ◽

Wave Activity ◽

Meteorological Conditions ◽

Background Information ◽

Stratospheric Warming ◽

Sudden Stratospheric Warming ◽

Airborne Measurements

<p>At the end of the austral winter 2019, a sudden stratospheric warming led to an early breakdown of the polar vortex. The meteorological conditions during this event are documented and analysed by means of operational analyses of the Intgrated Forecast System (IFS) of the ECMWF and ERA5 data. Especially, we focus on the decline of stratospheric wave activity over the southern tip of South America. For this region, ground-based and airborne measurements are employed to compare selected diagnostics with fields from the ECMWF's numerical weather prediction model IFS. Furthmore, the meteorological conditions for one selected research flight during the SOUTHTRAC campaign are presented. This part serves as background information for a case study presented by Tyler Mixa.</p>

The 11-year solar cycle in current reanalyses: a (non)linear attribution study of the middle atmosphere

10.5194/acp-15-6879-2015 ◽

2015 ◽

Vol 15 (12) ◽

pp. 6879-6895 ◽

Cited By ~ 16

Author(s):

A. Kuchar ◽

P. Sacha ◽

J. Miksovsky ◽

P. Pisoft

Keyword(s):

Solar Cycle ◽

Linear Regression ◽

Middle Atmosphere ◽

Polar Vortex ◽

Reanalysis Data ◽

Support Vector ◽

Data Sets ◽

Nonlinear Approach ◽

Hypothetical Mechanism ◽

Solar Signal

Abstract. This study focusses on the variability of temperature, ozone and circulation characteristics in the stratosphere and lower mesosphere with regard to the influence of the 11-year solar cycle. It is based on attribution analysis using multiple nonlinear techniques (support vector regression, neural networks) besides the multiple linear regression approach. The analysis was applied to several current reanalysis data sets for the 1979–2013 period, including MERRA, ERA-Interim and JRA-55, with the aim to compare how these types of data resolve especially the double-peaked solar response in temperature and ozone variables and the consequent changes induced by these anomalies. Equatorial temperature signals in the tropical stratosphere were found to be in qualitative agreement with previous attribution studies, although the agreement with observational results was incomplete, especially for JRA-55. The analysis also pointed to the solar signal in the ozone data sets (i.e. MERRA and ERA-Interim) not being consistent with the observed double-peaked ozone anomaly extracted from satellite measurements. The results obtained by linear regression were confirmed by the nonlinear approach through all data sets, suggesting that linear regression is a relevant tool to sufficiently resolve the solar signal in the middle atmosphere. The seasonal evolution of the solar response was also discussed in terms of dynamical causalities in the winter hemispheres. The hypothetical mechanism of a weaker Brewer–Dobson circulation at solar maxima was reviewed together with a discussion of polar vortex behaviour.

The effect of radar-based QPE on the Fractions Skill Score used at the QPF verification

Advances in Geosciences ◽

10.5194/adgeo-25-91-2010 ◽

2010 ◽

Vol 25 ◽

pp. 91-95 ◽

Cited By ~ 1

Author(s):

P. Zacharov ◽

D. Rezacova

Keyword(s):

Prediction Model ◽

Numerical Weather Prediction ◽

Small Difference ◽

Weather Prediction ◽

Skill Score ◽

Quantitative Precipitation Estimates

Data Sets ◽

Correction Technique ◽

Precipitation Estimates ◽

Abstract. In this paper we show the influence of gauge adjustment technique, applied to radar-based rainfalls, on the results of QPF verification. The results were obtained for four convective events which produced heavy local rainfalls and caused local flash floods at the Czech territory. Numerical weather prediction model COSMO was run to obtain rainfall forecast and Fractions Skill Score was employed in the QPF verification. Three different radar-based quantitative precipitation estimates (QPE) were used for the verification and the verification results were compared. The QPE data sets consisted of: (a) raw radar-based rainfall values, (b) gauge corrected radar-based rainfalls with a simple domain-wide correction, and (c) radar-based rainfalls with a pixel related gauge adjustment. The results indicate small difference in area-related verification results and prove that the simple domain wide correction technique is sufficient for applying radar-based rainfalls as the verification data.

Observations of middle atmospheric H2O and O3 during the 2010 major sudden stratospheric warming by a network of microwave radiometers

10.5194/acp-12-7753-2012 ◽

2012 ◽

Vol 12 (16) ◽

pp. 7753-7765 ◽

Cited By ~ 31

Author(s):

D. Scheiben ◽

C. Straub ◽

K. Hocke ◽

P. Forkman ◽

N. Kämpfer

Keyword(s):

Large Scale ◽

Polar Vortex ◽

Mapping Technique ◽

Sudden Increase ◽

Stratospheric Warming ◽

Sudden Stratospheric Warming ◽

Trajectory Mapping ◽

Northern Winter ◽

Microwave Radiometers ◽

Middle Stratosphere

Abstract. In this study, we present middle atmospheric water vapor (H2O) and ozone (O3) measurements obtained by ground-based microwave radiometers at three European locations in Bern (47° N), Onsala (57° N) and Sodankylä (67° N) during Northern winter 2009/2010. In January 2010, a major sudden stratospheric warming (SSW) occurred in the Northern Hemisphere whose signatures are evident in the ground-based observations of H2O and O3. The observed anomalies in H2O and O3 are mostly explained by the relative location of the polar vortex with respect to the measurement locations. The SSW started on 26 January 2010 and was most pronounced by the end of January. The zonal mean temperature in the middle stratosphere (10 hPa) increased by approximately 25 Kelvin within a few days. The stratospheric vortex weakened during the SSW and shifted towards Europe. In the mesosphere, the vortex broke down, which lead to large scale mixing of polar and midlatitudinal air. After the warming, the polar vortex in the stratosphere split into two weaker vortices and in the mesosphere, a new, pole-centered vortex formed with maximum wind speed of 70 m s−1 at approximately 40° N. The shift of the stratospheric vortex towards Europe was observed in Bern as an increase in stratospheric H2O and a decrease in O3. The breakdown of the mesospheric vortex during the SSW was observed at Onsala and Sodankylä as a sudden increase in mesospheric H2O. The following large-scale descent inside the newly formed mesospheric vortex was well captured by the H2O observations in Sodankylä. In order to combine the H2O observations from the three different locations, we applied the trajectory mapping technique on our H2O observations to derive synoptic scale maps of the H2O distribution. Based on our observations and the 3-D wind field, this method allows determining the approximate development of the stratospheric and mesospheric polar vortex and demonstrates the potential of a network of ground-based instruments.

MOS, Perfect Prog, and Reanalysis

Monthly Weather Review ◽

10.1175/mwr3088.1 ◽

2006 ◽

Vol 134 (2) ◽

pp. 657-663 ◽

Cited By ~ 23

Author(s):

Caren Marzban ◽

Scott Sandgathe ◽

Eugenia Kalnay

Keyword(s):

Mean Squared Error ◽

Weather Prediction ◽

Error Variance ◽

Reanalysis Data ◽

Point Of View ◽

Model Output ◽

Squared Error ◽

Error Bias ◽

Model Output Statistics

Abstract Statistical postprocessing methods have been successful in correcting many defects inherent in numerical weather prediction model forecasts. Among them, model output statistics (MOS) and perfect prog have been most common, each with its own strengths and weaknesses. Here, an alternative method (called RAN) is examined that combines the two, while at the same time utilizes the information in reanalysis data. The three methods are examined from a purely formal/mathematical point of view. The results suggest that whereas MOS is expected to outperform perfect prog and RAN in terms of mean squared error, bias, and error variance, the RAN approach is expected to yield more certain and bias-free forecasts. It is suggested therefore that a real-time RAN-based postprocessor be developed for further testing.

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

10.5194/acp-18-11205-2018 ◽

2018 ◽

Vol 18 (15) ◽

pp. 11205-11219 ◽

Cited By ~ 12

Author(s):

David Ian Duncan ◽

Patrick Eriksson

Keyword(s):

General Circulation ◽

Large Scale ◽

Principal Component ◽

Reanalysis Data ◽

Data Sets ◽

Diurnal Variability ◽

Weather Forecasts ◽

Earth Observing System ◽

The Difference ◽

Ice Water

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 analysed and compared with estimates from two reanalysis data sets, ERA5 (European Centre for Medium-range Weather Forecasts Reanalysis 5, ECMWF) and MERRA-2 (Modern-Era Retrospective Analysis for Research and Applications 2). Large discrepancies in IWP exist between the satellite data sets themselves, making validation of the model results problematic and indicating that progress towards a consensus on the distribution of atmospheric ice has been limited. Comparing the data sets, zonal means of IWP exhibit similar shapes but differing magnitudes, with large IWP values causing much of the difference in means. Diurnal analysis centred on A-Train overpasses shows similar 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 data sets, as principal component analysis shows that the patterns of seasonal variability line up well between the data sets 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.