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 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 On the intermittency of orographic gravity wave hotspots and its importance for middle atmosphere dynamics

2020 ◽  
Author(s):  
Ales Kuchar ◽  
Petr Sacha ◽  
Roland Eichinger ◽  
Christoph Jacobi ◽  
Petr Pisoft ◽  
...  
Keyword(s):  
Climate Model ◽  
Middle Atmosphere ◽  
Model Simulation ◽  
Three Dimensional ◽  
Detection Algorithm ◽  
Dynamics Simulation ◽  
Dynamical Structure ◽  
Wave Forcing ◽  
Peak Detection Algorithm ◽  
Opposing Effects

Abstract. When orographic gravity waves (OGWs) break, they dissipate their momentum and energy and thereby influence the thermal and dynamical structure of the atmosphere. This OGW forcing mainly takes place in the middle atmosphere. It is zonally asymmetric and strongly intermittent. So-called OGW hotspot regions have been shown to exert a large impact on the total wave forcing, in particular in the lower stratosphere (LS). Motivated by this we investigate the asymmetrical distribution of the three-dimensional OGW drag (OGWD) for selected hotspot regions in the specified dynamics simulation of the chemistry-climate model CMAM (Canadian Middle Atmosphere Model) for the period 1979–2010. As an evaluation, we first compare zonal mean OGW fluxes and GW drag (GWD) of the model simulation with observations and reanalyses in the northern hemisphere. We find an overestimation of GW momentum fluxes and GWD in the model's LS, presumably attributable to the GW parameterizations which are tuned to correctly represent the dynamics of the southern hemisphere. In the following, we define three hotspot regions which are of particular interest for OGW studies, namely the Himalayas, the Rocky Mountains and East Asia. The GW drags in these hotspot regions emerge as strongly intermittent, a result that can also quantitatively be corroborated with observational studies. Moreover, a peak-detection algorithm is applied to capture the intermittent and zonally asymmetric character of OGWs breaking in the LS and to assess composites for the three hotspot regions. This shows that LS peak OGW events can have opposing effects on the upper stratosphere and mesosphere depending on the hotspot region. Our analysis constitutes a new method for studying the intermittency of OGWs, thereby facilitating a new possibility to assess the effect of particular OGW hotspot regions on middle atmospheric dynamics.

Rapid neoglaciation on Ellesmere Island promoted by enhanced summer snowfall in a transient climate model simulation of the middle-late-Holocene

The Holocene ◽  
2020 ◽  
Vol 30 (10) ◽  
pp. 1474-1480
Author(s):  
Stephen J Vavrus ◽  
Feng He ◽  
John E Kutzbach ◽  
William F Ruddiman
Keyword(s):  
Snow Depth ◽  
Late Holocene ◽  
Climate Model ◽  
Model Simulation ◽  
Short Circuit ◽  
Ellesmere Island ◽  
The Arctic ◽  
Holocene Thermal Maximum ◽  
Model Driven ◽  
The Arctic Oscillation

Arctic neoglaciation following the Holocene Thermal Maximum is an important feature of late-Holocene climate. We investigated this phenomenon using a transient 6000-year simulation with the CESM-CAM5 climate model driven by orbital forcing, greenhouse gas concentrations, and a land use reconstruction. During the first three millennia analyzed here (6–3 ka), mean Arctic snow depth increases, despite enhanced greenhouse forcing. Superimposed on this secular trend is a very abrupt increase in snow depth between 5 and 4.9 ka on Ellesmere Island and the Greenland coasts, in rough agreement with the timing of observed neoglaciation in the region. This transition is especially extreme on Ellesmere Island, where end-of-summer snow coverage jumps from nearly 0 to virtually 100% in 1 year, and snow depth increases to the model’s imposed maximum within 15 years. This climatic shift involves more than the Milankovitch-based expectation of cooler summers causing less snow melt. Coincident with the onset of the cold regime are two consecutive summers with heavy snowfall on Ellesmere Island that help to short-circuit the normal seasonal melt cycle. These heavy snow seasons are caused by synoptic-scale, cyclonic circulation anomalies over the Arctic Ocean and Canadian Archipelago, including an extremely positive phase of the Arctic Oscillation. Our study reveals that a climate model can produce sudden climatic transitions in this region prone to glacial inception and exceptional variability, due to a dynamic mechanism (more summer snowfall induced by an extreme circulation anomaly) that augments the traditional Milankovitch thermodynamic explanation of orbitally induced glacier development.

scholarly journals The Changing Energy Balance of the Polar Regions in a Warmer Climate

2013 ◽  
Vol 26 (10) ◽  
pp. 3112-3129 ◽  
Author(s):  
Lennart Bengtsson ◽  
Kevin I. Hodges ◽  
Symeon Koumoutsaris ◽  
Matthias Zahn ◽  
Paul Berrisford
Keyword(s):  
Polar Region ◽  
Energy Transport ◽  
Climate Model ◽  
Radiant Energy ◽  
Surface Radiation ◽  
The Arctic ◽  
Polar Regions ◽  
Energy Fluxes ◽  
Intergovernmental Panel ◽  
Static Energy

Abstract Energy fluxes for polar regions are examined for two 30-yr periods, representing the end of the twentieth and twenty-first centuries, using data from high-resolution simulations with the ECHAM5 climate model. The net radiation to space for the present climate agrees well with data from the Clouds and the Earth’s Radiant Energy System (CERES) over the northern polar region but shows an underestimation in planetary albedo for the southern polar region. This suggests there are systematic errors in the atmospheric circulation or in the net surface energy fluxes in the southern polar region. The simulation of the future climate is based on the Intergovernmental Panel on Climate Change (IPCC) A1B scenario. The total energy transport is broadly the same for the two 30-yr periods, but there is an increase in the moist energy transport on the order of 6 W m−2 and a corresponding reduction in the dry static energy. For the southern polar region the proportion of moist energy transport is larger and the dry static energy correspondingly smaller for both periods. The results suggest a possible mechanism for the warming of the Arctic that is discussed. Changes between the twentieth and twenty-first centuries in the northern polar region show the net ocean surface radiation flux in summer increases ~18 W m−2 (24%). For the southern polar region the response is different as there is a decrease in surface solar radiation. It is suggested that this is caused by changes in cloudiness associated with the poleward migration of the storm tracks.

scholarly journals On the intermittency of orographic gravity wave hotspots and its importance for middle atmosphere dynamics

2020 ◽  
Vol 1 (2) ◽  
pp. 481-495 ◽  
Author(s):  
Ales Kuchar ◽  
Petr Sacha ◽  
Roland Eichinger ◽  
Christoph Jacobi ◽  
Petr Pisoft ◽  
...  
Keyword(s):  
Climate Model ◽  
Middle Atmosphere ◽  
Model Simulation ◽  
Three Dimensional ◽  
Detection Algorithm ◽  
Dynamics Simulation ◽  
Dynamical Structure ◽  
Wave Forcing ◽  
Peak Detection Algorithm ◽  
Opposing Effects

Abstract. When orographic gravity waves (OGWs) break, they dissipate their momentum and energy and thereby influence the thermal and dynamical structure of the atmosphere. This OGW forcing mainly takes place in the middle atmosphere. It is zonally asymmetric and strongly intermittent. So-called “OGW hotspot regions” have been shown to exert a large impact on the total wave forcing, in particular in the lower stratosphere (LS). Motivated by this we investigate the asymmetrical distribution of the three-dimensional OGW drag (OGWD) for selected hotspot regions in the specified dynamics simulation of the chemistry-climate model CMAM (Canadian Middle Atmosphere Model) for the period 1979–2010. As an evaluation, we first compare zonal mean OGW fluxes and GW drag (GWD) of the model simulation with observations and reanalyses in the Northern Hemisphere. We find an overestimation of GW momentum fluxes and GWD in the model's LS, presumably attributable to the GW parameterizations which are tuned to correctly represent the dynamics of the Southern Hemisphere. In the following, we define three hotspot regions which are of particular interest for OGW studies, namely the Himalayas, the Rocky Mountains and East Asia. The GW drags in these hotspot regions emerge as strongly intermittent, a result that can also quantitatively be corroborated with observational studies. Moreover, a peak-detection algorithm is applied to capture the intermittent and zonally asymmetric character of OGWs breaking in the LS and to assess composites for the three hotspot regions. This shows that LS peak OGW events can have opposing effects on the upper stratosphere and mesosphere depending on the hotspot region. Our analysis constitutes a new method for studying the intermittency of OGWs, thereby facilitating a new possibility to assess the effect of particular OGW hotspot regions on middle atmospheric dynamics.

The Impact of Poleward Moisture and Sensible Heat Flux on Arctic Winter Sea Ice Variability*

2015 ◽  
Vol 28 (13) ◽  
pp. 5030-5040 ◽  
Author(s):  
Hyo-Seok Park ◽  
Sukyoung Lee ◽  
Seok-Woo Son ◽  
Steven B. Feldstein ◽  
Yu Kosaka
Keyword(s):  
Sea Ice ◽  
Climate Model ◽  
Model Simulation ◽  
Early Stage ◽  
Sensible Heat Flux ◽  
The Arctic ◽  
Sea Ice Concentration ◽  
Sea Ice Thickness ◽  
Surface Warming ◽  
The Impact

Abstract The surface warming in recent decades has been most rapid in the Arctic, especially during the winter. Here, by utilizing global reanalysis and satellite datasets, it is shown that the northward flux of moisture into the Arctic during the winter strengthens the downward infrared radiation (IR) by 30–40 W m−2 over 1–2 weeks. This is followed by a decline of up to 10% in sea ice concentration over the Greenland, Barents, and Kara Seas. A climate model simulation indicates that the wind-induced sea ice drift leads the decline of sea ice thickness during the early stage of the strong downward IR events, but that within one week the cumulative downward IR effect appears to be dominant. Further analysis indicates that strong downward IR events are preceded several days earlier by enhanced convection over the tropical Indian and western Pacific Oceans. This finding suggests that sea ice predictions can benefit from an improved understanding of tropical convection and ensuing planetary wave dynamics.

scholarly journals Polar Cooling Effect Due to Increase of Phytoplankton and Dimethyl-Sulfide Emission

Atmosphere ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 384 ◽  
Author(s):  
Ah-Hyun Kim ◽  
Seong Yum ◽  
Hannah Lee ◽  
Dong Chang ◽  
Sungbo Shim
Keyword(s):  
Sea Ice ◽  
Large Scale ◽  
Climate Models ◽  
Dimethyl Sulfide ◽  
Climate Model ◽  
Cloud Condensation Nuclei ◽  
Marine Phytoplankton ◽  
The Arctic ◽  
Polar Regions ◽  
Cloud Albedo

The effects of increased dimethyl-sulfide (DMS) emissions due to increased marine phytoplankton activity are examined using an atmosphere-ocean coupled climate model. As the DMS emission flux from the ocean increases globally, large-scale cooling occurs due to the DMS-cloud condensation nuclei (CCN)-cloud albedo interactions. This cooling increases as DMS emissions are further increased, with the most pronounced effect occurring over the Arctic, which is likely associated with a change in sea-ice fraction as sea ice mediates the air-sea exchange of the radiation, moisture and heat flux. These results differ from recent studies that only considered the bio-physical feedback that led to amplified Arctic warming under greenhouse warming conditions. Therefore, climate negative feedback from DMS-CCN-cloud albedo interactions that involve marine phytoplankton and its impact on polar climate should be properly reflected in future climate models to better estimate climate change, especially over the polar regions.

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 CO at 40–80 km above Kiruna observed by the ground-based microwave radiometer KIMRA and simulated by the whole atmosphere community climate model

2012 ◽  
Vol 12 (1) ◽  
pp. 559-587 ◽  
Author(s):  
C. G. Hoffmann ◽  
D. E. Kinnison ◽  
R. R. Garcia ◽  
M. Palm ◽  
J. Notholt ◽  
...  
Keyword(s):  
Time Series ◽  
Gravity Wave ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Microwave Radiometer ◽  
The Arctic ◽  
Mutual Correlation ◽  
Community Climate Model ◽  
Middle Atmosphere Dynamics ◽  
Community Climate

Abstract. This study compares CO in the Arctic stratosphere and mesosphere measured by ground-based microwave radiometry with simulations made with the Whole Atmosphere Community Climate Model driven with specified dynamical fields (SD-WACCM4) for the Arctic winters 2008/2009 and 2009/2010. CO is a tracer for polar winter middle atmosphere dynamics, hence the representation of polar dynamics in the model is examined indirectly. Measurements were taken with the Kiruna Microwave Radiometer (KIMRA). The instrument, which is located in Kiruna, Northern Sweden (67.8° N, 20.4° E), provides CO profiles between 40 and 80 km altitude. The present comparison, which is one of the first between SD-WACCM4 and measurements, is performed on the smallest space and time scales currently simulated by the model; the global model is evaluated daily at the particular model grid-point closest to Kiruna. As a guide to what can generally be expected from such a comparison, the same analysis is repeated for observations of CO from the Microwave Limb Sounder (MLS), a microwave radiometer onboard NASA's Aura satellite, which has global coverage. First, time-mean profiles of CO are compared, revealing that the profile shape of KIMRA deviates from SD-WACCM4 and MLS, especially in the upper mesosphere. SD-WACCM4 and MLS are mostly consistent throughout the range of altitude considered; however, SD-WACCM4 shows slightly lower values above 60 km and this discrepancy increases with altitude. Second, the time evolution is compared for the complete time series, as well as for the slowly and rapidly evolving parts alone. Overall, the agreement among the datasets is very good and the model is almost as consistent with the measurements as the measurements are with each other. Mutual correlation coefficients of the slowly varying part of the CO time series are ≥0.9 over a wide altitude range. This demonstrates that the polar winter middle atmosphere dynamics is very well represented in SD-WACCM4 and that the relaxation to analyzed meteorological fields below 50 km constrains the behavior of the simulation sufficiently, even at higher altitudes, such that the simulation above 50 km is close to the measurements. However, above 50 km, the model-measurement correlation for the rapidly varying part of the CO time series is lower (0.3) than the measurement-measurement correlation (0.6). This is attributed to the fact that the gravity wave parametrization in WACCM is based on a generic gravity wave spectrum and cannot be expected to capture the instantaneous behavior of the actual gravity wave field present in the atmosphere.

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