CIRRUS in High Latitudes

Mission status: Enry

HALO Deployment Base

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Project description

Most rapid climate changes occur in the Arctic. In polar winter, ice clouds may exert a substantial positive forcing (warming) onto the below-cloud layer temperatures. However, direct observations of ice clouds in high latitudes, in particular in the Arctic, and their variability in terms of microphysical and macrophysical properties are sparse and incomplete, and therefore ice clouds and related aerosol effects may not adequately be represented in today’s climate models. Only a few aircraft campaigns specifically dedicated to cirrus have been performed in the Arctic, most were focused on low and mid-level clouds in summer. Thus, our understanding of the effects of Arctic cirrus on climate, in a region of the world where surface temperatures increase most, is limited.

Figure 3.24: BAMS cover with ML-CIRRUS (left), cloud probes on HALO (middle) and microphysical properties of in situ and liquid origin cirrus clouds in mid latitudes (right) as observed with the lidar and with in situ cloud probes.

CIRRUS-HL, the only HALO cloud mission combining in situ and remote sensing cloud instrumentation since 2014, will use state-of-the-art cloud probes, and novel ice residual, aerosol, trace gas and radiation instruments to investigate nucleation, life cycle, and radiative impact of ice clouds in the Arctic. The aircraft observations will be accompanied by remote sensing from satellite and by numerical simulations with global and process-based models. The campaign will complementary be linked to international polar research activities by focusing on the physics of ice clouds. From October to December 2020, HALO will perform 20 flights in the Arctic and Northern Europe with a focus on cirrus, induced by different meteorological regimes including synoptic cirrus with slow updrafts, frontal or warm conveyor belt cirrus with moderate updrafts, and orographic or convective cirrus characterized by high updrafts. A differentiation will be made between in situ cirrus, which formed homogeneously or heterogeneously at temperatures below 238 K, and liquid-origin cirrus. To get more insight into liquid-origin cirrus and ice nucleation, mixed phase and ice clouds will also be probed at temperatures above 238 K. The science questions of CIRRUS–HL are grouped around three topics:

(a) Microphysical properties of ice clouds in the Arctic winter,

(b) Aerosol transport into the Arctic and effects on ice clouds, and

(c) Radiative properties, radiation budget, and climate impact of cirrus in the Arctic.

(a) Microphysical properties of ice clouds in the Arctic winter
Dynamical conditions and updraft strongly affect cirrus formation and evolution. Therefore, the properties of cirrus in the Arctic in terms of abundance and microphysics are expected to differ from cirrus in other latitudes. In situ observations of cirrus in high latitudes have been performed sporadically during previous aircraft missions in the Arctic, however a dedicated aircraft mission with in situ instrumentation focusing on cirrus in the Arctic winter is missing. CIRRUS–HL will provide a novel data set on microphysical cirrus properties in the Arctic formed in different updraft regimes. Microphysical ice properties will be measured with advanced cloud probes using forward and backward scattering and imaging methods. Climatologies of microphysical ice cloud properties, e.g., ice crystal number concentration, effective diameter, and ice water content will be derived versus temperature to extend the current observational range of ice clouds up to the North Pole. The observations will be compared to properties from mid latitude cirrus and to convective cirrus. The following specific scientific questions will be answered:
  • What is the distribution of microphysical properties of ice clouds (ICNC, deff, IWC) in early winter in the Arctic?
  • Do microphysical properties of ice clouds
(b) Aerosol transport into the Arctic and effects on ice clouds

Particles in the free and upper troposphere of the Arctic mainly originate from long-range transport from lower latitudes, often related to WCBs. In addition, sedimentation of aerosol from the stratosphere may play a role, especially in the winter months due to the subsiding polar vortex. Aerosol size distribution, composition and properties of ice nucleating particles will be measured with an advanced instrumentation on HALO including the ALABAMA laser ablation mass spectrometer, the HALO–CVI Counterflow Virtual Impactor inlet with aerosol characterization by CPC/UHSAS/PSAP and the high volume particle sampler Hera4HALO, which is a new development for HALO. The following specific scientific questions will be answered:

  • What are the major aerosol and ice nucleating particles sources in high latitudes in winter? Are WCB a significant source to Arctic aerosol and INP?
  • What are the effects of ice nucleating particles on ice cloud properties for liquidorigin and in situ formed cirrus?
(c) Radiative properties, radiation budget, and climate impact of cirrus in the Arctic

During polar night, the infrared warming by cirrus is not compensated by shortwave cooling, hence leading to a strong positive cloud radiative effect and to a warming of below-cloud temperatures (Figure 3.23). Especially for optically thin cirrus, which are not opaque for thermal radiation, the cloud radiative effects crucially depend on the ice crystal microphysical properties like number concentration, size, and shape (Zhang et al., 1999). A slight increase of ice water path can significantly increase the radiation emitted by the cirrus. For high subtropical cirrus, Wendisch et al. (2007) quantified the effect of ice crystal shape on the top-of-atmosphere (TOA) longwave radiative effect of the cirrus by up to 70 %. During CIRRUS–HL, we will quantify the radiative effects of cirrus in high latitudes. The cirrus measured climatology will further be used for comparisons to global climate models to investigate the ice particle representation in global models and to evaluate cirrus radiative effects in the Arctic. The following specific scientific questions will be answered:

  • Does the ice crystal shape significantly change the radiative effects of Arctic cirrus or do cloud macrophysical properties dominate?
  • Are microphysical properties of ice clouds in high latitudes adequately represented in global climate models and what is their climate impact?

Figure 3.25: HALO’s comprehensive cabin instrumentation. New instruments that contribute to
the CIRRUS–HL proposal are marked in bold.

Since 2014, CIRRUS–HL will be the only HALO mission that will deploy the advanced in situ cloud instrumentation on HALO (six cloud probes, two aerosol spectrometers and a microwave temperature profiler). Combining the in situ cloud instrumentation with remote sensing instruments will help to reduce uncertainties in selected cloud parameters and to achieve closures of microphysical and radiative cloud properties in order to get new insights into nucleation, life cycle and climate impact of cirrus in the Arctic.

Persons in Charge


    •  Christiane Voigt

Mission coordinator

    •  Christiane Voigt (tbd)

Contact point at DLR-FX for this mission:



    • DLR-IPA
    • Karlsruhe Institute of Technology
    • Universität Leipzig
    • Johannes Gutenberg-Universität
    • Max Planck Institut für Chemie
    • Ludwig-Maximilians-Universität
    • Forschungszentrum Jülich
    • Goethe-Universität Frankfurt
    • Ruprecht-Karls-Universität Heidelberg
    • Leibniz–Institut für Troposphärenforschung

Scientific instruments and payload configuration

  • List of scientific instruments for the mission:

DescriptionPrincipal investigatorInstitution
Hera4HALO High
volume particle
DescriptionFrank Stratmann
Hartmut Herrmann (TROPOS)
Aerosol Inlet)
DescriptionMarkus Hermann
Frank Stratmann
Pyrgeometer and
2D-S 2 Dimensional
Stereo Probe
HALO AIMSDescriptionVoigtGomolzig
HALO_ CVI-RackDescriptionMertesGomolzig
HALO FAIRODescriptionZahnGomolzig
HALO Intake _ CVITable DataMertesGomolzig
HALO- lntake- HASITable DataSauerGomolzig
HALO_PRUTable DataTable DataGomolzig
HALO_SMARTTable DataWendischGomolzig
IPA-NOYTable DataZiereisDLR
miniDOASTable DataPfeilstickerDLR
WALESTable DataWirthDLR
DIAL Kühlflansch
Table DataWirthDLR
PMS Carriers mit InstrumentenTable DataTable DataGulfstream

Cabin and exterior configuration of HALO for the mission

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HALO flights for this mission

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More information

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Press releases, media etc

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