Seminar

Abstract

Accurate measurements of the optical depth from contrails are required to determine their radiative forcing and hence their impact on climate. Still in situ measurements of the contrail optical depths are spare. In the first part of my talk I will present direct measurements of contrails performed in November 2008 with the DLR research aircraft Falcon during the CONCERT - CONtrail and Cirrus ExpeRimenT - campaign. More than 22 contrails produced by a representative fleet of 11 different aircraft have been detected in the mid latitude tropopause region. The contrails with ages of less than 10 minutes have a mean effective radius of 2.6 μm and a mean number concentration of 120 cm^-3. Probability density functions of the contrail extinction and optical depth will be used in radiative transfer calculations to derive a new estimate of the radiative forcing from persistent contrails.

Volcanic eruptions contribute to the stratospheric sulfate aerosol loading and have a cooling effect on climate. The second part of my talk will address in situ measurements in an aged volcanic plume originating from the eruption of the Aleutian volcano Mt Kasatochi on 7/8 August 2008. Three months later a sulfate aerosol layer was detected with the DLR chemical ionization ion trap mass spectrometer (ITCIMS) and the MPI-C aerosol mass spectrometer (AMS) onboard the Falcon during CONCERT. We derive the northern latitude lower stratospheric conversion time of SO₂ to sulfate aerosol of 60 days and discuss organic compounds observed in the aerosol layer. The measurements are compared to recent Falcon observations of the Iceland's Eyjafjallajökull eruption on 14 April 2010, leading to a closure of 75% of the European aerodrome network and affecting over 10 million passenger journeys.