On the stability of the troposphere/lower stratosphere and its relationships with cirrus clouds and three mandatory levels over Buenos Aires

2016 ◽  
Vol 37 (7) ◽  
pp. 1541-1552
Author(s):  
Adrián E. Yuchechen ◽  
S. Gabriela Lakkis ◽  
Mario B. Lavorato
Keyword(s):  
Lower Stratosphere ◽  
Buenos Aires ◽  
Cirrus Clouds ◽  
The Stability

Open discussion

1982 ◽  
Vol 99 ◽  
pp. 605-613
Author(s):  
P. S. Conti
Keyword(s):  
Buenos Aires ◽  
Large Mass ◽  
List Type ◽  
Common Phenomenon ◽  
Open Discussion ◽  
The Stability ◽  
Ring Nebulae

Conti: One of the main conclusions of the Wolf-Rayet symposium in Buenos Aires was that Wolf-Rayet stars are evolutionary products of massive objects. Some questions:–Do hot helium-rich stars, that are not Wolf-Rayet stars, exist?–What about the stability of helium rich stars of large mass? We know a helium rich star of ∼40 MO. Has the stability something to do with the wind?–Ring nebulae and bubbles : this seems to be a much more common phenomenon than we thought of some years age.–What is the origin of the subtypes? This is important to find a possible matching of scenarios to subtypes.

Dehydration of the upper troposphere and lower stratosphere by subvisible cirrus clouds near the tropical tropopause

1996 ◽  
Vol 23 (8) ◽  
pp. 825-828 ◽  
Author(s):  
Eric J. Jensen ◽  
Owen B. Toon ◽  
Leonard Pfister ◽  
Henry B. Selkirk
Keyword(s):  
Lower Stratosphere ◽  
Cirrus Clouds ◽  
Upper Troposphere ◽  
Tropical Tropopause

scholarly journals Lidar observations of cirrus clouds in Buenos Aires

2015 ◽  
Vol 130-131 ◽  
pp. 89-95 ◽  
Author(s):  
S. Gabriela Lakkis ◽  
Mario Lavorato ◽  
Pablo Canziani ◽  
Hector Lacomi
Keyword(s):  
Buenos Aires ◽  
Cirrus Clouds ◽  
Lidar Observations

scholarly journals Revisiting global satellite observations of stratospheric cirrus clouds

2020 ◽  
Author(s):  
Ling Zou ◽  
Sabine Griessbach ◽  
Lars Hoffmann ◽  
Bing Gong ◽  
Lunche Wang
Keyword(s):  
Radiative Forcing ◽  
Lower Stratosphere ◽  
Deep Convection ◽  
Michelson Interferometer ◽  
Satellite Observations ◽  
Cirrus Clouds ◽  
Detection Sensitivity ◽  
Lapse Rate ◽  
Cirrus Cloud ◽  
The Tropics

Abstract. As knowledge about the cirrus clouds in the lower stratosphere is limited, reliable long-term measurements are needed to assess their characteristics, radiative impact and important role in upper troposphere and lower stratosphere (UTLS) chemistry. To investigate the global and seasonal distribution of stratospheric cirrus clouds, we used the latest version (V4.x) of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) data. For the identification of stratospheric cirrus clouds, precise information on both, the cloud top height (CTH) and the tropopause height is crucial. Here, we used lapse rate tropopause heights estimated from the ERA-Interim global reanalysis. Considering the uncertainties of the tropopause heights and the vertical sampling grid of the CALIPSO data, we considered cirrus clouds with CTHs more than 0.5 km above the tropopause as being stratospheric. We focused on nighttime CALIPSO measurements, because of their higher detection sensitivity. A six-year mean (2006–2012) global distribution of stratospheric cirrus cloud from CALIPSO showed that higher CTH occurrence frequencies are observed in the tropics than in the extra-tropics. Tropical hotspots of stratospheric cirrus clouds associated with deep convection are located over Equatorial Africa, South and Southeast Asia, the western Pacific and South America. Stratospheric cirrus clouds were more often detected in December–February (15 %) than June–August (8 %) in the tropics (± 20°). At middle (40–60°) and higher latitudes (> 60°), CALIPSO observed on average about 2 % stratospheric cirrus clouds. Observations of stratospheric cirrus cloud with MIPAS are presented here for the first time. Taking into account the MIPAS vertical sampling and broad field of view, we considered cirrus CTHs detected not less than 0.75 km above the tropopause as being stratospheric. Compared to CALIPSO, MIPAS observed twice as many stratospheric cirrus clouds at northern and southern middle latitudes (occurrence frequencies of 4–5 % for MIPAS rather than about 2 % for CALIPSO). We attribute more frequent observations of stratospheric cirrus clouds with MIPAS to higher detection sensitivity of the instrument to optically thin clouds. Sensitivity tests on MIPAS stratospheric cloud detections have been conducted to rule out sampling artefacts. Future work should focus on better understanding the origin of the stratospheric cirrus clouds and their impact on radiative forcing and climate.

scholarly journals Monitoring cirrus clouds with lidar in the Southern Hemisphere: A local study over Buenos Aires. 1. Tropopause heights

2009 ◽  
Vol 92 (1) ◽  
pp. 18-26 ◽  
Author(s):  
Susan Gabriela Lakkis ◽  
Mario Lavorato ◽  
Pablo Osvaldo Canziani
Keyword(s):  
Southern Hemisphere ◽  
Buenos Aires ◽  
Cirrus Clouds ◽  
Local Study

scholarly journals On the Development of Above-Anvil Cirrus Plumes in Extratropical Convection

2017 ◽  
Vol 74 (5) ◽  
pp. 1617-1633 ◽  
Author(s):  
Cameron R. Homeyer ◽  
Joel D. McAuliffe ◽  
Kristopher M. Bedka
Keyword(s):  
Gravity Wave ◽  
Wave Breaking ◽  
Lower Stratosphere ◽  
Atmospheric Conditions ◽  
Upper Troposphere ◽  
Using Data ◽  
The Stability ◽  
Anvil Cirrus ◽  
Cloud Material ◽  
Relative Wind

Abstract Expansive cirrus clouds present above the anvils of extratropical convection have been observed in satellite and aircraft-based imagery for several decades. Despite knowledge of their occurrence, the precise mechanisms and atmospheric conditions leading to their formation and maintenance are not entirely known. Here, the formation of these cirrus “plumes” is examined using a combination of satellite imagery, four-dimensional ground-based radar observations, assimilated atmospheric states from a state-of-the-art reanalysis, and idealized numerical simulations with explicitly resolved convection. Using data from 20 recent events (2013–present), it is found that convective cores of storms with above-anvil cirrus plumes reach altitudes 1–6 km above the tropopause. Thus, it is likely that these clouds represent the injection of cloud material into the lower stratosphere. Comparison of storms with above-anvil cirrus plumes and observed tropopause-penetrating convection without plumes reveals an association with large vector differences between the motion of a storm and the environmental wind in the upper troposphere and lower stratosphere (UTLS), suggesting that gravity wave breaking and/or stretching of the tropopause-penetrating cloud are/is more prevalent in plume-producing storms. A weak relationship is found between plume occurrence and the stability of the lower stratosphere (or tropopause structure), and no relationship is found with the duration of stratospheric penetration or stratospheric humidity. Idealized model simulations of tropopause-penetrating convection with small and large magnitudes of storm-relative wind in the UTLS are found to reproduce the observationally established storm-relative wind relationship and show that frequent gravity wave breaking is the primary mechanism responsible for plume formation.

scholarly journals Global cloud top height retrieval using SCIAMACHY limb spectra: model studies and first results

2016 ◽  
Vol 9 (2) ◽  
pp. 793-815 ◽  
Author(s):  
Kai-Uwe Eichmann ◽  
Luca Lelli ◽  
Christian von Savigny ◽  
Harjinder Sembhi ◽  
John P. Burrows
Keyword(s):  
Lower Stratosphere ◽  
Michelson Interferometer ◽  
Volcanic Eruptions ◽  
Cirrus Clouds ◽  
Detection Sensitivity ◽  
Retrieval Algorithm ◽  
Transfer Model ◽  
Aerosol Layer ◽  
Cloud Detection ◽  
The Tropics

Abstract. Cloud top heights (CTHs) are retrieved for the period 1 January 2003 to 7 April 2012 using height-resolved limb spectra measured with the SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) on board ENVISAT (ENVIronmental SATellite). In this study, we present the retrieval code SCODA (SCIAMACHY cloud detection algorithm) based on a colour index method and test the accuracy of the retrieved CTHs in comparison to other methods. Sensitivity studies using the radiative transfer model SCIATRAN show that the method is capable of detecting cloud tops down to about 5 km and very thin cirrus clouds up to the tropopause. Volcanic particles can be detected that occasionally reach the lower stratosphere. Upper tropospheric ice clouds are observable for a nadir cloud optical thickness (COT)  ≥  0.01, which is in the subvisual range. This detection sensitivity decreases towards the lowermost troposphere. The COT detection limit for a water cloud top height of 5 km is roughly 0.1. This value is much lower than thresholds reported for passive cloud detection methods in nadir-viewing direction. Low clouds at 2 to 3 km can only be retrieved under very clean atmospheric conditions, as light scattering of aerosol particles interferes with the cloud particle scattering. We compare co-located SCIAMACHY limb and nadir cloud parameters that are retrieved with the Semi-Analytical CloUd Retrieval Algorithm (SACURA). Only opaque clouds (τN,c > 5) are detected with the nadir passive retrieval technique in the UV–visible and infrared wavelength ranges. Thus, due to the frequent occurrence of thin clouds and subvisual cirrus clouds in the tropics, larger CTH deviations are detected between both viewing geometries. Zonal mean CTH differences can be as high as 4 km in the tropics. The agreement in global cloud fields is sufficiently good. However, the land–sea contrast, as seen in nadir cloud occurrence frequency distributions, is not observed in limb geometry. Co-located cloud top height measurements of the limb-viewing Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on ENVISAT are compared for the period from January 2008 to March 2012. The global CTH agreement of about 1 km is observed, which is smaller than the vertical field of view of both instruments. Lower stratospheric aerosols from volcanic eruptions occasionally interfere with the cloud retrieval and inhibit the detection of tropospheric clouds. The aerosol impact on cloud retrievals was studied for the volcanoes Kasatochi (August 2008), Sarychev Peak (June 2009), and Nabro (June 2011). Long-lasting aerosol scattering is detected after these events in the Northern Hemisphere for heights above 12.5 km in tropical and polar latitudes. Aerosol top heights up to about 22 km are found in 2009 and the enhanced lower stratospheric aerosol layer persisted for about 7 months. In August 2009 about 82 % of the lower stratosphere between 30 and 70° N was filled with scattering particles and nearly 50 % in October 2008.

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