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K Hausler - One of the best experts on this subject based on the ideXlab platform.
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Longitudinal Variations of the Thermospheric Zonal Wind Induced by Nonmigrating Tides as Observed by CHAMP
Aeronomy of the Earth's Atmosphere and Ionosphere, 2011Co-Authors: K Hausler, Hermann LührAbstract:In July 2000 the very successful German mini-satellite mission CHAMP, an acronym for Challenging Minisatellite Payload, was launched. One of the scientific instruments on board is an accelerometer that allows us to derive the Zonal Wind at CHAMP’s altitude (~ 400 km). Previous to its launch, continuous and globally distributed measurements of the upper thermospheric Wind have been rather sparse. With the launch of the CHAMP satellite we are now able to investigate the upper thermospheric Zonal Wind, and in particular its longitudinal variability, in a climatological sense. This capability has led to exciting and unanticipated findings such as the coupling from the troposphere to the thermosphere via nonmigrating tides. In this chapter we talk about the longitudinal variations of the CHAMP Zonal Wind at equatorial latitudes. Further, we present the nonmigrating tidal spectra embedded in the CHAMP Zonal Wind with special emphasis on the eastward propagating diurnal tide with Zonal wavenumber 3 (DE3).
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comparison of champ and time gcm nonmigrating tidal signals in the thermospheric Zonal Wind
Journal of Geophysical Research, 2010Co-Authors: K Hausler, H Luhr, M E Hagan, Astrid Maute, R G RobleAbstract:[1] Four years (2002–2005) of continuous accelerometer measurements taken onboard the CHAMP satellite (orbit altitude ∼400 km) offer a unique opportunity to investigate the thermospheric Zonal Wind on a global scale. Recently, we were able to relate the longitudinal wave-4 structure in the Zonal Wind at equatorial latitudes to the influence of nonmigrating tides and in particular to the eastward propagating diurnal tide with Zonal wave number 3 (DE3). The DE3 tide is primarily excited by latent heat release in the tropical troposphere in deep convective clouds. In order to investigate the mechanisms that couple the tidal signals to the upper thermosphere, we undertook a comparison with the thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) developed at the National Center for Atmospheric Research (NCAR). We ran the model for a day in March, June, September, and December and applied the same processing steps to the model output as was done for the CHAMP tidal analysis. The main results of the comparison can be summarized as follows: (1) TIME-GCM simulations do not correctly reproduce the observed intra-annual variations of DE3 and the eastward propagating diurnal tide with Zonal wave number 2 (DE2). (2) Simulations of DE3 for June are more successful. Both TIME-GCM and CHAMP show an increase in DE3 amplitudes with decreasing solar flux level. (3) The amplitudes of the simulated westward propagating diurnal tide with Zonal wave number 2 (DW2) and the standing diurnal tide (D0) increase with increasing solar flux in June. The predicted dependence of DW2 and DO on solar flux is also observed by CHAMP.
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comparison of champ and time gcm nonmigrating tidal signals in the thermospheric Zonal Wind
Journal of Geophysical Research, 2010Co-Authors: K Hausler, H Luhr, M E Hagan, Astrid Maute, R G RobleAbstract:[1] Four years (2002–2005) of continuous accelerometer measurements taken onboard the CHAMP satellite (orbit altitude ∼400 km) offer a unique opportunity to investigate the thermospheric Zonal Wind on a global scale. Recently, we were able to relate the longitudinal wave-4 structure in the Zonal Wind at equatorial latitudes to the influence of nonmigrating tides and in particular to the eastward propagating diurnal tide with Zonal wave number 3 (DE3). The DE3 tide is primarily excited by latent heat release in the tropical troposphere in deep convective clouds. In order to investigate the mechanisms that couple the tidal signals to the upper thermosphere, we undertook a comparison with the thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) developed at the National Center for Atmospheric Research (NCAR). We ran the model for a day in March, June, September, and December and applied the same processing steps to the model output as was done for the CHAMP tidal analysis. The main results of the comparison can be summarized as follows: (1) TIME-GCM simulations do not correctly reproduce the observed intra-annual variations of DE3 and the eastward propagating diurnal tide with Zonal wave number 2 (DE2). (2) Simulations of DE3 for June are more successful. Both TIME-GCM and CHAMP show an increase in DE3 amplitudes with decreasing solar flux level. (3) The amplitudes of the simulated westward propagating diurnal tide with Zonal wave number 2 (DW2) and the standing diurnal tide (D0) increase with increasing solar flux in June. The predicted dependence of DW2 and DO on solar flux is also observed by CHAMP.
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nonmigrating tidal signals in the upper thermospheric Zonal Wind at equatorial latitudes as observed by champ
Annales Geophysicae, 2009Co-Authors: K Hausler, H LuhrAbstract:Abstract. The accelerometer onboard CHAMP enables us to derive the thermospheric Zonal Wind at orbit altitudes (~400 km). Numerous equatorial overflights (~45 250) are used to investigate the influence of nonmigrating tides on the thermospheric Zonal Wind. In a previous study a so called "wave-4" longitudinally signal observed in the satellite frame was identified in the Zonal Wind residuals during equinox. Using four years of data (2002–2005), we determine the annual variation of this prominent feature which is strongest during the months of July through October and has a smaller second maximum during March/April. Due to the large data set we were able to separate the observed wavenumbers into the tidal components. Thereby, we can identify the eastward propagating diurnal tide with Zonal wavenumber s=3 (DE3) as the prime cause for the observed wave-4 pattern in the Zonal Wind. Analyzing the Zonal Wind along the geographic and the dip equator revealed that the largest amplitudes of DE3 are found along the dip equator. Besides DE3 we present the full spectrum of nonmigrating tides in the upper thermosphere.
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Nonmigrating tidal signals in the upper thermospheric Zonal Wind at equatorial latitudes as observed by CHAMP
Annales Geophysicae, 2009Co-Authors: K Hausler, H LuhrAbstract:Abstract. The accelerometer onboard CHAMP enables us to derive the thermospheric Zonal Wind at orbit altitudes (~400 km). Numerous equatorial overflights (~45 250) are used to investigate the influence of nonmigrating tides on the thermospheric Zonal Wind. In a previous study a so called "wave-4" longitudinally signal observed in the satellite frame was identified in the Zonal Wind residuals during equinox. Using four years of data (2002–2005), we determine the annual variation of this prominent feature which is strongest during the months of July through October and has a smaller second maximum during March/April. Due to the large data set we were able to separate the observed wavenumbers into the tidal components. Thereby, we can identify the eastward propagating diurnal tide with Zonal wavenumber s=3 (DE3) as the prime cause for the observed wave-4 pattern in the Zonal Wind. Analyzing the Zonal Wind along the geographic and the dip equator revealed that the largest amplitudes of DE3 are found along the dip equator. Besides DE3 we present the full spectrum of nonmigrating tides in the upper thermosphere.
H Luhr - One of the best experts on this subject based on the ideXlab platform.
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comparison of champ and time gcm nonmigrating tidal signals in the thermospheric Zonal Wind
Journal of Geophysical Research, 2010Co-Authors: K Hausler, H Luhr, M E Hagan, Astrid Maute, R G RobleAbstract:[1] Four years (2002–2005) of continuous accelerometer measurements taken onboard the CHAMP satellite (orbit altitude ∼400 km) offer a unique opportunity to investigate the thermospheric Zonal Wind on a global scale. Recently, we were able to relate the longitudinal wave-4 structure in the Zonal Wind at equatorial latitudes to the influence of nonmigrating tides and in particular to the eastward propagating diurnal tide with Zonal wave number 3 (DE3). The DE3 tide is primarily excited by latent heat release in the tropical troposphere in deep convective clouds. In order to investigate the mechanisms that couple the tidal signals to the upper thermosphere, we undertook a comparison with the thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) developed at the National Center for Atmospheric Research (NCAR). We ran the model for a day in March, June, September, and December and applied the same processing steps to the model output as was done for the CHAMP tidal analysis. The main results of the comparison can be summarized as follows: (1) TIME-GCM simulations do not correctly reproduce the observed intra-annual variations of DE3 and the eastward propagating diurnal tide with Zonal wave number 2 (DE2). (2) Simulations of DE3 for June are more successful. Both TIME-GCM and CHAMP show an increase in DE3 amplitudes with decreasing solar flux level. (3) The amplitudes of the simulated westward propagating diurnal tide with Zonal wave number 2 (DW2) and the standing diurnal tide (D0) increase with increasing solar flux in June. The predicted dependence of DW2 and DO on solar flux is also observed by CHAMP.
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comparison of champ and time gcm nonmigrating tidal signals in the thermospheric Zonal Wind
Journal of Geophysical Research, 2010Co-Authors: K Hausler, H Luhr, M E Hagan, Astrid Maute, R G RobleAbstract:[1] Four years (2002–2005) of continuous accelerometer measurements taken onboard the CHAMP satellite (orbit altitude ∼400 km) offer a unique opportunity to investigate the thermospheric Zonal Wind on a global scale. Recently, we were able to relate the longitudinal wave-4 structure in the Zonal Wind at equatorial latitudes to the influence of nonmigrating tides and in particular to the eastward propagating diurnal tide with Zonal wave number 3 (DE3). The DE3 tide is primarily excited by latent heat release in the tropical troposphere in deep convective clouds. In order to investigate the mechanisms that couple the tidal signals to the upper thermosphere, we undertook a comparison with the thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) developed at the National Center for Atmospheric Research (NCAR). We ran the model for a day in March, June, September, and December and applied the same processing steps to the model output as was done for the CHAMP tidal analysis. The main results of the comparison can be summarized as follows: (1) TIME-GCM simulations do not correctly reproduce the observed intra-annual variations of DE3 and the eastward propagating diurnal tide with Zonal wave number 2 (DE2). (2) Simulations of DE3 for June are more successful. Both TIME-GCM and CHAMP show an increase in DE3 amplitudes with decreasing solar flux level. (3) The amplitudes of the simulated westward propagating diurnal tide with Zonal wave number 2 (DW2) and the standing diurnal tide (D0) increase with increasing solar flux in June. The predicted dependence of DW2 and DO on solar flux is also observed by CHAMP.
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nonmigrating tidal signals in the upper thermospheric Zonal Wind at equatorial latitudes as observed by champ
Annales Geophysicae, 2009Co-Authors: K Hausler, H LuhrAbstract:Abstract. The accelerometer onboard CHAMP enables us to derive the thermospheric Zonal Wind at orbit altitudes (~400 km). Numerous equatorial overflights (~45 250) are used to investigate the influence of nonmigrating tides on the thermospheric Zonal Wind. In a previous study a so called "wave-4" longitudinally signal observed in the satellite frame was identified in the Zonal Wind residuals during equinox. Using four years of data (2002–2005), we determine the annual variation of this prominent feature which is strongest during the months of July through October and has a smaller second maximum during March/April. Due to the large data set we were able to separate the observed wavenumbers into the tidal components. Thereby, we can identify the eastward propagating diurnal tide with Zonal wavenumber s=3 (DE3) as the prime cause for the observed wave-4 pattern in the Zonal Wind. Analyzing the Zonal Wind along the geographic and the dip equator revealed that the largest amplitudes of DE3 are found along the dip equator. Besides DE3 we present the full spectrum of nonmigrating tides in the upper thermosphere.
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Nonmigrating tidal signals in the upper thermospheric Zonal Wind at equatorial latitudes as observed by CHAMP
Annales Geophysicae, 2009Co-Authors: K Hausler, H LuhrAbstract:Abstract. The accelerometer onboard CHAMP enables us to derive the thermospheric Zonal Wind at orbit altitudes (~400 km). Numerous equatorial overflights (~45 250) are used to investigate the influence of nonmigrating tides on the thermospheric Zonal Wind. In a previous study a so called "wave-4" longitudinally signal observed in the satellite frame was identified in the Zonal Wind residuals during equinox. Using four years of data (2002–2005), we determine the annual variation of this prominent feature which is strongest during the months of July through October and has a smaller second maximum during March/April. Due to the large data set we were able to separate the observed wavenumbers into the tidal components. Thereby, we can identify the eastward propagating diurnal tide with Zonal wavenumber s=3 (DE3) as the prime cause for the observed wave-4 pattern in the Zonal Wind. Analyzing the Zonal Wind along the geographic and the dip equator revealed that the largest amplitudes of DE3 are found along the dip equator. Besides DE3 we present the full spectrum of nonmigrating tides in the upper thermosphere.
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longitudinal variation of f region electron density and thermospheric Zonal Wind caused by atmospheric tides
Geophysical Research Letters, 2007Co-Authors: H Luhr, K Hausler, Claudia StolleAbstract:[1] Simultaneous observations of the electron density and the Zonal Wind obtained by the CHAMP satellite at 400 km are used to study systematic longitudinal variations. The time period selected is August–September 2004 allowing observations at pre-noon and post-sunset hours. The equatorial ionization anomaly (EIA) and the Zonal delta-Wind (deviation from Zonal average) show a persistent and dominant 4-peaked longitudinal variation. We interpret this structure as caused by the wavenumber-3 nonmigrating diurnal tide (DE3). The EIA and the Zonal delta-Wind exhibit extrema at about the same longitudes. But, while the intensifications of the EIA and the delta-Wind are in phase during the evening hours, they are out of phase in the morning. Possible coupling mechanisms are investigated.
Joshua Tollefson - One of the best experts on this subject based on the ideXlab platform.
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changes in jupiter s Zonal Wind profile preceding and during the juno mission
Icarus, 2017Co-Authors: Joshua Tollefson, Michael H. Wong, Imke De Pater, Amy A. Simon, Glenn S. Orton, Sushil K. Atreya, William Januszewski, John Rogers, Richard Cosentino, Raul MoralesjuberiasAbstract:Abstract We present five epochs of WFC3 HST Jupiter observations taken between 2009–2016 and extract global Zonal Wind profiles for each epoch. Jupiter’s Zonal Wind field is globally stable throughout these years, but significant variations in certain latitude regions persist. We find that the largest uncertainties in the Wind field are due to vortices or hot-spots, and show residual maps which identify the strongest vortex flows. The strongest year-to-year variation in the Zonal Wind profiles is the 24°N jet peak. Numerous plume outbreaks have been observed in the Northern Temperate Belt and are associated with decreases in the Zonal velocity and brightness. We show that the 24°N jet peak velocity and brightness decreased in 2012 and again in late 2016, following outbreaks during these years. Our February 2016 Zonal Wind profile was the last highly spatially resolved measurement prior to Juno's first science observations. The final 2016 data were taken in conjunction with Juno’s perijove 3 pass on 11 December 2016, and show the Zonal Wind profile following the plume outbreak at 24°N in October 2016.
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Changes in Jupiter’s Zonal Wind Profile preceding and during the Juno mission
Icarus, 2017Co-Authors: Joshua Tollefson, Michael H. Wong, Imke De Pater, Amy A. Simon, Glenn S. Orton, John H. Rogers, Sushil K. Atreya, Richard G. Cosentino, William Januszewski, Raul Morales-juberiasAbstract:Abstract We present five epochs of WFC3 HST Jupiter observations taken between 2009–2016 and extract global Zonal Wind profiles for each epoch. Jupiter’s Zonal Wind field is globally stable throughout these years, but significant variations in certain latitude regions persist. We find that the largest uncertainties in the Wind field are due to vortices or hot-spots, and show residual maps which identify the strongest vortex flows. The strongest year-to-year variation in the Zonal Wind profiles is the 24°N jet peak. Numerous plume outbreaks have been observed in the Northern Temperate Belt and are associated with decreases in the Zonal velocity and brightness. We show that the 24°N jet peak velocity and brightness decreased in 2012 and again in late 2016, following outbreaks during these years. Our February 2016 Zonal Wind profile was the last highly spatially resolved measurement prior to Juno's first science observations. The final 2016 data were taken in conjunction with Juno’s perijove 3 pass on 11 December 2016, and show the Zonal Wind profile following the plume outbreak at 24°N in October 2016.
R H Brown - One of the best experts on this subject based on the ideXlab platform.
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cloud features and Zonal Wind measurements of saturn s atmosphere as observed by cassini vims
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: David S Choi, Adam P Showman, R H BrownAbstract:We present an analysis of data about Saturn's atmosphere from Cassini's Visual and Infrared Mapping Spectrometer (VIMS), focusing on the meteorology of the features seen in the 5-micron spectral Window. We present VIMS mosaics and discuss the morphology and general characteristics of the features backlit by Saturn's thermal emission. We have also constructed a Zonal Wind profile from VIMS feature tracking observation sequences using an automated cloud feature tracker. Comparison with previously constructed profiles from Voyager and Cassini imaging data reveals broad similarities, suggesting minimal vertical shear of the Zonal Wind. However, areas of apparent Wind shear are present in the VIMS Zonal Wind profile at jet stream cores. In particular, our analysis shows that the equatorial jet reaches speeds exceeding 450 m/s, similar to speeds obtained during the Voyager era. This suggests that recent inferences of relatively slower jet speeds of ~275-375 m/s are confined to the upper troposphere and that the deep (>1 bar) jet has not experienced a significant slowdown. Our measurements of the numerous dark, spotted features seen in the VIMS mosaics reveals that most of these features have diameters less than 1000 km and reside in confined Zonal bands between jet stream cores. We propose that these spot features are vortices and that VIMS and ISS are sensing the same vortices at two different pressure levels. The local structure at the Zonal jet streams remains complex, as VIMS may be sensing cloud features that are deeper than the NH3 cloud deck.
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cloud features and Zonal Wind measurements of saturn s atmosphere as observed by cassini vims
Journal of Geophysical Research, 2009Co-Authors: David S Choi, Adam P Showman, R H BrownAbstract:[1] We present an analysis of data about Saturn's atmosphere from Cassini's Visual and Infrared Mapping Spectrometer (VIMS), focusing on the meteorology of the features seen in the 5 μm spectral Window. We present VIMS mosaics and discuss the morphology and general characteristics of the features backlit by Saturn's thermal emission. We have also constructed a Zonal Wind profile from VIMS feature tracking observation sequences using an automated cloud feature tracker. Comparison with previously constructed profiles from Voyager and Cassini imaging data reveals broad similarities, suggesting minimal vertical shear of the Zonal Wind. However, areas of apparent Wind shear are present in the VIMS Zonal Wind profile at jet stream cores. In particular, our analysis shows that the equatorial jet reaches speeds exceeding 450 m s−1, similar to speeds obtained during the Voyager era. This suggests that recent inferences of relatively slower jet speeds of ∼275–375 m s−1 are confined to the upper troposphere and that the deep (>1 bar) jet has not experienced a significant slowdown. Our measurements of the numerous dark, spotted features seen in the VIMS mosaics reveals that most of these features have diameters less than 1000 km and reside in confined Zonal bands between jet stream cores. We propose that these spot features are vortices and that VIMS and Imaging Science Subsystem are sensing the same vortices at two different pressure levels. The local structure at the Zonal jet streams remains complex, as VIMS may be sensing cloud features that are deeper than the NH3 cloud deck.
Bruce Hundermark - One of the best experts on this subject based on the ideXlab platform.
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Zonal-Wind Oscillations over the Western Hemisphere during Winter: Further Evidence of a Zonal-Eddy Relationship
Monthly Weather Review, 1992Co-Authors: Steven W. Lyons, Bruce HundermarkAbstract:Abstract The European Centre for Medium-Range Weather Forecasts (ECMWF) 500-mb height analyses and 7-day forecasts are examined during ten winters (1981–90) for oscillations of geostrophic Zonal Wind over the western hemisphere. A well-defined Zonal-Wind oscillation is isolated in the first two eigenvectors. This Zonal-Wind oscillation accounts for about 55% of the total Zonal-Wind variance over the western hemisphere during this ten-winter period. The oscillation is characterized by Zonal-Wind anomalies that are in phase between 30° and 70°N and out of phase with Zonal-Wind anomalies along 50°N. The oscillation clearly displays southward propagation from 85° through 30°N, with standing components along 30°, 50°, and 70°N. The dominant temporal period associated with the oscillation is found to be in the range of 15–35 days with large interannual variability. Composites of 500-mb heights through 25 cycles of Zonal-Wind oscillations over ten winters were performed for unfiltered and 15–39-day filtered data...
