Observations of the mesospheric semi-annual oscillation (MSAO) in water vapour by Odin/SMR

Lossow, Stefan; Urban, Joachim; Gumbel, J.; Eriksson, Patrick; Murtagh, Donal

doi:10.5194/acp-8-6527-2008

Cited by 22 publications

(22 citation statements)

References 63 publications

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“…In the mesosphere (0.1-0.007 hPa), the dataset, based on the HCl line measured in band-B, is quite sparse. It shows that the wind flow also varies over a large velocity range (between −60 and +60 m s −1 ) but, as expected, the wind direction changes in anti-phase with the stratosphere (Hitchman et al, 1997;Lossow et al, 2008). At lower altitudes (below 5 hPa), the SAO amplitude decreases and is mixed with the QBO (Hirota, 1980;Baldwin and Gray, 2005).…”

Section: The Sudden Stratospheric Warming Eventsmentioning

confidence: 78%

Observation of horizontal winds in the middle-atmosphere between 30° S and 55° N during the northern winter 2009–2010

et al. 2013

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Abstract. Although the links between stratospheric dynamics, climate and weather have been demonstrated, direct observations of stratospheric winds are lacking, in particular at altitudes above 30 km. We report observations of winds between 8 and 0.01 hPa (~35–80 km) from October 2009 to April 2010 by the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the International Space Station. The altitude range covers the region between 35–60 km where previous space-borne wind instruments show a lack of sensitivity. Both zonal and meridional wind components were obtained, though not simultaneously, in the latitude range from 30° S to 55° N and with a single profile precision of 7–9 m s–1 between 8 and 0.6 hPa and better than 20 m s–1 at altitudes above. The vertical resolution is 5–7 km except in the upper part of the retrieval range (10 km at 0.01 hPa). In the region between 1–0.05 hPa, an absolute value of the mean difference < 2 m s–1 is found between SMILES profiles retrieved from different spectroscopic lines and instrumental settings. Good agreement (absolute value of the mean difference of ~2 m s–1) is also found with the European Centre for Medium-Range Weather Forecasts (ECMWF) analysis in most of the stratosphere except for the zonal winds over the equator (difference > 5 m s−1). In the mesosphere, SMILES and ECMWF zonal winds exhibit large differences (> 20 m s–1), especially in the tropics. We illustrate our results by showing daily and monthly zonal wind variations, namely the semi-annual oscillation in the tropics and reversals of the flow direction between 50–55° N during sudden stratospheric warmings. The daily comparison with ECMWF winds reveals that in the beginning of February, a significantly stronger zonal westward flow is measured in the tropics at 2 hPa compared to the flow computed in the analysis (difference of ~20 m s–1). The results show that the comparison between SMILES and ECMWF winds is not only relevant for the quality assessment of the new SMILES winds, but it also provides insights on the quality of the ECMWF winds themselves. Although the instrument was not specifically designed for measuring winds, the results demonstrate that space-borne sub-mm wave radiometers have the potential to provide good quality data for improving the stratospheric winds in atmospheric models.

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Section: The Sudden Stratospheric Warming Eventsmentioning

confidence: 78%

Observation of horizontal winds in the middle-atmosphere between 30° S and 55° N during the northern winter 2009–2010

et al. 2013

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“…Various observations are compared here and their merits briefly discussed. A strong equatorial MSAO was observed in the H 2 O mixing ratio by Lossow et al (2008) with the 90 km mixing ratio varying from approximately 0.1 ppm in April to approximately 0.4 ppm in July. The upper altitude limit of their published profiles is 100 km.…”

Section: Msao Data Driving the Model Simulationmentioning

confidence: 97%

“…Diurnal tides, eddy diffusion and the prevailing background vertical winds make up the dynamic components included in the 1-D model. More detailed examples of such combined photochemical and dynamical model comparisons with observations are those of Marsh et al (2003), Smith and Marsh (2005) based on the ROSE model, Wu et al (2008) with the TIME-GCM model, and Dikty et al (2010) using the HAMMONIA model.…”

Section: R L Gattinger Et Al: the Roles Of Vertical Advection And mentioning

confidence: 99%

“…Chandra et al (1997) observed seasonal variations in water vapour (H 2 O) using UARS/MLS (Microwave Limb Sounder) and HALOE (HALogen Occultation Experiment) data and, in addition, obtained good agreement with a twodimensional (2-D) photochemical and transport model. Lossow et al (2008), using sub-mm radiometer (SMR) data from the Odin spacecraft (Murtagh et al, 2002), observed the MSAO in H 2 O mixing ratio, the maxima at 90 km occurring in the solstice periods. Kyrölä et al (2006Kyrölä et al ( , 2010, using Envisat/GOMOS (Global Ozone Monitoring by Occultation of Stars) data, found that ozone (O 3 ) at 90 km peaked in equinox periods and was approximately a factor of three lower in solstice periods.…”

Section: R L Gattinger Et Al: the Roles Of Vertical Advection And mentioning

confidence: 99%

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The roles of vertical advection and eddy diffusion in the equatorial mesospheric semi-annual oscillation (MSAO)

et al. 2013

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Observations of the mesospheric semi-annual oscillation (MSAO) in the equatorial region have been reported dating back several decades. Seasonal variations in both species densities and airglow emissions are well documented. The extensive observations available offer an excellent case study for comparison with model simulations. A broad range of MSAO measurements is summarised with emphasis on the 80–100 km region. The objective here is not to address directly the complicated driving forces of the MSAO, but rather to employ a combination of observations and model simulations to estimate the limits of some of the underlying dynamical processes. Photochemical model simulations are included for near-equinox and near-solstice conditions, the two times with notable differences in the observed MSAO parameters. Diurnal tides are incorporated in the model to facilitate comparisons of observations made at different local times. The roles of water vapour as the "driver" species and ozone as the "response" species are examined to test for consistency between the model results and observations. The simulations suggest the interactions between vertical eddy diffusion and background vertical advection play a significant role in the MSAO phenomenon. Further, the simulations imply there are rigid limits on vertical advection rates and eddy diffusion rates. For August at the Equator, 90 km altitude, the derived eddy diffusion rate is approximately 1 × 10⁶ cm² s⁻¹ and the vertical advection is upwards at 0.8 cm s⁻¹. For April the corresponding values are 4 × 10⁵ cm² s⁻¹ and 0.1 cm s⁻¹. These results from the current 1-D model simulations will need to be verified by a full 3-D simulation. Exactly how vertical advection and eddy diffusion are related to gravity wave momentum as discussed by Dunkerton (1982) three decades ago remains to be addressed

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“…These results are based on observations of the Sub-Millimetre Radiometer (SMR) aboard the Odin satellite (Murtagh et al, 2002) from 2001 to 2014. More information on the SMR water vapour measurements can be found in Lossow et al (2008). Below about 0.005 hPa (∼ 85.5 km) the largest annual variation is found in the polar regions, similarly to the stratosphere.…”

Section: Descriptionmentioning

confidence: 99%

An “island” in the stratosphere – on the enhanced annual variation of water vapour in the middle and upper stratosphere in the southern tropics and subtropics

2017

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Abstract. The amplitude of the annual variation in water vapour exhibits a distinct isolated maximum in the middle and upper stratosphere in the southern tropics and subtropics, peaking typically around 15 • S in latitude and close to 3 hPa (∼ 40.5 km) in altitude. This enhanced annual variation is primarily related to the Brewer-Dobson circulation and hence also visible in other trace gases. So far this feature has not gained much attention in the literature and the present work aims to add more prominence. Using Envisat/MIPAS (Environmental Satellite/Michelson Interferometer for Passive Atmospheric Sounding) observations and ECHAM/MESSy (European Centre for Medium-Range Weather Forecasts Hamburg/Modular Earth Submodel System) Atmospheric Chemistry (EMAC) simulations we provide a dedicated illustration and a full account of the reasons for this enhanced annual variation.

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Observations of the mesospheric semi-annual oscillation (MSAO) in water vapour by Odin/SMR

Cited by 22 publications

References 63 publications

Observation of horizontal winds in the middle-atmosphere between 30° S and 55° N during the northern winter 2009–2010

Observation of horizontal winds in the middle-atmosphere between 30° S and 55° N during the northern winter 2009–2010

The roles of vertical advection and eddy diffusion in the equatorial mesospheric semi-annual oscillation (MSAO)

An “island” in the stratosphere – on the enhanced annual variation of water vapour in the middle and upper stratosphere in the southern tropics and subtropics

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