The Role of the Middle Atmosphere in Simulations of the Troposphere during Northern Hemisphere Winter: Differences between High- and Low-Top Models

2010 ◽  
Vol 67 (9) ◽  
pp. 3048-3064 ◽  
Author(s):  
Fabrizio Sassi ◽  
R. R. Garcia ◽  
D. Marsh ◽  
K. W. Hoppel
Keyword(s):  
Climate Models ◽  
Middle Atmosphere ◽  
State Of The Art ◽  
Lower Thermosphere ◽  
Numerical Algorithms ◽  
Conventional Model ◽  
Downward Propagation ◽  
Hemisphere Winter ◽  
Mean State

Abstract This paper compares present-day simulations made with two state-of-the-art climate models: a conventional model specifically designed to represent the tropospheric climate, which has a poorly resolved middle atmosphere, and a configuration that is built on the same physics and numerical algorithms but represents realistically the middle atmosphere and lower thermosphere. The atmospheric behavior is found to be different between the two model configurations, and it is shown that the differences in the two simulations can be attributed to differences in the behavior of the zonal mean state of the stratosphere, where reflection of quasi-stationary resolved planetary waves from the lid of the low-top model is prominent; the more realistic physics in the high-top model is not relevant. It is also shown that downward propagation of zonal wind anomalies during weak stratospheric vortex events is substantially different in the two model configurations. These findings extend earlier results that a poorly resolved stratosphere can influence simulations throughout the troposphere.

scholarly journals Assessing stratospheric transport in the CMAM30 simulations using ACE-FTS measurements

2017 ◽  
Author(s):  
Felicia Kolonjari ◽  
David A. Plummer ◽  
Kaley A. Walker ◽  
Chris D. Boone ◽  
James W. Elkins ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Climate Models ◽  
Middle Atmosphere ◽  
Polar Vortex ◽  
Sampling Technique ◽  
Dynamics Simulation ◽  
Global Circulation Models ◽  
Extratropical Tropopause ◽  
Hemisphere Winter ◽  
June July

Abstract. Stratospheric transport in global circulation models and chemistry-climate models is an important component in simulating the recovery of the ozone layer as well as changes in the climate system. The Brewer-Dobson circulation is not well constrained by observations and further investigation is required to resolve uncertainties related to the mechanisms driving the circulation. This study has assessed the specified dynamics mode of the Canadian Middle Atmosphere Model (CMAM30) by comparing to the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) profile measurements of CFC-11 (CCl3F), CFC-12 (CCl2F2), and N2O. In the CMAM30 specified dynamics simulation, the meteorological fields are nudged using the ERA-Interim Reanalysis and a specified tracer was used for each species, with hemispherically-defined surface measurements used as the boundary condition. A comprehensive sampling technique along the line-of-sight of the ACE-FTS measurements has been employed to allow for direct comparisons between the simulated and measured tracer concentrations. The model consistently overpredicts tracer concentrations in the lower stratosphere, particularly in the Northern Hemisphere winter and spring seasons. The three mixing barriers investigated, including the polar vortex, the extratropical tropopause, and the tropical pipe, show that there are significant inconsistencies between the measurements and the simulations. In particular, the CMAM30 simulation exhibits too little isentropic mixing in the June-July-August season.

ARISE - Atmospheric Dynamics Research InfraStructure in Europe

2021 ◽  
Author(s):  
Patrick Hupe ◽  
Keyword(s):  
Climate Models ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Volcanic Eruptions ◽  
Atmospheric Dynamics ◽  
Research Infrastructure ◽  
Atmospheric Composition ◽  
The European Union ◽  
Horizon 2020 ◽  
Ctbt Verification

<p>The Atmospheric dynamics Research InfraStructure in Europe (ARISE) project has integrated different meteorological and geophysical station networks and technologies providing observations from the ground to the lower thermosphere. A particular emphasis is on improving observations in the middle atmosphere, as this is a crucial region affecting tropospheric weather and climate. Besides supporting innovative prototypes of mobile lidars and microwave radiometers, ARISE utilized the global infrasound network developed for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) verification, the lidar Network for the Detection of Atmospheric Composition Change (NDACC), meteor radars, wind radiometers, ionospheric sounders and satellites.</p> <p>This presentation highlights the objectives and results as well as perspectives of the first two project phases – one within the European Union’s 7th Framework Programme and the second within the Horizon 2020 programme. ARISE has facilitated multi-instrument stations and collocated measurement campaigns at different latitudes in Europe, including the observatories ALOMAR in northern Norway, OHP in southern France and Maïdo on Reunion Island (France), as well as the infrasound station in southern Germany. One ARISE study, for instance, analyzed different ground-based and space-borne observation technologies, revealing systematic biases for temperature and wind in both analysis and reanalysis models. Such biases are critical to the CTBT verification when validating infrasound signal detections by propagation modelling. Also, the potential of infrasound to be assimilated in weather or climate models was proposed, as infrasound can be used to probe winds and cross-wind effects in the middle atmosphere. Meanwhile, offline assimilation tests relying on infrasound data from ground-truth explosion events and wind data of ECMWF’s ERA5 model have been conducted. Overall, the interest of ARISE is to provide atmospheric data products and services for both scientific and civilian-security applications, including the monitoring of extreme events that have an atmospheric signature, such as meteors, thunderstorms or volcanic eruptions. For early warnings on volcanic eruptions, the Volcano Information System (VIS) was proposed as an ARISE product in cooperation with the CTBT organization and the Toulouse Volcanic Ash Advisory Center (VAAC).</p>

scholarly journals First multi-year occultation observations of CO<sub>2</sub> in the MLT by ACE satellite: observations and analysis using the extended CMAM

2010 ◽  
Vol 10 (3) ◽  
pp. 1133-1153 ◽  
Author(s):  
S. R. Beagley ◽  
C. D. Boone ◽  
V. I. Fomichev ◽  
J. J. Jin ◽  
K. Semeniuk ◽  
...  
Keyword(s):  
Middle Atmosphere ◽  
Formation Rate ◽  
Lower Thermosphere ◽  
Eddy Diffusion ◽  
Photolysis Rates ◽  
Candidate Species ◽  
Rocket Measurements ◽  
The Impact ◽  
Co Observations

Abstract. This paper presents the first global set of observations of CO2 in the mesosphere and lower thermosphere (MLT) obtained by the ACE-FTS instrument on SCISAT-I, a small Canadian satellite launched in 2003. The observations use the solar occultation technique and document the fall-off in the mixing ratio of CO2 in the MLT region. The beginning of the fall-off of the CO2, or "knee" occurs at about 78 km and lies higher than in the CRISTA-1 measurements (~70 km) but lower than in the SABER 1.06 (~80 km) and much lower than in rocket measurements. We also present the measurements of CO obtained concurrently which provide important constraints for analysis. We have compared the ACE measurements with simulations of the CO2 and CO distributions in the vertically extended version of the Canadian Middle Atmosphere Model (CMAM). Applying standard chemistry we find that we cannot get agreement between the model and ACE CO2 observations although the CO observations are adequately reproduced. There appears to be about a 10 km offset compared to the observed ACE CO2, with the model "knee" occurring too high. In analyzing the disagreement, we have investigated the variation of several parameters of interest (photolysis rates, formation rate for CO2, and the impact of uncertainty in turbulent eddy diffusion) in order to explore parameter space for this problem. Our conclusions are that there must be a loss process for CO2, about 2–4~times faster than photolysis that will sequester the carbon in some form other than CO and we have speculated on the role of meteoritic dust as a possible candidate. In addition, from this study we have highlighted a possible important role for unresolved vertical eddy diffusion in 3-D models in determining the distribution of candidate species in the mesosphere which requires further study.

scholarly journals Numerical Bifurcation Methods applied to Climate Models: Analysis beyond Simulation

2019 ◽  
Author(s):  
Henk A. Dijkstra
Keyword(s):  
Degrees Of Freedom ◽  
Climate Models ◽  
State Of The Art ◽  
Climate System ◽  
Special Issue ◽  
Personal View ◽  
Spatially Extended ◽  
System Variability ◽  
Numerical Bifurcation

Abstract. In this special issue contribution, I provide a personal view on the role of bifurcation analysis of climate models in the development of a theory of climate system variability. The state-of-the-art of the methodology is shortly outlined and the main part of the paper deals with examples of what has been done and what has been learned. In addressing these issues, I will discuss the role of a hierarchy of climate models, concentrate on results for spatially extended (stochastic) models (having many degrees of freedom) and evaluate the importance of these results for a theory of climate system variability.

Middle atmosphere ionization from auroral particle precipitation as observed by the SSUSI satellite instruments

2020 ◽  
Author(s):  
Stefan Bender ◽  
Patrick Espy ◽  
Larry Paxton
Keyword(s):  
Climate Models ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Auroral Zone ◽  
Polar Regions ◽  
Electron Densities ◽  
Current Standard ◽  
Initial Comparison ◽  
Eiscat Radar ◽  
Satellite Instruments

&lt;p&gt;Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. Climate models usually parametrize this ionization and the related changes in chemistry based on satellite particle measurements. Precise measurements of the particle and energy influx into the upper atmosphere are difficult because they vary substantially in location and time. Widely used particle data are derived from the POES and GOES satellite measurements which provide electron and proton spectra.&lt;/p&gt;&lt;p&gt;We present electron energy and flux measurements from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) satellite instruments on board the Defense Meteorological Satellite Program (DMSP) satellites. This formation of now four satellites observes the auroral zone in the UV from which electron energies and fluxes are inferred in the range from 2 keV to 20 keV. We use these observed electron energies and fluxes to calculate ionization rates and electron densities in the upper mesosphere and lower thermosphere (&amp;#8776; 70&amp;#8211;200 km). We present an initial comparison of these rates to other models and compare the electron densities to those measured by the EISCAT radar. This comparison shows that with the current standard parametrizations, the SSUSI inferred auroral (90&amp;#8211;120 km) electron densities are larger than the ground-based measured ones by a factor of 2&amp;#8211;5. It is still under investigation if this difference is due to collocation (in space and time) and EISCAT mode characteristics or caused by incompletely modelling the ionization and recombination in that energy range.&lt;/p&gt;

scholarly journals Intercomparison of Middle Atmospheric Meteorological Analyses for the Northern Hemisphere Winter 2009–2010

2021 ◽  
Author(s):  
John P. McCormack ◽  
V. Lynn Harvey ◽  
Nicholas Pedatella ◽  
Dai Koshin ◽  
Kaoru Sato ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Planetary Waves ◽  
Wave Number ◽  
Physical Mechanisms ◽  
Wide Range ◽  
Zonal Wave Number ◽  
Analysis System ◽  
Hemisphere Winter

Abstract. Detailed meteorological analyses based on observations extending through the middle atmosphere (~15–100 km altitude) can provide key information to whole atmosphere modelling systems regarding the physical mechanisms linking day-to-day changes in ionospheric electron density to meteorological variability near the Earth’s surface. It is currently unclear how middle atmosphere analyses produced by various research groups consistently represent the wide range of proposed linking mechanisms involving migrating and non-migrating tides, planetary waves, gravity waves, and their impact on the zonal mean state in the mesosphere and lower thermosphere (MLT) region. To begin to address this issue, we present the first intercomparison among four such analyses, JAGUAR-DAS, MERRA-2, NAVGEM-HA, and WACCMX+DART, focusing on the Northern Hemisphere (NH) 2009–2010 winter that includes a major stratospheric sudden warming (SSW) in late January. This intercomparison examines the altitude, latitude, and time dependences of zonal mean zonal winds and temperatures among these four analyses over the 1 December 2009–31 March 2010 period, as well as latitude and altitude dependences of monthly mean amplitudes of the diurnal and semidiurnal migrating solar tides, the eastward propagating diurnal zonal wave number 3 nonmigrating tide, and traveling planetary waves associated with the quasi-5 day and quasi-2-day Rossby modes. Our results show generally good agreement among the four analyses up to the stratopause (~50 km altitude). Large discrepancies begin to emerge in the MLT owing to (1) differences in the types of satellite data assimilated by each system and (2) differences in the details of the global atmospheric models used by each analysis system. The results of this intercomparison provide initial estimates of uncertainty in analyses commonly used to constrain middle atmospheric meteorological variability in whole atmosphere model simulations.

scholarly journals Numerical bifurcation methods applied to climate models: analysis beyond simulation

2019 ◽  
Vol 26 (4) ◽  
pp. 359-369 ◽  
Author(s):  
Henk A. Dijkstra
Keyword(s):  
Degrees Of Freedom ◽  
Climate Models ◽  
State Of The Art ◽  
Climate System ◽  
Special Issue ◽  
Personal View ◽  
Spatially Extended ◽  
System Variability ◽  
Numerical Bifurcation

Abstract. In this special issue contribution, I provide a personal view on the role of bifurcation analysis of climate models in the development of a theory of climate system variability. The state of the art of the methodology is shortly outlined, and the main part of the paper deals with examples of what has been done and what has been learned. In addressing these issues, I will discuss the role of a hierarchy of climate models, concentrate on results for spatially extended (stochastic) models (having many degrees of freedom) and evaluate the importance of these results for a theory of climate system variability.

scholarly journals Intercomparison of middle atmospheric meteorological analyses for the Northern Hemisphere winter 2009–2010

2021 ◽  
Vol 21 (23) ◽  
pp. 17577-17605
Author(s):  
John P. McCormack ◽  
V. Lynn Harvey ◽  
Cora E. Randall ◽  
Nicholas Pedatella ◽  
Dai Koshin ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Wave Number ◽  
Physical Mechanisms ◽  
Modeling Systems ◽  
Zonal Wave Number ◽  
Analysis System ◽  
Hemisphere Winter ◽  
Wave Induced

Abstract. Detailed meteorological analyses based on observations extending through the middle atmosphere (∼ 15 to 100 km altitude) can provide key information to whole atmosphere modeling systems regarding the physical mechanisms linking day-to-day changes in ionospheric electron density to meteorological variability near the Earth's surface. However, the extent to which independent middle atmosphere analyses differ in their representation of wave-induced coupling to the ionosphere is unclear. To begin to address this issue, we present the first intercomparison among four such analyses, JAGUAR-DAS, MERRA-2, NAVGEM-HA, and WACCMX+DART, focusing on the Northern Hemisphere (NH) 2009–2010 winter, which includes a major sudden stratospheric warming (SSW). This intercomparison examines the altitude, latitude, and time dependences of zonal mean zonal winds and temperatures among these four analyses over the 1 December 2009 to 31 March 2010 period, as well as latitude and altitude dependences of monthly mean amplitudes of the diurnal and semidiurnal migrating solar tides, the eastward-propagating diurnal zonal wave number 3 nonmigrating tide, and traveling planetary waves associated with the quasi-5 d and quasi-2 d Rossby modes. Our results show generally good agreement among the four analyses up to the stratopause (∼ 50 km altitude). Large discrepancies begin to emerge in the mesosphere and lower thermosphere owing to (1) differences in the types of satellite data assimilated by each system and (2) differences in the details of the global atmospheric models used by each analysis system. The results of this intercomparison provide initial estimates of uncertainty in analyses commonly used to constrain middle atmospheric meteorological variability in whole atmosphere model simulations.

scholarly journals First multi-year occultation observations of CO<sub>2</sub> in the MLT by ACE satellite: observations and analysis using the extended CMAM

2009 ◽  
Vol 9 (3) ◽  
pp. 11551-11587
Author(s):  
S. R. Beagley ◽  
C. D. Boone ◽  
V. I. Fomichev ◽  
J. J. Jin ◽  
K. Semeniuk ◽  
...  
Keyword(s):  
Middle Atmosphere ◽  
Formation Rate ◽  
Lower Thermosphere ◽  
Eddy Diffusion ◽  
Photolysis Rates ◽  
Candidate Species ◽  
Rocket Measurements ◽  
The Impact ◽  
Co Observations

Abstract. This paper presents the first multi-year global set of observations of CO2 in the mesosphere and lower thermosphere (MLT) obtained by the ACE-FTS instrument on SCISAT-I, a small Canadian satellite launched in 2003. The observations use the solar occultation technique and document the fall-off in the mixing ratio of CO2 in the MLT region. The beginning of the fall-off of the CO2, or "knee" occurs at about 78 km and lies higher than in the CRISTA measurements (~70 km) but lower than in the SABER 1.06 (~82 km) and much lower than in rocket measurements. We also present the measurements of CO obtained concurrently which provide important constraints for analysis. We have compared the ACE measurements with simulations of the CO2 and CO distributions in the vertically extended version of the Canadian Middle Atmosphere Model (CMAM). Applying standard chemistry we find that we cannot get agreement between the model and ACE CO2 observations although the CO observations are adequately reproduced. There appears to be about a 10 km offset compared to the observed ACE CO2, with the model knee occurring too high. In analysing the disagreement, we have investigated the variation of several parameters of interest, photolysis rates, formation rate for CO2, and the impact of uncertainty in eddy diffusion, in order to explore parameter space for this problem. Our conclusions are that there must be a loss process for CO2, about 2–4 times faster than photolysis that will sequester the carbon in some form other than CO and we have speculated on the role of meteoritic dust as a possible candidate. In addition, from this study we have highlighted a possible important role for vertical eddy diffusion in 3-D models in determining the distribution of candidate species in the mesosphere which requires further study.

Coinage and the Tributary Mode of Production

2018 ◽  
Author(s):  
Eduardo Manzano Moreno
Keyword(s):  
Roman Empire ◽  
Middle Ages ◽  
Social Role ◽  
State Of The Art ◽  
Early Middle Ages ◽  
The Social ◽  
Simple Question ◽  
Mode Of Production

This chapter addresses a very simple question: is it possible to frame coinage in the Early Middle Ages? The answer will be certainly yes, but will also acknowledge that we lack considerable amounts of relevant data potentially available through state-of-the-art methodologies. One problem is, though, that many times we do not really know the relevant questions we can pose on coins; another is that we still have not figured out the social role of coinage in the aftermath of the Roman Empire. This chapter shows a number of things that could only be known thanks to the analysis of coins. And as its title suggests it will also include some reflections on greed and generosity.

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