Impact of ENSO on ice supersaturated regions

Master project suitable for master studies in
Atmosphere and Climate Science/Computational Sciences and Engineering/Earth Sciences/ Environmental Sciences/ Physics

Background:

The El Niño-Southern Oscillation (ENSO) is a climate pattern that occurs over the Pacific Ocean (roughly with a period of 3-7 years). ENSO has a very strong impact on the weather conditions as well as agriculture and fishing in the Pacific region. It is probably one of the strongest signals in ‘natural’ climate variations, which can be observed. ENSO is composed of an oceanic component (El Niño) and an atmospheric component (Southern Oscillation). El Nino is characterized by a strong warming of the surface water in the eastern Pacific Ocean, while the Southern Oscillation is characterized by strong changes in the pressure field (high pressure in the western Pacific region). It is clear that ENSO strongly influences the tropical atmospheric dynamics (e.g. Madden-Julian Oscillation and Walker circulation) and thus influences also some parts of the mid latitude atmosphere. However, it is not clear up to know how ‘far’ this influence can be.

Ice-supersaturated regions (ISSRs) are large air masses in the upper troposphere/lowermost stratosphere (UTLS) in the status of supersaturation with respect to ice. These regions are horizontally largely extended; they can reach extensions up to few thousands of kilometres. ISSRs are potential formation regions of cirrus clouds and contrails. For ice formation at low temperatures (T<235K, i.e. typical for the UTLS region) high ice supersaturation is needed – in contrast to the formation of water clouds, where only a few tenth of water supersaturation is needed for droplet formation.

Concept:

At the moment it is not really clear how ice-supersaturated regions are triggered by large-scale dynamics and climate variations. However, there are some indications that ENSO could affect the humidity field in the UTLS regions. Since the link is not clear, this should be studied for the strong ENSO event during winter 1997/1998.

Master project:

The impact of the ENSO event during winter 1997/1998 should be studied in order to determine a possible link between ENSO events and UTLS humidity and/or the occurrence and properties of ISSRs. For this purpose, in situ measurements (humidity, temperature, pressure) from the ‘Measurements of OZone, water vapour, carbon monoxide and nitrogen oxides by in-service AIrbus airCraft’ (MOZAIC) project will be used. During this project measurements were take onboard of commercial long-range aircrafts. These measurements obtained in the ULTS region will be used for detailed investigations of the occurrence of ISSRs and their properties.
In a first step, the in situ measurements will be used for determining the impact of the ENSO event (1998) vs. the ‘normal’ years 1995-1997/1999. In a second step the analysis can be widened by additional use of meteorological analyses/reanalyses from the European Centre of Medium-Range Weather Forecasts (ECMWF) in order to investigate the impact of ENSO in terms of temperature and humidity fields

Requirements:
•    (Basic) Knowledge of a higher programming language (MATLAB, FORTRAN etc.)
•    (Basic) Knowledge in atmospheric physics and atmospheric dynamics


Contact:
Dr. Peter Spichtinger
Institute for Atmosphere and Climate Science
Universitaetstrasse 16, CHN O16.2
8092 Zurich
Tel.: 044/63 27315
Email: peter.spichtinger@env.ethz.ch