Cloud Condensation Nuclei Counter (CCN-100 and CCN-200)

 

About Clouds and Cloud Nuclei

Clouds are a key factor in moderating climate change. Cloud condensation nuclei (CCN) are those aerosol particles that can form into cloud droplets, and an understanding of CCN concentrations in space and time is necessary if models are to accurately predict the magnitude of global climate change. The DMT CCN counter measures the concentration of these particles and can be operated on the ground or on aircraft.

The DMT CCN counter is being used in laboratories to measure how different materials form cloud droplets, in urban environments to study how pollution affects cloud and precipitation formation, and in weather modification studies to determine when and where to seed clouds. This popular instrument comes equipped with single (CCN-100) or dual (CCN-200) columns for extended versatility.       

Advantages of the CCN Counter

  • Measures the spectrum of cloud condensation nuclei (CCN) concentration as a function of supersaturation continuously using uninterrupted flow and a multi-channel, optical particle counter that measures the size of the activated droplets
  • Features supersaturation as low as 0.07% and as high as 2%
  • Offers complete automation of up to 250 programmable and scanned supersaturation settings
  • Minimizes size and buoyancy effects with cylindrical geometry
  • Features onboard computer for control and data logging
  • Provides fast response and continuous flow, which allows airborne as well as ground-based applications

 

 

Applications

  • Atmospheric research
  • Climate change studies
  • Pollution research
  • Weather modification

Photo at right: The CCN (inset) at a research station in Barrow, Alaska (main photo).

Photos by Robert Albee, NOAA Earth System Research Laboratory.

 

 

Software

The CCN comes with a software program that provides a user-friendly virtual instrument panel for the control, data display, and data logging of the CCN instrument. For instance, the program enables the user to do the following tasks: 

  • Collect data
  • Change supersaturation settings
  • Adjust temperature and air flow settings
  • Manipulate instrument pumps (e.g., turn air pumps on high to prevent condensation)
  • Quickly detect any operational problems
  • Update instrument calibration parameters
  • Adjust the instrument to prepare it for shipping or re-humidify it after shipping

Information gathered during sampling sessions is written to output files that can be viewed in real-time and played back later for detailed analysis. 

The software also regulates the instrument to prevent hardware damage due to factors such as excessive temperature, leaks, and laser problems.

In addition to the standard software, the CCN Counter interfaces with DMT's Particle Analysis and Display System (PADS). PADS allows the user to analyze data collected from the CCN Counter and other DMT instruments simultaneously, but does not allow control of the CCN Counter.

 

 

How It Works

 

The CCN Counter is a continuous-flow thermal-gradient diffusion chamber for measuring aerosols that can act as cloud condensation nuclei. The CCN-100 draws an aerosol sample into 50-cm tall column, while the CCN-200 features two identical such columns. Inside the column(s), a thermodynamically unstable, supersaturated water vapor condition is created by taking advantage of the difference in diffusion rates between water vapor and heat. Water vapor diffuses from the warm, wet column walls toward the centerline at a faster rate than the heat. The wall temperature along the column gradually increases to create a well-controlled and quasi-uniform centerline supersaturation. Through software controls, the user can modify the temperature gradient and flow rate to change supersaturations and obtain the CCN spectra. 

In the figure at left, we show point C along the centerline where the diffusing heat originated higher on the column (red-line, point A) than the diffusing mass (blue line, point B). Assuming the water vapor is saturated at the column wall at all points and the temperature is greater at point B than at point A, the water vapor partial pressure is also greater at point B than at point A. The actual partial pressure of water vapor at point C is equal to the partial pressure of water vapor at point B. The temperature at point C is lower than at point B, however, which means that there is more water vapor (corresponding to the saturation vapor pressure at point B) than thermodynamically allowed. 

Seeking equilibrium, the supersaturated water vapor condenses on the cloud condensation nuclei in the sample air to form droplets, just as cloud drops form in the atmosphere. An Optical Particle Counter (OPC) using side-scattering technology counts and sizes the activated droplets.

See the CCN Operator Manual for more information.

 

Specifications

Parameter Specification
Technique Activation of CCN particles at constant supersaturation maintained in a 50-cm-high column with continuously wetted walls and a longitudinal thermal gradient; sizing of the activated droplets using an optical particle counter
Aerosol Medium Air, 5 - 40 °C (41 - 104°F) 
Number Concentration Range Depends on supersaturation:
  • 6,000 particles/sec at supersaturations below 0.2%
  • 20,000 particles/sec at supersaturations above 0.3% 
Measured Particle Size Range (from OPC, after supersaturation) 0.75 – 10 µm 
Number of Particle Size Bins 20
Sampling Frequency 1 Hz / 1 Second
Supersaturation Range 0.07% - 2.0%
Time Required for Supersaturation Change ~30 seconds for 0.2% change
Maximum Number of Automatically Scanned Supersaturation Settings 250
Optical Particle Counter Laser 660 nm, 35 mW
Flow Range
  • Total flow: 200 – 1000 vol. cc/min (factory calibrated at 500 Vccm)
  • Sample flow: 20 – 100 Vccm
  • Sheath flow: 180 – 900 Vccm 
Flow Control
  • Total flow is adjustable from within CCN Counter software
  • Sample/Sheath flow ratio is adjustable using manual metering valve 
Pump Solenoid pumps for water; diaphragm pump for air
Routine Maintenance Every Four Days/Before Every Flight:
  • Empty and refill water bottles
  • Check OPC water trap and bottom of case for water leakage

Monthly:
  • Check air inlet filters
  • Check flow calibration
  • Check desiccant tube

Every Three Months:
  • Replace airflow filter
Recommended Service Annual cleaning and calibration at DMT service facility
Front Panel Display Computer monitor, water supply bottle 
Side Panel Connections
  • System power switch
  • LED for overall system power
  • Watchdog light
  • Air vents
  • Inlet and exhaust valves
  • +28 VDC pin connector
  • Ethernet connection
  • USB connection
  • Mouse and keyboard connections
  • Touchscreen connection
  • Video connection
  • Serial data port
  • LED power connection
Computer System
  • On-board Intel® Celeron® 1 GHz processor
  • 512 MB RAM
  • 80 GB hard drive for data storage 
  • User interface via standard keyboard and monitor (included) 
Software
  • CCN Counter Software, Playback Software
  • Optional Particle Analysis and Display System (PADS) to record data in an aircraft system (Not required to operate the instrument; PADS requires an external computer, which is not included) 
Data System Interface RS-232, 9.6 Kb/sec Baud Rate (single CCN Counter) or 57.6 Kb/sec (Dual CCN Counter) 
Data System Features
  • Onboard computer for control and data logging
  • Touch screen control and display
  • Serial data output for external computer
Calibration DMT recommends periodically calibrating the CCN Counter supersaturation rate, flow sensors, pressure transducers, and the optical particle counter. The user can calibrate the supersaturation rate themselves by comparing the instrument’s output to that of reference instruments Differential Mobility Analyzer (DMA) and a CN Counter. A complete cleaning and calibration is also available from DMT.
  • The supersaturation rate is calibrated annually using a DMA and CN Counter.
  • The flow sensors are calibrated monthly using a flow meter and soap bubble unit/automated system.
  • The OPC is calibrated annually using DMT aerosol generator and 2.0 µm polystyrene latex (PSL) particles.

Once the calibration analysis is complete, the user can easily adjust the instrument by entering new values into the CCN software
Features for Easy Aircraft Mounting
  • Rack-mount compatible 
  • Center of gravity located 15.5” from bottom of back base plate 
  • Instrument plumbing system sealed for operation on pressurized aircraft
Power Requirements 28 VDC
Current CCN-100: 15 A at startup, nominal 7 A during regular operation
CCN-200: 25 A at startup, nominal 20 A during regular operation
Shipping Container Durable Atlas Case Corporation ATA Transit Case that conforms to the Air Transport Association’s Specification 300 Category 1 standards
Size (for both CCN-100 and 200) For lab use (with frame):
  • 35.0” H x 19.3” W x 15.6” D / 
  • 88.9 cm H x 48.9 cm W x 39.7 cm D

For aircraft use (without frame):
  • 32.0”H x 15.25” W x 10.6 D /
  • 81.3 cm H x 38.7 cm W x 27 cm D 
Weight CCN-100:
  • For lab use (with frame): 35.2 kg / 77.5 lb 
  • For aircraft use (without frame): 29.0 kg / 64.0 lb

CCN-200:
  • For lab use (with frame): 50 kg / 110 lb
  • For aircraft use (without frame): 43.8 kg / 96.5 lb
Environmental Operating Conditions Temperature: 5 – 40°C (41 – 104 °F)
RH: 0 – 100% RH non-condensing 

Specifications are subject to change without notice.


Included Items

  • Instrument
  • CCN software
  • Ship kit
  • Operator manual
  • One-year warranty
  • One day of training at DMT facility
  • Email and phone technical support

Optional Software

  • Particle Analysis and Display System (PADS)

Kits

Several are available for the CCN. A selection of these are listed below.

Ship kits are supplied with the CCN-100 and CCN-200. A list of contents for the CCN-200 ship kit appears below.
  • 15" Touch Screen Monitor
  • Power Cord for Touch Screen
  • Stylus for Touch Screen
  • Keyboard with Touch Pad
  • Spinning Disk ATA Hard Drive
  • 28V Power Cable
  • 28V Power Cable, Filtered
  • Power Gate HRP-600 Assembly
  • Null Modem - DB9 Female 6 ft
  • Adapter Slip
  • Cord AC power with plugs
  • Plug Manifold
  • Threaded Rod
  • Operator Manual
  • Disposable Inline Filters
  • Fuses
  • 4" Mini Black Cable Ties
  • Screws, Washers and Ferrules
  • Bottle Neck Holder
  • Nafion Insertion Tool
  • Bottles with Caps and Labels
  • Disposable Syringe
  • Plugs Flat-Bottom
  • Nuts Female 1/4" Tube OD
  • Hex L-Key Set and Wrenches

Not pictured:
  • CCN-200 Custom Shipping Case
  • CCN-200 Custom Pallet
  • Packing Box

The CCN Consumables Kit (Kit-0009) includes the items below.
  • Disposable Inline Filters
  • Disposable Syringe
  • Drain and Supply Labels
  • Nylon Ferrules
  • TEFZEL® Ferrules
  • Bottles with Caps
  • CCN Pump Repair Kit
  • Nafion Humidifier Element
  • Super-flangeless Nuts
  • 1/8” Polyurethane Tubing
  • 3/8” Conductive Rubber Tubing
The CCN Field Repair Kit (Kit-0010) includes the items below.
  • Thermoelectric Cooler (TEC) Connectors
  • Computer Power Cable
  • Flat Ribbon and Connectors
  • Spinning Disk ATA Hard Drive
  • CCN TEC-Servicing Manual
  • Thermal Ribbon Sensor
  • Temperature Controller
  • Stainless Steel Washers
  • Nylon Washers
  • Screws
  • Screw Hex Nuts
  • Heat-sink Compound
  • Grounding Wrist Strap
  • Screwdriver
  • Hex Insert Bit
  • Diaphragm Pump
  • Self-Priming 60μl Pump
  • Proportional Valve
  • 30A Circuit Breaker
  • Hex L-Key Set
  • Wrenches
The airborne inlet assembly kit facilitates aircraft mounting of the CCN-100 and CCN-200. It includes the following items:
  • CCN rail mount
  • CCN aircraft inlet
  • Constant pressure inlet

 

Acknowledgements

The Cloud Condensation Nuclei (CCN) Counter is based on the design of Dr. Greg Roberts of Scripps Institute of Oceanography and Dr. Athanasios Nenes of the Georgia Institute of Technology. The patent for their design is licensed exclusively to DMT, patent number 7,656,510.

 

How to Order

Email: customer-contact@dropletmeasurement.com

Phone: +001 303 440 5576
Fax: +001 303 440 1965

Please specify single or dual growth columns (CCN-100 or CCN-200) when ordering.

 

Selected Bibliography

The following papers provide a representative sample of research conducted with the DMT CCN Counter. A comprehensive bibliography of CCN-related publications will be available soon.

Asa-Awuku, A., Engelhart, G. J., Lee, B. H., Pandis, S. N., and Nenes, A. (2009) "Relating CCN activity, volatility, and droplet growth kinetics of β-caryophyllene secondary organic aerosol," Atmos. Chem. Phys., 9, 795-812. Link

Koehler, K. A., S. M. Kreidenweis, P. J. DeMott, M. D. Petters, A. J. Prenni, and C. M. Carrico (2009), "Hygroscopicity and cloud droplet activation of mineral dust aerosol," Geophys. Res. Lett., 36, L08805, doi:10.1029/2009GL037348. Link

Lance, S., et al. (2009), "Cloud condensation nuclei activity, closure, and droplet growth kinetics of Houston aerosol during the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS)," Journal of Geophysical Research, 114, D00F15, doi:10.1029/2008JD011699. Link

Padró, L., D. Tkacik et al. “Investigation of Cloud Condensation Nuclei Properties and Droplet Growth Kinetics of Water-Soluble Aerosol Fraction in Mexico City.” Journal of Geophysical Research, 115: D09204, 2010. Link

Roberts, G., and Nenes, A. (2005) “A Continuous-Flow Streamwise Thermal-Gradient CCN Chamber for Atmospheric Measurements,” Aerosol Science and Technology, 39, 206–221, oi:10.1080/027868290913988. Link

Snider, J.R., H. Wex et al. “Intercomparison of Cloud Condensation Nuclei and Hygroscopic Fraction Measurements: Coated Soot Particles Investigated During the LACIS Experiment in November (LExNo) Campaign.” Journal of Geophysical Research, 115: D11205, 2010. Link