Information Regarding Trace-A Images
In an attempt to make the airborne DIAL ozone and aerosol scattering images included in this WWW document easy to use, the images were generated using a limited number of ozone and aerosol color scales. The altitude scale is consistent between images, but the horizontal scale may change by a factor of two from one image to the next. The spacing of time ticks should be sufficient to indicate when this has occurred. The majority of the aerosol scattering images are from the infrared channel (1064 nm), and they are reported as relative scattering values. Due to lack of infrared data, or when the visible channel (599 nm) showed an aerosol feature more clearly, visible relative scattering images were used. If neither infrared nor visible aerosol information was available, an image of the aerosol scattering ratio from the ultraviolet channel (offline 299.5 nm, online 292.625 nm) was substituted. Ozone nadir and zenith profiles where combined. The ozone is interpolated from DIAL nadir/zenith to in-situ. "Modeled" data is only used to extrapolate the DIAL profiles to the ground. Archival data has flag values to allow identification of interpolated and extrapolated values.
Resolution of the data are:
VERTICAL RESOLUTION:
Vertical averaging interval
Aerosol 30 meters
Ozone 300 meters (nadir)
450 meters (zenith)
Vertical display interval for averaged data
Aerosol 30 meters
Ozone 60 meters
HORIZONTAL RESOLUTION:
Horizontal averaging interval
Aerosol 3.5 seconds, or approximately 817 meters
Ozone 300 seconds, or approximately 70 kilometers
Horizontal display interval for averaged data
Aerosol either 3.5 or 7 seconds, or
approximately 817 or 1634 meters respectively
Ozone either 3.5 or 7 seconds, or
approximately 817 or 1634 meters respectively,
except for whole flight images which vary,
averaging 21 seconds, or approximately 4900 meters
Times on the images are Universal Time (UT).
The GIF aerosol and ozone image dimensions are 1050 X 850 pixels in order to retain resolution. Your WWW browser/GIF viewer may handle the image in various ways. On displays of less than 1050 X 850 pixels the image may have to be scrolled or the image may get resized, losing some clarity of the fonts.
The airborne DIAL data images are to be used as a reference to the digital data located in the Langley Distributed Active Archive Center (DAAC). The images (both aerosol and ozone) viewed on this WWW page are from a full resolution data set, whereas, the digital data archived at the DAAC are a sub-sampled data set (1 profile/minute). If full resolution digital data are required, please contact the Lidar Applications Group. Images are not to be published without permission from NASA.
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