This study presents results obtained with a Rayleigh-Mie Doppler wind lidar on mesoscale fluctuat... more This study presents results obtained with a Rayleigh-Mie Doppler wind lidar on mesoscale fluctuations of horizontal winds in the lower stratosphere. The instrument, which is located at the Observatory of Haute-Provence, France (44°N, 6°E), and its capabilities are briefly described. The technique enables the computation of the kinetic energy content in the [13 km; ~20 km] altitude range, as well
The observed decrease of ozone in the northern midlatitude lower stratosphere is only partially r... more The observed decrease of ozone in the northern midlatitude lower stratosphere is only partially reproduced by chemical models. The transport of ozone-depleted air from the polar vortex is one of the proposed mechanisms to explain the discrepancy. Here we present a study on the quantification of the air mass transported from the polar vortex to midlatitude during the four winters 1996-1997 to 1999-2000, in relation with vortex filamentation and break up, using the high-resolution advection model MIMOSA on isentropic surfaces. Sensitivity tests show that the advection model is able to predict the location of polar filaments with accuracy better than 100 km, limited by uncertainties in meteorological advecting wind fields. The effective diffusivity diagnostic is used to evaluate the intensity of the vortex edge barrier and to quantify the transport of air from the polar vortex to midlatitude. The intensity of the polar barrier is increasing with height from 400 to 550 K and is nearly constant above. During periods with a cold and undisturbed vortex, favorable to chlorine activation, the transport is very weak. This suggests that the midwinter vortex filamentation plays a minor role in the midlatitude ozone decline. In the opposite limit, during a stratospheric warming up to 30% of the polar vortex air is transported to midlatitudes. The cumulative transport from early January to end of April across the polar edge varies from almost 5% of the polar vortex air at 675 K in 1997 to 50% at 435 K in 1999.
Odin is a small satellite launched in February 2001 with a combined astronomy and aeronomy missio... more Odin is a small satellite launched in February 2001 with a combined astronomy and aeronomy mission. It carries the SMR instrument that performs atmospheric observa- tions in a limb-sounding mode at sub-mm wavelengths (480-580 GHz). The vertical profiles of species such as O3, ClO and H2O are retrieved between 20 and 65km using the optimal estimation method. SMR ozone profiles
ABSTRACT European Space Agency's Global Ozone Monitoring by Occultation of Stars (GOMOS) ... more ABSTRACT European Space Agency's Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument on-board the Envisat satellite has operated for more than 6 years. The UV-VIS spectrometers are used to retrieve night time profiles of ozone, NO2, NO3 and aerosols. The stellar occultation technique allows constituent retrievals with a high vertical resolution from pole to pole. The self-calibrated measurement technique together with minimal use of a priori information is especially well suited for long term trend studies. The GOMOS inverse problem, data characterization, error sources and the vertical resolution are discussed. It is shown that the random errors (measurement noise and scintillations) are the largest error components whereas the systematic errors have minor impact --- a feature which is important for trend studies. The effect of random errors can be reduced significantly and whithout sacrificing the resolution too much by using a Tikhonov-type smoothing in the data retrieval. As a novel technique to perform data characterization we also investigate the full model space by applying the Markov chain Monte Carlo sampling technique.
ABSTRACT Following recent studies evidencing the effect of deep overshooting convection on the ch... more ABSTRACT Following recent studies evidencing the effect of deep overshooting convection on the chemical composition of the tropical lower stratosphere by injection of tropospheric air across the cold-point tropopause we explore its impact on the thermal structure of the tropical tropopause layer (TTL) and the lower stratosphere using the high-resolution COSMIC GPS radio-occultation temperature measurements spanning from 2006 through 2011. The temperature of the lower tropical stratosphere is shown to display a systematic mean cooling of 0.6 K up to 20 km in the late afternoon in the summer over land compared to oceanic areas where little or no diurnal variation is observed. The temperature cycle is fully consistent with the diurnal cycle and geographical location of deep convective systems reported by the Tropical Rainfall Measurement Mission (TRMM) precipitation radar suggesting strong injection of adiabatically cooled air into the lower tropical stratosphere in the afternoon over tropical continents. But most unexpected is the difference between the southern and Northern Hemispheres, the first displaying systematic larger cooling suggesting more intense convection in the southern than in the northern tropics.
... The X-axis is the distance on the limb in milli arcseconds. The differents tracks correspond ... more ... The X-axis is the distance on the limb in milli arcseconds. The differents tracks correspond to different models and the intensity is normalized to unity at the origin of the X-axis. ... (2011). Theorigin of the horizontal axis of Figure 2 corresponds to the optical depth unity at 500 nm. ...
Mesospheric temperature profiles obtained by Rayleigh lidar in the south of France frequently sho... more Mesospheric temperature profiles obtained by Rayleigh lidar in the south of France frequently show temperature inversions, with an amplitude as large as 40 K over a few km. A 2D dynamical model, developed to interpret these observations, showed that mesospheric inversions were mainly due to the vertical circulation induced by the breaking of gravity waves in the upper mesosphere.
The snare drum is one of the more complex musical instruments from a modeling and synthesis persp... more The snare drum is one of the more complex musical instruments from a modeling and synthesis perspectiveit includes elements modeled as 0D (the drum stick), 1D (the snares), 2D (a pair of mem-branes) and 3D (the cavity and perhaps the surrounding space), as well as ...
OMOS (Global Ozone Monitoring by Occultation of Stars) on board Envisat measures O3, NO2, NO3, ne... more OMOS (Global Ozone Monitoring by Occultation of Stars) on board Envisat measures O3, NO2, NO3, neutral density, temperature, aerosols, H2O, and O2, in the stratosphere and mesosphere. Since 20th of March 2002 GOMOS has performed over 50000 occultations. The validation of GOMOS products is still ongoing and major improvements of retrievals are expected to happen during 2003. In this talk
This study presents results obtained with a Rayleigh-Mie Doppler wind lidar on mesoscale fluctuat... more This study presents results obtained with a Rayleigh-Mie Doppler wind lidar on mesoscale fluctuations of horizontal winds in the lower stratosphere. The instrument, which is located at the Observatory of Haute-Provence, France (44°N, 6°E), and its capabilities are briefly described. The technique enables the computation of the kinetic energy content in the [13 km; ~20 km] altitude range, as well
The observed decrease of ozone in the northern midlatitude lower stratosphere is only partially r... more The observed decrease of ozone in the northern midlatitude lower stratosphere is only partially reproduced by chemical models. The transport of ozone-depleted air from the polar vortex is one of the proposed mechanisms to explain the discrepancy. Here we present a study on the quantification of the air mass transported from the polar vortex to midlatitude during the four winters 1996-1997 to 1999-2000, in relation with vortex filamentation and break up, using the high-resolution advection model MIMOSA on isentropic surfaces. Sensitivity tests show that the advection model is able to predict the location of polar filaments with accuracy better than 100 km, limited by uncertainties in meteorological advecting wind fields. The effective diffusivity diagnostic is used to evaluate the intensity of the vortex edge barrier and to quantify the transport of air from the polar vortex to midlatitude. The intensity of the polar barrier is increasing with height from 400 to 550 K and is nearly constant above. During periods with a cold and undisturbed vortex, favorable to chlorine activation, the transport is very weak. This suggests that the midwinter vortex filamentation plays a minor role in the midlatitude ozone decline. In the opposite limit, during a stratospheric warming up to 30% of the polar vortex air is transported to midlatitudes. The cumulative transport from early January to end of April across the polar edge varies from almost 5% of the polar vortex air at 675 K in 1997 to 50% at 435 K in 1999.
Odin is a small satellite launched in February 2001 with a combined astronomy and aeronomy missio... more Odin is a small satellite launched in February 2001 with a combined astronomy and aeronomy mission. It carries the SMR instrument that performs atmospheric observa- tions in a limb-sounding mode at sub-mm wavelengths (480-580 GHz). The vertical profiles of species such as O3, ClO and H2O are retrieved between 20 and 65km using the optimal estimation method. SMR ozone profiles
ABSTRACT European Space Agency's Global Ozone Monitoring by Occultation of Stars (GOMOS) ... more ABSTRACT European Space Agency's Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument on-board the Envisat satellite has operated for more than 6 years. The UV-VIS spectrometers are used to retrieve night time profiles of ozone, NO2, NO3 and aerosols. The stellar occultation technique allows constituent retrievals with a high vertical resolution from pole to pole. The self-calibrated measurement technique together with minimal use of a priori information is especially well suited for long term trend studies. The GOMOS inverse problem, data characterization, error sources and the vertical resolution are discussed. It is shown that the random errors (measurement noise and scintillations) are the largest error components whereas the systematic errors have minor impact --- a feature which is important for trend studies. The effect of random errors can be reduced significantly and whithout sacrificing the resolution too much by using a Tikhonov-type smoothing in the data retrieval. As a novel technique to perform data characterization we also investigate the full model space by applying the Markov chain Monte Carlo sampling technique.
ABSTRACT Following recent studies evidencing the effect of deep overshooting convection on the ch... more ABSTRACT Following recent studies evidencing the effect of deep overshooting convection on the chemical composition of the tropical lower stratosphere by injection of tropospheric air across the cold-point tropopause we explore its impact on the thermal structure of the tropical tropopause layer (TTL) and the lower stratosphere using the high-resolution COSMIC GPS radio-occultation temperature measurements spanning from 2006 through 2011. The temperature of the lower tropical stratosphere is shown to display a systematic mean cooling of 0.6 K up to 20 km in the late afternoon in the summer over land compared to oceanic areas where little or no diurnal variation is observed. The temperature cycle is fully consistent with the diurnal cycle and geographical location of deep convective systems reported by the Tropical Rainfall Measurement Mission (TRMM) precipitation radar suggesting strong injection of adiabatically cooled air into the lower tropical stratosphere in the afternoon over tropical continents. But most unexpected is the difference between the southern and Northern Hemispheres, the first displaying systematic larger cooling suggesting more intense convection in the southern than in the northern tropics.
... The X-axis is the distance on the limb in milli arcseconds. The differents tracks correspond ... more ... The X-axis is the distance on the limb in milli arcseconds. The differents tracks correspond to different models and the intensity is normalized to unity at the origin of the X-axis. ... (2011). Theorigin of the horizontal axis of Figure 2 corresponds to the optical depth unity at 500 nm. ...
Mesospheric temperature profiles obtained by Rayleigh lidar in the south of France frequently sho... more Mesospheric temperature profiles obtained by Rayleigh lidar in the south of France frequently show temperature inversions, with an amplitude as large as 40 K over a few km. A 2D dynamical model, developed to interpret these observations, showed that mesospheric inversions were mainly due to the vertical circulation induced by the breaking of gravity waves in the upper mesosphere.
The snare drum is one of the more complex musical instruments from a modeling and synthesis persp... more The snare drum is one of the more complex musical instruments from a modeling and synthesis perspectiveit includes elements modeled as 0D (the drum stick), 1D (the snares), 2D (a pair of mem-branes) and 3D (the cavity and perhaps the surrounding space), as well as ...
OMOS (Global Ozone Monitoring by Occultation of Stars) on board Envisat measures O3, NO2, NO3, ne... more OMOS (Global Ozone Monitoring by Occultation of Stars) on board Envisat measures O3, NO2, NO3, neutral density, temperature, aerosols, H2O, and O2, in the stratosphere and mesosphere. Since 20th of March 2002 GOMOS has performed over 50000 occultations. The validation of GOMOS products is still ongoing and major improvements of retrievals are expected to happen during 2003. In this talk
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