Structure of the mean winds and tides in the meteor region over Cachoeira Paulista, Brazil (22.7°S,45°W) and its comparison with models

Batista, P. P.; Clemesha, B. R.; Tokumoto, Aparecido S.; Lima, Lourivaldo Mota

doi:10.1016/j.jastp.2004.01.014

Cited by 84 publications

(87 citation statements)

References 24 publications

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“…This annual component causes a strong enhancement of the autumnal equinox peak in the wind velocities. Note that detailed analyses of the winds at Cachoeira Paulista and São João do Cariri have been published by Batista et al (2004) and Buriti et al (2008), respectively.…”

Section: Resultsmentioning

confidence: 97%

Seasonal variations in gravity wave activity at three locations in Brazil

et al. 2009

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Abstract. Using the variance in meteor radar winds as a measure of gravity wave activity, we investigate the temporal variations in gravity waves at three locations in Brazil: São João do Cariri (2005) which makes it possible to separate the zonal and meridional components of the fluctuating wind velocity. We find that the seasonal variation of the fluctuating wind is similar to that of the amplitude of the diurnal tide, showing a predominantly semi-annual variation, stronger at Cachoeira Paulista and Santa Maria than at the quasi-equatorial station, Cariri. Both with respect to the seasonal trend and shorter term variations, strong coupling between gravity wave activity and tides is indicated by a remarkably close correlation between the fluctuating velocity and the vertical shear in the tidal winds. It is not clear as to whether this is caused by gravity wave forcing of the tides or whether it results from in situ generation of gravity waves by tidal wind shear.

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Section: Resultsmentioning

confidence: 97%

Seasonal variations in gravity wave activity at three locations in Brazil

et al. 2009

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“…Meteor radar data was obtained at 2 sites in Brazil during this experiment to determine the zonal and meridional horizontal winds from z=80−100 km. Here, the sites were Cariri (São João do Cariri) located at 7.4 o S, 36.5 o W, and Cachoeira Paulista, located at 22.7 o S, 45.0 o W (Batista et al, 2004;Buriti et al, 2008). The equipment used to observe winds in the mesosphere at Cariri and at Cachoeira Paulista are similar to the SKiYMET All-Sky Interferometric Meteor Radar which uses an antenna array composed of 2-element yagi antennas (5 in total) for reception, and a 3-element yagi transmitting antenna.…”

Section: Temperature and Wind Modelsmentioning

confidence: 99%

Convection: the likely source of the medium-scale gravity waves observed in the OH airglow layer near Brasilia, Brazil, during the SpreadFEx campaign

et al. 2009

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Abstract. Six medium-scale gravity waves (GWs) with horizontal wavelengths of λ H =60-160 km were detected on four nights by Taylor et al. (2009) in the OH airglow layer near Brasilia, at 15 • S, 47 • W, during the Spread F Experiment (SpreadFEx) in Brazil in 2005. We reverse and forward ray trace these GWs to the tropopause and into the thermosphere using a ray trace model which includes thermospheric dissipation. We identify the convective plumes, convective clusters, and convective regions which may have generated these GWs. We find that deep convection is the highly likely source of four of these GWs. We pinpoint the specific deep convective plumes which likely excited two of these GWs on the nights of 30 September and 1 October. On these nights, the source location/time uncertainties were small and deep convection was sporadic near the modeled source locations. We locate the regions containing deep convective plumes and clusters which likely excited the other two GWs. The last 2 GWs were probably also excited from deep convection; however, they must have been ducted ∼500-700 km if so. Two of the GWs were likely downwards-propagating initially (after which they reflected upwards from the Earth's surface), while one of the GWs was likely upwards-propagating initially from the convective plume/cluster. We also estimate the amplitudes and vertical scales of these waves at the tropopause, and compare their scales with those from a simple, linear convection model. Finally, we calculate each GW's dissipation altitude, location, and amplitude. We find that the dissiCorrespondence to: S. L. Vadas (vasha@cora.nwra.com) pation altitude depends sensitively on the winds at and above the OH layer. We also find that several of these GWs may have penetrated to high enough altitudes to potentially seed equatorial spread F (ESF) if located somewhat farther from the magnetic equator.

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“…The bubbles are readily observed in radar plots and appear as towering plumes extending from the lower ionosphere to the top side (e.g. Hysell and Burcham, 2002;de Paula and Hysell, 2004;Batista et al, 2004;Buriti et al, 2008). As the plumes raise in altitude their electron density signatures map down the magnetic flux tubes to lower latitudes where they are detected in the Fregion airglow emissions as field-aligned plasma depletions (Rishbeth, 1971;Batista et al, 1986;Abdu, 2001).…”

Section: Introductionmentioning

confidence: 99%

Characteristics of mesospheric gravity waves near the magnetic equator, Brazil, during the SpreadFEx campaign

et al. 2009

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Abstract. As part of the SpreadFEx campaign, coordinated optical and radio measurements were made from Brazil to investigate the occurrence and properties of equatorial Spread F, and to characterize the regional mesospheric gravity wave field. All-sky image measurements were made from two sites: Brasilia and Cariri located ∼10 • S of the magnetic equator and separated by ∼1500 km. In particular, the observations from Brasilia provided key data in relatively close proximity to expected convective sources of the gravity waves. High-quality image measurements of the mesospheric OH emission and the thermospheric OI (630 nm) emission were made during two consecutive new moon periods (22 September to 9 November 2005) providing extensive data on the occurrence and properties of F-region depletions and regional measurements of the dominant gravity wave characteristics at each site.A total of 120 wave displays were observed, comprising 94 short-period events and 26 medium-scale gravity waves. The characteristics of the small-scale waves agreed well with previous gravity wave studies from Brazil and other sites. However, significant differences in the wave propagation headings indicate dissimilar source regions for the Brasilia and Cariri datasets. The observed medium-scale gravity wave events constitute an important new dataset to study their mesospheric properties at equatorial latitudes. These data exhibited similar propagation headings to the shortperiod events, suggesting they originated from the same source regions. Medium-scale waves are generally less susceptible to wind filtering effects and modeling studies utilizing these data have successfully identified localized regions

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Structure of the mean winds and tides in the meteor region over Cachoeira Paulista, Brazil (22.7°S,45°W) and its comparison with models

Cited by 84 publications

References 24 publications

Seasonal variations in gravity wave activity at three locations in Brazil

Seasonal variations in gravity wave activity at three locations in Brazil

Convection: the likely source of the medium-scale gravity waves observed in the OH airglow layer near Brasilia, Brazil, during the SpreadFEx campaign

Characteristics of mesospheric gravity waves near the magnetic equator, Brazil, during the SpreadFEx campaign

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