CVI

• Full Name: Counter-flow Virtual Impactor inlet

• Short Name or Acronym: CVI

• Measurements Provided: Depends on the choice of instruments that are fed by CVI. May include cloud particle concentration, condensate mass, water vapor (for isotopic analysis) and aerosol particle residuals.

• Manufacturer or Builder of the Instrument: CVI designed and built by NCAR/EOL

• Operational Status:

  • requestable, ready for deployment (special request)

  • requestable, but has problems, needs work before deployment
  • not on request list but could be available if requested
  • still under development and not requestable
  • obsolete, should be or is retired

• General Description:

• The CVI is a specialty inlet that separates cloud particles from air. Cloud particles larger than the “cut-size” are injected into dry carrier gas flow (usually N2) where they evaporate. A variety of instruments can be fed from the CVI, and they monitor characteristics of the evaporated cloud residuals. CVI is anti-ice heated and suitable for supercooled liquid water clouds. System uses heated tubing, fittings to divide the sample, and flow control for the cut-size. RAF operates two independent CVI systems that are specially designed for the GV or C-130. These systems have been used on NASA DC-8 and UND Citation-II.

• Measurement Characteristics:

  • Overall estimate of uncertainty: depends on downstream instrument characteristics
  • Response time: ~1 to 3 sec, depending on flow rates
  • Precision:
  • Other measurement characteristics (comments on signal/noise, bias limits, etc): Susceptible to artifact contamination when cloud particles hit the tip and break into fragments. May exhibit long hysteresis times when passing through high water content clouds.

• Lead Contact: Cindy Twohy; Dave Rogers

Documentation

• see also EOL web page CVI General information

• Descriptive Publications
• Documentation of the Processing Algorithm(s): See the Technical Note on Processing Algorithms at this URL (fix when available)