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.

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 Monitoring of the evolution of H2O vapor in the stratosphere of Jupiter over an 18-yr period with the Odin space telescope

2020 ◽  
Vol 641 ◽  
pp. A140
Author(s):  
◽  
B. Benmahi ◽  
T. Cavalié ◽  
M. Dobrijevic ◽  
N. Biver ◽  
...  
Keyword(s):  
Pressure Range ◽  
Temporal Evolution ◽  
Line Emission ◽  
Eddy Diffusion ◽  
Space Telescope ◽  
1D Modeling ◽  
The Impact ◽  
Vertical Eddy ◽  
Vertical Eddy Diffusion

Context. The comet Shoemaker-Levy 9 impacted Jupiter in July 1994, leaving its stratosphere with several new species, with water vapor (H2O) among them. Aims. With the aid of a photochemical model, H2O can be used as a dynamical tracer in the Jovian stratosphere. In this paper, we aim to constrain the vertical eddy diffusion (Kzz) at levels where H2O is present. Methods. We monitored the H2O disk-averaged emission at 556.936 GHz with the space telescope between 2002 and 2019, covering nearly two decades. We analyzed the data with a combination of 1D photochemical and radiative transfer models to constrain the vertical eddy diffusion in the stratosphere of Jupiter. Results. Odin observations show us that the emission of H2O has an almost linear decrease of about 40% between 2002 and 2019. We can only reproduce our time series if we increase the magnitude of Kzz in the pressure range where H2O diffuses downward from 2002 to 2019, that is, from ~0.2 mbar to ~5 mbar. However, this modified Kzz is incompatible with hydrocarbon observations. We find that even if an allowance is made for the initially large abundances of H2O and CO at the impact latitudes, the photochemical conversion of H2O to CO2 is not sufficient to explain the progressive decline of the H2O line emission, which is suggestive of additional loss mechanisms. Conclusions. The Kzz we derived from the Odin observations of H2O can only be viewed as an upper limit in the ~0.2 mbar to ~5 mbar pressure range. The incompatibility between the interpretations made from H2O and hydrocarbon observations probably results from 1D modeling limitations. Meridional variability of H2O, most probably at auroral latitudes, would need to be assessed and compared with that of hydrocarbons to quantify the role of auroral chemistry in the temporal evolution of the H2O abundance since the SL9 impacts. Modeling the temporal evolution of SL9 species with a 2D model would naturally be the next step in this area of study.

scholarly journals The urban canopy meteorological forcing and its impact on ozone and PM<sub>2.5</sub>: role of the vertical turbulent transport

2019 ◽  
Author(s):  
Peter Huszar ◽  
Jan Karlický ◽  
Jana Ďoubalová ◽  
Kateřina Šindelářová ◽  
Tereza Nováková ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Turbulent Transport ◽  
Urban Canopy ◽  
Eddy Diffusion ◽  
Meteorological Forcing ◽  
Eddy Diffusion Coefficient ◽  
The Impact ◽  
Vertical Eddy ◽  
Vertical Eddy Diffusion

Abstract. Urban surfaces due to specific geometry and physical properties bring modified transport of momentum, moisture and heat between them and the air above and perturb the radiative, thermal and mechanical balance resulting in changed meteorological condition (e.g. the UHI – urban heat island phenomenon). From an air quality perspective, many studies argue that one of the most important changes is the increased turbulence enhancing vertical mixing of pollutants above cities, although increased temperatures and wind stilling play an important role too. Using the regional climate model RegCM4 coupled to chemistry transport model CAMx over central Europe we study how urban surfaces affect the vertical turbulent transport of selected pollutants through modifications of the vertical eddy diffusion coefficient (Kv). For the period of 2007–2011 and over central Europe numerous experiments are carried out in order to evaluate the impact of six different methods for Kv calculation on the surface concentrations as well as vertical profiles of ozone and PM2.5 over selected cities (Prague and Berlin). Three cascading domains are set up at 27 km, 9 km and 3 km resolutions, which further enables to analyze the sensitivity to model grid resolution. Numerous experiments are performed where urban surfaces are considered or replaced by rural ones in order to isolate the urban canopy meteorological forcing. Apart from the well pronounced and expected impact on temperature (increases up to 2 °C) and wind (decreases up to −2 m s−1) there is strong impact on vertical eddy diffusion in all of the six Kv methods. The Kv enhancement ranges from a few 0.5 up to 30 m2 s−1 at the surface and from 1 to 100 m2 s−1 at higher levels depending on the methods, while the turbulent kinetic energy (TKE) based methods produce the largest impact. The range of impact on the vertical eddy diffusion coefficient propagates to a range of ozone (O3) increase of 0.4 to 4 ppbv near the surface in both summer and winter, while at higher levels, decreases occur from a few −0.4 ppbv to as much as −2 ppbv. In case of PM2.5, enhanced vertical eddy diffusion leads to decrease of near surface concentrations ranging from almost zero to −1 μg m−3 in summer and to decreases from −0.5 to −2 μg m−3 in winter. Comparing these results to the total-impact, i.e. to the impact of all considered urban meteorological changes, we can conclude that much of the overall urban meteorological forcing is explained by acting of the enhanced vertical eddy diffusion, which counterweights the opposing effects of other components of this forcing (temperature, humidity and wind impact). The results further show that this conclusion holds regardless of the resolution chosen and in both the warm and cold part of the year. Our study demonstrates the dominant role of turbulent transport of pollutants above urban areas and stresses the need for further investigation how variation of urban land-use influence the pollutant transport from the urban canopy.

scholarly journals Estimates of eddy turbulence consistent with seasonal variations of atomic oxygen and its possible role in the seasonal cycle of mesopause temperature

2010 ◽  
Vol 28 (11) ◽  
pp. 2103-2110 ◽  
Author(s):  
M. N. Vlasov ◽  
M. C. Kelley
Keyword(s):  
Diffusion Coefficient ◽  
Gravity Waves ◽  
Seasonal Variations ◽  
Atomic Oxygen ◽  
Lower Thermosphere ◽  
Eddy Diffusion ◽  
Downward Motion ◽  
Adiabatic Cooling ◽  
Eddy Diffusion Coefficient ◽  
The Impact

Abstract. According to current understanding, adiabatic cooling and heating induced by the meridional circulation driven by gravity waves is the major process for the cold summer and warm winter polar upper mesosphere. However, our calculations show that the upward/downward motion needed for adiabatic cooling/heating of the summer/winter polar mesopause simultaneously induces a seasonal variation in both the O maximum density and the altitude of the [O] peak that is opposite to the observed variables generalized by the MSISE-90 model. It is usually accepted that eddy turbulence can produce the [O] seasonal variations. Using this approach, we can infer the eddy diffusion coefficient for the different seasons. Taking these results and experimental data on the eddy diffusion coefficient, we consider in detail and estimate the heating and cooling caused by eddy turbulence in the summer and winter polar upper mesosphere. The seasonal variations of these processes are similar to the seasonal variations of the temperature and mesopause. These results lead to the conclusion that heating/cooling by eddy turbulence is an important component in the energy budget and that adiabatic cooling/heating induced by upward/downward motion cannot dominate in the mesopause region. Our study shows that the impact of the dynamic process, induced by gravity waves, on [O] distributions must be included in models of thermal balance in the upper mesosphere and lower thermosphere (MLT) for a consistent description because (a) the [O] distribution is very sensitive to dynamic processes, and (b) atomic oxygen plays a very important role in chemical heating and infrared cooling in the MLT. To our knowledge, this is the first attempt to consider this aspect of the problem.

scholarly journals Cloud impacts on photochemistry: a new climatology of photolysis rates from the Atmospheric Tomography mission

2018 ◽  
Author(s):  
Samuel R. Hall ◽  
Kirk Ullmann ◽  
Michael J. Prather ◽  
Clare M. Flynn ◽  
Lee T. Murray ◽  
...  
Keyword(s):  
Tropospheric Chemistry ◽  
Transport Models ◽  
Clear Sky ◽  
Photolysis Rates ◽  
Four Seasons ◽  
The Pacific ◽  
Greenhouse Effects ◽  
The Impact

Abstract. Measurements from actinic flux spectroradiometers on board the NASA DC-8 during the Atmospheric Tomography (ATom) mission provide an extensive set of statistics on how clouds alter photolysis rates (J-values) throughout the remote Pacific and Atlantic Ocean basins. ATom made profiling circumnavigations of the troposphere over four seasons during 2016–2018. J-values are a primary chemical control over tropospheric ozone and methane abundances and their greenhouse effects. Clouds have been recognized for more than three decades as being an important factor in tropospheric chemistry. The ATom climatology of J-values is a unique test of how the chemistry models treat clouds. This work focuses on measurements over the Pacific during the first deployment (ATom-1) in August 2016. Nine global chemistry–climate or –transport models provide J-values for the domains measured in ATom-1. We compare mean profiles over a range of cloudy and clear conditions; but, more importantly, we build a statistical picture of the impact of clouds on J-values through the distribution of the ratio of J-cloudy to J-clear. In detail, the models show largely disparate patterns. When compared with measurements, there is some limited, broad agreement. Models here have resolutions of 50–200 km and thus reduce the occurrence of clear sky when averaging over grid cells. In situ measurements also average the scattered sunlight, but only out to scales of 10 s of km. A primary uncertainty remains in the role of clouds in chemistry, in particular, how models average over cloud fields, and how such averages can simulate measurements.

scholarly journals Variability of NO<sub>x</sub> in the polar middle atmosphere from October 2003 to March 2004: vertical transport versus local production by energetic particles

2014 ◽  
Vol 14 (1) ◽  
pp. 1-29 ◽  
Author(s):  
M. Sinnhuber ◽  
B. Funke ◽  
T. von Clarmann ◽  
M. Lopez-Puertas ◽  
G. P. Stiller
Keyword(s):  
Geomagnetic Activity ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Solar Proton ◽  
Electron Precipitation ◽  
Proton Event ◽  
Local Production ◽  
Altitude Range ◽  
Order Of Magnitude ◽  
The Impact

Abstract. We use NO, NO2 and CO from MIPAS/ENVISAT to investigate the impact of energetic particle precipitation onto the NOx budget from the stratosphere to the lower mesosphere in the period from October 2003 to March 2004, a time of high solar and geomagnetic activity. We find that in the winter hemisphere the indirect effect of auroral electron precipitation due to downwelling of upper mesospheric/lower thermospheric air into the stratosphere prevails. Its effect exceeds even the direct impact of the very large solar proton event in October/November 2003 by nearly one order of magnitude. Correlations of NOx and CO show that the unprecedented high NOx values observed in the Northern Hemisphere lower mesosphere and upper stratosphere in late January and early February are fully consistent with transport from the upper mesosphere/lower thermosphere and subsequent mixing at lower altitudes; an additional source of NOx due to local production by precipitating electrons at altitudes below 70 km as discussed in previous publications appears unlikely. In the polar summer Southern Hemisphere, we observed an enhanced variability of NO and NO2 on days with enhanced geomagnetic activity but they seem to indicate enhanced instrument noise rather than a direct increase due to electron precipitation. A direct effect of electron precipitation onto NOx can not be ruled out, but if any, it is lower than 3 ppb in the altitude range 40–56 km and lower than 6 ppb in the altitude range 56–70 km.

The mid- to high-latitude migrating semidiurnal tide: Results from a mechanistic tide model and SuperDARN observations

2021 ◽  
Author(s):  
Willem van Caspel ◽  
Patrick Espy
Keyword(s):  
High Latitude ◽  
Seasonal Variations ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Surface Friction ◽  
Equation Model ◽  
Tidal Forcing ◽  
Hourly Temperature ◽  
The Impact

&lt;p&gt;Simulations of the solar thermal migrating semidiurnal (SW2) tide in the mesosphere-lower-thermosphere (MLT) are compared against meteor wind observations from a longitudinal chain of high-latitude SuperDARN radars. The simulations span two full years and are performed using a 3D non-linear mechanistic primitive equation model. In our model, the background Middle Atmosphere is specified to daily mean zonal mean winds and temperatures from the Navy Global Environmental Model - High Altitude (NAVGEM-HA) meteorological analysis system. Thermal tides are forced from the surface to the thermosphere using 3-hourly temperature tendency fields from the Specified Dynamics Whole Atmosphere Community Climate Model With Thermosphere and Ionosphere Extension (SD-WACCMX). Our model accurately reproduces the observed seasonal cycle in the SW2 amplitude and phase, with the exception of summertime amplitudes being overestimated. Sensitivity studies reveal the impact of the seasonal variations in the background atmosphere and tidal forcing. The tropospheric forcing response is found to be highly sensitive to the seasonal variations in the background atmosphere, leading to strong amplification during the summer and mid-winter months. In contrast, the stratospheric forcing response is found to be much less sensitive to the background atmosphere, while being similar in magnitude to the tropospheric forcing response. Based on simulations using a zero-wind atmosphere, the impact of seasonal variations in the tidal forcing is found to be very small for both the tropospheric and stratospheric forcing response. Furthermore, the inclusion of an idealized surface friction profile is found to delay the phase of the tropospheric forcing response, which can strongly impact the simulated tide at MLT altitudes. Both the tropospheric forcing response and the surface friction specification are identified as being possible factors contributing to summertime amplitudes being overestimated.&lt;/p&gt;

scholarly journals Stratospheric warming influence on the mesosphere/lower thermosphere as seen by the extended CMAM

2014 ◽  
Vol 32 (6) ◽  
pp. 589-608 ◽  
Author(s):  
M. G. Shepherd ◽  
S. R. Beagley ◽  
V. I. Fomichev
Keyword(s):  
Atmospheric Chemistry ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Lower Atmosphere ◽  
Fourier Transform Spectrometer ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
New Information ◽  
The Impact ◽  
Chemistry Experiment

Abstract. The response of the upper mesosphere/lower thermosphere region to major sudden stratospheric warming (SSW) is examined employing temperature, winds, NOX and CO constituents from the extended Canadian Middle Atmosphere Model (CMAM) with continuous incremental nudging below 10 hPa (~ 30 km). The model results considered cover high latitudes (60–85° N) from 10 to 150 km height for the December–March period of 2003/2004, 2005/2006 and 2008/2009, when some of the strongest SSWs in recent years were observed. NOX and CO are used as proxies for examining transport. Comparisons with ACE-FTS (Atmospheric Chemistry Experiment–Fourier Transform Spectrometer) satellite observations show that the model represents well the dynamics of the upper mesosphere/lower thermosphere region, the coupling of the stratosphere–mesosphere, and the NOX and CO transport. New information is obtained on the upper mesosphere/lower thermosphere up to 150 km showing that the NOX volume mixing ratio in the 2003/2004 winter was very perturbed indicating transport from the lower atmosphere and intense mixing with large NOX influx from the thermosphere compared to 2006 and 2009. These results, together with those from other models and observations, clearly show the impact of stratospheric warmings on the thermosphere.

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 Variability of NO<sub>x</sub> in the polar middle atmosphere from October 2003 to March 2004: vertical transport vs. local production by energetic particles

2014 ◽  
Vol 14 (14) ◽  
pp. 7681-7692 ◽  
Author(s):  
M. Sinnhuber ◽  
B. Funke ◽  
T. von Clarmann ◽  
M. Lopez-Puertas ◽  
G. P. Stiller ◽  
...  
Keyword(s):  
Geomagnetic Activity ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Solar Proton ◽  
Electron Precipitation ◽  
Proton Event ◽  
Local Production ◽  
Altitude Range ◽  
Order Of Magnitude ◽  
The Impact

Abstract. We use NO, NO2 and CO from MIPAS/ENVISAT to investigate the impact of energetic particle precipitation onto the NOx budget from the stratosphere to the lower mesosphere in the period from October 2003 to March 2004, a time of high solar and geomagnetic activity. We find that in the winter hemisphere the indirect effect of auroral electron precipitation due to downwelling of upper mesospheric/lower thermospheric air into the stratosphere prevails. Its effect exceeds even the direct impact of the very large solar proton event in October/November 2003 by nearly 1 order of magnitude. Correlations of NOx and CO show that the unprecedented high NOx values observed in the Northern Hemisphere lower mesosphere and upper stratosphere in late January and early February are fully consistent with transport from the upper mesosphere/lower thermosphere and subsequent mixing at lower altitudes. In the polar summer Southern Hemisphere, we observed an enhanced variability of NO and NO2 on days with enhanced geomagnetic activity, but this seems to indicate enhanced instrument noise rather than a direct increase due to electron precipitation. A direct effect of electron precipitation onto NOx can not be ruled out, but, if any, it is lower than 3 ppbv in the altitude range 40–56 km and lower than 6 ppbv in the altitude range 56–64 km. An additional significant source of NOx due to local production by precipitating electrons below 70 km exceeding several parts per billion as discussed in previous publications appears unlikely.

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