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Atmospheric Radiation and Applications

HALO Southtrac Flugzeug
HALO aircraft arrives at Rio Grande/Argentina for the SOUTHTRAC campaign in fall 2019
Launch of the LPMA/DOAS balloon from Esrange/Kiruna during the ENRICHED campaign in early 2011
Solar photovoltaic system in the Allgäu region as part of the MetPVNet measurement campaign in summer 2019

Our research group investigates physical processes in the lower and middle atmosphere by means of optical spectroscopy, photochemical and radiative transfer modelling, and mathematical inversion techniques. The primary focus of our research is the photochemistry of ozone, and our central experimental method is Differential Optical Absorption Spectrometry (DOAS) in the UV/VIS/NIR, with which the detection of many relevant trace gases (O3, NO2, HONO, BrO, IO, OClO, CH2O, C2H2O2 ...) as well as water in all three phases is possible. A more recent application of our skills in radiative transfer modelling and inversion is in the monitoring of global radiation and the derivation of corresponding optical properties (aerosol and cloud optical depth) of the atmosphere using photovoltaic installations.

To date (April 2019), the group has authored125 peer-reviewed publications in international journals and contributed to various international assessment reports, for example the UNEP/WMO assessment reports on stratospheric ozone published in 2002, 2006, 2010, 2014 and 2018.


Physics and Chemistry of the Atmosphere

Bromine trend Nov 2021
Trend of stratospheric bromine as of November 2021

The primary research focus of our group is the photochemistry of ozone, which we investigate using Differential Optical Absorption Spectrometry (DOAS) in the UV/VIS/NIR. This allows the detection of many relevant trace gases (O3, NO2, HONO, BrO, IO, OClO, CH2O, C2H2O2 ...) as well as water in all three phases. The measurements are taken with optical grating spectrometers using either direct sunlight or scattered skylight, and different observation platforms such as aircraft (Falcon, HALO, Geophysica), unmanned air vehicles (UAV), or high altitude balloons are used. The spatial and temporal reconstruction of concentration fields of the targeted trace gases is performed either with traditional inversion techniques assisted by radiative transport calculations, or more recently by employing the scaling method to a (scaling) gas of which the atmospheric concentration is known.

Our measurements contribute to the following overarching scientific objectives:

  1. The photochemistry and budget of atmospheric halogens (Cl, Br, I) and their role in the destruction of stratospheric ozone, with air-borne measurements of BrO, IO, and OClO often performed with complementary measurements of a suite of halogenated source gases, including short-lived species and product gases (HCl, ClONO2, ClO, BrONO2 ...).
  2. Detection of all three phases of water in mixed-phased clouds and cirrus clouds.
  3. The photochemistry of volatile organic compounds, with specific emphasis on formaldehyde (CH2O) and the carbonyl compounds glyoxal (C2H2O2) and methylglyoxal (C3H4O2), which are either directly emitted by biomass burning or from cities, or photo-chemically formed in the oxidation of CH4 (CH2O) or in the oxidation of VOCs (CH2O, C2H2O2, and C3H4O2).
  4. The photochemistry of NOx and NOy species and their contribution to atmospheric oxidation capacity. Our measurements of NO2 and HONO often complement measurements of other NOx and NOy species (NO, HNO3, PAN …).

Solar Radiation and Renewable Energy

Solar PV system

A second, more recent research objective that builds on our skills in atmospheric radiative transfer modelling and inversion techniques addresses the deposition of solar radiation at the ground and its relation to the generation of electricity using solar photovoltaic (PV) installations. In this regard a particularly exciting aspect is the relationship between atmospheric conditions (aerosol abundance and cloud cover) and electricity production, both in the forward (i.e. from atmospheric conditions to global radiation and PV power) and backward (i.e. from PV power to global radiation and thus to atmospheric conditions) sense.

The initial goal of the MetPVNet project is to use a physically-motivated forward model to calibrate individual PV installations under clear sky conditions – the measured PV power from several well-understood PV systems can then be used to reconstruct the corresponding atmospheric conditions under all sky conditions and to compare these results with the reanalysed weather from weather prediction models. In a second step, the power from a larger ensemble of PV installations will be used to reconstruct the aerosol and cloud cover for a greater area, commensurate with the electricity grid of a distribution network operator. In a final step, the actual PV power will be compared with meteorology-based PV power predictions, and machine learning tools will be used to improve PV power forecasts.


Gruppenbild 2019
Group photo, July 2019

Current group members

Name Position Room Tel.
Prof. Dr. Klaus Pfeilsticker Group leader 229 / R422 6401
Dr. James Barry Postdoc 229 / R312 6334
Dr. Flora Kluge Postdoc 229 / R442 6316
Dr. Meike Rotermund Postdoc 229 / R414 6315
Ben Weyland PhD Student 229 / R442 6316
Karolin Voss PhD Student 229 / R308 6527

Alumni (PhD and Masters)