DRI Photoacoustic Instrument Pat Arnott, DRI, PA in operation, sampling from a dyno. Consists of laptop, tan colored box where instrument is housed, and black 19” equipment rack for electronics. Aircraft version will be smaller and able to fit in 19” rack.

Status 1.Ground based unit ready. May have 2 wavelength operation ready for IOP (532 nm, 675 nm and or 1047 nm). 2.Trying to reduce the size of instrument for aircraft use. Parts are being machined for the reduced size unit. Will probably use 523 nm or 675 nm laser. 675 nm would go well with NASA CRD. 3.Could use existing unit if necessary for aircraft use.

Summary of Current SGP Measurement by NOAA: What to expect aloft and at the ground (purple). Boxes are 25%, 50%, and 75% values, whisker ends are 5% and 95%.

Interesting reduction of Single Scatter Albedo with height from the NOAA CMDL data set (Pat Sheridan) Altitude in meters, Extinction is on left in Mm -1, and single scatter albedo on the right. AOS ground based values are in purple

Estimated Leg lengths as a function of altitude for good Photoacoustic Data

Estimated Leg Lengths: The numbers Median Babs values aloft from NOAA were used to estimate the time necessary to achieve good photoacoustic measurements at different altitudes. Clean or dirty days could change the picture dramatically. These are integration times for a SINGLE good measurement. Decide the number of measurements needed at each level, and multiply the times by this value. These estimates are based on experience, should be realistic.

ISSUES 1.RH conditioning? Are we going to take the aerosol at whatever RH appears, or measure the RH in each instrument? (scattering and extinction measurements especially need thought). Filter-based light absorption instruments should be presented with DRY aerosol (RH < 30% ideally). 2.Leg durations need to be much longer as the altitude increases to get good data, likely from all aerosol instruments.