Book/Dissertation / PhD Thesis

FZJ-2022-00964

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Cirrus clouds in the extratropical tropopause and lowermost stratosphere region

Bartolomé García, I. (Corresponding author)FZJ*

2022
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-610-6

Please use a persistent id in citations: http://hdl.handle.net/2128/30829

Abstract: Cirrus clouds play a fundamental role in the radiative balance of the Earth and have an important impact on the climate. Their net effect depends on their physical characteristics, i.e., altitude, vertical extent, optical thickness and particle size. Quantifying the properties of ice crystals from the observations is a very challenging task. Consequently, models used for climate projections lack observational constrains when predicting the processes related to the evolution of cirrus and their properties. The aim of this thesis was to gain a deeper understanding of cirrus macro-physical properties (cloud top and bottom height, vertical extent, position with respect to the tropopause) and of the micro-physical properties (ice water content (IWC), particle size). For this purpose, data measured by GLORIA (Gimballed Limb Observation for Radiance Imaging of the Atmosphere) during the WISE (Wave-driven ISentropic Exchange) campaign were analyzed. GLORIA is an airborne limb remote sensor that measures radiance in the thermal infrared region (700 cm$^{−1}$ to 1400cm$^{−1}$). Two identification methods were used to detect clouds in the measurements. One method is based on the cloud index (CI) and the other method, on the use of the extinction coefficient in the spectral range 832cm$^{−1}$ to 834cm$^{−1}$. Between 13 – 27% of the total number of observations presented a cloud top located above the tropopause(TP). However, no cirrus layers were found unambiguously above the TP (i.e., both cloud top and cloud bottom above the TP). To estimate the micro-physical properties a combination of two approaches was used. The IWC was then integrated to obtain the ice water path (IWP). The IWP was compared to the ERA5-based dataset, giving satisfactory results (qualitatively) and highlighting that the ERA5 reanalysis does not reproduce most of the very thin clouds close to the tropopause. Quantitatively, the retrieved IWP was smaller than the ERA5-based IWP, pointing to the need of reducing uncertainties to obtain a more accurate product. Additionally, observed cloudy regions close to the TP were selected as case studies to simulate with CLaMS-Ice (Chemical Lagrangian Model of the Stratosphere). The model was able to sucessfully form clouds in the region of interest.

Note: Bergische Universität Wuppertal, Diss., 2021

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Contributing Institute(s):

1. Stratosphäre (IEK-7)

Research Program(s):

1. 2112 - Climate Feedbacks (POF4-211) (POF4-211)

Appears in the scientific report 2021

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Database coverage:
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