ML-CIRRUS: The Airborne Experiment on Natural Cirrus and Contrail Cirrus with the High-Altitude Long-Range Research Aircraft HALO

Abstract

The Midlatitude Cirrus experiment (ML-CIRRUS) deployed the High Altitude and Long Range Research Aircraft (HALO) to obtain new insights into nucleation, life cycle, and climate impact of natural cirrus and aircraft-induced contrail cirrus. Direct observations of cirrus properties and their variability are still incomplete, currently limiting our understanding of the clouds’ impact on climate. Also, dynamical effects on clouds and feedbacks are not adequately represented in today’s weather prediction models. Here, we present the rationale, objectives, and selected scientific highlights of ML-CIRRUS using the G-550 aircraft of the German atmospheric science community. The first combined in situ–remote sensing cloud mission with HALO united state-of-the-art cloud probes, a lidar and novel ice residual, aerosol, trace gas, and radiation instrumentation. The aircraft observations were accompanied by remote sensing from satellite and ground and by numerical simulations. In spring 2014, HALO performed 16 flights above Europe with a focus on anthropogenic contrail cirrus and midlatitude cirrus induced by frontal systems including warm conveyor belts and other dynamical regimes (jet streams, mountain waves, and convection). Highlights from ML-CIRRUS include 1) new observations of microphysical and radiative cirrus properties and their variability in meteorological regimes typical for midlatitudes, 2) insights into occurrence of in situ–formed and lifted liquid-origin cirrus, 3) validation of cloud forecasts and satellite products, 4) assessment of contrail predictability, and 5) direct observations of contrail cirrus and their distinction from natural cirrus. Hence, ML-CIRRUS provides a comprehensive dataset on cirrus in the densely populated European midlatitudes with the scope to enhance our understanding of cirrus clouds and their role for climate and weather

Comparing parameterized versus measured microphysical properties of tropical convective cloud bases during the ACRIDICON–CHUVA campaign

“…We therefore estimate an uncertainty in particle size for particle diameters above 40 µm on the order of 13 to 15 %; the estimate is less for smaller particles. The instrument had been previously installed on HALO and the DLR Falcon aircraft during the campaigns ML-CIRRUS (The Midlatitude Cirrus; Voigt et al, 2017), ACCESS II (Alternative Fuel Effects on Contrails and Cruise Emissions; Moore et al, 2017), and DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa; Knippertz et al, 2015).…”

Determining stages of cirrus evolution: a cloud classification scheme

“…Categories include synoptic, orographic, lee wave and anvil cirrus. Recently a more general classification was introduced that distinguishes the groups of liquid origin and in situ clouds that describe whether the cirrus is formed by existing water droplets freezing at water saturation or by the freezing of solution droplets or heterogeneous nucleation at ice supersaturation but below water saturation Wernli et al, 2016). Such classifications of recorded data are a prerequisite for statistically investigating the specific properties and influences of different clouds and to extract the governing mechanisms and parameters from remote sensing and in situ measurements.…”

Comparing Airborne and Satellite Retrievals of Optical and Microphysical Properties of Cirrus and Deep Convective Clouds using a Radiance Ratio Technique

“…HALO with its long endurance of up to 8 hours and high ceiling of up to 15 km altitude is optimally suited to fly above cirrus and DCCs (Wendisch et al, 2016;Voigt et al, 2017).…”

“…For the purpose of airborne-satellite validation, designated flights above clouds were carried out during the ML-CIRRUS and ACRIDICON-CHUVA campaign (Wendisch et al, 2016;Voigt et al, 2017), which were closely collocated with overpasses of the A-Train constellation (Savtchenko et al, 2008).…”

“…During the ML-CIRRUS and ACRIDICON-CHUVA campaign, a comprehensive set of in situ and remote sensing instruments were operated on board of HALO (Wendisch et al, 2016;Voigt et al, 2017). SMART measured spectral upward radiance .…”