Cloud phase identification of low-level Arctic clouds from airborne spectral radiation measurements: test of three approaches

2008

Abstract. Boundary layer clouds were investigated with a complementary set of remote sensing and in situ instruments during the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) campaign in March and April 2007. The clouds that formed in a cold air outbreak over the open Greenland sea showed a variety in their thermodynamic state. Beside the predominant mixed-phase clouds pure liquid and ice clouds were observed. Utilizing the measurements of solar radiation reflected by the clouds three methods to retrieve the thermodynamic phase of the cloud were defined and compared. Two ice indices IS and IP were obtained by analyzing the spectral pattern of the cloud top reflectance in…

Spectral optical layer properties of cirrus from collocated airborne measurements and simulations

2016

Abstract. Spectral upward and downward solar irradiances from vertically collocated measurements above and below a cirrus layer are used to derive cirrus optical layer properties such as spectral transmissivity, absorptivity, reflectivity, and cloud top albedo. The radiation measurements are complemented by in situ cirrus crystal size distribution measurements and radiative transfer simulations based on the microphysical data. The close collocation of the radiative and microphysical measurements, above, beneath, and inside the cirrus, is accomplished by using a research aircraft (Learjet 35A) in tandem with the towed sensor platform AIRTOSS (AIRcraft TOwed Sensor Shuttle). AIRTOSS can be re…

A tandem approach for collocated measurements of microphysical and radiative cirrus properties

2017

Microphysical and radiation measurements were collected with the novel AIRcraft TOwed Sensor Shuttle (AIRTOSS) – Learjet tandem platform. The platform is a combination of an instrumented Learjet 35A research aircraft and an aerodynamic bird, which is detached from and retracted back to the aircraft during flight via a steel wire with a length of 4000 m. Both platforms are equipped with radiative, cloud microphysical, trace gas, and meteorological instruments. The purpose of the development of this tandem set-up is to study the inhomogeneity of cirrus as well as other stratiform clouds. Sophisticated numerical flow simulations were conducted in order to optimally integrate an axially asymmet…

Airborne observations of a subvisible midlevel Arctic ice cloud: microphysical and radiative characterization

2009

Abstract. During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) campaign, which was conducted in March and April 2007, an optically thin ice cloud was observed at around 3 km altitude south of Svalbard. The microphysical and radiative properties of this particular subvisible midlevel cloud were investigated with complementary remote sensing and in-situ instruments. Collocated airborne lidar remote-sensing and spectral solar radiation measurements were performed at a flight altitude of 2300 m below the cloud base. Under almost stationary atmospheric conditions, the same subvisible midlevel cloud was probed with various in-situ sensors roughly 30 min later. From indivi…

189TiP Phase IV trial of afatinib followed by osimertinib versus osimertinib alone as first-line treatment in patients (pts) with advanced EGFR mutat…

2021

Mixed-Phase Clouds in the Arctic A Synopsis of Airborne Lidar, In-situ, and Albedometer Observations, Complemented by Meteorological Analyses

2008

During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) 2007 campaign, airborne cloud observations were performed over the Arctic Ocean around Svalbard in the period from March till April 2007. On board of the AWI (Alfred Wegener Institute) Polar-2 aircraft, lidar remote sensing, in-situ cloud and albedometer solar radiation measurements were combined to investigate the properties of tropospheric clouds in the Arctic. On April 8th, a mixed-phase cloud formation was observed in a cold-air outbreak over open water. On April 9th, mixed-phase clouds were probed in two different air masses. First we observed remnants of the northerly cold-air outbreak which was gradually re…