scholarly journals Diagnosis of Local Gravity Wave Properties during a Sudden Stratospheric Warming

2017 ◽  
Author(s):  
Lena Schoon ◽  
Christoph Zülicke
Keyword(s):  
Wave Propagation ◽  
Gravity Wave ◽  
Wave Activity ◽  
Wave Number ◽  
Complex Signal ◽  
Unexpected Finding ◽  
Stratospheric Warming ◽  
Local Wave ◽  
The Hilbert Transform ◽  
A Minor

Abstract. Commonly, wave quantities are maintained in zonal mean averages. Hence, local wave phenomena remain unclear. Here, we introduce a diagnostic tool for studies of wave packets locally. The "Unified Wave Diagnosis" (UWaDi) uses the Hilbert Transform to obtain a complex signal from a real-valued function and estimates the amplitude and wave number locally. Operational data from the European Centre for Medium-Range Weather Forecasts is used to perform the analysis. Restrictions on gravity wave propagation due to model sponge layers are identified well above the 10 hPa altitude. From a minor stratospheric warming in January 2016 three cases for vertical gravity wave propagation in different background wind conditions are selected. It is shown that zonal mean wind quantities cannot reveal local "valves" allowing gravity waves to propagate into the mid-stratosphere. The unexpected finding of high gravity wave activity at the minor warming of 30 January 2016 is related to strong planetary wave activity and a strong local "pump". Accordingly, the advantages of a local wave packet analysis are demonstrated for profiles up to the model sponge layer.

scholarly journals A Study of False Alarms of a Major Sudden Stratospheric Warming by Real-Time Subseasonal-to-Seasonal Forecasts for the 2017/2018 Northern Winter

Atmosphere ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 875
Author(s):  
Masakazu Taguchi
Keyword(s):  
False Alarm ◽  
Real Time ◽  
Winter Season ◽  
Wave Activity ◽  
Wave Number ◽  
False Alarms ◽  
Stratospheric Warming ◽  
Seasonal Forecasts ◽  
Sudden Stratospheric Warming ◽  
First Case

This study investigates false alarms of a major sudden stratospheric warming (MSSW) by real-time subseasonal-to-seasonal forecast data of the European Centre for Medium-Range Weather Forecasts system for the 2017/2018 Northern Hemisphere winter season. The analysis reveals two false alarm cases in the season, one in early December and the other in early February. Each case is characterized by ensembles of which a considerable part of the members (MSSW members) show an MSSW, that is, reversal of the zonal mean zonal wind in the extratropical stratosphere on similar calendar dates. Ensemble forecasts that are initialized earlier or later basically lack an MSSW, demonstrating clear intraseasonal variability in the frequency of forecasted MSSWs. For each false alarm case, the MSSW member mean field shows equatorward displacement of the polar vortex around the onset date. For both cases, the MSSW members accompany stronger wave activity in the lower stratosphere than other non-MSSW members and reanalysis data. They are further associated with higher geopotential height than the non-MSSW members, in the upper troposphere over northeastern Canada and Greenland before the first case, and lower height over northeastern Eurasia before the second case. These are located over the ridge and trough, respectively, of the climatological planetary wave of zonal wave number one, and are consistent with the increased wave activity.

scholarly journals Observations of OH airglow from ground, aircraft, and satellite: investigation of wave-like structures before a minor stratospheric warming

2019 ◽  
Vol 19 (9) ◽  
pp. 6401-6418 ◽  
Author(s):  
Sabine Wüst ◽  
Carsten Schmidt ◽  
Patrick Hannawald ◽  
Michael Bittner ◽  
Martin G. Mlynczak ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Middle Atmosphere ◽  
Periodic Structures ◽  
Occurrence Rate ◽  
Small Scale ◽  
Stratospheric Warming ◽  
Camera System ◽  
Data Set ◽  
Mountainous Regions ◽  
A Minor

Abstract. In January and February 2016, the OH airglow camera system FAIM (Fast Airglow Imager) measured during six flights on board the research aircraft FALCON in northern Scandinavia. Flight 1 (14 January 2016) covering the same ground track in several flight legs and flight 5 (28 January 2016) along the shoreline of Norway are discussed in detail in this study. The images of the OH airglow intensity are analysed with a two-dimensional FFT regarding horizontal periodic structures between 3 and 26 km horizontal wavelength and their direction of propagation. Two ground-based spectrometers (GRIPS, Ground-based Infrared P-branch Spectrometer) provided OH airglow temperatures. One was placed at ALOMAR, Northern Norway (Arctic Lidar Observatory for Middle Atmosphere Research; 69.28∘ N, 16.01∘ E) and the other one at Kiruna, northern Sweden (67.86∘ N, 20.24∘ E). Especially during the last third of January 2016, the weather conditions at Kiruna were good enough for the computation of nightly means of gravity wave potential energy density. Coincident TIMED-SABER (Thermosphere Ionosphere Mesosphere Energetics Dynamics–Sounding of the Atmosphere using Broadband Emission Radiometry) measurements complete the data set. They allow for the derivation of information about the Brunt–Väisälä frequency and about the height of the OH airglow layer as well as its thickness. The data are analysed with respect to the temporal and spatial evolution of mesopause gravity wave activity just before a minor stratospheric warming at the end of January 2016. Wave events with periods longer (shorter) than 60 min might mainly be generated in the troposphere (at or above the height of the stratospheric jet). Special emphasis is placed on small-scale signatures, i.e. on ripples, which may be signatures of local instability and which may be related to a step in a wave-breaking process. The most mountainous regions are characterized by the highest occurrence rate of wave-like structures in both flights.

scholarly journals Observations of OH-airglow from ground, aircraft, and satellite: investigation of wave-like structures before a minor stratospheric warming

2018 ◽  
Author(s):  
Sabine Wüst ◽  
Carsten Schmidt ◽  
Patrick Hannawald ◽  
Michael Bittner ◽  
Martin G. Mlynczak ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Middle Atmosphere ◽  
Periodic Structures ◽  
Occurrence Rate ◽  
Small Scale ◽  
Stratospheric Warming ◽  
Camera System ◽  
Data Set ◽  
Mountainous Regions ◽  
A Minor

Abstract. In January and February 2016, the OH-airglow camera system FAIM (Fast Airglow Imager) measured during six flights on board the research aircraft FALCON in Northern Scandinavia. Flight 1 (14th January 2016) covering the same ground track in several flight legs and flight 5 (28th January 2016) along the shoreline of Norway are discussed in detail in this study. The images of the OH-airglow intensity are analysed with a two-dimensional FFT regarding horizontal periodic structures between 3 km and 26 km horizontal wavelength and their direction of propagation. Two ground-based spectrometers (GRIPS, Ground based Infrared P-branch Spectrometer) provided OH-airglow temperatures. One was placed at ALOMAR, Northern Norway (Arctic Lidar Observatory for Middle Atmosphere Research; 69.28 °N, 16.01 °E) and the other one at Kiruna, Northern Sweden (67.86 °N, 20.24 °E). Especially during the last third of January 2016, the weather conditions at Kiruna were good enough for the computation of nightly means of gravity wave potential energy density. Coincident TIMED-SABER (Thermosphere Ionosphere Mesosphere Energetics Dynamics, Sounding of the Atmosphere using Broadband Emission Radiometry) measurements complete the data set. They allow for the derivation of information about the Brunt-Väisälä frequency and about the height of the OH-airglow layer as well as its thickness. The data are analysed with respect to the temporal and spatial evolution of mesopause gravity wave activity just before a minor stratospheric warming at the end of January 2016. Wave events with periods longer (shorter) than 60 min might mainly be generated in the troposphere (at or above the height of the stratospheric jet). Special emphasize is put on small-scale signatures, i.e. on ripples, which are signatures of local instability and which may be related to a step in a wave breaking process. The most mountainous regions are characterized by the highest occurrence rate of wave-like structures in both flights.

scholarly journals INVESTIGATION OF NORTHERN HEMISPHERE STRATOSPHERE VARIABILITY IN XXI CENTURY IN INM CM5 CLIMATE MODEL SIMULATIONS

2020 ◽  
Vol 1 (5) ◽  
pp. 27-34
Author(s):  
P. N. Vargin ◽  
◽  
E. M. Volodin ◽  
Keyword(s):  
Planetary Wave ◽  
Climate Model ◽  
Meridional Circulation ◽  
Wave Activity ◽  
Wave Number ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Stratospheric Polar Vortex ◽  
Spring Break ◽  
Break Up

Simulations of 5th version of INM RAS (Institute of Numerical Mathematics of the Russian Academy of Science) climate model performed in the framework of CMIP6 project for the future climate under ssp2–4.5 (moderate) and ssp5–8.5 (business as usual or hard) scenarios of green house gases (GHG) increase are employed to analyze temperature, zonal mean wind, stratospheric polar vortex, planetary wave activity, meridional circulation, sudden stratospheric warming (SSW) events, and stratospheric circulation spring break-up date changes during boreal winters from 2015 to 2100. Comparison of averages over two periods of 2080–2100 and 2015–2035 revealed that temperature will decrease from 1° in the lower stratosphere to 4° in the upper stratosphere under moderate scenario and up to 11° under hard scenario. Cooling of stratosphere will be accompanied by strengthening of zonal circulation and planetary wave activity propagation in the middle – upper stratosphere that in turn leads to increase (stronger under hard scenario) of planetary wave with zonal wave number 1 amplitude (wavenumber 1). 13 major sudden stratospheric warming events and 16 very cold stratospheric winter seasons were revealed under hard scenario. Under both scenarios early spring break-up dates will be accompanied by stronger wavenumber 1 in comparison with winter seasons with later spring break-up dates. Strengthening of zonal mean meridional circulation is expected in the late XXI century

Influence of the upper atmosphere inhomogeneity on acoustic gravity wave propagation

2012 ◽  
Vol 18 (4(77)) ◽  
pp. 30-36 ◽  
Author(s):  
Y.I. Kryuchkov ◽  
◽  
O.K. Cheremnykh ◽  
A.K. Fedorenko ◽  
◽  
...  
Keyword(s):  
Wave Propagation ◽  
Gravity Wave ◽  
Upper Atmosphere ◽  
Acoustic Gravity Wave
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