scholarly journals Persistence and photochemical decay of springtime total ozone anomalies in the Canadian Middle Atmosphere Model

2006 ◽  
Vol 6 (2) ◽  
pp. 3403-3417 ◽  
Author(s):  
S. Tegtmeier ◽  
T. G. Shepherd
Keyword(s):  
Seasonal Cycle ◽  
Total Ozone ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Model Performance ◽  
Correlation Coefficients ◽  
Polar Regions ◽  
External Forcing ◽  
Atmosphere Model ◽  
Very High

Abstract. The persistence and decay of springtime total ozone anomalies over the entire extratropics (midlatitudes plus polar regions) is analysed using results from the Canadian Middle Atmosphere Model (CMAM), a comprehensive chemistry-climate model. As in the observations, interannual anomalies established through winter and spring persist with very high correlation coefficients (above 0.8) through summer until early autumn, while decaying in amplitude as a result of photochemical relaxation in the quiescent summertime stratosphere. The persistence and decay of the ozone anomalies in CMAM agrees extremely well with observations, even in the southern hemisphere when the model is run without heterogeneous chemistry (in which case there is no ozone hole and the seasonal cycle of ozone is quite different from observations), and even in the northern hemisphere where this version of CMAM (run with fixed external forcing) strongly underestimates the observed interannual variability. This shows that ozone anomaly persistence and decay does not depend on how the springtime anomalies are created or on their magnitude, but reflects the transport and photochemical decay in the model. It is thus a robust diagnostic of model performance.

scholarly journals Persistence and photochemical decay of springtime total ozone anomalies in the Canadian Middle Atmosphere Model

2007 ◽  
Vol 7 (2) ◽  
pp. 485-493 ◽  
Author(s):  
S. Tegtmeier ◽  
T. G. Shepherd
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Total Ozone ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Correlation Coefficients ◽  
Polar Regions ◽  
Vertical Diffusion ◽  
Ozone Loss ◽  
Atmosphere Model

Abstract. The persistence and decay of springtime total ozone anomalies over the entire extratropics (midlatitudes plus polar regions) is analysed using results from the Canadian Middle Atmosphere Model (CMAM), a comprehensive chemistry-climate model. As in the observations, interannual anomalies established through winter and spring persist with very high correlation coefficients (above 0.8) through summer until early autumn, while decaying in amplitude as a result of photochemical relaxation in the quiescent summertime stratosphere. The persistence and decay of the ozone anomalies in CMAM agrees extremely well with observations, even in the southern hemisphere when the model is run without heterogeneous chemistry (in which case there is no ozone hole and the seasonal cycle of ozone is quite different from observations). However in a version of CMAM with strong vertical diffusion, the northern hemisphere anomalies decay far too rapidly compared to observations. This shows that ozone anomaly persistence and decay does not depend on how the springtime anomalies are created or on their magnitude, but reflects the transport and photochemical decay in the model. The seasonality of the long-term trends over the entire extratropics is found to be explained by the persistence of the interannual anomalies, as in the observations, demonstrating that summertime ozone trends reflect winter/spring trends rather than any change in summertime ozone chemistry. However this mechanism fails in the northern hemisphere midlatitudes because of the relatively large impact, compared to observations, of the CMAM polar anomalies. As in the southern hemisphere, the influence of polar ozone loss in CMAM increases the midlatitude summertime loss, leading to a relatively weak seasonal dependence of ozone loss in the Northern Hemisphere compared to the observations.

scholarly journals Middle atmospheric ozone, nitrogen dioxide and nitrogen trioxide in 2002–2011: SD-WACCM simulations compared to GOMOS observations

2018 ◽  
Vol 18 (7) ◽  
pp. 5001-5019 ◽  
Author(s):  
Erkki Kyrölä ◽  
Monika E. Andersson ◽  
Pekka T. Verronen ◽  
Marko Laine ◽  
Simo Tukiainen ◽  
...  
Keyword(s):  
Climate Model ◽  
Middle Atmosphere ◽  
Model Simulation ◽  
The Arctic ◽  
Tropical Region ◽  
Satellite Measurement ◽  
Polar Regions ◽  
Wind Fields ◽  
Meteorological Model ◽  
Very High

Abstract. Most of our understanding of the atmosphere is based on observations and their comparison with model simulations. In middle atmosphere studies it is common practice to use an approach, where the model dynamics are at least partly based on temperature and wind fields from an external meteorological model. In this work we test how closely satellite measurements of a few central trace gases agree with this kind of model simulation. We use collocated vertical profiles where each satellite measurement is compared to the closest model data. We compare profiles and distributions of O3, NO2 and NO3 from the Global Ozone Monitoring by Occultation of Stars instrument (GOMOS) on the Envisat satellite with simulations by the Whole Atmosphere Community Climate Model (WACCM). GOMOS measurements are from nighttime. Our comparisons show that in the stratosphere outside the polar regions differences in ozone between WACCM and GOMOS are small, between 0 and 6%. The correlation of 5-day time series show a very high 0.9–0.95. In the tropical region 10° S–10° N below 10 hPa WACCM values are up to 20 % larger than GOMOS. In the Arctic below 6 hPa WACCM ozone values are up to 20 % larger than GOMOS. In the mesosphere between 0.04 and 1 hPa the WACCM is at most 20 % smaller than GOMOS. Above the ozone minimum at 0.01 hPa (or 80 km) large differences are found between WACCM and GOMOS. The correlation can still be high, but at the second ozone peak the correlation falls strongly and the ozone abundance from WACCM is about 60 % smaller than that from GOMOS. The total ozone columns (above 50 hPa) of GOMOS and WACCM agree within ±2 % except in the Arctic where WACCM is 10 % larger than GOMOS. Outside the polar areas and in the validity region of GOMOS NO2 measurements (0.3–37 hPa) WACCM and GOMOS NO2 agree within −5 to +25 % and the correlation is high (0.7–0.95) except in the upper stratosphere at the southern latitudes. In the polar areas, where solar particle precipitation and downward transport from the thermosphere enhance NO2 abundance, large differences up to −90 % are found between WACCM and GOMOS NO2 and the correlation varies between 0.3 and 0.9. For NO3, we find that the WACCM and GOMOS difference is between −20 and 5 % with a very high correlation of 0.7–0.95. We show that NO3 values strongly depend on temperature and the dependency can be fitted by the exponential function of temperature. The ratio of NO3 to O3 from WACCM and GOMOS closely follow the prediction from the equilibrium chemical theory. Abrupt temperature increases from sudden stratospheric warmings (SSWs) are reflected as sudden enhancements of WACCM and GOMOS NO3 values.

scholarly journals Middle atmospheric ozone, nitrogen dioxide, and nitrogen trioxide in 2002–2011: SD-WACCM simulations compared to GOMOS observations

2017 ◽  
Author(s):  
Erkki Kyrölä ◽  
Monika E. Andersson ◽  
Pekka T. Verronen ◽  
Marko Laine ◽  
Simo Tukiainen ◽  
...  
Keyword(s):  
Climate Model ◽  
Middle Atmosphere ◽  
Model Simulation ◽  
Tropical Region ◽  
Satellite Measurement ◽  
Polar Regions ◽  
Wind Fields ◽  
Meteorological Model ◽  
Solar Storms ◽  
Very High

Abstract. Most of our understanding of the atmosphere is based on observations and their comparison with model simulations. In the middle atmosphere studies it is common practice to use an approach, where the model dynamics is at least partly based on temperature and wind fields from an external meteorological model. In this work we test how closely satellite measurements of a few central trace gases agree with this kind of model simulation. We use collocated vertical profiles where each satellite measurement is compared to the closest model data. 
We compare profiles and distributions of O3, NO2, and NO3 from the Global Ozone Monitoring by Occultation of Stars instrument (GOMOS) on ENVISAT with simulations by the Whole Atmosphere Community Climate Model (WACCM). GOMOS measurements are from nighttime. Our comparisons show that in the stratosphere outside the polar regions differences in ozone between GOMOS and WACCM are small. The correlation of monthly and 5-day time series show very high correlation. In the tropical region in the lower stratosphere WACCM shows consistently larger values than GOMOS. In the polar areas GOMOS measurements show ozone losses that can be connected to the elevated NO2 concentrations from solar storms and strong down draft events from the thermosphere that take place in the winter polar regions. In the mesosphere above the ozone minimum at 0.01 hPa (or 80 km) large differences are found between WACCM and GOMOS. Correlation can still be high, but at the second ozone peak correlation falls strongly and the ozone abundance from WACCM is about 60 % smaller than from GOMOS. Outside the polar areas and in the validity region 25–0.3 hPa GOMOS and WACCM NO2 agree reasonably well and the correlation is reasonably high except in the upper stratosphere in the southern latitudes. In the polar areas, where solar particle precipitation and downward transport from the thermosphere enhance NOX abundance, large differences are found between GOMOS and WACCM NO2. For NO3, we find WACCM values agreeing largely with GOMOS with very high correlation. We show that NO3 values depend very sensitively on temperature. The ratio of O3 to NO3 follows closely to the prediction from the equilibrium chemical theory. Abrupt temperature increases from Sudden Stratospheric Warmings are reflected as sudden enhancements of GOMOS and WACCM NO3 values. NO3 values can therefore be used as a proxy for major stratospheric warmings.

scholarly journals Interannual variation patterns of total ozone and temperature in observations and model simulations

2005 ◽  
Vol 5 (5) ◽  
pp. 9207-9248 ◽  
Author(s):  
W. Steinbrecht ◽  
B. Haßler ◽  
C. Brühl ◽  
M. Dameris ◽  
M. A. Giorgetta ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Total Ozone ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Linear Regression Analysis ◽  
Volcanic Eruptions ◽  
Interannual Variations ◽  
Quasi Biennial Oscillation ◽  
Model Simulations ◽  
Stratospheric Temperature

Abstract. We report results from a multiple linear regression analysis of long-term total ozone observations (1979 to 2002, by TOMS/SBUV), of temperature reanalyses (1958 to 2002, NCEP), and of two chemistry-climate model simulations (1960 to 1999, by ECHAM4.L39(DLR)/CHEM (=E39/C), and MAECHAM4-CHEM). The model runs are transient experiments, where observed sea surface temperatures, increasing source gas concentrations (CO2, CFCs, CH4, N2O, NOx), 11-year solar cycle, volcanic aerosols and the quasi-biennial oscillation (QBO) are all accounted for. MAECHAM4-CHEM covers the atmosphere from the surface up to 0.01 hPa (≈80 km). For a proper representation of middle atmosphere (MA) dynamics, it includes a parametrization for momentum deposition by dissipating gravity wave spectra. E39/C, on the other hand, has its top layer centered at 10 hPa (≈30 km). It is targeted on processes near the tropopause, and has more levels in this region. Both models reproduce the observed amplitudes and much of the observed low-latitude patterns of the various modes of interannual variability, MAECHAM4-CHEM somewhat better than E39/C. Total ozone and lower stratospheric temperature show similar patterns. Main contributions to the interannual variations of total ozone and lower stratospheric temperature at 50 hPa come from a linear trend (up to −30 Dobson Units (DU) per decade, or −1.5 K/decade), the QBO (up to 25 DU, or 2.5 K peak to peak), the intensity of the polar vortices (up to 50 DU, or 5 K peak to peak), and from tropospheric weather (up to 30 DU, or 3 K peak to peak). Smaller variations are related to the 11-year solar cycle (generally less than 25 DU, or 2.5 K), and to ENSO (up to 15 DU, or 1.5 K). Volcanic eruptions have resulted in sporadic changes (up to −40 DU, or +3 K). Most stratospheric variations are connected to the troposphere, both in observations and simulations. At low latitudes, patterns are zonally symmetric. At higher latitudes, however, strong, zonally non-symmetric signals are found close to the Aleutian Islands or south of Australia. Such asymmetric features appear in the model runs as well, but often at different longitudes than in the observations. The results point to a key role of the zonally asymmetric Aleutian (or Australian) stratospheric anti-cyclones for interannual variations at high- latitudes, and for coupling between polar vortex strength, QBO, 11-year solar cycle and ENSO.

scholarly journals Climatological Ertel's potential-vorticity flux and mean meridional circulation in the extratropical troposphere − lower stratosphere

1998 ◽  
Vol 16 (2) ◽  
pp. 250-265 ◽  
Author(s):  
J. Bartels ◽  
D. Peters ◽  
G. Schmitz
Keyword(s):  
Potential Vorticity ◽  
Seasonal Cycle ◽  
General Circulation ◽  
Lower Stratosphere ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Meridional Circulation ◽  
Statistical Significance ◽  
Baroclinic Wave ◽  
Mean Meridional Circulation

Abstract. We investigated to what extent the isentropic, non-geostrophic formulation of zonally averaged circulation derived for stratospheric conditions is applicable to climatological transport in the extratropical troposphere and lower stratosphere. The study is based on 10 years of daily data of ECMWF analysis and on the ECHAM3 climate model of the German Climate Computing Centre. The main result is a scalar isentropic mixing coefficient, Kyy, and a mean meridional transport circulation consistently derived from the same data base. For both data sources, isentropic mean meridional circulation is derived from horizontal mass flow rate for 4 representative months. Alternatively, a mean meridional circulation is calculated from total diabatic heating rates of the ECHAM3 model. It is shown that only the latter is in good agreement with the ECMWF mean meridional circulation. Isentropic analysis also comprises the seasonal cycle of the climatological meridional gradient and flux of Ertel's potential vorticity (PV). Application of Tung's flux-gradient relation yields that for all seasons Kyy is positive in height-latitude regions where statistical significance is reached. Large Kyy values, marking regions of more efficient mixing, have been found in the subtropical vertical band of weak westerly wind and in mid-latitudes in regions of upward-propagating baroclinic wave activity in the middle and upper troposphere. Based on the ECMWF data and results of baroclinic-wave behaviour, strong indications are presented that positive zonally averaged PV flux polewards of the jet core in the NH is strengthened by stationary waves and nonlinear effects. Reduced eddy transport is apparent in winter and spring slightly below the subtropical tropopause jet. The seasonal cycle of Kyy from ECHAM3 data is to a great extent in agreement with the result based on ECMWF analysis. In the model, reduced interannual variability enlarges the height-latitude range where sign of Kyy is significant.Key words. Meteorology and atmospheric dynamics · Climatology · General circulation · Middle atmosphere is significant.

scholarly journals Odd hydrogen response thresholds for indication of solar proton and electron impact in the mesosphere and stratosphere

2020 ◽  
Vol 38 (6) ◽  
pp. 1299-1312
Author(s):  
Tuomas Häkkilä ◽  
Pekka T. Verronen ◽  
Luis Millán ◽  
Monika E. Szeląg ◽  
Niilo Kalakoski ◽  
...  
Keyword(s):  
Climate Model ◽  
Middle Atmosphere ◽  
Signal To Noise Ratio ◽  
Solar Proton ◽  
Polar Regions ◽  
Impact Detection ◽  
Flux Measurements ◽  
Hydrogen Response ◽  
Response Thresholds ◽  
Offline Processing

Abstract. Understanding the atmospheric forcing from energetic particle precipitation (EPP) is important for climate simulations on decadal time scales. However, presently there are large uncertainties in energy flux measurements of electron precipitation. One approach to narrowing these uncertainties is by analyses of EPP direct atmospheric impacts and their relation to measured EPP fluxes. Here we use observations from the microwave limb sounder (MLS) and Whole Atmosphere Community Climate Model (WACCM) simulations, together with EPP fluxes from the Geostationary Operational Environmental Satellite (GOES) and Polar-orbiting Operational Environmental Satellite (POES) to determine the OH and HO2 response thresholds to solar proton events (SPEs) and radiation belt electron (RBE) precipitation. Because of their better signal-to-noise ratio and extended altitude range, we utilize MLS HO2 data from an improved offline processing instead of the standard operational product. We consider a range of altitudes in the middle atmosphere and all magnetic latitudes from pole to pole. We find that the nighttime flux limits for day-to-day EPP impact detection using OH and HO2 are 50–130 protonscm-2s-1sr-1 (E>10 MeV) and 1.0–2.5×104 electronscm-2s-1sr-1 (E = 100–300 keV). Based on the WACCM simulations, nighttime OH and HO2 are good EPP indicators in the polar regions and provide best coverage in altitude and latitude. Due to larger background concentrations, daytime detection requires larger EPP fluxes and is possible in the mesosphere only. SPE detection is easier than RBE detection because a wider range of polar latitudes is affected, i.e., the SPE impact is rather uniform poleward of 60∘, while the RBE impact is focused at 60∘. Altitude-wise, the SPE and RBE detection are possible at ≈ 35–80 and ≈ 65–75 km, respectively. We also find that the MLS OH observations indicate a clear nighttime response to SPE and RBE in the mesosphere, similar to the simulations. However, the MLS OH data are too noisy for response detection in the stratosphere below 50 km, and the HO2 measurements are overall too noisy for confident EPP detection on a day-to-day basis.

scholarly journals Long-term variations and trends in the simulation of the middle atmosphere 1980–2004 by the chemistry-climate model of the Meteorological Research Institute

2008 ◽  
Vol 26 (5) ◽  
pp. 1299-1326 ◽  
Author(s):  
K. Shibata ◽  
M. Deushi
Keyword(s):  
Zonal Wind ◽  
Solar Irradiance ◽  
Total Ozone ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Mount Pinatubo ◽  
Meteorological Research Institute ◽  
Mean Temperature ◽  
Volcanic Aerosols ◽  
Research Institute

Abstract. A middle-atmosphere simulation of the past 25 years (from 1980 to 2004) has been performed with a chemistry-climate model (CCM) of the Meteorological Research Institute (MRI) under observed forcings of sea-surface temperature, greenhouse gases, halogens, volcanic aerosols, and solar irradiance variations. The dynamics module of MRI-CCM is a spectral global model truncated triangularly at a maximum wavenumber of 42 with 68 layers extending from the surface to 0.01 hPa (about 80 km), wherein the vertical spacing is 500 m from 100 to 10 hPa. The chemistry-transport module treats 51 species with 124 reactions including heterogeneous reactions. Transport of chemical species is based on a hybrid semi-Lagrangian scheme, which is a flux form in the vertical direction and an ordinary semi-Lagrangian form in the horizontal direction. The MRI-CCM used in this study reproduced a quasi-biennial oscillation (QBO) of about a 20-month period for wind and ozone in the equatorial stratosphere. Multiple linear regression analysis with time lags for volcanic aerosols was performed on the zonal-mean quantities of the simulated result to separate the trend, the QBO, the El Chichón and Mount Pinatubo, the 11-year solar cycle, and the El Niño/Southern Oscillation (ENSO) signals. It is found that MRI-CCM can more or less realistically reproduce observed trends of annual mean temperature and ozone, and those of total ozone in each month. MRI-CCM also reproduced the vertical multi-cell structures of tropical temperature, zonal-wind, and ozone associated with the QBO, and the mid-latitude total ozone QBO in each winter hemisphere. Solar irradiance variations of the 11-year cycle were found to affect radiation alone (not photodissociation) because of an error in making the photolysis lookup table. Nevertheless, though the heights of the maximum temperature (ozone) in the tropics are much higher (lower) than observations, MRI-CCM could reproduce the second maxima of temperature and ozone in the lower stratosphere, demonstrating that the dynamic effect outweighs the photochemical effect there. The ENSO signals of annual mean temperature, zonal wind, and ozone are generally reproduced in the troposphere and below the middle stratosphere. The volcanic signals of temperature increase and ozone decrease are much overestimated for both El Chichón and Mount Pinatubo.

scholarly journals Odd hydrogen response thresholds for indication of solar proton and electron impact in the mesosphere and stratosphere

2020 ◽  
Author(s):  
Tuomas Häkkilä ◽  
Pekka T. Verronen ◽  
Luis Millán ◽  
Monika E. Szela̧g ◽  
Niilo Kalakoski ◽  
...  
Keyword(s):  
Climate Model ◽  
Middle Atmosphere ◽  
Solar Proton ◽  
Polar Regions ◽  
Impact Detection ◽  
Climate Simulations ◽  
Flux Measurements ◽  
Hydrogen Response ◽  
Response Thresholds ◽  
Climate Model Simulations

Abstract. Understanding the atmospheric forcing from energetic particle precipitation (EPP) is important for climate simulations on decadal time scales. However, presently there are large uncertainties in energy-flux measurements of electron precipitation. One approach to narrow these uncertainties is by analyses of EPP direct atmospheric impacts and their relation to measured EPP fluxes. Here we use odd hydrogen observations from the Microwave Limb Sounder and Whole Atmosphere Community Climate Model simulations, together with EPP fluxes from the GOES and POES satellites, to determine the response thresholds to solar proton events (SPEs) and radiation belt electron (RBE) precipitation. We consider a range of altitudes in the middle atmosphere, and all magnetic latitudes from pole to pole. We find that the lower flux limits for day-to-day EPP impact detection using OH and HO2 are of the order of 102 protons/cm2/s/sr (E > 10 MeV) and 104 electrons/cm2/s/sr (E = 100–300 keV). Based on the simulations, nighttime OH and HO2 are good EPP indicators in the polar regions, and provide best coverage in altitude and latitude. Due to larger background concentrations, daytime detection requires larger EPP fluxes and is possible in the mesosphere only. SPE detection is easier than RBE detection because a wider range of polar latitudes is affected. We also find that MLS OH observations indicate a clear nighttime response to SPE and RBE in the mesosphere, similar to the simulations, while HO2 data are overall too noisy for confident EPP detection.

Ocean Water Clarity and the Ocean General Circulation in a Coupled Climate Model

2009 ◽  
Vol 39 (2) ◽  
pp. 314-332 ◽  
Author(s):  
Anand Gnanadesikan ◽  
Whit G. Anderson
Keyword(s):  
Water Column ◽  
Seasonal Cycle ◽  
General Circulation ◽  
Climate Model ◽  
Coupled Model ◽  
Water Clarity ◽  
Shortwave Radiation ◽  
Polar Regions ◽  
Ocean Water ◽  
Mode Water

Abstract Ocean water clarity affects the distribution of shortwave heating in the water column. In a one-dimensional time-mean sense, increased clarity would be expected to cool the surface and heat subsurface depths as shortwave radiation penetrates deeper into the water column. However, wind-driven upwelling, boundary currents, and the seasonal cycle of mixing can bring water heated at depth back to the surface. This warms the equator and cools the subtropics throughout the year while reducing the amplitude of the seasonal cycle of temperature in polar regions. This paper examines how these changes propagate through the climate system in a coupled model with an isopycnal ocean component focusing on the different impacts associated with removing shading from different regions. Increasing shortwave penetration along the equator causes warming to the south of the equator. Increasing it in the relatively clear gyres off the equator causes the Hadley cells to strengthen and the subtropical gyres to shift equatorward. Increasing shortwave penetration in the less clear regions overlying the oxygen minimum zones causes the cold tongue to warm and the Walker circulation to weaken. Increasing shortwave penetration in the high-latitude Southern Ocean causes an increase in the formation of mode water from subtropical water. The results suggest that more attention be paid to the processes distributing heat below the mixed layer.

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