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Investigation of midlatitude high clouds characteristics and processes

English title Investigation of midlatitude high clouds characteristics and processes
Applicant Peter Thomas
Number 159950
Funding scheme Project funding (Div. I-III)
Research institution Institut für Atmosphäre und Klima ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Meteorology
Start/End 01.01.2016 - 31.12.2019
Approved amount 291'050.00
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All Disciplines (2)

Discipline
Meteorology
Climatology. Atmospherical Chemistry, Aeronomy

Keywords (4)

Humidity Measurements; Cirrus Modelling; Midlatitude Cirrus Clouds; Backscatter Measurements

Lay Summary (German)

Lead
Eigenschaften und Prozesse in Zirruswolken mittlerer BreiteDer Einfluss von Zirruswolken auf den Klimawandel ist unklar, da wesentliche Prozesse in diesen Wolken zu wenig bekannt sind, um sie in globalen Klimamodellen gut darzustellen. Dieses Projekt misst und modelliert Schlüsselparameter in Eiswolken über mittelern Breiten, den zeitlichen Ablauf der wichtigsten Vorgänge zu erschliessen.
Lay summary

Dazu werden Messung von Wasserdampf und Lichtstreuung an Wolkenpartikeln durch ein Raman-LIDAR mit solchen spezieller Sonden auf  Wetterballons zusammengeführt. Durch Realisierung von „Cloud Matches“, bei denen die gleiche Luftmasse nacheinander im zeitlichen Abstand von 10 bis 40 Minuten und mit einer räumlichen Abweichung von weniger als 2 km gemessen wird, kann die zeitliche Entwicklung der gemessenen Parameter verfolgt und so der Prozessablauf eingegrenzt werden. Dazu werden die Messungen mit einem hochentwickelten Wolkenmodell nachgebildet, das in einer vertikalen Säule mit  20 bis 50 m Höhenauflösung die unterschiedliche Grösse der Eisteilchen berücksichtigt. Für eine hinreichende statistisch Basis sollen im monatlichen Abstand über drei Jahre 36 dieser „Matches“ realisiert werden. 

 

So verbessert das Projekt das Verständnis mikrophysikalische Abläufe in den Wolken und klärt, ob ihre Beschreibung in atmosphärischen Lehrbüchern zutrifft oder ergänzt werden muss. Zusätzlich wird die Kenntnis über die Strahlungswirksamkeit der Wolken erhöht. Schliesslich wird die Grösse der Über- und Untersättigung von Wasserdampf in den Wolken präzisiert und so ihr Potenzial zur Entfernung von Wasserdampf aus der Atmosphäre genauer bestimmt. Durch diese Ergebnisse werden langfristig die  globale Klimamodelle und damit unsere Einschätzung des menschlichen Einflusses auf das Erdklima verbessert.

Direct link to Lay Summary Last update: 17.11.2015

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
Water Vapor in the Asian Summer Monsoon Anticyclone: Comparison of Balloon-Borne Measurements and ECMWF Data
BrunamontiSImone (2019), Water Vapor in the Asian Summer Monsoon Anticyclone: Comparison of Balloon-Borne Measurements and ECMWF Data, in JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 124(13), 7053-7068.

Collaboration

Group / person Country
Types of collaboration
DWD, Lindenberg, Dr. H. Vömel Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
NOAA, Boulder, CO, Dr. Karen Rosenlof United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
NOAA, Boulder, Dr. David Fahey United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
ETH Zurich, Prof. Ulrike Lohmann Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results

Associated projects

Number Title Start Funding scheme
147127 BATTREX-CH: The Swiss contribution to the international BAlloonsonde Tropical TRopopause EXperiment 01.09.2014 Project funding (Div. I-III)
103651 Physical states of mixed organic / inorganic aerosols 01.11.2004 Project funding (Div. I-III)
117987 Particle Backscatter and Relative Humidity in and around Cirrus Clouds Measured with a Lightweight Balloon Sonde 01.12.2007 Project funding (Div. I-III)

Abstract

This project combines Raman lidar measurements of water vapor and particle backscatter with frost point hygrometer and backscatter sonde measurements to derive midlatitude ice cloud properties including the in-cloud humidity. Processes in ice clouds will be constrained by tracking the evolution of cloud backscatter and humidity in an unprecedented manner by obtaining “cloud matches”, i.e. measuring the same cloud-filled air parcel twice. Match points are some 10 to 40 minutes apart and with a match error of less than 2 km. Cloud matches will be analyzed systematically by sophisticated size-resolving cloud modeling, using the full air mass column with a vertical resolution of 20-50 m. The projects intends to deliver 36 such cloud matches (one per month), which will allow to obtain a statistically sound analysis The general goal is a better understanding of microphysical and radiative processes of tropospheric aerosol and cloud particles, in particular concerning the conditions leading to supersaturation with respect to ice and impeded dehydration of the upper troposphere. The work proposed will contribute to the closure of the following questions: Are super- and subsaturations as observed within midlatitude ice clouds compatible with common (textbook) knowledge? Specifically, do they equilibrate within expected times or do we need non-conservative explanations (such as minute mass accommodation)? Can we better constrain the magnitude and effect of small-scale temperature fluctuations? Furthermore, how important is the presence of ice nuclei in midlatitude cirrus clouds?The proposed research project will approach these questions by addressing the following objectives: -analyze Lidar measurements over Payerne, Switzerland (with the Raman Lidar for Meteorological Observations, RALMO) to characterize cirrus cloud occurrence, altitude and morphology; -perform monthly radio soundings from Payerne using SnowWhite chilled mirror frost point hygrometers in tandem with COBALD (Compact Optical AerosoL Detector) backscatter sondes on the same payload, occasionally together with a modified Kipp and Zonen CNR4 net radiometer;-analyze all data statistically to assess the frequency distribution of relative humidity with respect to ice over Switzerland in cloud free and cloudy environments;-identify cloud matches between RALMO (upstream) and the SnowWhite/COBALD tandem (down-stream) from high spatial and temporal resolution air parcel trajectories based on the COSMO model to investigate cloud evolution;-analyze the cloud match data using the Zurich Optical and Microphysical Model (ZOMM) to determine whether the observed supersaturated cases can be reconciled with expected microphysical behavior, whether heterogeneous nucleation plays a role for the cirrus formation, and if so at which number concentration of heterogonous ice nuclei;-scrutinize data quality, especially with respect to potential measurement errors and uncertainties of SnowWhite and RALMO;-examine the tropospheric backscatter and water vapor profiles to derive the radiative effect of aerosol and clouds encountered in the soundings, and compare the radiative impact modelled with ZOMM and inferred from the measured radiometer profiles.
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