Title: INDOEX: Aircraft C-130 Aerosol Optical Properties Contact: John A. Ogren NOAA Climate Monitoring and Diagnostics Laboratory (CMDL) 325 Broadway R/E/CG1 Boulder, CO 80303, USA Phone: (303)497-6210 Fax: (303)497-5590 Email: jogren@cmdl.noaa.gov Web: http://www.cmdl.noaa.gov/aerosol/ Or Dr. Patrick J. Sheridan NOAA/Climate Monitoring and Diagnostics Laboratory Mail Code R/E/CG1 325 Broadway Boulder, CO 80303, USA Phone: 303-497-6672 Fax: 303-497-6290 Email: psheridan@cmdl.noaa.gov Data Set Description: November 1, 1999 The data files in this data set contain measurements of aerosol light scattering and absorption on the C-130 aircraft during INDOEX. A discussion of corrections made to the data can be found at the following URL: http://www.cmdl.noaa.gov/aero/net/c130/indoex/ The aerosol data file format specification is located on the Aerosol Group web page (http://www.cmdl.noaa.gov/aero) under the "DATA" header. The document path is http://www.cmdl.noaa.gov/aero/data/datafmt.html The files follow the basic format of CMDL humidigraph files(File-Code: h_). Look in the document under "File: h__<timecode>.<STN>". The Flags field gives basic information on aerosol cut size and which corrections to the data have been applied. Note that the Flags field is the 4-character hexadecimal representation of a 16-bit integer. A detailed discussion of the Flags field is provided in http://www.cmdl.noaa.gov/aero/data/datafmt.html. Several project-specific modifications to this generic flagging scheme were used. The first bit of the last character (bit 0x0001) of the Flags field rather than denoting times when the air was "contaminated" instead represents times when we were unable to correct the data for dilution of the airstream from system leaks due to NCAR C130 cabin pressure data being unavailable at that time. This happened infrequently during the project. The aerosol scattering and absorption values when this bi "1" are thus a lower limit and the true values are likely higher by 1 to 10% depending on the difference between ambient and cabin pressures. The second bit of the last character (bit 0x0002) was used to denote times in the files that should be ignored, like before takeoff times and after landing times. This bit was set when detailed analysis of our data indicated that heater volatilization was thought to be a problem. The first and second bits of the first character (bits 0x1000 and 0x2000) are used to flag when certain corrections that could affect data quality were made. A "1" in bit 0x1000 means that this was a time when cabin pressure was greater than internal aerosol system pressure, and at least some dilution correction was made. A "1" in bit 0x2000 means that the RH at the inlet of our aerosol system was greater than 40%, that our heater was therefore activated, and that the possibility of particle volatilization exists. These bits were defined so that if data are desired where there is no chance of leak or volatilization effects being present, the data can be filtered. If you have questions concerning the data, please contact us. References: None