Indications of thin cirrus clouds in the stratosphere at mid-latitudes

Keckhut, Philippe; Hauchecorne, Alain; Bekki, Slimane; Colette, Augustin; David, Christine; Jumelet, Julien

doi:10.5194/acp-5-3407-2005

Cited by 34 publications

(28 citation statements)

References 29 publications

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“…The LTA system includes a separate telescope and detection channel for clouds and aerosol (Chazette et al, 1995;Keckhut et al, 2005;Hoareau et al, 2013). In contrast to the previous studies, we use for the first time the primary lowgain detection channel of the LTA system for stratospheric aerosol retrieval.…”

Section: Observatoire De Haute-provence Lidarsmentioning

confidence: 99%

Variability and evolution of the midlatitude stratospheric aerosol budget from 22 years of ground-based lidar and satellite observations

et al. 2017

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Section: Observatoire De Haute-provence Lidarsmentioning

confidence: 99%

Variability and evolution of the midlatitude stratospheric aerosol budget from 22 years of ground-based lidar and satellite observations

et al. 2017

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“…Keckhut et al, 2005;Rolf, 2013). Many of them coincide with the observations of a secondary tropopause (Noël and Haeffelin, 2007).…”

Section: R Spang Et Al: Satellite Observations Of Cirrus Clouds In mentioning

confidence: 99%

Satellite observations of cirrus clouds in the Northern Hemisphere lowermost stratosphere

Spang¹,

Günther²,

Riese³

et al. 2015

Atmos. Chem. Phys.

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Abstract.Here we present observations of the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) of cirrus cloud and water vapour in August 1997 in the upper troposphere and lower stratosphere (UTLS). The observations indicate a considerable flux of moisture from the upper tropical troposphere into the extratropical lowermost stratosphere (LMS), resulting in the occurrence of highaltitude optically thin cirrus clouds in the LMS.The locations of the LMS cloud events observed by CRISTA are consistent with the tropopause height determined from coinciding radiosonde data. For a hemispheric analysis in tropopause relative coordinates an improved tropopause determination has been applied to the European Centre for Medium-Range Weather Forecasts (ECMWF) temperature profiles. We found that a significant fraction of the cloud occurrences in the tropopause region are located in the LMS, even if a conservative overestimate of the cloud top height (CTH) determination by CRISTA of 500 m is assumed. The results show rather high occurrence frequencies ( ∼ 5 %) up to high northern latitudes (70 • N) and altitudes well above the tropopause (> 500 m at ∼ 350 K and above) in large areas at mid-and high latitudes.Comparisons with model runs of the Chemical Lagrangian Model of the Stratosphere (CLaMS) over the CRISTA period show a reasonable consistency in the retrieved cloud pattern. For this purpose a limb ray tracing approach was applied through the 3-D model fields to obtain integrated measurement information through the atmosphere along the limb path of the instrument. The simplified cirrus scheme implemented in CLaMS seems to cause a systematic underestimation in the CTH occurrence frequencies in the LMS with respect to the observations. The observations together with the model results demonstrate the importance of isentropic, quasi-horizontal transport of water vapour from the subtropics and the potential for the occurrence of cirrus clouds in the lowermost stratosphere and tropopause region.

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“…Cirrus cloud formation is associated with upwelling motions, either due to frontogenesis or convection. It is also strongly driven by horizontal water vapor transport over a wide range of scales (local to continental), including isentropic advection (Fueglistaler et al, 2004;Keckhut et al, 2005;Montoux et al, 2010) and phase changes. Also, cyclones and airplane contrails provide conditions for cirrus cloud generation, presenting particular unique characteristics.…”

Section: E G Larroza Et Al: Towards An Automatic Lidar Cirrus Cloumentioning

confidence: 99%

Towards an automatic lidar cirrus cloud retrieval for climate studies

et al. 2013

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Abstract. This paper presents a methodology to calculate lidar ratios for distinct cirrus clouds that has been developed and implemented for a site located in the Southern Hemisphere. The cirrus cloud lidar data processing aims to consider a large cloud variability and cirrus cloud monitoring through a robust retrieval process. Among cirrus features estimates for complex scenes that lidar systems can provide, we highlight cloud geometrical information and extinctionto-backscatter ratio (known as lidar ratio or LR). In general, direct information on cirrus cloud microphysics is difficult to derive because LR depends on the presence of ice crystals and their properties such as shape, size, composition and orientation of particles. An iterative process to derive a stable LR value has been proposed. One of the keys is to restrict the analysis to conditions allowing accurate multilayer events. This method uses nonparametric statistical approaches to identify stationary periods according to cloud features and variability. Measurements performed in the region of the metropolitan city of São Paulo (MSP) have been used to implement and test the methodology developed for cirrus cloud characterization. Good results are represented by examining specific cases with multilayer cirrus cloud occurrence. In addition to the geometrical parameters obtained, cirrus LR values were calculated for a single day ranging from 19 ± 01 sr to 74 ± 13 sr for 2 observed layers. This large difference in LR can indicate a mixture of ice crystal particles with different sizes and shapes in both layers of the cirrus clouds. Trajectory analyses indicate that both of these cloud layers can be associated with different air mass and should be considered as 2 distinct clouds in climatology.

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Indications of thin cirrus clouds in the stratosphere at mid-latitudes

Cited by 34 publications

References 29 publications

Variability and evolution of the midlatitude stratospheric aerosol budget from 22 years of ground-based lidar and satellite observations

Variability and evolution of the midlatitude stratospheric aerosol budget from 22 years of ground-based lidar and satellite observations

Satellite observations of cirrus clouds in the Northern Hemisphere lowermost stratosphere

Towards an automatic lidar cirrus cloud retrieval for climate studies

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