The NARVAL-North campaign: Postfrontal convective cloud research using the HALO aircraft

Felix Ament, Nicole Albern, Stephan Bakan, Felix Erdmann, Lutz Hirsch, Friedhelm Jansen, Christian Klepp, Heike Konow

Motivation

Platform & campaign

HALO aircraft & NARVAL instruments

University of Cologne

Cloud regimes

Sensor Synergy

Results

Outlook Next steps in the NARVAL consortium

• Product generation: Development of microwave radiometer retrievals (U-Cologne) for vertically integrated water vapor content (IWV) and liquid water path (LWP) based on high resolution model simulations (U-Hamburg, MPI-M). Advanced radar data analysis to account for convoluted Doppler spectra and for polarimetric quantities (DLR, MPI-M, U-Hamburg).

• Satellite validation: Cloudsat intercomparison (MPI-M) and HOAPS validation (U-Hamburg).

Cloudsat underflights

Case study intercomparison of a post-frontal low located inside the red box on 17 February 1997 using different satellite and model based estimates of precipitation.

Clouds and precipitation are key variables in the earth’s water cycle and radiation budget. Satellite retrieved data and model output produce somewhat different results regarding postfrontal precipitation in higher latitudes. The NARVAL-North campaign aimed for refined investigations of those variables in high latitudes above the Atlantic ocean utilizing the High Altitude Long Range Research Aircraft HALO.

NARVAL-North campaign

• January 2014 (NARVAL-North)

• 5 research flights out of Keflavik (Iceland)

• 2 transfer flights between Germany and Iceland with overpassing of supersites (Jülich, Mace Head, Cabauw, Chilbolton)

• 50 flight hours in total

• Gulfstream G550• Range of 10h / 10000 km• Cruise speed ~ 200 m/s• Belly Pod below the fuselage

for remote sensing sensors.

• Microwave radiometer: 26 channels (22 to 183 GHz)

• MIRA36 Cloud Radar:Pulsed polarimetric Doppler radar at 36 GHz (-38 dBZ sensitivity @ 5 km range)

• WALES Lidar:Water vapor absorption lidar with four wavelength.

AcknowledgementsNARVAL is a joint research initative by DLR Oberpfaffenhofen, MPI-M, Universität Hamburg, Universität zu Köln, Universität Heidelberg, Universität Leipzig, FZ Jülich funded by DFG, MPG and DLR.

Microwave radiometer

Cloud radar

Lidar

Microwave radiometer

Cloud radar

Example: Research Flight 12.01.2014• 6,5 hour research flight over tiltback

occlusion with several dropsondes launched (yellow circles in Figure, right)

• Cloud regimes range from shallow cumuli in the cold air region of the occlusion to higher frontal clouds

Lidar

Cloud radar Sensors detect very different aspects of clouds, resulting e.g. in rather different cloud occurrences (top). Therefore we devel-op synergetic products.

High ice clouds

Enhanced cumulus

Shallow cumulus

Postfrontal low

Spiral bands

Occlusion

Postfrontal subsidence

Cold front

Clear to low stratiform clouds

0% 5% 10% 15% 20% 25%

Overall range and frequency of observed cloud regimes during NARVAL-North.

Trajectories of Cloudsat underflights during NARVAL-North (top). Two examples of radar reflectivity comparisons (right)

NARVAL-North features four collocated Cloudsat underflights.• The overall cloud structures

agree remarkably well,…• but effects due to different

sensitivity and resolution are apparent. Likewise systematic deviation due to calibration issues need to be further investigated.

Regime frequency (top)• Clouds have been detected

during NARVAL for 90% of the flight time.

• Dominant regimes are shallow and enhanced cumulus

• Brightness temperature peaks (microwave radiometer) at 20 GHz indicate liquid water (emission) whereas drops at 183 GHz are due to cloud ice (scattering).

• Cloud Radar gives insights about internal cloud structure. Bright band depicts the melting layer.

• Lidar detects cloud top boundaries and provides aerosol and water vapor information at the cloud environment.

frequency of cloud occurrence [%]

Cloud radar

Lidar

Complementary information by the cloud radar (top) and the Lidar (bottom), describing the cloud structure and absolute water vapor content in the cloud environment, respectively.

(Bos, 2014)

(Orlandi, University of Cologne)

(Wirth, DLR)

(Wirth, DLR)