scholarly journals Trends of HCl, ClONO<sub>2</sub>, and HF column abundances from ground-based FTIR measurements in Kiruna (Sweden) in comparison with KASIMA model calculations

2011 ◽  
Vol 11 (10) ◽  
pp. 4669-4677 ◽  
Author(s):  
R. Kohlhepp ◽  
S. Barthlott ◽  
T. Blumenstock ◽  
F. Hase ◽  
I. Kaiser ◽  
...  
Keyword(s):  
Annual Cycle ◽  
Middle Atmosphere ◽  
Least Squares Method ◽  
Transport Model ◽  
Montreal Protocol ◽  
Positive Trend ◽  
Model Data ◽  
Model Calculations ◽  
The Difference ◽  
Total Column

Abstract. Trends of hydrogen chloride (HCl), chlorine nitrate (ClONO2), and hydrogen fluoride (HF) total column abundances above Kiruna (Northern Sweden, 67.84° N, 20.41° E) derived from nearly 14 years (1996–2009) of measurement and model data are presented. The measurements have been performed with a Bruker 120 HR (later Bruker 125 HR) Fourier transform infrared (FTIR) spectrometer and the chemistry-transport model (CTM) used was KASIMA (KArlsruhe SImulation model of the Middle Atmosphere). The total column abundances of ClONO2 and HF calculated by KASIMA agree quite well with the FTIR measurements while KASIMA tends to underestimate the HCl columns. To calculate the long-term trends, a linear function combined with an annual cycle was fitted to the data using a least squares method. The precision of the resulting trends was estimated with the bootstrap resampling method. For HF, both model and measurements show a positive trend that seems to decrease in the last few years. This suggests a stabilisation of the HF total column abundance. Between 1996 and 2009, KASIMA simulates an increase of (+1.51±0.07) %/yr which exceeds the FTIR result of (+0.65±0.25) %/yr. The trends determined for HCl and ClONO2 are significantly negative over the time period considered here. This is expected because the emission of their precursors (chlorofluorocarbons and hydrochlorofluorocarbons) has been restricted in the Montreal Protocol in 1987 and its amendments and adjustments. The trend for ClONO2 from the FTIR measurements amounts to (−3.28±0.56) %/yr and the one for HCl to (−0.81±0.23) %/yr. KASIMA simulates a weaker decrease: For ClONO2, the result is (−0.90±0.10) %/yr and for HCl (−0.17±0.06) %/yr. Part of the difference between measurement and model data can be explained by sampling and the stronger annual cycle indicated by the measurements. There is a factor of about four between the trends of HCl and ClONO2 above Kiruna for both measurement and model data.

scholarly journals Trends of HCl, ClONO <sub>2</sub> and HF column abundances from ground-based FTIR measurements in Kiruna (Sweden) in comparison with KASIMA model calculations

2011 ◽  
Vol 11 (1) ◽  
pp. 1489-1510
Author(s):  
R. Kohlhepp ◽  
S. Barthlott ◽  
T. Blumenstock ◽  
F. Hase ◽  
I. Kaiser ◽  
...  
Keyword(s):  
Hydrogen Fluoride ◽  
Annual Cycle ◽  
Middle Atmosphere ◽  
Least Squares Method ◽  
Montreal Protocol ◽  
Positive Trend ◽  
Model Data ◽  
Model Calculations ◽  
The Difference ◽  
The One

Abstract. Trends of hydrogen chloride (HCl), chlorine nitrate (ClONO2) and hydrogen fluoride (HF) column abundances above Kiruna (Northern Sweden, 67.84° N, 20.41° E) derived from nearly 14 years (1996–2009) of measurement and model data are presented. The measurements have been performed with a Bruker 120 HR (later Bruker 125 HR) Fourier transform infrared (FTIR) spectrometer and the model used was KASIMA (KArlsruhe SImulation model of the Middle Atmosphere). To calculate the long-term trends, a linear function combined with an annual cycle was fitted to the data using a least squares method. The precision of the resulting trends was estimated with the so-called bootstrap resampling method. The relative trends were calculated on the basis of the linear fit result on 1 January 2000, 12:00 UTC. For hydrogen fluoride, both model and measurements show a positive trend that seems to decrease in the last few years. This suggests a stabilisation of the HF total column abundance. For the summer data (August to November), the FTIR trend of (+1.25 ± 0.28)%/yr agrees within errors with the KASIMA one of (+1.55 ± 0.11)%/yr. The trends determined for HCl and ClONO2 are significantly negative over the time period considered here. This corresponds to the expectations because the emission of their precursors (chlorofluorocarbons and hydrochlorofluorocarbons) has been restricted in the Montreal Protocol in 1987 and its amendments and adjustments. The relative trend for ClONO2 from the FTIR measurements amounts to (−3.28 ± 0.56)%/yr and the one for HCl to (−0.81± 0.23)%/yr. KASIMA simulates a weaker decrease: For ClONO2, the result is (−0.90 ± 0.10)%/yr and for HCl (−0.17± 0.06)%/yr. Part of the difference between measurement and model data can be explained by sampling and the stronger annual cycle indicated by the measurements. There is a factor of about four between the trends of HCl and ClONO2 above Kiruna for both measurement and model data. The absolute values of ClONO2 and HF calculated by KASIMA agree quite well with the FTIR measurements while KASIMA tends to underestimate the HCl column abundances.

scholarly journals Trends of UV Radiation in Antarctica

Atmosphere ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 795
Author(s):  
Germar Bernhard ◽  
Scott Stierle
Keyword(s):  
Uv Radiation ◽  
Montreal Protocol ◽  
Spectral Irradiance ◽  
Positive Trend ◽  
South Pole ◽  
The South ◽  
Model Calculations ◽  
Uv Index ◽  
Palmer Station ◽  
Decadal Trend

The success of the Montreal Protocol in curbing increases in harmful solar ultraviolet (UV) radiation at the Earth’s surface has recently been demonstrated. This study also provided evidence that the UV Index (UVI) measured by SUV-100 spectroradiometers at three Antarctic sites (South Pole, Arrival Heights, and Palmer Station) is now decreasing. For example, a significant (95% confidence level) downward trend of −5.5% per decade was reported at Arrival Heights for summer (December through February). However, it was also noted that these measurements are potentially affected by long-term drifts in calibrations of approximately 1% per decade. To address this issue, we have reviewed the chain of calibrations implemented at the three sites between 1996 and 2018 and applied corrections for changes in the scales of spectral irradiance (SoSI) that have occurred over this period (Method 1). This analysis resulted in an upward correction of UVI data measured after 2012 by 1.7% to 1.8%, plus smaller adjustments for several shorter periods. In addition, we have compared measurements during clear skies with model calculations to identify and correct anomalies in the measurements (Method 2). Corrections from both methods reduced decadal trends in UVI on average by 1.7% at the South Pole, 2.1% at Arrival Heights, and 1.6% at Palmer Station. Trends in UVI calculated from the corrected dataset are consistent with concomitant trends in ozone. The decadal trend in UVI calculated from the corrected dataset for summer at Arrival Heights is −3.3% and is significant at the 90% level. Analysis of spectral irradiance measurements at 340 nm suggests that this trend is partially caused by changes in sea ice cover adjacent to the station. For the South Pole, a significant (95% level) trend in UVI of −3.9% per decade was derived for January. This trend can partly be explained by a significant positive trend in total ozone of about 3% per decade, which was calculated from SUV-100 and Dobson measurements. Our study provides further evidence that UVIs are now decreasing in Antarctica during summer months. Reductions have not yet emerged during spring when the ozone hole leads to large UVI variability.

scholarly journals Effects of mixing on resolved and unresolved scales on stratospheric age of air

2017 ◽  
Author(s):  
Simone Dietmüller ◽  
Hella Garny ◽  
Felix Plöger ◽  
Patrick Jöckel ◽  
Cai Duy
Keyword(s):  
Climate Model ◽  
Transport Model ◽  
Mixing Efficiency ◽  
Minor Role ◽  
Positive Trend ◽  
Residual Circulation ◽  
Advection Schemes ◽  
Residual Transport ◽  
The Difference ◽  
A Minor

Abstract. Mean age of air (AoA) is a widely used metric to describe the transport along the Brewer-Dobson circulation. We seek to untangle the effects of different processes on the simulation of AoA, using the chemistry-climate model EMAC and the Lagrangian chemistry transport model CLaMS. Here, the effects of residual transport and two-way mixing on AoA are calculated. To do so, we calculate the residual circulation transit time (RCTT). The difference of AoA and RCTT is defined as aging by mixing. However, as diffusion is also included in this difference, we further use a method to directly calculate aging by mixing on resolved scales. Comparing these two methods of calculating aging by mixing allows for separating the effect of unresolved aging by mixing (which we term "aging by diffusion" in the following) in EMAC and CLaMS. We find that diffusion impacts AoA by making air older, but its contribution plays a minor role (order of 10 %) in all simulations. However, due to the different advection schemes of the two models, aging by diffusion has a larger effect on AoA and mixing efficiency in EMAC, compared to CLaMS. Regarding the trends in AoA, in CLaMS the AoA trend is negative throughout the stratosphere except in the northern hemisphere middle stratosphere, consistent with observations. This slight positive trend is neither reproduced in a free-running nor in a nudged simulation with EMAC – in both simulations the AoA trend is negative throughout the stratosphere. Trends in AoA are mainly driven by the contributions of RCTT and aging by mixing, whereas the contribution of aging by diffusion plays a minor role.

scholarly journals Equatorial total column of nitrous oxide as measured by IASI on MetOp-A: implications for transport processes

2009 ◽  
Vol 9 (1) ◽  
pp. 3243-3264 ◽  
Author(s):  
P. Ricaud ◽  
J.-L. Attié ◽  
H. Teyssèdre ◽  
L. El Amraoui ◽  
V.-H. Peuch ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Transport Model ◽  
Local Maximum ◽  
Transport Processes ◽  
Western Pacific ◽  
Chemical Transport Model ◽  
Data Set ◽  
Model Calculations ◽  
Equatorial Band ◽  
Total Column

Abstract. In this paper we use the total columns of nitrous oxide (N2O) as retrieved from the radiance spectra as measured by the Infrared Atmospheric Sounding Interferometer (IASI) instrument aboard the MetOp-A platform and distributed by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) during the March–May (MAM) 2008 period. Since the total column of N2O reflects concentrations in the middle troposphere, cloud-free columnar N2O measurements are used to assess transport processes in the equatorial band (10° S–10° N). We compare the measured data set with the outputs produced by the 3-D chemical-transport model MOCAGE during the period MAM 2002–2004. To reflect MAM 2008 concentrations, MOCAGE results have been scaled by a factor 1.25% in order to represent the change in concentration of N2O since 2004. IASI N2O equatorial measurements show a maximum over Africa (4.96×10−3 kg m−2) and a minimum over South America (4.86×10−3 kg m−2) in very good agreement with the outputs from MOCAGE despite the fact that emissions of N2O are more intense over America than over Africa. The amplitude of the longitudinal variation of total column N2O along the equatorial band is twice as intense in the measurements (~1.6%) than as in the model calculations (~0.8%), and much greater than the IASI mean random error (0.16–0.33%). A difference between the two data sets is observed above the Western Pacific (110° E–150° E) with a marked minimum in IASI compared to MOCAGE. Recent theoretical studies (Ricaud et al., 2007, 2008) have shown the potentially important effect of the Walker and the Hadley cells on the tropospheric distribution of N2O in producing a local maximum in N2O above Africa. Based on equatorial total columns of N2O measured by IASI, we provide measurement evidence that Africa is a zone of convergence of airmasses coming from different convective regions whilst Western Pacific behaves more like a divergence zone.

scholarly journals Global distribution of mean age of stratospheric air from MIPAS SF<sub>6</sub> measurements

2008 ◽  
Vol 8 (3) ◽  
pp. 677-695 ◽  
Author(s):  
G. P. Stiller ◽  
T. von Clarmann ◽  
M. Höpfner ◽  
N. Glatthor ◽  
U. Grabowski ◽  
...  
Keyword(s):  
Standard Error ◽  
Middle Atmosphere ◽  
Transport Model ◽  
Michelson Interferometer ◽  
Latitudinal Gradients ◽  
Data Set ◽  
Model Calculations ◽  
Short Period ◽  
The Mean

Abstract. Global distributions of profiles of sulphur hexafluoride (SF6) have been retrieved from limb emission spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat covering the period September 2002 to March 2004. Individual SF6 profiles have a precision of 0.5 pptv below 25 km altitude and a vertical resolution of 4–6 km up to 35 km altitude. These data have been validated versus in situ observations obtained during balloon flights of a cryogenic whole-air sampler. For the tropical troposphere a trend of 0.230±0.008 pptv/yr has been derived from the MIPAS data, which is in excellent agreement with the trend from ground-based flask and in situ measurements from the National Oceanic and Atmospheric Administration Earth System Research Laboratory, Global Monitoring Division. For the data set currently available, based on at least three days of data per month, monthly 5° latitude mean values have a 1σ standard error of 1%. From the global SF6 distributions, global daily and monthly distributions of the apparent mean age of air are inferred by application of the tropical tropospheric trend derived from MIPAS data. The inferred mean ages are provided for the full globe up to 90° N/S, and have a 1σ standard error of 0.25 yr. They range between 0 (near the tropical tropopause) and 7 years (except for situations of mesospheric intrusions) and agree well with earlier observations. The seasonal variation of the mean age of stratospheric air indicates episodes of severe intrusion of mesospheric air during each Northern and Southern polar winter observed, long-lasting remnants of old, subsided polar winter air over the spring and summer poles, and a rather short period of mixing with midlatitude air and/or upward transport during fall in October/November (NH) and April/May (SH), respectively, with small latitudinal gradients, immediately before the new polar vortex starts to form. The mean age distributions further confirm that SF6 is destroyed in the mesosphere to a considerable degree. Model calculations with the Karlsruhe simulation model of the middle atmosphere (KASIMA) chemical transport model agree well with observed global distributions of the mean age only if the SF6 sink reactions in the mesosphere are included in the model.

scholarly journals The impact of MM5 and WRF meteorology over complex terrain on CHIMERE model calculations

2009 ◽  
Vol 9 (1) ◽  
pp. 2319-2380 ◽  
Author(s):  
A. de Meij ◽  
A. Gzella ◽  
P. Thunis ◽  
C. Cuvelier ◽  
B. Bessagnet ◽  
...  
Keyword(s):  
Land Surface ◽  
Transport Model ◽  
Land Surface Model ◽  
Heat Fluxes ◽  
Surface Model ◽  
Microphysics Scheme ◽  
Model Calculations ◽  
Po Valley ◽  
The Difference ◽  
The Impact

Abstract. The objective of this study is to evaluate the impact of meteorological input data on calculated gas and aerosol concentrations. We use two different meteorological models (MM5 and WRF) together with the chemistry transport model CHIMERE. We focus on the Po valley area (Italy) for January and June 2005. Firstly we evaluate the meteorological parameters with observations. The analysis shows that the performance of both models is similar, however some small differences are still noticeable. Secondly, we analyze the impact of using MM5 and WRF on calculated PM10 and O3 concentrations. In general CHIMERE/MM5 and CHIMERE/WRF underestimate the PM10 concentrations for January. The difference in PM10 concentrations for January between CHIMERE/MM5 and CHIMERE/WRF is around a factor 1.6 (PM10 higher for CHIMERE/MM5). This difference and the larger underestimation in PM10 concentrations by CHIMERE/WRF are related to the differences in heat fluxes and the resulting PBL heights calculated by WRF. In general the PBL height by WRF meteorology is a factor 2.8 higher at noon in January than calculated by MM5. This study showed that the difference in microphysics scheme has an impact on the profile of cloud liquid water (CLW) calculated by the meteorological driver and therefore on the production of SO4 aerosol. A sensitivity analysis shows that changing the Noah Land Surface Model (LSM) for the 5-layer soil temperature model, the calculated monthly mean PM10 concentrations increase by 30%, due to the change in the heat fluxes and the resulting PBL heights. For June, PM10 calculated concentrations by CHIMERE/MM5 and CHIMERE/WRF are similar and agree with the observations. Calculated O3 values for June are in general overestimated by a factor 1.3 by CHIMERE/MM5 and CHIMRE/WRF. The reason for this is that daytime NO2 concentrations are a higher than the observations and nighttime NO concentrations (titration effect) are underestimated.

scholarly journals Probing the QCD phase boundary with elliptic flow in relativistic heavy ion collisions at STAR

Open Physics ◽  
2012 ◽  
Vol 10 (6) ◽  
Author(s):  
Shusu Shi
Keyword(s):  
Transport Model ◽  
Elliptic Flow ◽  
Heavy Ion ◽  
Charged Hadron ◽  
Relativistic Heavy Ion Collisions ◽  
Present Measurement ◽  
Model Calculations ◽  
Ion Collisions ◽  
Urqmd Model ◽  
The Difference

AbstractWe present measurement of elliptic flow, v 2, for charged and identified particles at midrapidity in Au+Au collisions at $\sqrt {s_{NN} } $ = 7.7–39 GeV. We compare the inclusive charged hadron v 2 to those from transport model calculations, such as the UrQMD model, AMPT default model and AMPT string-melting model. We discuss the energy dependence of the difference in v 2 between particles and anti-particles. The v 2 of ϕ meson is observed to be systematically lower than other particles in Au+Au collisions at $\sqrt {s_{NN} } $ = 11.5 GeV.

scholarly journals Equatorial total column of nitrous oxide as measured by IASI on MetOp-A: implications for transport processes

2009 ◽  
Vol 9 (12) ◽  
pp. 3947-3956 ◽  
Author(s):  
P. Ricaud ◽  
J.-L. Attié ◽  
H. Teyssèdre ◽  
L. El Amraoui ◽  
V.-H. Peuch ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Transport Model ◽  
Local Maximum ◽  
Transport Processes ◽  
Western Pacific ◽  
Chemical Transport Model ◽  
Data Set ◽  
Model Calculations ◽  
Equatorial Band ◽  
Total Column

Abstract. In this paper we use the total columns of nitrous oxide (N2O) as retrieved from the radiance spectra as measured by the Infrared Atmospheric Sounding Interferometer (IASI) instrument aboard the MetOp-A platform and distributed by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) during the March–May (MAM) 2008 period. Since the total column of N2O reflects concentrations in the middle troposphere, cloud-free columnar N2O measurements are used to assess transport processes in the equatorial band (10° S–10° N). We compare the measured data set with the outputs produced by the 3-D chemical-transport model MOCAGE during the period MAM 2002–2004. To reflect MAM 2008 concentrations, MOCAGE results have been scaled by a factor 1.0125 in order to represent the change in concentration of N2O since 2004. IASI N2O equatorial measurements show a maximum over Africa (4.96×10−3 kg m−2) and a minimum over South America (4.86×10−3 kg m−2) in reasonable agreement with the outputs from MOCAGE despite the fact that emissions of N2O are more intense over America than over Africa. The amplitude of the longitudinal variation of total column N2O along the equatorial band is twice as intense in the measurements (~1.6%) than as in the model calculations (~0.8%), and much greater than the IASI mean random error (0.16–0.33%). A difference between the two data sets is observed above the Western Pacific (110° E–150° E) with a marked minimum in IASI compared to MOCAGE. Recent theoretical studies (Ricaud et al., 2007 and 2009) have shown the potentially important effect of the Walker and the Hadley cells on the tropospheric distribution of N2O in producing a local maximum in N2O above Africa. Based on equatorial total columns of N2O retrieved from IASI, our results are consistent with the fact that Africa is a zone of convergence of airmasses coming from different convective regions whilst Western Pacific behaves more like a divergence zone.

scholarly journals Global distribution of mean age of stratospheric air from MIPAS SF<sub>6</sub> measurements

2007 ◽  
Vol 7 (5) ◽  
pp. 13653-13697 ◽  
Author(s):  
G. P. Stiller ◽  
T. von Clarmann ◽  
M. Höpfner ◽  
N. Glatthor ◽  
U. Grabowski ◽  
...  
Keyword(s):  
Standard Error ◽  
Middle Atmosphere ◽  
Transport Model ◽  
Michelson Interferometer ◽  
Latitudinal Gradients ◽  
Data Set ◽  
Model Calculations ◽  
Short Period ◽  
The Mean

Abstract. Global distributions of profiles of sulphur hexafluoride (SF6) have been retrieved from limb emission spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat covering the period September 2002 to March 2004. Individual SF6 profiles have a precision of 0.5 pptv below 25 km altitude and a vertical resolution of 4–6 km up to 35 km altitude. These data have been validated versus in situ observations obtained during balloon flights of a cryogenic whole-air sampler. For the tropical troposphere a trend of 0.227±0.008 pptv/yr has been derived from the MIPAS data, which is in excellent agreement with the trend from ground-based flask and in situ measurements from the National Oceanic and Atmospheric Administration Earth System Research Laboratory, Global Monitoring Division. For the data set currently available, based on at least three days of data per month, monthly 5° latitude mean values have a 1σ standard error of 1%. From the global SF6 distributions, global daily and monthly distributions of the apparent mean age of air are inferred by application of the tropical tropospheric trend derived from MIPAS data. The inferred mean ages are provided for the full globe up to 90° N/S, and have a 1σ standard error of 0.25 yr. They range between 0 (near the tropical tropopause) and 7 years (except for situations of mesospheric intrusions) and agree well with earlier observations. The seasonal variation of the mean age of stratospheric air indicates episodes of severe intrusion of mesospheric air during each Northern and Southern polar winter observed, long-lasting remnants of old, subsided polar winter air over the spring and summer poles, and a rather short period of mixing with midlatitude air and/or upward transport during fall in October/November (NH) and April/May (SH), respectively, with small latitudinal gradients, immediately before the new polar vortex starts to form. The mean age distributions further confirm that SF6 is destroyed in the mesosphere to a considerable amount. Model calculations with the Karlsruhe simulation model of the middle atmosphere (KASIMA) chemical transport model agree well with observed global distributions of the mean age only if the SF6 sink reactions in the mesosphere are included in the model.

scholarly journals The impact of MM5 and WRF meteorology over complex terrain on CHIMERE model calculations

2009 ◽  
Vol 9 (17) ◽  
pp. 6611-6632 ◽  
Author(s):  
A. de Meij ◽  
A. Gzella ◽  
C. Cuvelier ◽  
P. Thunis ◽  
B. Bessagnet ◽  
...  
Keyword(s):  
Land Surface ◽  
Transport Model ◽  
Land Surface Model ◽  
Heat Fluxes ◽  
Surface Model ◽  
Microphysics Scheme ◽  
Model Calculations ◽  
Temporal Correlations ◽  
The Difference ◽  
The Impact

Abstract. The objective of this study is to evaluate the impact of meteorological input data on calculated gas and aerosol concentrations. We use two different meteorological models (MM5 and WRF) together with the chemistry transport model CHIMERE. We focus on the Po valley area (Italy) for January and June 2005. Firstly we evaluate the meteorological parameters with observations. The analysis shows that the performance of both models in calculating surface parameters is similar, however differences are still observed. Secondly, we analyze the impact of using MM5 and WRF on calculated PM10 and O3 concentrations. In general CHIMERE/MM5 and CHIMERE/WRF underestimate the PMv concentrations for January. The difference in PM10 concentrations for January between CHIMERE/MM5 and CHIMERE/WRF is around a factor 1.6 (PM10 higher for CHIMERE/MM5). This difference and the larger underestimation in PM10 concentrations by CHIMERE/WRF are related to the differences in heat fluxes and the resulting PBL heights calculated by WRF. In general the PBL height by WRF meteorology is a factor 2.8 higher at noon in January than calculated by MM5. This study showed that the difference in microphysics scheme has an impact on the profile of cloud liquid water (CLW) calculated by the meteorological driver and therefore on the production of SO4 aerosol. A sensitivity analysis shows that changing the Noah Land Surface Model (LSM) in our WRF pre-processing for the 5-layer soil temperature model, calculated monthly mean PMv concentrations increase by 30%, due to the change in the heat fluxes and the resulting PBL heights. For June, PM10 calculated concentrations by CHIMERE/MM5 and CHIMERE/WRF are similar and agree with the observations. Calculated O3 values for June are in general overestimated by a factor 1.3 by CHIMERE/MM5 and CHIMERE/WRF. High temporal correlations are found between modeled and observed O3 concentrations.

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