Results from the International Halocarbons in Air Comparison Experiment (IHALACE)

Abstract. The International Halocarbons in Air Comparison Experiment (IHALACE) was conducted to document relationships between calibration scales among various laboratories that measure atmospheric greenhouse and ozone depleting gases. This study included trace gases such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs), as well as nitrous oxide, methane, sulfur hexafluoride, very short-lived halocompounds, and carbonyl sulfide. Many of these gases are present in the unpolluted atmosphere at pmol mol−1 (parts per trillion) or nmol mol−1 (parts per billion) levels. Six stainless steel cylinders containing natural and modified natural air samples were circulated among 19 laboratories. Results from this experiment reveal relatively good agreement (within a few percent) among commonly used calibration scales. Scale relationships for some gases, such as CFC-12 and CCl4, were found to be consistent with those derived from estimates of global mean mole fractions, while others, such as halon-1211 and CH3Br, revealed discrepancies. The transfer of calibration scales among laboratories was problematic in many cases, meaning that measurements tied to a particular scale may not, in fact, be compatible. Large scale transfer errors were observed for CH3CCl3 (10–100%) and CCl4 (2–30%), while much smaller scale transfer errors (< 1%) were observed for halon-1211, HCFC-22, and HCFC-142b. These results reveal substantial improvements in calibration over previous comparisons. However, there is room for improvement in communication and coordination of calibration activities with respect to the measurement of halogenated and related trace gases.

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Results from the International Halocarbons in Air Comparison Experiment (IHALACE)

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-6-8021-2013 ◽

2013 ◽

Vol 6 (4) ◽

pp. 8021-8069 ◽

Cited By ~ 4

Author(s):

B. D. Hall ◽

A. Engel ◽

J. Mühle ◽

J. W. Elkins ◽

F. Artuso ◽

...

Keyword(s):

Stainless Steel ◽

Trace Gases ◽

Air Samples ◽

Comparison Experiment ◽

Atmospheric Data ◽

Common Scale ◽

Communication And Coordination ◽

Document Relationships ◽

Good Agreement

Abstract. The International Halocarbons in Air Comparison Experiment (IHALACE) was conducted to document relationships between calibration scales among various laboratories that measure atmospheric greenhouse and ozone depleting gases. Six stainless steel cylinders containing natural and modified natural air samples were circulated among 19 laboratories. Results from this experiment reveal relatively good agreement among commonly used calibration scales for a number of trace gases present in the unpolluted atmosphere at pmol mol−1 (parts per trillion) levels, such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). Some scale relationships were found to be consistent with those derived from bi-lateral experiments or from analysis of atmospheric data, while others revealed discrepancies. The transfer of calibration scales among laboratories was found to be problematic in many cases, meaning that measurements tied to a common scale may not, in fact, be compatible. These results reveal substantial improvements in calibration over previous comparisons. However there is room for improvement in communication and coordination of calibration activities with respect to the measurement of halogenated and related trace gases.

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Estimating the Earth’s Outgoing Longwave Radiation Measured from a Moon-Based Platform

Remote Sensing ◽

10.3390/rs13112201 ◽

2021 ◽

Vol 13 (11) ◽

pp. 2201

Author(s):

Hanlin Ye ◽

Huadong Guo ◽

Guang Liu ◽

Jinsong Ping ◽

Lu Zhang ◽

...

Keyword(s):

Outgoing Longwave Radiation ◽

Large Scale ◽

Single Point ◽

Longwave Radiation ◽

Earth Observation ◽

Artificial Satellites ◽

Earth Observations ◽

The Earth ◽

Observation Geometry ◽

Global Mean

Moon-based Earth observations have attracted significant attention across many large-scale phenomena. As the only natural satellite of the Earth, and having a stable lunar surface as well as a particular orbit, Moon-based Earth observations allow the Earth to be viewed as a single point. Furthermore, in contrast with artificial satellites, the varied inclination of Moon-based observations can improve angular samplings of specific locations on Earth. However, the potential for estimating the global outgoing longwave radiation (OLR) from the Earth with such a platform has not yet been fully explored. To evaluate the possibility of calculating OLR using specific Earth observation geometry, we constructed a model to estimate Moon-based OLR measurements and investigated the potential of a Moon-based platform to acquire the necessary data to estimate global mean OLR. The primary method of our study is the discretization of the observational scope into various elements and the consequent integration of the OLR of all elements. Our results indicate that a Moon-based platform is suitable for global sampling related to the calculation of global mean OLR. By separating the geometric and anisotropic factors from the measurement calculations, we ensured that measured values include the effects of the Moon-based Earth observation geometry and the anisotropy of the scenes in the observational scope. Although our results indicate that higher measured values can be achieved if the platform is located near the center of the lunar disk, a maximum difference between locations of approximately 9 × 10−4 W m−2 indicates that the effect of location is too small to remarkably improve observation performance of the platform. In conclusion, our analysis demonstrates that a Moon-based platform has the potential to provide continuous, adequate, and long-term data for estimating global mean OLR.

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EZ-ALBI Score for Predicting Hepatocellular Carcinoma Prognosis

Liver Cancer ◽

10.1159/000508971 ◽

2020 ◽

Vol 9 (6) ◽

pp. 734-743

Author(s):

Kazuya Kariyama ◽

Kazuhiro Nouso ◽

Atsushi Hiraoka ◽

Akiko Wakuta ◽

Ayano Oonishi ◽

...

Keyword(s):

Hepatocellular Carcinoma ◽

Liver Function ◽

Large Scale ◽

Regression Coefficient ◽

Information Criterion ◽

Proportional Hazard ◽

Cox Proportional Hazard ◽

Highly Correlated ◽

Survival Risk ◽

Good Agreement

Introduction: The ALBI score is acknowledged as the gold standard for the assessment of liver function in patients with hepatocellular carcinoma (HCC). Unlike the Child-Pugh score, the ALBI score uses only objective parameters, albumin (Alb) and total bilirubin (T.Bil), enabling a better evaluation. However, the complex calculation of the ALBI score limits its applicability. Therefore, we developed a simplified ALBI score, based on data from a large-scale HCC database.We used the data of 5,249 naïve HCC cases registered in eight collaborating hospitals. Methods: We developed a new score, the EZ (Easy)-ALBI score, based on regression coefficients of Alb and T.Bil for survival risk in a multivariate Cox proportional hazard model. We also developed the EZ-ALBI grade and EZ-ALBI-T grade as alternative options for the ALBI grade and ALBI-T grade and evaluated their stratifying ability. Results: The equation used to calculate the EZ-ALBI score was simple {[T.Bil (mg/dL)] – [9 × Alb (g/dL)]}; this value highly correlated with the ALBI score (correlation coefficient, 0.981; p < 0.0001). The correlation was preserved across different Barcelona clinic liver cancer grade scores (regression coefficient, 0.93–0.98) and across different hospitals (regression coefficient, 0.98–0.99), indicating good generalizability. Although a good agreement was observed between ALBI and EZ-ALBI, discrepancies were observed in patients with poor liver function (T.Bil, ≥3 mg/dL; regression coefficient, 0.877). The stratifying ability of EZ-ALBI grade and EZ-ALBI-T grade were good and their Akaike’s information criterion values (35,897 and 34,812, respectively) were comparable with those of ALBI grade and ALBI-T grade (35,914 and 34,816, respectively). Conclusions: The EZ-ALBI score, EZ-ALBI grade, and EZ-ALBI-T grade are useful, simple scores, which might replace the conventional ALBI score in the future.

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The Role of Equatorial Rossby Waves in Tropical Cyclogenesis. Part I: Idealized Numerical Simulations in an Initially Quiescent Background Environment

Monthly Weather Review ◽

10.1175/2009mwr3114.1 ◽

2010 ◽

Vol 138 (4) ◽

pp. 1368-1382 ◽

Cited By ~ 15

Author(s):

Jeffrey S. Gall ◽

William M. Frank ◽

Matthew C. Wheeler

Keyword(s):

Tropical Cyclone ◽

Large Scale ◽

Phase Speed ◽

Tropical Cyclogenesis ◽

Initial Amplitude ◽

Low Level ◽

Wave Simulation ◽

Horizontal Momentum ◽

Good Agreement

Abstract This two-part series of papers examines the role of equatorial Rossby (ER) waves in tropical cyclone (TC) genesis. To do this, a unique initialization procedure is utilized to insert n = 1 ER waves into a numerical model that is able to faithfully produce TCs. In this first paper, experiments are carried out under the idealized condition of an initially quiescent background environment. Experiments are performed with varying initial wave amplitudes and with and without diabatic effects. This is done to both investigate how the properties of the simulated ER waves compare to the properties of observed ER waves and explore the role of the initial perturbation strength of the ER wave on genesis. In the dry, frictionless ER wave simulation the phase speed is slightly slower than the phase speed predicted from linear theory. Large-scale ascent develops in the region of low-level poleward flow, which is in good agreement with the theoretical structure of an n = 1 ER wave. The structures and phase speeds of the simulated full-physics ER waves are in good agreement with recent observational studies of ER waves that utilize wavenumber–frequency filtering techniques. Convection occurs primarily in the eastern half of the cyclonic gyre, as do the most favorable conditions for TC genesis. This region features sufficient midlevel moisture, anomalously strong low-level cyclonic vorticity, enhanced convection, and minimal vertical shear. Tropical cyclogenesis occurs only in the largest initial-amplitude ER wave simulation. The formation of the initial tropical disturbance that ultimately develops into a tropical cyclone is shown to be sensitive to the nonlinear horizontal momentum advection terms. When the largest initial-amplitude simulation is rerun with the nonlinear horizontal momentum advection terms turned off, tropical cyclogenesis does not occur, but the convectively coupled ER wave retains the properties of the ER wave observed in the smaller initial-amplitude simulations. It is shown that this isolated wave-only genesis process only occurs for strong ER waves in which the nonlinear advection is large. Part II will look at the more realistic case of ER wave–related genesis in which a sufficiently intense ER wave interacts with favorable large-scale flow features.

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Drivers of (non-)linear Eocene surface warming in the DeepMIP ensemble

10.5194/egusphere-egu21-14127 ◽

2021 ◽

Author(s):

Sebastian Steinig ◽

Jiang Zhu ◽

Ran Feng ◽

Keyword(s):

Temperature Gradient ◽

Heat Transport ◽

Climate Sensitivity ◽

Radiative Forcing ◽

Large Scale ◽

Surface Albedo ◽

Early Eocene ◽

Meridional Heat Transport ◽

Surface Warming ◽

Global Mean

The early Eocene greenhouse represents the warmest interval of the Cenozoic and therefore provides a unique opportunity to understand how the climate system operates under elevated atmospheric CO2 levels similar to those projected for the end of the 21st century. Early Eocene geological records indicate a large increase in global mean surface temperatures compared to present day (by ~14&#176;C) and a greatly reduced meridional temperature gradient (by ~30% in SST). However, reproducing these large-scale climate features at reasonable CO2 levels still poses a challenge for current climate models. Recent modelling studies indicate an important role for shortwave (SW) cloud feedbacks to drive increases in climate sensitivity with global warming, which helps to close the gap between simulated and reconstructed Eocene global warmth and temperature gradient. Nevertheless, the presence of such state-dependent feedbacks and their relative strengths in other models remain unclear.In this study, we perform a systematic investigation of the simulated surface warming and the underlying mechanisms in the recently published DeepMIP ensemble. The DeepMIP early Eocene simulations use identical paleogeographic boundary conditions and include six models with suitable output: CESM1.2_CAM5, GFDL_CM2.1, HadCM3B_M2.1aN, IPSLCM5A2, MIROC4m and NorESM1_F. We advance previous energy balance analysis by applying the approximate partial radiative perturbation (APRP) technique to quantify the individual contributions of surface albedo, cloud and non-cloud atmospheric changes to the simulated Eocene top-of-the-atmosphere SW flux anomalies. We further compare the strength of these planetary albedo feedbacks to changes in the longwave atmospheric emissivity and meridional heat transport in the warm Eocene climate. Particular focus lies in the sensitivity of the feedback strengths to increasing global mean temperatures in experiments at a range of atmospheric CO2 concentrations between x1 to x9 preindustrial levels.Preliminary results indicate that all models that provide data for at least 3 different CO2 levels show an increase of the equilibrium climate sensitivity at higher global mean temperatures. This is associated with an increase of the overall strength of the positive SW cloud feedback with warming in those models. This nonlinear behavior seems to be related to both a reduction and optical thinning of low-level clouds, albeit with intermodel differences in the relative importance of the two mechanisms. We further show that our new APRP results can differ significantly from previous estimates based on cloud radiative forcing alone, especially in high-latitude areas with large surface albedo changes. We also find large intermodel variability and state-dependence in meridional heat transport modulated by changes in the atmospheric latent heat transport. Ongoing work focuses on the spatial patterns of the climate feedbacks and the implications for the simulated meridional temperature gradients.

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Data-model Comparison for the mid-Pliocene Warm Period

10.5194/egusphere-egu21-4802 ◽

2021 ◽

Author(s):

Julia Tindall ◽

Alan Haywood ◽

Ulrich Salzmann ◽

Aisling Dolan

Keyword(s):

Data Model ◽

Model Comparison ◽

Surface Air Temperature ◽

High Latitudes ◽

Orbital Forcing ◽

Local Site ◽

Modern Analogue ◽

Intercomparison Project ◽

Global Mean ◽

Good Agreement

Modelling results from PlioMIP2 (the Pliocene Model Intercomparison Project Phase 2) focussing on MIS KM5c; ~3.205Ma, suggest that global mean surface air temperature was 1.7 &#8211; 5.2 &#176;C higher than the preindustrial.&#160; This warming was amplified at the poles and over land.&#160; The results are in reasonable agreement with paleodata over the ocean.&#160; &#160;Over the land the situation is more complicated.&#160; Model and data are in very good agreement at lower latitudes, however at high latitudes an initial data-model comparison shows much warmer mPWP temperatures from data than from models.&#160; &#160;Here we consider possible reasons for this data-model discord at high latitudes.&#160; These include uncertainties in model boundary conditions (such as CO2 and orbital forcing), and whether there are local site-specific conditions which need to be accounted for.&#160; We also show that the seasonal cycle in mPWP temperatures at these high latitude sites has no modern analogue.&#160; This could lead to inaccuracies when comparing model derived mean annual temperatures with quantitative climatic estimates from palaeobotanical data using Nearest Living Relative methods.

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Mercury distribution in the upper troposphere and lower most stratosphere according to measurements by the IAGOS-CARIBIC observatory, 2014–2016

10.5194/acp-2017-1233 ◽

2018 ◽

Author(s):

Franz Slemr ◽

Andreas Weigelt ◽

Ralf Ebinghaus ◽

Johannes Bieser ◽

Carl A. M. Brenninkmeijer ◽

...

Keyword(s):

Large Scale ◽

Total Mercury ◽

Trace Gases ◽

Boreal Winter ◽

Signal Integration ◽

Upper Troposphere ◽

Cloud Scavenging ◽

Passenger Aircraft ◽

North And South America ◽

North And South

Abstract. Mercury was measured onboard the IAGOS-CARIBIC passenger aircraft since May 2005 until February 2016 during nearly monthly sequences of mostly four intercontinental flights from Germany to destinations in North and South America, Africa, and South and East Asia. Most of these mercury data were obtained using an internal default signal integration procedure of the Tekran instrument but since April 2014 more precise and accurate data were obtained using post-flight manual integration of the instrument raw signal. In this paper we use the latter data. Elevated upper tropospheric total mercury (TM) concentrations due to large scale biomass burning were observed in the upper troposphere (UT) at the equator and southern latitudes during the flights to Latin America and South Africa in boreal autumn (SON) and boreal winter (DJF). TM concentrations in the lowermost stratosphere (LMS) decrease with altitude above the thermal tropopause but the gradient is less steep than reported before. Seasonal variation of the vertical TM distribution in the UT and LMS is similar to that of other trace gases with surface sources and stratospheric sinks. Using speciation experiments, we show that nearly identical TM and gaseous elementary mercury (GEM) concentrations exist at and below the tropopause. Above the thermal tropopause GEM concentrations are almost always smaller than those of TM and the TM – GEM (i.e. Hg2+) difference increases up to ~ 40 % of TM at ~ 2 km and more above the thermal tropopause. Correlations with N2O as a reference tracer suggest stratospheric lifetimes of 72 ± 37 and 74 ± 27 yr for TM and GEM, respectively, comparable to the stratospheric lifetime of COS. This coincidence, combined with pieces of evidence from us and other researchers, corroborates the hypothesis that Hg2+ formed by oxidation in the stratosphere attaches to sulfate particles formed mainly by oxidation of COS and is removed with them from the stratosphere by air mass exchange, gravitational sedimentation, and cloud scavenging processes.

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Disordering of MgAl2O4 spinel from first principles

Mineralogical Magazine ◽

10.1180/002646100549210 ◽

2000 ◽

Vol 64 (2) ◽

pp. 311-317 ◽

Cited By ~ 29

Author(s):

M. C. Warren ◽

M. T. Dove ◽

S. A. T. Redfern

Keyword(s):

Free Energy ◽

Electronic Structure ◽

First Principles ◽

Large Scale ◽

Experimental Measurements ◽

Zero Temperature ◽

Macroscopic Models ◽

Tetrahedral Sites ◽

Degree Of Order ◽

Good Agreement

AbstractAt high temperature, MgAl2O4 spinel is stabilized by disorder of Mg and Al between octahedral and tetrahedral sites. This behaviour has been measured up to 1700 K in recent neutron experiments, but the extrapolation of subsequently fitted thermodynamic models is not reliable. First principles simulation of the electronic structure of such minerals can in principle accurately predict disorder, but would require unfeasibly large computing resources. We have instead parameterized on-site and short-ranged cluster potentials using a small number of electronic structure simulations at zero temperature. These potentials were then used in large-scale statistical simulations at finite temperatures to predict disordering thermodynamics beyond the range of experimental measurements. Within the temperature range of the experiment, good agreement is obtained for the degree of order. The entropy and free energy are calculated and compared to those from macroscopic models.

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The advective Brewer-Dobson circulation in the ERA5 reanalysis: variability and trends

10.5194/acp-2020-881 ◽

2020 ◽

Author(s):

Mohamadou Diallo ◽

Manfred Ern ◽

Felix Ploeger

Keyword(s):

Gravity Wave ◽

Large Scale ◽

Climate Model ◽

Southern Oscillation ◽

Natural Variability ◽

Radiation Budget ◽

Residual Circulation ◽

Quasi Biennial Oscillation ◽

Acceleration Rate ◽

Good Agreement

Abstract. The stratospheric Brewer-Dobson circulation (BDC) is an important element of climate as it determines the transport and distributions of key radiatively active atmospheric trace gases, which affect the Earth’s radiation budget and surface climate. Here, we evaluate the inter-annual variability and trends of the BDC in the ERA5 reanalysis and inter-compare with the ERA-Interim reanalysis for the 1979–2018 period. We also assess the modulation of the circulation by the Quasi-Biennial Oscillation (QBO) and the El Niño-Southern Oscillation (ENSO), and the forcings of the circulation by the planetary and gravity wave drag. A comparison of ERA5 and ERA-Interim reanalyses shows a very good agreement in the morphology of the BDC and in its structural modulations by the natural variability related to QBO and ENSO. Despite the good agreement in the spatial structure, there are substantial differences in the strength of the BDC and of the natural variability impacts on the BDC between the two reanalyses, particularly in the upper troposphere and lower stratosphere (UTLS), and in the upper stratosphere. Throughout most regions of the stratosphere, the variability and trends of the advective BDC are stronger in the ERA5 reanalysis due to stronger planetary and gravity wave forcings, except in the UTLS below 20 km where the tropical upwelling is about 40 % weaker due to a weaker gravity wave forcings at the equatorial flank of the subtropical jet. In the extra-tropics, the large-scale downwelling is stronger in ERA5 than in ERA-Interim linked to significant differences in planetary and gravity wave forcings. Analysis of the BDC trend shows a global acceleration of the annual mean residual circulation with an acceleration rate of about 1.5 % per decade at 70 hPa due to the long-term intensification in gravity and planetary wave breaking, consistent with observed and future climate model predicted BDC changes.

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Ethane, ethyne and carbon monoxide concentrations in the upper troposphere and lower stratosphere from ACE and GEOS-Chem: a comparison study

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-13099-2011 ◽

2011 ◽

Vol 11 (4) ◽

pp. 13099-13139 ◽

Cited By ~ 1

Author(s):

G. González Abad ◽

N. D. C. Allen ◽

P. F. Bernath ◽

C. D. Boone ◽

S. D. McLeod ◽

...

Keyword(s):

Carbon Monoxide ◽

Atmospheric Chemistry ◽

Transport Model ◽

Chemical Mechanism ◽

Chemical Transport Model ◽

Spectrometer Data ◽

Chemistry Experiment ◽

Global Mean ◽

Tropospheric Concentrations ◽

Good Agreement

Abstract. Near global upper tropospheric concentrations of carbon monoxide (CO), ethane (C2H6) and ethyne (C2H2) from ACE (Atmospheric Chemistry Experiment) Fourier transform spectrometer on board the Canadian satellite SCISAT-1 are presented and compared with the output from the Chemical Transport Model (CTM) GEOS-Chem. The retrievals of ethane and ethyne from ACE have been improved for this paper by using new sets of microwindows compared with those for previous versions of ACE data. With the improved ethyne retrieval we have been able to produce a near global upper tropospheric distribution of C2H2 from space. Carbon monoxide, ethane and ethyne concentrations retrieved using ACE spectra show the expected seasonality linked to variations in the anthropogenic emissions and destruction rates as well as seasonal biomass burning activity. The GEOS-Chem model was run using the dicarbonyl chemistry suite, an extended chemical mechanism in which ethyne is treated explicitly. Seasonal cycles observed from satellite data are well reproduced by the model output, however the simulated CO concentrations are found to be systematically biased low over the Northern Hemisphere. An average negative global mean bias of 12% and 7% of the model relative to the satellite observations has been found for CO and C2H6 respectively and a positive global mean bias of 1% has been found for C2H2. ACE data are compared for validation purposes with MkIV spectrometer data and Global Tropospheric Experiment (GTE) TRACE-A campaign data showing good agreement with all of them.

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