scholarly journals On the Gravity Wave Forcing during the Southern Stratospheric Final Warming in LMDZ

2016 ◽  
Vol 73 (8) ◽  
pp. 3213-3226 ◽  
Author(s):  
Alvaro de la Cámara ◽  
François Lott ◽  
Valérian Jewtoukoff ◽  
Riwal Plougonven ◽  
Albert Hertzog
Keyword(s):  
Gravity Wave ◽  
General Circulation ◽  
Climate Models ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
High Amplitude ◽  
Austral Spring ◽  
Wave Forcing ◽  
Stratospheric Final Warming ◽  
Good Agreement

Abstract The austral stratospheric final warming date is often predicted with substantial delay in several climate models. This systematic error is generally attributed to insufficient parameterized gravity wave (GW) drag in the stratosphere around 60°S. A simulation with a general circulation model [Laboratoire de Météorologie Dynamique zoom model (LMDZ)] with a much less pronounced bias is used to analyze the contribution of the different types of waves to the dynamics of the final warming. For this purpose, the resolved and unresolved wave forcing of the middle atmosphere during the austral spring are examined in LMDZ and reanalysis data, and a good agreement is found between the two datasets. The role of parameterized orographic and nonorographic GWs in LMDZ is further examined, and it is found that orographic and nonorographic GWs contribute evenly to the GW forcing in the stratosphere, unlike in other climate models, where orographic GWs are the main contributor. This result is shown to be in good agreement with GW-resolving operational analysis products. It is demonstrated that the significant contribution of the nonorographic GWs is due to highly intermittent momentum fluxes produced by the source-related parameterizations used in LMDZ, in qualitative agreement with recent observations. This yields sporadic high-amplitude GWs that break in the stratosphere and force the circulation at lower altitudes than more homogeneously distributed nonorographic GW parameterizations do.

scholarly journals Improved Simulation of the Antarctic Stratospheric Final Warming by Modifying the Orographic Gravity Wave Parameterization in the Beijing Climate Center Atmospheric General Circulation Model

Atmosphere ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 576
Author(s):  
Yixiong Lu ◽  
Tongwen Wu ◽  
Xin Xu ◽  
Li Zhang ◽  
Min Chu
Keyword(s):  
Gravity Wave ◽  
General Circulation Model ◽  
General Circulation ◽  
Climate Models ◽  
Atmospheric General Circulation Model ◽  
Circulation Model ◽  
Wave Drag ◽  
Atmospheric General Circulation ◽  
Stratospheric Final Warming ◽  
The Antarctic

The Antarctic stratospheric final warming (SFW) is usually simulated with a substantial delay in climate models, and the corresponding temperatures in austral spring are lower than observations, implying insufficient stratospheric wave drag. To investigate the role of orographic gravity wave drag (GWD) in modeling the Antarctic SFW, in this study the orographic GWD parameterization scheme is modified in the middle-atmosphere version of the Beijing Climate Center Atmospheric General Circulation Model. A pair of simulations are conducted to compare two orographic GWD schemes in simulating the breakdown of the stratospheric polar vortex over Antarctica. The control simulation with the default orographic GWD scheme exhibits delayed vortex breakdown and the cold-pole bias seen in most climate models. In the simulation with modified orographic GWD scheme, the simulated vortex breaks down earlier by 8 days, and the associated cold-pole bias is reduced by more than 2 K. The modified scheme provides stronger orographic GWD in the lower stratosphere, which drives an accelerated polar downwelling branch of the Brewer–Dobson circulation and, in turn, produces adiabatic warming. Our study suggests that modifying orographic GWD parameterizations in climate models would be a valid way of improving the SFW simulation over Antarctica.

scholarly journals Forcing mechanisms of the quarterdiurnal tide

2019 ◽  
Author(s):  
Christoph Geißler ◽  
Christoph Jacobi ◽  
Friederike Lilienthal
Keyword(s):  
Gravity Wave ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Destructive Interference ◽  
Global Circulation Model ◽  
Wave Forcing ◽  
Global Circulation ◽  
Tidal Interactions ◽  
Forcing Mechanisms ◽  
The Individual

Abstract. We used a nonlinear mechanistic global circulation model to analyze the migrating quarterdiurnal tide (QDT) in the middle atmosphere with focus on its possible forcing mechanisms. These are absorption of solar radiation by ozone and water vapor, nonlinear tidal interactions, and gravity wave-tide interactions. We show a climatology of the QDT amplitudes, and we examined the contribution of the different forcing mechanisms on the QDT amplitude. To this end, we first extracted the QDT in the model tendency terms. Then, we separately removed the QDT contribution in different tendency terms. We find that the solar forcing mechanism is the most important one for the QDT, but also the nonlinear and gravity wave forcing mechanism play a role in certain seasons, latitudes and altitudes. Furthermore, destructive interference between the individual forcing mechanisms are observed. Therefore, tidal amplitudes partly become even larger in simulations with removed nonlinear or gravity wave forcing mechanism.

Improved sea-ice prediction in the Weddell Sea using sea-ice thickness initialization

2021 ◽  
Author(s):  
Yushi Morioka ◽  
Doroteaciro Iovino ◽  
Andrea Cipollone ◽  
Simona Masina ◽  
Swadhin Behera
Keyword(s):  
Sea Ice ◽  
General Circulation ◽  
Climate Models ◽  
Circulation Model ◽  
Weddell Sea ◽  
Ice Thickness ◽  
Austral Spring ◽  
Sea Ice Concentration ◽  
Sea Ice Thickness ◽  
The Antarctic

<p>Skillful sea-ice prediction in the Antarctic Ocean remains a big challenge due to paucity of sea-ice observations and insufficient representation of sea-ice processes in climate models. This study demonstrates that the Antarctic sea-ice concentration (SIC) prediction is significantly improved using a coupled general circulation model (SINTEX-F2) in which the model’s SIC and sea-ice thickness (SIT) are initialized with the ocean/sea-ice reanalysis product (C-GLORSv7). It is found that the wintertime SIT initialization adds positive values to the prediction skills of the summertime SIC, most effectively in the Weddell Sea where the SIT climatology and variability are the largest among the Antarctic Seas. Examination of the SIT balance during low sea-ice years of the Weddell Sea shows that negative SIT anomalies initialized in June retain the memory throughout austral winter (July-September) owing to horizontal advection of the SIT anomalies by sea-ice velocities. The negative SIT anomalies continue to develop in austral spring (October-December) owing to more incoming solar radiation via ice-albedo feedback and the associated warming of mixed layer. This results in further sea-ice decrease during austral summer (January-March). Concomitantly, the model reasonably reproduces atmospheric circulation anomalies in the Amundsen-Bellingshausen Seas as well as the Weddell Sea during the development of the negative sea-ice anomalies. These results provide solid evidence that the wintertime SIT initialization benefits skillful summertime sea-ice prediction in the Antarctic Seas.</p>

scholarly journals Energetic particle precipitation in ECHAM5/MESSy – Part 2: Solar proton events

2010 ◽  
Vol 10 (15) ◽  
pp. 7285-7302 ◽  
Author(s):  
A. J. G. Baumgaertner ◽  
P. Jöckel ◽  
H. Riede ◽  
G. Stiller ◽  
B. Funke
Keyword(s):  
Atmospheric Chemistry ◽  
General Circulation ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Solar Proton ◽  
No Production ◽  
Particle Precipitation ◽  
Total Column Ozone ◽  
Solar Proton Events ◽  
Good Agreement

Abstract. The atmospheric chemistry general circulation model ECHAM5/MESSy (EMAC) has been extended by processes that parameterize particle precipitation. Several types of particle precipitation that directly affect NOy and HOx concentrations in the middle atmosphere are accounted for and discussed in a series of papers. In part 1, the EMAC parameterization for NOx produced in the upper atmosphere by low-energy electrons is presented. Here, we discuss production of NOy and HOx associated with Solar Proton Events (SPEs). A submodel that parameterizes the effects of precipitating protons, based on flux measurements by instruments on the IMP or GOES satellites, was added to the EMAC model. Production and transport of NOy and HOx, as well as effects on other chemical species and dynamics during the 2003 Halloween SPEs are presented. Comparisons with MIPAS/ENVISAT measurements of a number of species affected by the SPE are shown and discussed. There is good agreement for NO2, but a severe disagreement is found for N2O similar to other studies. We discuss the effects of an altitude dependence of the N/NO production rate on the N2O and NOy changes during the SPE. This yields a modified parameterization that shows mostly good agreement between MIPAS and model results for NO2, N2O, O3, and HOCl. With the ability of EMAC to relax the model meteorology to observations, accurate assessment of total column ozone loss is also possible, yielding a loss of approximately 10 DU at the end of November. Discrepancies remain for HNO3, N2O5, and ClONO2, which are likely a consequence from the missing cluster ion chemistry and ion-ion recombination in the EMAC model as well as known issues with the model's NOy partitioning.

scholarly journals Climatology and Forcing of the Quasi-Biennial Oscillation in the MAECHAM5 Model

2006 ◽  
Vol 19 (16) ◽  
pp. 3882-3901 ◽  
Author(s):  
M. A. Giorgetta ◽  
E. Manzini ◽  
E. Roeckner ◽  
M. Esch ◽  
L. Bengtsson
Keyword(s):  
Gravity Wave ◽  
Zonal Wind ◽  
General Circulation ◽  
Large Scale ◽  
Climate Models ◽  
Middle Atmosphere ◽  
General Circulation Models ◽  
Wave Drag ◽  
Quasi Biennial Oscillation ◽  
Biennial Oscillation

Abstract The quasi-biennial oscillation (QBO) in the equatorial zonal wind is an outstanding phenomenon of the atmosphere. The QBO is driven by a broad spectrum of waves excited in the tropical troposphere and modulates transport and mixing of chemical compounds in the whole middle atmosphere. Therefore, the simulation of the QBO in general circulation models and chemistry climate models is an important issue. Here, aspects of the climatology and forcing of a spontaneously occurring QBO in a middle-atmosphere model are evaluated, and its influence on the climate and variability of the tropical middle atmosphere is investigated. Westerly and easterly phases are considered separately, and 40-yr ECMWF Re-Analysis (ERA-40) data are used as a reference where appropriate. It is found that the simulated QBO is realistic in many details. Resolved large-scale waves are particularly important for the westerly phase, while parameterized gravity wave drag is more important for the easterly phase. Advective zonal wind tendencies are important for asymmetries between westerly and easterly phases, as found for the suppression of the easterly phase downward propagation. The simulation of the QBO improves the tropical upwelling and the atmospheric tape recorder compared to a model without a QBO. The semiannual oscillation is simulated realistically only if the QBO is represented. In sensitivity tests, it is found that the simulated QBO is strongly sensitive to changes in the gravity wave sources. The sensitivity to the tested range of horizontal resolutions is small. The stratospheric vertical resolution must be better than 1 km to simulate a realistic QBO.

scholarly journals Energetic particle precipitation in ECHAM5/MESSy – Part 2: Solar Proton Events

2010 ◽  
Vol 10 (2) ◽  
pp. 4501-4542 ◽  
Author(s):  
A. J. G. Baumgaertner ◽  
P. Jöckel ◽  
H. Riede ◽  
G. Stiller ◽  
B. Funke
Keyword(s):  
Atmospheric Chemistry ◽  
General Circulation ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Solar Proton ◽  
No Production ◽  
Particle Precipitation ◽  
Total Column Ozone ◽  
Solar Proton Events ◽  
Good Agreement

Abstract. The atmospheric chemistry general circulation model ECHAM5/MESSy (EMAC) has been extended by processes that parameterize particle precipitation. Several types of particle precipitation that directly affect NOy and HOx concentrations in the middle atmosphere are accounted for and discussed in a series of papers. In part 1, the EMAC parameterization for NOx produced in the upper atmosphere by low-energy electrons is presented. Here, we discuss production of NOy and HOx associated with Solar Proton Events (SPEs). A submodel that parameterizes the effects of precipitating protons, based on flux measurements by instruments on the IMP or GOES satellites, was added to the EMAC model. Production and transport of NOy and HOx, as well as effects on other chemical species and dynamics during the 2003 Halloween SPEs are presented. Comparisons with MIPAS/ENVISAT measurements of a number of species affected by the SPE are shown and discussed. There is good agreement for NO2, but a severe disagreement is found for N2O similar to other studies. We discuss the effects of an altitude dependence of the N/NO production rate on the N2O and NOy changes during the SPE. This yields a modified parameterization that shows good agreement between MIPAS and model results for NO2, N2O, O3, and HOCl. With the ability of EMAC to relax the model meteorology to observations, accurate assessment of total column ozone loss is also possible, yielding a loss of approximately 10 DU at the end of November. Discrepancies remain for HNO3, N2O5, and ClONO2, which are likely a consequence from the missing cluster ion chemistry in the EMAC model as well as known issues with the model's NOy partitioning.

scholarly journals The atmospheric chemistry general circulation model ECHAM5/MESSy1: consistent simulation of ozone from the surface to the mesosphere

2006 ◽  
Vol 6 (4) ◽  
pp. 6957-7050 ◽  
Author(s):  
P. Jöckel ◽  
H. Tost ◽  
A. Pozzer ◽  
C. Brühl ◽  
J. Buchholz ◽  
...  
Keyword(s):  
General Circulation Model ◽  
Atmospheric Chemistry ◽  
General Circulation ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Tropospheric Chemistry ◽  
Atmospheric Composition ◽  
Quasi Biennial Oscillation ◽  
Wave Forcing ◽  
Characteristic Features

Abstract. The new Modular Earth Submodel System (MESSy) describes atmospheric chemistry and meteorological processes in a modular framework, following strict coding standards. It has been coupled to the ECHAM5 general circulation model, which has been slightly modified for this purpose. A 90-layer model version up to 0.01 hPa was used at T42 resolution (~2.8 latitude and longitude) to simulate the lower and middle atmosphere. The model meteorology has been tested to check the influence of the changes to ECHAM5 and the radiation interactions with the new representation of atmospheric composition. A Newtonian relaxation technique was applied in the tropospheric part of the domain to weakly nudge the model towards the analysed meteorology during the period 1998–2005. It is shown that the tropospheric wave forcing of the stratosphere in the model suffices to reproduce the Quasi-Biennial Oscillation and major stratospheric warming events leading e.g. to the vortex split over Antarctica in 2002. Characteristic features such as dehydration and denitrification caused by the sedimentation of polar stratospheric cloud particles and ozone depletion during winter and spring are simulated accurately, although ozone loss in the lower polar stratosphere is slightly underestimated. The model realistically simulates stratosphere-troposphere exchange processes as indicated by comparisons with satellite and in situ measurements. The evaluation of tropospheric chemistry presented here focuses on the distributions of ozone, hydroxyl radicals, carbon monoxide and reactive nitrogen compounds. In spite of minor shortcomings, mostly related to the relatively coarse T42 resolution and the neglect of interannual changes in biomass burning emissions, the main characteristics of the trace gas distributions are generally reproduced well. The MESSy submodels and the ECHAM5/MESSy1 model output are available through the internet on request.

scholarly journals Southern Hemisphere Extratropical Gravity Wave Sources and Intermittency Revealed by a Middle-Atmosphere General Circulation Model

2016 ◽  
Vol 73 (3) ◽  
pp. 1335-1349 ◽  
Author(s):  
Simon P. Alexander ◽  
Kaoru Sato ◽  
Shingo Watanabe ◽  
Yoshio Kawatani ◽  
Damian J. Murphy
Keyword(s):  
Gravity Wave ◽  
Southern Hemisphere ◽  
General Circulation Model ◽  
Gravity Waves ◽  
General Circulation ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Absolute Gravity ◽  
Atmosphere General Circulation Model ◽  
Time Of Year

Abstract Southern Hemisphere extratropical gravity wave activity is examined using simulations from a free-running middle-atmosphere general circulation model called Kanto that contains no gravity wave parameterizations. The total absolute gravity wave momentum flux (MF) and its intermittency, diagnosed by the Gini coefficient, are examined during January and July. The MF and intermittency results calculated from the Kanto model agree well with results from satellite limb and superpressure balloon observations. The analysis of the Kanto model simulations indicates the following results. Nonorographic gravity waves are generated in Kanto in the frontal regions of extratropical depressions and around tropopause-level jets. Regions with lower (higher) intermittency in the July midstratosphere become more (less) intermittent by the mesosphere as a result of lower-level wave removal. The gravity wave intermittency is low and nearly homogeneous throughout the SH middle atmosphere during January. This indicates that nonorographic waves dominate at this time of year, with sources including continental convection as well as oceanic depressions. Most of the zonal-mean MF at 40°–65°S in January and July is due to gravity waves located above the oceans. The zonal-mean MF at lower latitudes in both months has a larger contribution from the land regions but the fraction above the oceans remains larger.

scholarly journals Gravity Wave Characteristics in the Southern Hemisphere Revealed by a High-Resolution Middle-Atmosphere General Circulation Model

2012 ◽  
Vol 69 (4) ◽  
pp. 1378-1396 ◽  
Author(s):  
Kaoru Sato ◽  
Satoshi Tateno ◽  
Shingo Watanabe ◽  
Yoshio Kawatani
Keyword(s):  
Gravity Wave ◽  
Energy Flux ◽  
Gravity Waves ◽  
Wave Energy ◽  
General Circulation ◽  
Middle Atmosphere ◽  
Polar Vortex ◽  
Circulation Model ◽  
Southern Andes ◽  
Atmosphere General Circulation Model

Abstract Gravity wave characteristics in the middle- to high-latitude Southern Hemisphere are analyzed using simulation data over 3 yr from a high-resolution middle-atmosphere general circulation model without using any gravity wave parameterizations. Gravity waves have large amplitudes in winter and are mainly distributed in the region surrounding the polar vortex in the middle and upper stratosphere, while the gravity wave energy is generally weak in summer. The wave energy distribution in winter is not zonally uniform, but it is large leeward of the southern Andes and Antarctic Peninsula. Linear theory in the three-dimensional framework indicates that orographic gravity waves are advected leeward significantly by the mean wind component perpendicular to the wavenumber vector. Results of ray-tracing and cross-correlation analyses are consistent with this theoretical expectation. The leeward energy propagation extends to several thousand kilometers, which explains part of the gravity wave distribution around the polar vortex in winter. This result indicates that orographic gravity waves can affect the mean winds at horizontal locations that are far distant from the source mountains. Another interesting feature is a significant downward energy flux in winter, which is observed in the lower stratosphere to the south of the southern Andes. The frequency of the downward energy flux is positively correlated with the gravity wave energy over the southern Andes. Partial reflection from a rapid increase in static stability around 10 hPa and/or gravity wave generation through nonlinear processes are possible mechanisms to explain the downward energy flux.

Sign in / Sign up

Export Citation Format

Share Document