Field Projects

The group of P. Hoor was involved with measurements in the following field projects:

SouthTRAC is a joint project led by the universities Mainz and Frankfurt/Main and the DLR (Oberpfaffenhofen) with the research centers Juelich (IEK-7) and Karlsruhe. It involves partners from different german institutes universities (Heidelberg und Wuppertal) as well as international partners from Argentina and Chile. The participating universities are strongly supported by the Deutsche Forschungsgemeinschaft (DFG) in the frame of the SPP-1294 (HALO) (DFG magazine about SOUTHTRAC).

Beginning in August with the integration of the experiments into HALO, SouthTRAC will lead us twice to the southern tip of Rio Grande/Argentina, first in September until the beginning of October and then again from early November to the last day of November. In between HALO will come back for a three week long break.

A blog from our group can be found here (only German).

A public (external) homepage of the SouthTRAC campaign can be found here. This page is hosted by DLR.

Changes in the distribution of trace gases, like water vapor and ozone, in the upper troposphere and lower stratosphere (UTLS) strongly impact radiative forcing and the Earth's climate and surface temperatures, and are of key importance for understanding climate change. Due to the high sensitivity of atmospheric radiative forcing to changes in greenhouse gases in the cold tropopause region even small variations e. g. in water vapor in the lower stratosphere are an important source of the decadal variability of the surface temperature. There is also large uncertainty in future changes of ozone and water vapour in the UTLS, limiting the ability to predict the radiative forcing due to stratospheric ozone recovery and related processes during the 21st century: Several studies  have shown that different chemistry climate models do not even agree on the sign of radiative forcing due to ozone recovery because of large uncertainties in modeled ozone changes in the vicinity of the tropopause.

Due to different wave forcing and strong differences in the polar vortices of both hemispheres, significant differences between the UTLS of the Southern and Northern Hemisphere are expected. Despite the importance of the global UTLS dedicated field deployments studying transport processes and structure of the southern UTLS have not yet been performed. Previous field campaigns focused on Antarctic ozone depletion and vortex processes or the tropics or tropospheric composition.

In addition, the winter southern hemisphere affects the global stratospheric circulation since the Andes constitute a global hot spot for gravity wave activity. The propagation of these waves and their impact are not yet fully understood.

During SouthTRAC the following specific topics will be studied with respect to interactions between dynamics, transport and composition in the southern hemisphere:

1. Exchange processes at the southern hemisphere tropopause
2. Gravity waves in the southern hemisphere
3. Influence of biomass burning on the southern hemisphere UTLS
4. Impact of the Antarctic vortex on the UTLS

Martin Riese (1), Martin Kaufmann (1), Peter Hoor (2) and Daniel Kunkel (2) 
(Forschungszentrum Jülich (1)  and Johannes Gutenberg University Mainz (2))

Changes in the distributions of trace gases, like water vapor and ozone, and thin cirrus clouds in the upper troposphere and lower stratosphere (UTLS) strongly impact radiative forcing of the Earth's climate and surface temperatures (e .g. Riese et al., 2012), and are of key importance for understanding climate change (e. g. Solomon et al., 2010). Mixing processes at the tropopause cover a scale range from the micro scale to planetary scales and have to be parameterized in global models. Uncertainties in the description of mixing, however, introduce large errors to the estimates of the radiative forcing and are thus of key importance for understanding climate change (Riese et al., 2012). It is therefore of great importance to quantify the physical and chemical processes (e.g. exchange of air masses, cirrus formation) that govern the composition of the UTLS. The so-called overworld above θ ≥ 380 K influences directly the composition of the extra-tropical stratosphere with significant contributions of air originating from the Asian monsoon circulation (Vogel et al., 2014; Ploeger et al., 2013). Below, the extra-tropical transition layer (ExTL) is strongly affected by bidirectional (quasi-isentropic) mixing across the tropopause (Hoor et al., 2010). The upper bound of the ExTL roughly coincides with the tropopause inversion layer (TIL), which constitutes a region of enhanced stability above the tropopause. The impact of radiatively active species like water vapour and ozone on the temperature structure makes the TIL a sensitive indicator for changes of ozone chemistry or changes of tropopause temperatures which directly affect water vapour which in turn feeds back into the static stability.

WISE addressed the relation between composition and dynamical structure of the UTLS by focusing on the following three main research topics:

ST1) Interrelation of the tropopause inversion layer (TIL) and trace gas distribution

ST2) Role of Planetary wave breaking for water vapor transport into the extra-tropical lower stratosphere

ST3) Role of halogenated substances for ozone and radiative forcing in the UTLS region

ST4) Occurrence and effects of sub-visual cirrus (SVC) in the lowermost stratosphere

Figure 1: Schematic of the UTLS. Major UTLS features are the extra-tropical transition layer (ExTL) and the Tropopause Inversion Layer (TIL). The lowermost stratosphere (LMS) is the region in the extra-tropical stratosphere that is directly connected with the troposphere by isentropic surfaces. Wind contours (solid black lines 10ms⁻¹ interval), potential temperature surfaces (dashed black lines), thermal tropopause (red dots) and potential vorticity surface (2PVU: light blue solid line) represent data from a cross section along 60^◦ longitude on February 15, 2006 (adapted from Gettelman et al., 2011)

 

• What is the impact of wave-driven large scale eddy mixing on the composition of the mid- to high-latitude LMS?
• What is the role of the Asian Monsoon in moistening the extra-tropical UTLS in summer?
• What are typical time scales for mixing and how are these related to the underlying dynamical processes and source regions
• Does the TIL affect transport and mixing into the lower stratosphere and within the lower stratosphere?
• Which factors determine the formation of the TIL and how do these in turn affect transport?
• What is the link between Rossby wave breaking events and associated transport of water vapor and cirrus formation at mid latitudes?

The group of P. Hoor was actively involved in the DEEPWAVE project in June and July 2014, which focused on gravity waves above the southern alps in New Zealand. The group of AG Hoor performed high precision in-situ measurements of carbon monoxide (CO) and nitrous oxide (N2O) on board the DLR FALCON aircraft. The measurements were performed with a modified Quantumcascade Laser IR-absorption spectrometer (Aerodyne Research). These measurements showed for the first time the effect of gravity waves with short wavelength of 15-40 km on transport and irreversible mixing in the tropopause region.

 

The NETCARE measurements took place as part of the NETCARE project led by Jon Abbatt (U.Toronto) in the high arctic in July 2014 following the RACEPAC campaign in spring.  The instruments onboard the POLAR 6 were virtually identical to the RACEPAC campaign measuring CO and CO2. Besides these measurements the AG Hoor provided the meteorological information and chemical predictions on transport of pollution on the basis of the MAC forecast system. The trace gas measurements were part of a large chemical payload which focused on the sources of aerosols in the high arctic and the processes controlling aerosol formation and transport into the Arctic. A part of the project was dedicated to the measurements of ship plumes and their impact on the arctic boundary layer, for which coordinated measurements with the research vessel were conducted. All instruments performed well without failures or data gaps. The project was done in close collaboration with the group of J.Schneider (MPI for Chemistry) and is part of the phd-project by Franziska Köllner (https://www.atmos-chem-phys.net/17/13747/2017/).

 

The RACEPAC-campaign took place from 24. April to 23. May in Inuvik (Canada). The measurements were performed using two polar research aircrafts (DC-3) from the Alfred Wegener Institute in Bremerhaven (Germany). The group of P Hoor measured CO2 and H2O using a modified Licor 7200 (NDIR). Carbon monoxide (CO) was measured using a VUV-spectrometer (AL 5002, Aerolaser). The data analysis is part of the phd-projects of Franziska Köllner and Christiane Schulz.

 

 

Während der AIRTOSS Kampagne im Mai und September 2013 hat die AG Hoor einen großen Teil der Kabinennutzlast gestellt, die im GFD Learjet geflogen wurde: Das Kerninstrument ist ein Quantenkaskadenlaserspektrometer der Firma Aerodyne, das CO und N2O Messungen mit bisher unerreichter Präzision bei einer Zeitauflösung von einer Sekunde erlaubt (limitiert durch den Fluss durch die Messzelle). Zusätzlich wurden zwei Geräte zur Messung von CO2 verwendet: Ein modifiziertes und druckstabilisiertes Licor 6262 (Gurk et al, 2005) und ein neues Licor 7200, das völlig ohne druck- und flussstabilisierende Elemente eingesetzt wurde. Philipp Franzen hat im Rahmen seiner Bachelorarbeit verschiedene Absorptionslinien des QCL-Spektrometers vermessen. Die technische und wissenschaftliche Auswertung der Flüge ist Bestandteil der Dissertation von Stefan Müller.

 

Die AG Hoor führte im Rahmen der ersten atmosphärenwissenschaftlichen Mission mit dem neuen deutschen Forschungsflugzeug HALO hochaufgelöste Messungen von CO, CO2, N2O und CH4 durch. Die Messungen im Rahmen des TACTS/ESMVal-Projektes decken den Breitenbereich von 70°N - 70°S ab und beinhalten eine Umrundung Afrikas. Ein Hauptziel der Messungen ist die Untersuchung von Austauschprozessen am Subtropenjet und des Transportes in der untersten Stratosphäre. Die Messungen wurden mit einem QCL-Spektrometer der AG Fischer des Max-Planck-Instituts für Chemie durchgeführt. Die wissenschaftliche Auswertung der Daten bildet den Schwerpunkt der Doktorarbeit von Stefan Müller.

 

Zur Untersuchung der planetaren Grenzschicht wurden Messungen mit einer Partenavia P68B der Firma enviscope GmbH durchgeführt. Damit wurde im September die Struktur der Grenzschicht am Feldberg bei Frankfurt/Main im Rahmen der PARADE Bodenmesskampagne des MPIC untersucht. Dabei wurden Messungen von CO, CO2, Ozon und Aerosolanzahlkonzentration (CPC, OPC der AG Weigel, Gruppe Borrmann) durchgeführt. Die Auswertung der PARADE Daten ist Bestandteil der Doktorarbeit von Florian Berkes. Im September 2012 konnte die AG Hoor mit CO2-Messungen die regulären Vulkanascheflüge des DWD unterstützen und dabei auch zum ersten Mal ein neues Gerät (Licor 7200) zur CO2-Messung am Flugzeug einsetzen. Darüberhinaus haben wir die Qualitätssicherung der Ozonmessungen übernommen und dazu umfangreiche Laborversuche zur H2O-Querempfindlichkeit und Druckabhängigkeit durchgeführt. Die Ergebnisse der Studien sind Gegenstand der Diplomarbeiten von Magdalena Berthelmann (jetzt beim DWD) und Franziska Köllner, die eine Promotion im Rahmen eines gemeinsamen Projektes der AG Hoor und AG Schneider (MPI Chemie) beginnt.

 

Die AG Hoor hat im Mai 2011 am DENCHAR (Development and evaluation of novel hygrometersfor airborne research) Projekt teilgenommen. Ziel des EU Projektes ist die Förderung neuer Wasserdampfmesstechniken und die Evaluierung von in-situ H2O-Messungen. Die AG Hoor hat ein modifiziertes Licor 6262 zur Messung von CO2 und H2O beigesteuert. Die H2O Messungen stimmen bis 30 ppmv exzellent mit den Referenzgeräten überein (FISH). Dieser Vergleich und die synoptische Interpretation der Messungen sind Gegenstand der Diplomarbeit von Jens Krause.