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On the linkage between tropospheric and Polar Stratospheric clouds in the Arctic as observed by space-borne lidar
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
2012 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 12, no 8, 3791-3798 p.Article in journal (Refereed) Published
Abstract [en]

The type of Polar stratospheric clouds (PSCs) as well as their temporal and spatial extent are important for the occurrence of heterogeneous reactions in the polar stratosphere. The formation of PSCs depends strongly on temperature. However, the mechanisms of the formation of solid PSCs are still poorly understood. Recent satellite studies of Antarctic PSCs have shown that their formation can be associated with deep-tropospheric clouds which have the ability to cool the lower stratosphere radiatively and/or adiabatically. In the present study, lidar measurements aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite were used to investigate whether the formation of Arctic PSCs can be associated with deep-tropospheric clouds as well. Deep-tropospheric cloud systems have a vertical extent of more than 6.5 km with a cloud top height above 7 km altitude. PSCs observed by CALIPSO during the Arctic winter 2007/2008 were classified according to their type (STS, NAT, or ice) and to the kind of underlying tropospheric clouds. Our analysis reveals that 172 out of 211 observed PSCs occurred in connection with tropospheric clouds. 72% of these 172 observed PSCs occurred above deep-tropospheric clouds. We also find that the type of PSC seems to be connected to the characteristics of the underlying tropospheric cloud system. During the Arctic winter 2007/2008 PSCs consisting of ice were mainly observed in connection with deep-tropospheric cloud systems while no ice PSC was detected above cirrus. Furthermore, we find no correlation between the occurrence of PSCs and the top temperature of tropospheric clouds. Thus, our findings suggest that Arctic PSC formation is connected to adiabatice cooling, i.e. dynamic effects rather than radiative cooling.

Place, publisher, year, edition, pages
2012. Vol. 12, no 8, 3791-3798 p.
National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences and Oceanography
Identifiers
URN: urn:nbn:se:su:diva-79722DOI: 10.5194/acp-12-3791-2012ISI: 000304054800016OAI: oai:DiVA.org:su-79722DiVA: diva2:551960
Note

AuthorCount:4;

Available from: 2012-09-12 Created: 2012-09-11 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Lidar Measurements of Polar Stratospheric Clouds in the Arctic
Open this publication in new window or tab >>Lidar Measurements of Polar Stratospheric Clouds in the Arctic
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Polar Stratospheric Clouds (PSCs) play a key role for ozone depletion in the polar stratosphere. Its magnitude depends on the type of PSC and its lifetime and extent. This thesis presents PSC observations conducted with the Esrange lidar and the space-borne CALIPSO lidar.

PSCs are separated into three types according to their optical properties. The occurrence rate of the different types which are often observed simultaneously as well as their interaction and connection is not well understood. To better understand the processes that govern PSC formation, observations need to be combined with a detailed view of the atmospheric background in which PSCs develop, exist, and are transformed from one type to another.

This thesis introduces a new channel of the Esrange lidar for temperature profiling at heights below 35 km. The design of this channel and first temperature measurements within PSCs and cirrus clouds are presented. This is an important step since the majority of PSC-related literature extracts temperatures within PSCs from reanalysis data.

In contrast to ground–based measurements space–borne lidar does not rely on cloud–free conditions. Hence, it provides an unprecedented opportunity for studying the connection between PSCs and the underlying synoptic–scale conditions which manifest as tropospheric clouds. This thesis shows that most of the PSCs observed in the Arctic during winter 2007/08 occurred in connection with tropospheric clouds.

A combined analysis of ground-based and space-borne lidar observation of PSCs in combination with microphysical modeling can improve our understanding of PSC formation. A first case study of this approach shows how a PSC that was formed by synoptic-scale processes is transformed into another type while passing the Scandinavian mountains.

Today a variety of classification schemes provides inconsistent information on PSC properties and types. This thesis suggests a unified classification scheme for lidar measurements of PSCs.

Place, publisher, year, edition, pages
Stockholm: Department of Meteorology, Stockholm University, 2013. 36 p.
National Category
Earth and Related Environmental Sciences
Research subject
Atmospheric Sciences and Oceanography
Identifiers
urn:nbn:se:su:diva-88054 (URN)978-91-7447-657-6 (ISBN)
Public defence
2013-04-05, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Submitted. 

 

Available from: 2013-03-14 Created: 2013-03-04 Last updated: 2017-11-27Bibliographically approved

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