Cloud Microphysical Properties Measured from Commercial Aircraft Karl Beswick and Martin Gallagher University of Manchester, United Kingdom Darrel Baumgardner Centro de Ciencias de la Atmósfera, UNAM, México Roy Newton Droplet Measurement Technologies, USA 3rd International Conference on Transport, Atmosphere and Climate June 2012 Prien am Chiemsee, Germany

Acknowledgements IAGOS Mike Poellet and David Delene University of North Dakota Bill Dawson Droplet Measurement Technologies Sarah Lance NOAA/CIRES UK Facility for Ground based Measurements A facility of the UK National Centre for Atmospheric Science This work has been supported in the UK by the NERC and FAAM.

Presentation Guide Background Instrument Description Laboratory Studies Preliminary Results Next Generation BCP

Background IAGOSis a program for long-term observations of atmospheric composition on a global scale from a fleet of long-range aircraft. Allows the collection of observations on a scale impossible to achieve using research aircraft. Large scale measurements of cloud microphysical properties will help climate modelers improve and validate their models and provide extensive data to improve retrieval algorithms for satellite measurements.

Particles pass through open laser beam Scattered light in the ° cone is collected by photo- detector Signal is amplified, digitised and sized into size bins, size range 5- 75µm diameter. No sample volume qualification: mathematical inversion is required. BCP (Backscatter Cloud Probe) 12.5 cm

Flight Testing FAAM BAe 146 CDP 2-50 µm BCP 5-75 µm CAS µm BCPD 1-50 µm

 NOTE: “Liquid Water” traces are NOT fully corrected and NOT relevant to cirrus ice clouds – only used as indicator of relative volume changes.  No T-Matrix corrections applied to size distributions for suspected ice conditions.  Particle Size Distribution data is currently produced using Version 2 of the backscatter retrieval algorithm.

Beam mapping with droplet stream was conducted at the NOAA/Boulder Laboratory (courtesy of Sara Lance)

Computer controlled 3D micro- positioning stages (0.5 µm accuracy) Piezo electric droplet generator High speed CCD imaging camera and microscope objective Glare CCD camera Air drier Liquid pump and solution reservoir Auto-scanning micro-positioner to direct mono-disperse droplets Reproducible size AND Concentration. IAGOS Facility – Manchester (with thanks to Sara Lance) Positioner rod Sheath air intake Sheath flow straighter Evaporation flow tube Flow tube nozzle Interchangeable Glare CCD camera Two Sizing Methods fringe separationglare technique 15 µm drops Constant inter-arrival time Δt Wave-form generator

Low Resolution Map of Cloud Spectrometer Sample Volume (no pin-hole mask used) Spatial resolution – 50 µm data Medium Resolution Map – 10 µm spatial data completed Data being processed System has been automated based on initial input of of sample area location. Time for auto-scanning of sample area varies depending on instrument used (CDP, BCP or CAS) and scan resolution used. 50 µm displacement takes 1-2 hours. 10 µm takes hours.

Inversion uses modified Twomy algorithm (Markowski, 1987, AST)

Laser isn’t eyesafe Operated with weight-on-wheels interlock switch

IAGOS-ERI Annual Meeting 2012, Lake Constance, June 18-20, 2012 Current well characterized Cloud Droplet Spectrometers

Total number concentrations from BCP show reasonable agreement with CDP even with the sample volume close to the aircraft skin.

The averaged size distribution, derived by inversion of the measured spectrum, agrees quite well with the CDP

The IAGOS instrument package was installed on board Lufthansa’s A 'Viersen’. The maiden test flight was launched from Frankfurt in July 2011

Summary of cloud concentrations : September, 2011 to May, 2012

Particle Characteristics Take Offs and Landngs Mid-Flight Total Cloud Events66%54% Cloud: Low Concentration (<100 L -1 ) 11%28% Cloud: High Concentration (>100 L -1 ) 50%26% Dust14%1% Cloud/Dust Particle Encounters: 319 Flights Average Flight Duration > 8 Hours

Analysis of Luana, Angola to Frankfurt Flight, May 18, 2012

Maximum concentration > 300,000 per liter over Nigeria Maximum ice water content > 2 grams per cubic meter (assumes spherical ice crystals (unrealistic)

Recent cloud particle measurements on May 18, 2012, Luanda, Angola to Frankfurt, Germany. More than 100,000 particles per liter at estimated temperature of C ! Note: Temperatures not corrected for dynamic heating.

30 Kt airspeed change

Aircraft takes avoidance action but remains in cloud for nearly half an hour and temperature measurements from IAGOS package remain corrupted by melted ice crystals.

Average diameters are dominated by small crystals Median volume diameters are biased by very largest crystals

Average size distribution during cloud encounter: Bimodal with maximum number at 10  m but maximum LWC at 70  m

Vertical Profiles During Take Off and Landing Show Cloud Structure (Landing in Frankfurt Shown Here) Multiple Cloud Layers

Next Generation Instrument The Backscatter Cloud Probe with Depolarization (BCPD)

Measurements with the Cloud Aerosol Spectrometer with Depolarization (CAS-DPOL) distinguish droplets from crystals (courtesy James Dorsey, U. Manchester)

Polarization Detector to Sizing Detector Polarization Ratio

The BCPD, under development for IAGOS, will measure the perpendicular and parallel components of the polarized scattered light and identfy water droplets, ice crystals and ash/dust.

BCP-DPOL Photo M. Gallagher, Manchester BCD-D First test Flight March Photo M. Gallagher, Manchester

Cloud Tunnel results are encouraging. A)The MVD as a function of time for the BCP-PD (red curve) and CDP (black), B) LWC, C) Number concentration and polarization ratio (blue curve) and D) average size distribution over the whole time period. Ice phase Water phase Ottawa Cloud Tunnel Data: Courtesy DMT

Summary The BCP is currently taking detailed size-resolved cloud measurements that will enhance the current data base and lead to a better understanding of how clouds form, evolve and impact climate, e.g. microphysical properties of  Contrails and Contrail induced cirrus  Cirrus and Sub-visible cirrus The BCP cloud data base will be available for comparisons with satellite-derived cloud products. BCPs can warn flight crews of very high ice crystal concentrations. The next generation BCP, BCP-D may distinguish water droplets, ice, volcanic ash and dust.

For more information on the BCP/BCPD: Thank you for your interest.

BCP-100 V1 Brief Summary 1.Software for assimilation and analysis of BCP database complete. Currently accepts, aircraft GPS position, altitude and temperature for interpretation. Software able to access multiple BCP data bases. 2.Database for BCP complete – includes UK BAe 146, Viersen, Falcon, and two US aircraft studies. 3.Data seems consistent. Lower threshold may be higher than expected 6 µm as opposed to 5 µm under operational conditions. 4.Intercomparison with BAe 146 CAPS-CAS, CDP-100 V2 complete. Data analysed and will be included in joint technical paper with DMT on BCP (in preparation, Baumgardner, Beswick et al.) together with data from US aircraft flights. 5.New pylon canister mount being purchased to allow for parallel mounting of BCP and CDP on BAe 46 for better intercomparison checks (NERC FAAM-Manchester MSc Student) 6.Routine detection over prevalent cloud regions e.g. Atlantic ITCZ. Profile data suggest consistent results. 7.BCP appears able to detect dust particles based on consistent Middle East profile data under cloudless skies. 8.Awaiting return of Viersen BCP to check 1.Calibration drift – this will be checked/validated using the new automated droplet gun calibration facility for sizing and absolute concentration. Two independent sizing methods – glare and interference fringe methods. 2.Diagnostics and laser inhomogeneity 3.Power supply check etc. 9.NERC Grant awarded to develop BCP 2 nd Generation instrument with polarisation capability. Delivery expected end 2012.