scholarly journals Evaluating Different Techniques for Constraining Lower Atmospheric Variability in an Upper Atmosphere General Circulation Model: A Case Study During the 2010 Sudden Stratospheric Warming

2018 ◽  
Author(s):  
McArthur Jones ◽  
Douglas P. Drob ◽  
David E. Siskind ◽  
John P. McCormack ◽  
Astrid Maute ◽  
...  
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Upper Atmosphere ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Atmospheric Variability ◽  
Atmosphere General Circulation Model

scholarly journals Strengthening of the Tropopause Inversion Layer during the 2009 Sudden Stratospheric Warming: A MERRA-2 Study

2016 ◽  
Vol 73 (5) ◽  
pp. 1871-1887 ◽  
Author(s):  
Krzysztof Wargan ◽  
Lawrence Coy
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Inversion Layer ◽  
Vertical Component ◽  
Circulation Model ◽  
Static Stability ◽  
Stratospheric Warming ◽  
Residual Circulation ◽  
Sudden Stratospheric Warming ◽  
Wave Forcing

Abstract The behavior of the tropopause inversion layer (TIL) during the 2009 sudden stratospheric warming (SSW) is analyzed using NASA’s Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), and short-term simulations with the MERRA-2 general circulation model. Consistent with previous studies, it is found that static stability in a shallow layer above the polar tropopause sharply increases following the SSW, leading to a strengthening of the high-latitude TIL. Simultaneously, the height of the thermal tropopause decreases by around 1 km. Similar behavior is also detected during other major SSW events between the years 2004 and 2013. Using an ensemble of general circulation model forecasts initialized from MERRA-2, it is demonstrated that the primary cause of the strengthening of the TIL is an increased convergence of the vertical component of the stratospheric residual circulation in response to an SSW-induced acceleration of the mean downward motion between 75° and 90°N. In addition, ~6% of the strengthening in 2009 is attributed to an enhanced anticyclonic circulation at the tropopause. A preliminary analysis indicates that during other recent SSW events there was a significant increase in the convergence of the vertical residual wind velocity throughout the middle and lower stratosphere. The static stability increase simulated by the model during the 2009 SSW is 60%–80% of that seen in MERRA-2. The underestimate is traced back to a tendency for the forecasts to underestimate the resolved planetary wave forcing on the stratosphere compared to the reanalysis.

scholarly journals Influence of the sudden stratospheric warming on quasi-2-day waves

2016 ◽  
Vol 16 (8) ◽  
pp. 4885-4896 ◽  
Author(s):  
Sheng-Yang Gu ◽  
Han-Li Liu ◽  
Xiankang Dou ◽  
Tao Li
Keyword(s):  
General Circulation ◽  
Phase Speed ◽  
Circulation Model ◽  
Meridional Wind ◽  
Equatorial Region ◽  
Wave Number ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Middle Latitudes ◽  
Zonal Wave Number

Abstract. The influence of the sudden stratospheric warming (SSW) on a quasi-2-day wave (QTDW) with westward zonal wave number 3 (W3) is investigated using the Thermosphere–Ionosphere–Mesosphere Electrodynamics General Circulation Model (TIME-GCM). The summer easterly jet below 90 km is strengthened during an SSW, which results in a larger refractive index and thus more favorable conditions for the propagation of W3. In the winter hemisphere, the Eliassen–Palm (EP) flux diagnostics indicate that the strong instabilities at middle and high latitudes in the mesopause region are important for the amplification of W3, which is weakened during SSW periods due to the deceleration or even reversal of the winter westerly winds. Nonlinear interactions between the W3 and the wave number 1 stationary planetary wave produce QTDW with westward zonal wave number 2 (W2). The meridional wind perturbations of the W2 peak in the equatorial region, while the zonal wind and temperature components maximize at middle latitudes. The EP flux diagnostics indicate that the W2 is capable of propagating upward in both winter and summer hemispheres, whereas the propagation of W3 is mostly confined to the summer hemisphere. This characteristic is likely due to the fact that the phase speed of W2 is larger, and therefore its waveguide has a broader latitudinal extension. The larger phase speed also makes W2 less vulnerable to dissipation and critical layer filtering by the background wind when propagating upward.

Sign in / Sign up

Export Citation Format

Share Document