HR: 1340h
AN: A23C-0966    [Abstracts]
TI: CCN Climatology For AIRS2
AU: * Mishra, S
EM: smishra@dri.edu
AF: Desert Research Institute, 2215, Raggio Parkway, Reno, NV 89512 United States
AU: Hudson, J G
EM: hudson@dri.edu
AF: Desert Research Institute, 2215, Raggio Parkway, Reno, NV 89512 United States
AB: In November and December 2003 the second Alliance Icing Research Study (AIRS2) was conducted near Montreal, Canada. One component of AIRS2 was cloud condensation nuclei (CCN) measurements aboard the NCAR C-130 airplane. Measurements were made with the two Desert Research Institute (DRI) CCN spectrometers (Hudson 1989). These instruments operated over different supersaturation (S) ranges in order to accurately cover both the traditional Aitken range (S greater than 0.1%) and the Large Nuclei (LN) range (0.01% - 0.1% S). Extensive comparisons of the concentrations in the overlapping S range of the two instruments are presented. The agreement between the two instruments in this overlapping range provides an S range of maximum confidence. Because these spectral measurements are the most challenging at the lower portion of their S ranges, the agreement between instruments also tends to verify higher S measurements of the higher S range instrument. Accuracy of the lower S instrument is supported by the fact that measurement uncertainties such as coincidence and vapor depletion are less for the lower particle concentrations that are encountered by a more limited S range. The airplane was based at Cleveland OH so that many of the 14 research flights could be done in air masses that were predicted to soon reach Montreal. Thus, flight tracks ranged as far as Kentucky and all Great Lakes and points between these and Montreal. The CCN spectrometers operated continuously throughout the 80 research flight hours and the two ferry flights between Colorado and Cleveland. Concentrations varied over more than 3 orders of magnitude. Concentrations active at various S are presented in both vertical and horizontal dimensions. Also representative complete (0.01-1% S) differential and cumulative spectra are presented from the two instruments. Also presented are CCN volatility and size measurements (dry size versus S). These sample-processing methods reveal clues about particle composition. The ultimate goal of these measurements is comparisons with concentrations of supercooled large droplets (SLD) and cloud ice concentrations to determine whether these are associated either with low total CCN concentrations and/or with high concentrations of LN. It has been hypothesized that either of these may promote SLD formation. SLD are especially dangerous for aircraft icing.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0320 Cloud physics and chemistry
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005