Download Master thesis project: The role of cloud

Master thesis project:
The role of cloud-diabatic processes for the predictability of atmospheric blocking
Description:
“Atmospheric blocking” denotes the formation of persistent and quasi-stationary, synopticscale anti-cyclonic circulation anomalies in the region of prevailing westerlies that “block” and
deviate transient eddies. Blocking represents a challenge for numerical weather forecasting,
because it may lead to high impact weather in a situation of increased forecast uncertainty.
The onset and decay of these systems are currently not well understood and they tend to be
relatively badly forecasted by operational NWP models.
A recent study by Pfahl et al. (2015) suggests that cloud-diabatic processes, and more
specifically the release of latent heat, can strongly influence the evolution and intensity of
blocks. Latent heating is not taken into account in current theories and might be the root
cause of forecast deficiencies during blocking episodes.
The aim of this project is to investigate selected blocking events and to assess the relevance
of diabatic processes for the forecast quality. For this purpose, model re-forecast simulations
with different lead times will be performed with the Integrated Forecasting System (IFS) of the
European Centre for Medium-Range Weather Forecasts (ECMWF), and the forecast
performance will be quantified with the help of different types of verification techniques. This
project will help to improve our dynamical understanding of the mechanism leading to the
formation and maintenance of atmospheric blocking and pinpointing potential shortcomings of
these systems in NWP models.
Supervisors:
Daniel Steinfeld ([email protected]), Stephan Pfahl ([email protected])
L
H
Figure: Blocking situation over Europe in summer 2015. Shown is the height of the dynamical tropopause (2pvu surface), sea
surface pressure and backward trajectories colored according to their pressure level.
Literature:
Croci-Maspoli, M., and H. C. Davies, 2009: Key Dynamical Features of the 2005/06 European
Winter. Mon. Wea. Rev., 137, 664–678
Grams, C. M., and H. M. Archambault, 2016: The key role of diabatic outflow in amplifying the
midlatitude flow: a representative case study of weather systems surrounding western North
Pacific extratropical transition. Mon. Wea. Rev., 144, 3847–3869
Madonna, E., Boettcher, M., Grams, C. M., Joos, H., Martius, O. and Wernli, H. (2015),
Verification of North Atlantic warm conveyor belt outflowsin ECMWF forecasts. Q.J.R.
Meteorol. Soc., 141: 1333–1344. doi:10.1002/qj.2442
Pfahl, S., C. Schwierz, M. Croci-Maspoli, C. M. Grams, and H. Wernli, 2015: Importance of
latent heat release in ascending air streams for atmospheric blocking. Nature Geosci, 8, 610–
614
Cold air outbreaks from Fram Strait into the Nordic Seas: characterisics and
dynamical processes
Marine cold air outbreaks (CAOs) denote the advecion of polar, cold airmasses over relaively
warm ocean waters. They are prevalent in the Nordic Seas and are of fundamental importance
for the climate system. For example, their occurrence controls intense upward sensible and latent
heat luxes, which are essenial for the formaion of dense waters in the Nordic Seas - an
important driver of the Atlanic Meridional Overturning Circulaion. In addiion, CAOs favour the
development of Arcic fronts and polar lows that bring about severe weather such as heavy
snowfall and strong winds.
A major part of the airmasses leading to CAOs over the Nordic Seas originates in the interior
Arcic and is transported through Fram Strait, the 500 km wide passage located between
Greenland and the Svalbard archipelago. The goal of this master thesis is to invesigate these
airstreams in case studies, as well as climatologically. The focus thereby lies on the characterisics
of these airmasses and the dynamical mechanisms that control these airmass transports. Some
speciic quesions that may be addressed are:
1. Are these airmasses especially cold already before they reach Fram Strait?
2. What are the processes that control their thermodynamic evoluion?
3. How is the occurrence of these CAOs linked to the large-scale low?
4. What weather systems control their variability?
A hypothesis that we would like to test, is that some of these events are linked to tropopause
polar vorices living in the interior Arcic. These vorices accumulate cold air, which can eventually
induce a CAO when the vorices approach Fram Strait.
Supervisors: Heini Wernli (ETH), Lukas Papritz (University of Bergen)
Left figure: Satellite image of CAO over
Fram
Strait
[1]
Right figure: Climatological pathway of CAO airmasses in the Greenland Sea (green box) [2]
Literature:
[1] Wacker, U., K. V. Jayaraman Poty, C. Lüpkes, J. Hartmann, and M. Raschendorfer, 2005: A
case study on a polar cold air outbreak over Fram Strait using a mesoscale
weather
predicion model. Bound.-Layer Meteor., 117, 301–336,
doi:10.1007/s10546-005-2189-1.
[2] Papritz, L. and T. Spengler, 2016: A Lagrangian climatology of cold air outbreaks in the
Irminger and Nordic seas and their role in shaping air-sea heat luxes, J. Climate,
doi:
10.1175/JCLI-D-16-0605.1
[3] Cavallo S. M. and G. J. Hakim, 2010: Composite structure of tropopause polar cyclones,
Mon. Wea. Rev., 138, 3840 - 3857, doi: 10.1175/2010MWR3371.1
On the properties of strong large-scale ocean evaporation
and their influence on isotope signals
in the Last Millennium
Master’s Thesis Project, Autumn Semester 2016
Supervisors:
Franziska Aemisegger (ETH Zurich, [email protected])
Jesper Sjolte (Lund University, Sweden)
Heini Wernli (ETH Zurich)
Strong large-scale ocean evaporation can lead to a significant input of moisture into the
atmosphere over relatively short time scales. Such events are frequently observed after the passage of an extratropical cyclone in a region of intense cold air advection, generally downstream
of continental areas. The influence of such strong evaporation events on the stable isotope
signals of near-surface atmospheric water vapour and precipitation in the polar regions are the
focus of this Master’s thesis. For three selected periods of 50 years (contemporary, little ice
age and medieval warm period) strong large-scale ocean evaporation events will be identified in
the 6-hourly ECHAM5-wiso data using a recently developed method. Sensitivity tests will be
performed to obtain the best possible configuration of the parameters for the identification of
the evaporation events. The meteorological properties (humidity variables, surface turbulent
heat fluxes, sea surface temperature and near surface temperature of the atmosphere, wind
speed) of these events will be analysed and related to isotope variables in the model. Potential
differences in the properties of strong ocean evaporation events between the selected climate
periods of the Last Millennium will be investigated and compared to differences in extratropical cyclone frequencies and tracks. A relevant contribution with respect to the question of the
importance of the properties of individual meteorological events on seasonal-interannual to the
centennial timescale is expected to arise from this project.
Surface latent heat flux [Wm-2]
Figure 1: Surface latent heat flux in the North Atlantic on 18 UTC on 1 March 2010, strong
large-scale ocean evaporation in red and cyclones in black contours.
Master thesis project:
Cyclone evolution – link to jet structure, Eady growth rate and quasi-geostrophic forcing
Description:
Cyclones are key dynamical features of the extra-tropical atmosphere. A clear understanding
of the mechanisms by which they form, intensify and decay is essential for reliable weather
forecasting, e.g., in Europe.
In this thesis we consider the life cycles of individual cyclones and investigate how they
evolve in relation to the jet stream structure and intensity, associated baroclinicity (Eady
growth rate) and quasi-geostrophic (QG) forcing for ascent (Q-vector convergence). In particular, we are interested how the core pressure of the cyclones evolves in response to these
factors. For instance, we would like to quantify whether cyclone intensification occurs in regions with strong QG forcing (leading to vortex stretching) and Eady growth rate.
First individual cyclones will be analyzed in case studies. As a second step, the analysis will
be extended to a climatological data base incorporating 10 years of cyclones. Some pertinent
questions that can be addressed include: (i) Do cyclones deepen most strongly when they
cross the jet axis?; (ii) Do they intensify more if they are found in the left-exit region of upperlevel jet streaks?; (iii) Are there phases in a cyclones life cycle when baroclinic instability
(Eady growth rate) is particulary strong compared to upper-level forcing (QG forcing)?
The data basis for this analysis is the ERA-Interim data set of ECMWF. Derived climatologies
of jet streaks and jet streams, Eady growth rate and QG forcing for ascent will be studied
along many cyclone tracks. The particular challenge of the thesis is to bring all these meteorological parameters together! To this aim, some experience in programming, or interest in
learning to do so, is required.
Supervisors:
Michael Sprenger ([email protected])
Heini Wernli ([email protected])
Clemens Spensberger ([email protected])
Evolution of upper-level PV and quasi-geostrophic forcing for storm Martin, 27 Dec 1999.
Representation of dry air intrusions in satellite imagery
Dry air intrusions (DIs) are descending air masses from the upper troposphere to the middle and
low levels, and are therefore typically very dry. In satellite images, dry atmospheric columns
appear as dark areas (dry slots) in the water vapour channel. However, it is yet unclear to what
extent do the dark slots correspond to DIs, and what is the spatio-temporal variability of this
correspondence. Here, this relationship is investigated by employing two datasets: a Lagrangian
dataset of DIs, i.e., air-parcel trajectories that descend significantly (>400 hPa in 48 h) in a
slantwise manner (non convective), and high resolution Eumetsat water-vapour images. In this
project, you will
- Establish a diagnostic for quantifying the geometrical overlap between the Lagrangian
and Eulerian features.
- Apply the diagnostic for test cases.
- Analyze statistically a larger region over a longer time period for a robust quantification
of the relationship.
Supervision: Shira Raveh ([email protected])
Michael Sprenger ([email protected])
hPa
Weather patterns and teleconnections in the Peruvian Andes - a study for the
development project CLIMANDES
Weather patterns, synoptic climatologies and teleconnections are common ways to describe
synoptic weather situations and find a small set of atmospheric indicators. This study will focus on
temperature and rainfall measured in Southern Peru, trying to relate the large-scale flow and
teleconnections (ENSO, MJO, Bolivian High) with the station observations. First the synoptic
climatologies (based on SLP, GPH, RTOT, ...) and feature climatologies (fronts, cyclones,
anticyclones, cutoffs,…) will be compiled from ECMWF reanalyses and analyzed. Then a suitable
set of classifications or indices will be chosen to compute the statistical relation between the largescale flow and the observed precipitation and temperature.
The overall goal of the development project is to investigate the seasonal predictability of these
variables (and derived agricultural indicators), cf. “Background”. To this end, we want to exploit the
large-scale signatures and features that are better captured by models and reanalyses than e.g.
the small-scale precipitation patterns.
Background
The project CLIMANDES (a development project between MeteoSwiss and the Peruvian weather
Service SENAMHI) aims at developing user-tailored Climate Services for the Andean region. A
focus is on seasonal forecast products for agriculture. The usefulness of such products relies
heavily on the predictability of the local climate phenomena by the models for which the complex
topography of the Andes poses a severe challenge.
Peruvian farmers harvesting crops
http://www.senamhi.gob.pe/climandes/
Weather systems influencing Peruvian
climate (from K. Correa, SENAMHI)
Links
http://www.wmo.int/gfcs/climandes; http://www.senamhi.gob.pe/climandes/
http://www.meteoschweiz.admin.ch >> Forschung und Zusammenarbeit >> Internationale Zusammenarbeit >>
Internationale Projekte >> CLIMANDES-2 [Link]
MeteoSchweiz Blog „Klimadienstleistungen für Entscheidungsträger am Beispiel Peru“ [Link]
Prerequisites: Statistics, climatology, R
Methods: Data processing, statistical analyses
Supervisors: Michael Sprenger (ETH), Katrin Sedlmeier, Cornelia Schwierz (both MeteoSwiss)
Literature: Janette Lindesay, Howard A. Bridgman; Climates of the Southern Continents - Present, Past
and Future; Wiley 1998. (available in ETH library)
Moisture sources climatology (1979-2017) of precipitation on
subantarctic islands
Master’s Thesis Project, Autumn Semester 2017
Little is known about the regional atmospheric water cycle affecting remote subantarctic
islands such as the Île de le Possession or Marion Island in the Southern Indian Ocean. These
islands represent an important remaining natural reserve for a wealth of species. This winter
(2016/2017) a large expedition around Antarctica (ACE) takes place on board of a Russian
research vessel (http://spi-ace-expedition.ch/) and samples of surface waters have been taken
by Iris Thurnherr and Pascal Graf on several of these small islands. In this Master Thesis,
the climatological evaporation footprint of the moisture leading to precipitation over these
islands will be established and characterised using the reanalysis dataset ERA-Interim for
the period 1979 to 2017. Evaporative moisture sources will be diagnosed using an existing
algorithm (Sodemann et al. 2008) based on three-dimensional kinematic backward trajectories
computed using LAGRANTO v2.0 (Sprenger and Wernli, 2015). Climate conditions associated
with atmospheric moisture uptakes during ocean evaporation as well as during precipitation
formation will be analysed and interpreted in terms of their possible influence on the stable
water isotope composition of the islands’ surface waters. The stable water isotope composition
of the island water samples collected during ACE will be measured at the University of Bergen
(Norway) using laser spectrometry. A stay of 2-3 weeks in Bergen at the beginning of the
Master Thesis will be dedicated to this purpose. The isotope data will then be interpreted
with the help of the same diagnostic tools as used for the moisture source climatology. The
climatological analysis will provide the broader perspective and the classification framework
for the specific events that affected the islands in the winter 2016/2017.
References:
Sodemann, H., C. Schwierz, and H. Wernli, 2008: Interannual variability of Greenland winter
precipitation sources: Lagrangian moisture diagnostic and North Atlantic Oscillation influence.
Journal of Geophysical Research: Atmospheres, 113 (D3), D03 107, doi:10.1029/2007JD008503.
Sprenger, M., and H. Wernli, 2015: The LAGRANTO Lagrangian analysis tool – version
2.0. Geoscientific Model Development, 8 (8), 2569–2586, doi:10.5194/gmd-8-2569-2015.
Supervisors:
Iris Thurnherr (ETH Zurich, [email protected])
Franziska Aemisegger (ETH Zurich, [email protected])
Prof. Harald Sodemann (University of Bergen)
Prof. Heini Wernli (ETH Zurich)
Figure 1: Impressions from Île de le Possession, where surface water samples have been collected
in January 2017 by Iris Thurnherr and Pascal Graf during the Antarctic Circumnavigation
Expedition (ACE). At the top the view of the Akademik Tryoshnikov, the russian research
vessel on board of which the expedition takes place, at the bottom the lakes panorama on the
island where the samples that will be used in this Master Thesis have been taken. Pictures are
from Florian Brucker (ACE Expedition).
2
Wind speed features over Europe in COSMO-2
Strong surface winds are among the most consequential phenomena associated with weather systems.
They have a wide range of causes and scales. Orography can generate stationary winds such as Mistral
(Figure 1a) or Föhn. In extratropical cyclones, very strong winds can occur along bent-back warm fronts
or in the rear of the center (Figure 1b), as well as along associated fronts. And last but not least, intense
convective systems can trigger strong gusts in intense downdrafts.
Feature-based analysis
Strong wind features will be identified by applying thresholds to a certain wind field (e.g. UV@850,
UV10m) at individual timesteps. By considering features at subsequent timesteps, these features are
then connected over time into tracks. From these tracks, conclusions can be drawn about lifecycle
development, stationarity, propagation speed, etc. Finally, the wind features/events can be related to
existing other feature data sets such as fronts, cyclones, or precipitation. As an example for feature-based
analysis, Figure 2 shows the temporal evolution of total precipitation along a front. Both precipitation
and the front have been identified using the feature-based aproach (features not shown). Similar featurebased analysis can be conducted in the proposed thesis, using wind instead of precipitation.
Which specific wind phenomena the focus will be on; what scientific questions will be answered; and
how exactly the features will be analyzed are all fairly open questions. This will allow the student to
actively take into account his or her interests, which makes the topic well suited for a creative, active,
and independent student who prefers a certain challenge over a fully ready-made topic.
Figure 1: 10 m wind speed (m/s, colors) and tracked surface cyclones (contours and lines with
symbols); ignore curved black/white lines. (left) Strong Mistral winds near the coast of France
accompany an Alpine lee cyclogenesis. (right) In the mature stage of the cyclone, very strong,
localized, and short-lived winds are present just to the rear of the center.
Simulation data
The master thesis will be conducted in the context of the CrClim project1 (spefically, it’s subproject
D). The goal of CrClim is to conduct a ten-year regional climate simulation at a convection-resolving
horizontal resolution of 2.2 km on a European-scale domain with the COSMO2 model. Most analysis
will eventually be run on-the-fly, i.e. in parallel to the model, to avoid huge amounts of output to disk.
A ten-year data set at hourly resolution of several fields at selected levels already exists and will be used
for both case-study and climatological analysis. In addition, it will be possible to conduct short-term
simulations for case studies with on-the-fly analysis at much higher temporal resolution, which provides
much better representation of short-lived, small-scale, and fast propagating features.
1 http://www.c2sm.ethz.ch/research/crCLIM.html
2 http://www.cosmo-model.org/
1
Figure 2: Example of feature-based analysis: evolution of precipitation along a front over
time. (left) Hourly precipitation (mm, colors) and tracked surface cyclones (contours and
lines with symbols); ignore curved black/white lines. (center) Total hourly precipitation along
various fronts; the dark blue line corresponds to the front shown in the left panel. (right)
Hourly precipitation intensity (horizontal axis, sum over log-bins) over time (top to bottom).
Vertical/horizontal line in center/right plot indicates timestep shown in the left panel.
Technical aspects
We are actively developing identification and tracking tools for feature-based analysis of high-resolution
regional climate model data. The tools are mainly being applied by us to fronts and precipitation, in
conjunction with cyclones. Application of these tools to wind features in the proposed master thesis will
complement existing analysis with another major component of European weather systems.
The tools are written in Python3 (around a core of mostly Cython4 ). The goal is to apply these tools
in Python scripts in a Linux-based environment. Familiarity with the Python language is not necessary,
but advantagous. A certain interest in and enthusiasm for programming will likewise be an advantage.
Supervision
• Stefan Rüdisühli ([email protected])
• Michael Sprenger ([email protected])
3 https://www.python.org/
4 http://cython.org/
2
The role of dry air intrusions for inducing strong large-scale ocean
evaporation events in the Western Mediterranean
Master’s Thesis Project, Autumn Semester 2017
The cold sectors of extratropical cyclones are associated with strongly descending, dry and cold
airstreams (Browning, 1997). Object-based composite analyses of extratropical cyclones and
their associated air-sea fluxes in the North Atlantic and the Southern Ocean have shown that
large areas of strong ocean evaporation can be observed at the rear of cyclones (e.g. Rudeva
and Gulev, 2011). The aim of this Master Thesis is to investigate the role of dry air intrusions,
arriving into the low levels in the cold sector, for the generation of strong basin-wide ocean
evaporation in the western Mediterranean in a climatological sense. In a first step the cooccurrence of strong ocean evaporation and dry air intrusions will be investigated in terms of
frequency, local conditions and large-scale environments. In a second step, using a trajectorybased approach, the fate of the strong moisture uptake of dry air intrusion air parcels will be
studied. A possible link with heavy precipitation events downstream of the evaporation hotspot
will be explored.
References:
Browning, K. A., 1997: The dry intrusion perspective of extra-tropical cyclone development.
Meteorological Applications, 4 (4), 317–324, doi:10.1017/S1350482797000613.
Rudeva, I., and S. K. Gulev, 2011: Composite Analysis of North Atlantic Extratropical
Cyclones in NCEP–NCAR Reanalysis Data. Monthly Weather Review, 139 (5), 1419–1446,
doi:10.1175/ 2010MWR3294.1.
Supervisors:
Franziska Aemisegger ([email protected])
Shira Raveh ([email protected])
Figure 1: (left) Dry air intrusion trajectories starting their descent on 18 UTC 26 October
2012, coloured according to their pressure (hPa), and (right) ocean evaporation with cyclones
shown in black contours and strong ocean evaporation into dry air in red contours for 18 UTC
28 October 2012 .
Origin and fate of oceanic boundary layer moisture in the subtropical
eastern North Atlantic
Master’s Thesis Project, Autumn Semester 2017
The weather in the subtropical eastern North Atlantic is generally characterised by subsidising
air masses along the descending branch of the Hadley cell and high surface pressure. The
oceanic boundary layer in these regions is frequently topped by stratocumulus clouds, which
have an important influence on the global radiation budget, but which are not well represented
in climate models. Previous studies have shown that observations of the stable isotopic composition of water vapour can provide important information about moisture exchange between
the boundary layer and the free troposphere due to turbulent mixing and shallow convection
(Bailey et al., 2013, Benetti, et al. 2015). This may ultimately help to better constrain the
formation of boundary layer clouds in these subtropical regions.
The aim of this Master Thesis is to provide further insights into the imprint of these mechanisms on water isotope data and characterise the moisture budget of the subtropical boundary
layer using the isotope-enabled numerical weather prediction and climate model COSMOiso
(Pfahl et al., 2012). Simulations of the isotopic composition of near-surface water vapour will
be compared to recent measurements that have been carried out on board the research vessel
Akademik Tryoshnikov in December 2016. Subsequently, trajectory calculations will be used to
study the fate of this near-surface moisture. In this way, we will be able to study the complex
relationship between moisture transport and its isotopic composition.
References:
Bailey, A., Noone, D., Berkelhammer, M., Steen-Larsen, H. C., and Sato, P.: The stability and
calibration of water vapor isotope ratio measurements during long-term deployments, Atmos.
Meas. Tech., 8, 4521–4538, doi:10.5194/amt-8-4521-2015, 2015.
Benetti, M., G. Aloisi, G. Reverdin, C. Risi, and G. Sèze (2015), Importance of boundary
layer mixing for the isotopic composition of surface vapor over the subtropical North Atlantic
Ocean, J. Geophys. Res. Atmos.,120, 2190–2209, doi:10.1002/2014JD021947.
Pfahl S., Wernli H. and Yoshimura K., 2012. The isotopic composition of precipitation from a
winter storm - a case study with the limited-area model COSMOiso. Atmos. Chem. Phys. 12,
1629-1648, doi:10.5194/acp-12-1629-2012.
Supervisors:
Fabienne Dahinden ([email protected])
Franziska Aemisegger ([email protected])
Stephan Pfahl ([email protected])
Figure 1: The subtropical eastern North Atlantic Ocean as seen from the Akademik Tryoshnikov, the russian research vessel on board of which the ACE expedition takes place. The
stable water isotope data measured in water vapour ∼20 m above the ocean surface in early
December 2016 will be used in this Master Thesis. The picture is from Victorine Sentilhes
(ACE Expedition).
Figure 2: Water vapour data (blue) and stable water isotope data (green) collected in the
subtropical eastern North Atlantic Ocean during the ACE expedition on board of the Akademik
Tryoshnikov. Credits: Iris Thurnherr.
2
Where do Warm Conveyor Belts ascend in a
cyclone?
Master thesis topic for autumn/winter 2017/18
Warm conveyor belts (WCBs) are strongly ascending air masses observed in extratropical
cyclones that produce large amounts of precipitaion and contribute signiicantly to the
poleward transport of heat in the mid-laitudes. These air masses are usually ideniied as
Lagrangian trajectories ascending at least 600 hPa within 2 days. During their slantwise ascent,
condensaion of moisture leads to strong heaing of the middle atmosphere producing a
signiicant posiive potenial voricity (PV) anomaly at low-levels. It was shown that this PV
anomaly can act to increase the cyclone’s rotaion and thereby modify its intensity. As can be
seen from the conceptual model (Fig. 1), WCBs start from the atmospheric boundary layer in
the warm sector of a cyclone and ascend gradually both along the cold front and above the
warm front.
Fig. 1: Lagrangian air streams in an
extratropical cyclone: The warm conveyor belt
(red), cold conveyor belt (blue) and dry
intrusion (yellow). Adapted from Carlson 1980.
Fig. 2: WCB trajectories in the ECMWF model, the
colors of the trajectories correspond to their
pressure level; sea level pressure in contours
(black).
However, observaional data shows that the strong ascent oten occurs within less than 24hrs
(Fig. 2) and can be linked to either the cold front, warm front or the cyclone center. Depending
on the exact posiion of the strong ascent and hence the locaion of the most intense
diabaically produced low-level PV anomaly, the WCB can contribute more or less to cyclone
intensiicaion.
The goal of this master thesis project is to systemaically invesigate the locaion of strongest
WCB ascent relaive to its associated cyclone (and fronts) and evaluate the potenial inluence
of the low-level PV anomaly on the cyclone’s intensity. To this end, ERA-Interim climatologies of
WCBs, cyclones and fronts are used and a tool has to be developed/adapted in order to
automaically apply the analysis to this large data set as well as to plot the results.
The candidate should ideally be:
-
interested in atmosphere dynamics (cyclones, WCBs, PV thinking)
technically adept (at least familiar with basic programming languages)
Contact: [email protected]; [email protected], [email protected]
Literature:
-
Binder et al. (2016): The Role of Warm Conveyor Belts for the Intensiicaion of
Extratropical Cyclones in Northern Hemisphere Winter. J. Atmos. Sci. 73, 3997-4020
Madonna et al. 2014: Warm conveyor belts in the ERA-Interim dataset (1979–2010).
Part I: Climatology and potenial voricity evoluion. J. Climate, 27, 3–26
Schemm et al. 2012: Warm conveyor belts in idealized moist baroclinic wave simulaions.
J. Atmos. Sci., 70, 627-652