Mass spectrometry for water vapor measurements in the UT/LS

Water vapor in the lower stratosphere plays a crucial role for the atmospheric radiation budget (Solomon et al., 2011). However, large uncertainties remain in measuring atmospheric water vapor mixing ratios below 10 ppmv typical for the lower stratosphere. To this end, we have developed the Atmospheric Ionization Mass Spectrometer (AIMS) for the accurate and fast detection of water vapor in the UT/LS from aircraft. In the AIMS instrument atmospheric air is directly ionized in a discharge ion source and the resulting water vapor clusters H3O+(H2O)n (n = 0..3) are detected with a linear quadrupole mass spectrometer as a direct measure of the atmospheric water vapor mixing ratio. AIMS is calibrated in-flight with a H2O calibration source using the catalytic reaction of H2 and O2 on a heated platinum surface to form gaseous H2O. This calibration set up combined with the water vapor mass spectrometry offers a powerful technical development in atmospheric hygrometry, enriching existing H2O measurement techniques by a new independent method. Here, we present AIMS water vapor measurements performed during the CONCERT2011 campaign (Contrail and Cirrus Experiment) with the DLR research aircraft Falcon. In September 2011 a deep stratospheric intrusion was probed over northern Europe with a dynamical tropopause lowered down to 6 km. We found sharp humidity gradients between tropospheric and stratospheric air at the edge of the tropopause fold, which we crossed 4 times at altitudes between 6 and 11 km. In the center of the tropopause fold, we measured water vapor mixing ratios down to 4 ppmv. The observed water vapor distribution is compared to water vapor analysis fields of the ECMWF’s Integrated Forecast System (IFS) to evaluate the representation water vapor in this specific meteorological situation

Mass spectrometric measurements of relative humidity in contrails

While contrail formation requires environments which are at least saturated with respect to ice, a majority of in situ observations in contrails shows values clearly below ice saturation. The reasons for that systematic deviation might be caused e.g. by measurement biases in absolute humidity and temperature or by contrail dynamics. The formation of vortices within a wing span behind the aircraft, their descent and the interaction with the ambient atmosphere may cause a decrease in saturation and spatially very inhomogeneous RHi fields in contrails. In order to improve the instrumental uncertainties, we further developed an accurate and fast method for airborne humidity measurements in the upper troposphere, the Atmospheric Ionization Mass Spectrometer (AIMS) with in-flight calibration. Inside its ion source ambient water vapor is directly ionized and the produced water vapor clusters H3O+(H2O)n are detected with the mass spectrometer as a direct measure of absolute ambient humidity. The AIMS instrument is calibrated in-flight with a catalytic water vapor calibration source. The time resolution of better than 4 Hz allows for humidity measurements on horizontal scales of 50 m. This new method differs significantly from previously used airborne hygrometers. Therefore our observations could provide a complementary piece in the ice-saturation puzzle and new insights to the set of, obviously difficult, humidity measurements in the upper troposphere. Here, we present water vapor measurements in young contrails performed during the CONCERT2011 (CONtrail and Cirrus ExpeRimenT) campaign onboard the DLR research aircraft Falcon. We distinguish between contrail, cirrus and clear sky observations using information on the extinction and the mixing ratio of reactive nitrogen (NOy) detected onboard the Falcon. We find differences in the distributions of relative humidity over ice (RHi) inside and out of contrails in clear-sky and cirrus environments. Further we investigate RHi profiles from different contrail producing passenger aircraft, 2 Boeing 777 and an Airbus 321. In contrast to most previous observations, our measurements generally confirm simulated RHi distributions in aircraft exhaust plumes

Development of community, capabilities and understanding through unmanned aircraft-based atmospheric research: The LAPSE-RATE campaign

Because unmanned aircraft systems (UAS) offer new perspectives on the atmosphere, their use in atmospheric science is expanding rapidly. In support of this growth, the International Society for Atmospheric Research Using Remotely-Piloted Aircraft (ISARRA) has been developed and has convened annual meetings and “flight weeks.” The 2018 flight week, dubbed the Lower Atmospheric Profiling Studies at Elevation–A Remotely-Piloted Aircraft Team Experiment (LAPSE-RATE), involved a 1-week deployment to Colorado’s San Luis Valley. Between 14 and 20 July 2018 over 100 students, scientists, engineers, pilots, and outreach coordinators conducted an intensive field operation using unmanned aircraft and ground-based assets to develop datasets, community, and capabilities. In addition to a coordinated “Community Day” which offered a chance for groups to share their aircraft and science with the San Luis Valley community, LAPSE-RATE participants conducted nearly 1,300 research flights totaling over 250 flight hours. The measurements collected have been used to advance capabilities (instrumentation, platforms, sampling techniques, and modeling tools), conduct a detailed system intercomparison study, develop new collaborations, and foster community support for the use of UAS in atmospheric science

Development of community, capabilities and understanding through unmanned aircraft-based atmospheric research: The LAPSE-RATE campaign

Because unmanned aircraft systems (UAS) offer new perspectives on the atmosphere, their use in atmospheric science is expanding rapidly. In support of this growth, the International Society for Atmospheric Research Using Remotely-Piloted Aircraft (ISARRA) has been developed and has convened annual meetings and “flight weeks.” The 2018 flight week, dubbed the Lower Atmospheric Profiling Studies at Elevation–A Remotely-Piloted Aircraft Team Experiment (LAPSE-RATE), involved a 1-week deployment to Colorado’s San Luis Valley. Between 14 and 20 July 2018 over 100 students, scientists, engineers, pilots, and outreach coordinators conducted an intensive field operation using unmanned aircraft and ground-based assets to develop datasets, community, and capabilities. In addition to a coordinated “Community Day” which offered a chance for groups to share their aircraft and science with the San Luis Valley community, LAPSE-RATE participants conducted nearly 1,300 research flights totaling over 250 flight hours. The measurements collected have been used to advance capabilities (instrumentation, platforms, sampling techniques, and modeling tools), conduct a detailed system intercomparison study, develop new collaborations, and foster community support for the use of UAS in atmospheric science