ACE-1 DATA, NCAR C-130, AEROSOL LIGHT SCATTERING Principle Investigator: Antony Clarke Department of Oceanography 1000 Pope Rd. Honolulu, HI 96822 phone: 808-956-6215 fax: 808-956-7112 e-mail: tclarke@soest.hawaii.edu The aerosol light scattering data collected aboard the C-130 was obtained using a TSI 3563 integrating nephelometer with total and backscatter coefficients determined for three wavelengths (450, 550, 700 nm) and averaged over 15 sec. The instrument was operated inside the aircraft and sampled from the C-130 community inlet. As a result the instrument relative humidity (RH) was generally well below ambient RH and the instrument pressure was a few percent above ambient due to ram air pressure increase. The file data includes the instrument RH, pressure and temperature along with the total scatter and backscatter data. Correction to ambient scattering will have to be made by the user. Preflight and post flight calibrations were used to scale operational values reported here and these corrections generally only affected the lowest scattering values present in the cleanest air. Values are reported for instrument operational conditions. The nephelometer was normally operated with 30sec. averaging on to reduce noise, consequently rapid transitions in signal will be "smoothed" by this averaging. This is independent of the 15 sec. data average interval used. The instrument was also operated with a Berner type impactor upstream at about 40% RH with a size cut at 1um. This was done in order in order to remove coarse particles and obtain a submicrometer scattering coefficient. The impactor could be set to cycle automatically usually for about 5 min. cycles or could be manually overridden for vertical profiles or other objectives. Some flights like Lagrangians (eg. Flight 19) seldom used the impactor. A separate column (#10) is used to indicate when the impactor is on/off. No impactor was operated on flights 11, 12, 26, 29, 30 and 31. Data has been edited for noted instrument problems, sample difficulties and obvious cloud contamination. However, the user is encouraged to evaluate anomalous behavior in conjunction with other concurrent C-130 data (eg. liquid water content). Please contact the PI above for any inexplicable or inconsistent data encountered. FILE ORGANIZATION col 1 = month col 2 = day col 3 = hour (UTC) col 4 = Total Scatter (1/m) at 450nm col 5 = Total Scatter (1/m) at 550nm col 6 = Total Scatter (1/m) at 700nm col 7 = Backscatter (1/m) at 450nm col 8 = Backscatter (1/m) at 550nm col 9 = Backscatter (1/m) at 700nm col 10= Impactor on (=1); No impactor (=0) col 11= Nephelometer Status - Aerosol measurement minus Rayleigh has status = 1 Filtered air with Rayleigh value has status = 0 col 12= Instrument pressure (mb) col 13= Instrument relative humidity col 14= Instrument Temperature (k)