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

<p>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.</p>

scholarly journals Self-consistent Global Transport of Metallic Ions with WACCM-X

2021 ◽  
Author(s):  
Jianfei Wu ◽  
Wuhu Feng ◽  
Han-Li Liu ◽  
Xianghui Xue ◽  
Daniel R. Marsh ◽  
...  
Keyword(s):  
Ion Transport ◽  
Seasonal Variations ◽  
Climate Model ◽  
Lower Thermosphere ◽  
Molecular Ions ◽  
The Self ◽  
Metallic Ions ◽  
Global Transport ◽  
Self Consistent ◽  
The Impact

Abstract. The NCAR Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension (WACCM-X) v2.1 has been developed to include the neutral and ion-molecule chemistry and dynamics of three metals (Mg, Na, and Fe), which are injected into the upper mesosphere/lower thermosphere by meteoric ablation. Here we focus on the self-consistent electrodynamical transport of metallic ions in both the E and F regions. The model with full ion transport significantly improves the simulation of global distribution and seasonal variations of Mg+. Near the magnetic equator, the diurnal variation in upward and downward transport of Mg+ is generally consistent with the ''ionosphere fountain effect''. The thermospheric distribution of Fe is shown to be closely coupled to the transport of Fe+. The effect of ion mass on ion transport is also examined: the lighter ions (Mg+ and Na+) are transported above 150 km more easily than the heavy Fe+. We also examine the impact of the transport of major molecular ions, NO+ and O2+, on the distribution of metallic ions.

scholarly journals Middle atmosphere response to the solar cycle in irradiance and ionizing particle precipitation

2011 ◽  
Vol 11 (10) ◽  
pp. 5045-5077 ◽  
Author(s):  
K. Semeniuk ◽  
V. I. Fomichev ◽  
J. C. McConnell ◽  
C. Fu ◽  
S. M. L. Melo ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Radiative Forcing ◽  
Climate Model ◽  
Middle Atmosphere ◽  
High Energy ◽  
Galactic Cosmic Rays ◽  
Particle Precipitation ◽  
Solar Cycle Variation ◽  
Cycle Variation ◽  
The Impact

Abstract. The impact of NOx and HOx production by three types of energetic particle precipitation (EPP), auroral zone medium and high energy electrons, solar proton events and galactic cosmic rays on the middle atmosphere is examined using a chemistry climate model. This process study uses ensemble simulations forced by transient EPP derived from observations with one-year repeating sea surface temperatures and fixed chemical boundary conditions for cases with and without solar cycle in irradiance. Our model results show a wintertime polar stratosphere ozone reduction of between 3 and 10 % in agreement with previous studies. EPP is found to modulate the radiative solar cycle effect in the middle atmosphere in a significant way, bringing temperature and ozone variations closer to observed patterns. The Southern Hemisphere polar vortex undergoes an intensification from solar minimum to solar maximum instead of a weakening. This changes the solar cycle variation of the Brewer-Dobson circulation, with a weakening during solar maxima compared to solar minima. In response, the tropical tropopause temperature manifests a statistically significant solar cycle variation resulting in about 4 % more water vapour transported into the lower tropical stratosphere during solar maxima compared to solar minima. This has implications for surface temperature variation due to the associated change in radiative forcing.

scholarly journals Evaluation of CLaMS, KASIMA and ECHAM5/MESSy1 simulations in the lower stratosphere using observations of Odin/SMR and ILAS/ILAS-II

2009 ◽  
Vol 9 (1) ◽  
pp. 1977-2020
Author(s):  
F. Khosrawi ◽  
R. Müller ◽  
M. H. Proffitt ◽  
R. Ruhnke ◽  
O. Kirner ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
General Circulation ◽  
Lower Stratosphere ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Lagrangian Model ◽  
Data Sets ◽  
Data Set ◽  
The Impact

Abstract. 1-year data sets of monthly averaged nitrous oxide (N2O) and ozone (O3) derived from satellite measurements were used as a tool for the evaluation of atmospheric photochemical models. Two 1-year data sets, one derived from the Improved Limb Atmospheric Spectrometer (ILAS and ILAS-II) and one from the Odin Sub-Millimetre Radiometer (Odin/SMR) were employed. Here, these data sets are used for the evaluation of two Chemical Transport Models (CTMs), the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA) and the Chemical Lagrangian Model of the Stratosphere (CLaMS) as well as for one Chemistry-Climate Model (CCM), the atmospheric chemistry general circulation model ECHAM5/MESSy1 (E5M1) in the lower stratosphere with focus on the Northern Hemisphere. Since the Odin/SMR measurements cover the entire hemisphere, the evaluation is performed for the entire hemisphere as well as for the low latitudes, midlatitudes and high latitudes using the Odin/SMR 1-year data set as reference. To assess the impact of using different data sets for such an evaluation study we repeat the evaluation for the polar lower stratosphere using the ILAS/ILAS-II data set. Only small differences were found using ILAS/ILAS-II instead of Odin/SMR as a reference, thus, showing that the results are not influenced by the particular satellite data set used for the evaluation. The evaluation of CLaMS, KASIMA and E5M1 shows that all models are in good agreement with Odin/SMR and ILAS/ILAS-II. Differences are generally in the range of ±20%. Larger differences (up to −40%) are found in all models at 500±25 K for N2O mixing ratios greater than 200 ppb. Generally, the largest differences were found for the tropics and the lowest for the polar regions. However, an underestimation of polar winter ozone loss was found both in KASIMA and E5M1 both in the Northern and Southern Hemisphere.

scholarly journals Middle atmosphere response to the solar cycle in irradiance and ionizing particle precipitation

2010 ◽  
Vol 10 (10) ◽  
pp. 24853-24917 ◽  
Author(s):  
K. Semeniuk ◽  
V. I. Fomichev ◽  
J. C. McConnell ◽  
C. Fu ◽  
S. M. L. Melo ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Radiative Forcing ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Polar Vortex ◽  
Galactic Cosmic Rays ◽  
Particle Precipitation ◽  
Solar Cycle Variation ◽  
Cycle Variation ◽  
The Impact

Abstract. The impact of NOx and HOx production by three types of energetic particle precipitation (EPP), aurora, solar proton events and galactic cosmic rays is examined using a chemistry climate model. Ensemble simulations forced by transient EPP derived from observations with one-year repeating sea surface temperatures and fixed chemical boundary conditions were conducted for cases with and without solar cycle in irradiance. Our model results show a wintertime polar stratosphere ozone reduction of between 3 and 10% in agreement with previous studies. EPP is found to modulate the radiative solar cycle effect in the middle atmosphere in a significant way, bringing temperature and ozone variations closer to observed patterns. The Southern Hemisphere polar vortex undergoes an intensification from solar minimum to solar maximum instead of a weakening. This changes the solar cycle variation of the Brewer-Dobson circulation, with a weakening during solar maxima compared to solar minima. In response, the tropical tropopause temperature manifests a statistically significant solar cycle variation resulting in about 4% more water vapour transported into the lower tropical stratosphere during solar maxima compared to solar minima. This has implications for surface temperature variation due to the associated change in radiative forcing.

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 The Impact of Different Absolute Solar Irradiance Values on Current Climate Model Simulations

2014 ◽  
Vol 27 (3) ◽  
pp. 1100-1120 ◽  
Author(s):  
David H. Rind ◽  
Judith L. Lean ◽  
Jeffrey Jonas
Keyword(s):  
Climate Change ◽  
Solar Irradiance ◽  
Cloud Cover ◽  
Climate Models ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Global Climate ◽  
Stratospheric Ozone ◽  
Model Simulations ◽  
The Impact

Abstract Simulations of the preindustrial and doubled CO2 climates are made with the GISS Global Climate Middle Atmosphere Model 3 using two different estimates of the absolute solar irradiance value: a higher value measured by solar radiometers in the 1990s and a lower value measured recently by the Solar Radiation and Climate Experiment. Each of the model simulations is adjusted to achieve global energy balance; without this adjustment the difference in irradiance produces a global temperature change of 0.4°C, comparable to the cooling estimated for the Maunder Minimum. The results indicate that by altering cloud cover the model properly compensates for the different absolute solar irradiance values on a global level when simulating both preindustrial and doubled CO2 climates. On a regional level, the preindustrial climate simulations and the patterns of change with doubled CO2 concentrations are again remarkably similar, but there are some differences. Using a higher absolute solar irradiance value and the requisite cloud cover affects the model’s depictions of high-latitude surface air temperature, sea level pressure, and stratospheric ozone, as well as tropical precipitation. In the climate change experiments it leads to an underestimation of North Atlantic warming, reduced precipitation in the tropical western Pacific, and smaller total ozone growth at high northern latitudes. Although significant, these differences are typically modest compared with the magnitude of the regional changes expected for doubled greenhouse gas concentrations. Nevertheless, the model simulations demonstrate that achieving the highest possible fidelity when simulating regional climate change requires that climate models use as input the most accurate (lower) solar irradiance value.

scholarly journals The impact of volcanic aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure

2014 ◽  
Vol 14 (11) ◽  
pp. 16777-16819
Author(s):  
M. Toohey ◽  
K. Krüger ◽  
M. Bittner ◽  
C. Timmreck ◽  
H. Schmidt
Keyword(s):  
High Latitude ◽  
Climate Model ◽  
Polar Vortex ◽  
Volcanic Aerosol ◽  
Stratospheric Polar Vortex ◽  
Model Simulations ◽  
Aerosol Forcing ◽  
Climate Model Simulations ◽  
The Impact ◽  
Forcing Set

Abstract. Observations and simple theoretical arguments suggest that the Northern Hemisphere (NH) stratospheric polar vortex is stronger in winters following major volcanic eruptions. However, recent studies show that climate models forced by prescribed volcanic aerosol fields fail to reproduce this effect. We investigate the impact of volcanic aerosol forcing on stratospheric dynamics, including the strength of the NH polar vortex, in ensemble simulations with the Max Planck Institute Earth System Model. The model is forced by four different prescribed forcing sets representing the radiative properties of stratospheric aerosol following the 1991 eruption of Mt. Pinatubo: two forcing sets are based on observations, and are commonly used in climate model simulations, and two forcing sets are constructed based on coupled aerosol–climate model simulations. For all forcings, we find that temperature and zonal wind anomalies in the NH high latitudes are not directly impacted by anomalous volcanic aerosol heating. Instead, high latitude effects result from robust enhancements in stratospheric residual circulation, which in turn result, at least in part, from enhanced stratospheric wave activity. High latitude effects are therefore much less robust than would be expected if they were the direct result of aerosol heating. While there is significant ensemble variability in the high latitude response to each aerosol forcing set, the mean response is sensitive to the forcing set used. Significant differences, for example, are found in the NH polar stratosphere temperature and zonal wind response to two different forcing data sets constructed from different versions of SAGE II aerosol observations. Significant strengthening of the polar vortex, in rough agreement with the expected response, is achieved only using aerosol forcing extracted from prior coupled aerosol–climate model simulations. Differences in the dynamical response to the different forcing sets used imply that reproducing the polar vortex responses to past eruptions, or predicting the response to future eruptions, depends on accurate representation of the space-time structure of the volcanic aerosol forcing.

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 Production and transport mechanisms of NO in observations and models

2018 ◽  
Author(s):  
Koen Hendrickx ◽  
Linda Megner ◽  
Daniel R. Marsh ◽  
Christine Smith-Johnsen
Keyword(s):  
Geomagnetic Activity ◽  
Climate Models ◽  
Climate Model ◽  
Heat Budget ◽  
Lower Thermosphere ◽  
Polar Vortex ◽  
Detailed Comparison ◽  
No Production ◽  
The Impact ◽  
Mlt Region

Abstract. A reservoir of Nitric Oxide (NO) in the lower thermosphere efficiently cools the atmosphere after periods of enhanced geomagnetic activity. Transport from this reservoir to the stratosphere within the winter polar vortex allows NO to deplete ozone levels and thereby affect the middle atmospheric heat budget. As more climate models resolve the mesosphere and lower thermosphere (MLT) region, the need for an improved representation of NO related processes increases. This work presents a detailed comparison of NO in the Antarctic MLT region between observations made by the Solar Occultation for Ice Experiment (SOFIE) instrument onboard the Aeronomy of Ice in the Mesosphere (AIM) satellite and simulations performed by the Whole Atmosphere Community Climate Model with Specified Dynamics (SD-WACCM). We investigate 7 years of SOFIE observations and focus on the Southern hemisphere, rather than on dynamical variability in the Northern hemisphere or a specific geomagnetic perturbed event. The morphology of the simulated NO is in agreement with observations though the long term mean is too high and the short term variability is too low. Number densities are more similar during winter, though the altitude of peak densities, which reaches between 102–106 km in WACCM and between 98–104 km in SOFIE, is most separated during winter. Using multiple linear regressions and superposed epoch analyses we investigate how well the NO production and transport are represented in the model. The impact of geomagnetic activity is shown to drive NO variations in the lower thermosphere similarly across both datasets. The dynamical transport from the lower thermosphere into the mesosphere during polar winter is found to agree very well, with a descent rate of about 2.2 km/day in the 80–110 km region in both datasets. The downward transported NO fluxes are however too low in WACCM, which is likely due to medium energy electrons and D-region chemistry that are not represented in the model.

scholarly journals The Effects of a Well-Resolved Stratosphere on the Simulated Boreal Winter Circulation in a Climate Model

2019 ◽  
Vol 76 (5) ◽  
pp. 1203-1226 ◽  
Author(s):  
Yoshio Kawatani ◽  
Kevin Hamilton ◽  
Lesley J. Gray ◽  
Scott M. Osprey ◽  
Shingo Watanabe ◽  
...  
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Boreal Winter ◽  
Quasi Biennial Oscillation ◽  
Westerly Jet ◽  
The Impact ◽  
Jet Structure ◽  
Biennial Oscillation

Abstract The impact of stratospheric representation is investigated using the Model for Interdisciplinary Research on Climate Atmospheric General Circulation Model (MIROC-AGCM) run with different model-lid heights and stratospheric vertical resolutions, but unchanged horizontal resolutions (~1.125°) and subgrid parameterizations. One-hundred-year integrations of the model were conducted using configurations with 34, 42, 72, and 168 vertical layers and model-lid heights of ~27 km (L34), 47 km (L42), 47 km (L72), and 100 km (L168). Analysis of the results focused on the Northern Hemisphere in winter. Compared with the L42 model, the L34 model produces a poorer simulation of the stratospheric Brewer–Dobson circulation (BDC) in the lower stratosphere, with weaker polar downwelling and accompanying cold-pole and westerly jet biases. The westerly bias extends into the troposphere and even to the surface. The tropospheric westerlies and zone of baroclinic wave activity shift northward; surface pressure has negative (positive) biases in the high (mid-) latitudes, with concomitant precipitation shifts. The L72 and L168 models generate a quasi-biennial oscillation (QBO) while the L34 and 42 models do not. The L168 model includes the mesosphere, and thus resolves the upper branch of the BDC. The L72 model simulates stronger polar downwelling associated with the BDC than does the L42 model. However, experiments with prescribed nudging of the tropical stratospheric winds suggest differences in the QBO representation cannot account for L72 − L42 differences in the climatological polar night jet structure. The results show that the stratospheric vertical resolution and inclusion of the full middle atmosphere significantly affect tropospheric circulations.

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