To whom it may concern:
Version 1.1 is the first calibrated data release for the NASA/GSFC Scanning Raman Lidar. The data are split into
four datasets that will cover the periods of 8/6-19, 8/20-9/9, 9/12-20, and all the YAG data, which includes
daytime and nighttime data. If some days are missing, its because more analysis is needed. The data presented
are done by merging the angle (10° off the horizon) with the vertical data between a range of 1.0-1.4 m,
where the data were merged using a linear interpolation based on altitude. Below the minimum altitude, the
data are all angle data, and above the maximum altitude, the data are all from the vertical. Merging the data
at these altitudes means that none of the submitted aerosol data is affected by the overlap function.
Data from the night of 9/14/98 UTC (which is part of dataset #3)are included here because that was the
calibration/validation night. The rest of dataset #3 will be delivered next week. Note that 24 UTC on
9/14/98 is actually 0 UTC. Data collection started on late on 9/13/98 and continued on into 9/14/98 UTC. The
times are presented in this manner for ease of data analysis.
These data were calibrated to 1.0 (Rayleigh only scattering) in a cloud-free region. Mie scattering at the
wavelngths used here are negligible.
There is some stippling in the data. This is due to clouds attenuating the laser signal, such
that, the data above the cloud (the stipled regime) is noisy and not considered good data.
On 8/19/98, we did not collect data in the low aerosol channel for an unknown reason. Therefore, only high
channel data are presented. The angle data is merged with the vertical data between 2.1 and 2.5 km. The data
start at 400 m.
On 8/20/98, we took data 80° and 85° from the horizontal. Therefore the start altitude is different for this day
the rest of the days. The 85° data was merged into the 80° between 700-800 m.
Data for 8/22/98 through 25/98, 8/31/98, 9/7/98 and 9/8/98 UTC are vertical only data. Therefore the start altitude
is different on these days than on days when we collected angle data as well.
On 8/31/98 we took 10 second time resolution (versus 1 minute) data from 0130-0300 UTC. On 9/1/98, we took 10 second
data from 0800-1000 UTC, and on 9/7/98 all the data is 10 second data from 0300-1000 UTC. These data were integrated
into 1 minute profiles to be consistent with the rest of the datasets. If you are interested in the 10 second data,
please contact us (see below).
Data for 9/10/98 and 9/11/98 will be delivered at a later time. If you are interested in this data, please contact
us (see below).
*** BEWARE ***: Of the data later than 0630 UTC on 8/16/98, the calibration is suspect. There seemed to be
dew on the window which transmitted the outgoing and incoming signals. This applies also to the
data later than 0645 UTC on 8/18/98 due to water on the window because of rain. Analysis is
ongoing to retrieve the best data from these days. If you happen to be interested in these time
periods, let us know so we change prioritize it properly.
*** BEWARE ***: Of data beyond 0730 UTC on 9/16/98. There is rain on the window and the calibration may
not be valid for data beyond that time. If you are interested in these data, let us know so that
we can prioritize our data analysis to look at that data quicker.
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This rest of this file describes the format of the NASA/GSFC Scanning Raman Lidar data.
These are ascii files. Here is a sample of the beginning of one of the file:
160 = number of files
0 3.2044 = file,time
2 286 = number of header, data lines
dummy line
Range(km) height(km) asr err res (km)
0 2.3115e-001 2.3115e-001 1.1870e+000 3.1799e-004 2.3115e-001
1 2.9198e-001 2.9198e-001 1.1908e+000 5.5582e-004 6.0830e-002
2 3.5281e-001 3.5281e-001 1.2360e+000 4.0816e-004 6.0830e-002
The first line contains the number of profiles (160) contained in this data file. This line occurs only
once. The next 4 lines occur for every profile.
The second line (first of 4) contains the profile number (0), then the time in UTC (3.2044). The
times will increment by 1 or 2 minutes, approximately.
The third line (second of 4) contains the number of header lines (2) to follow and the number of altitude
lines (286) following the header lines.
The fourth line (third of 4) is a dummy line. This exists to maintain compatiblity with
the current version of the software we are using.
The fifth line (fourth of 4) is a header line that describes the data columns. The first column, is the bin number
and there is no heading for this line.
The next 286 lines are the data in 6 columns. Column 1 is the bin number, 2-range in km from
the lidar, 3-altitude in km (this would be the same as the range if the angle is 0.00), the
4th column is the aerosol scattering ratio, the 5th column is the error in the aerosol
scattering ratio, and the last column is the vertical resolution of the data in km. An aerosol
scattering ratio of 1.0 means the scattering was entirely Rayleigh scattering, no Mie scattering.
Values above 1.0 indicate the amount of Mie scattering.
The error is calculated using Poisson statistics (the error is the square root of the total counts) and
propagated throught the equations to obtain the given error.
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Any questions, feel free to contact Keith Evans (301) 614-6282, evans@agnes.gsfc.nasa.gov or
Dave Whiteman (301) 614-6703, David.Whiteman@gsfc.nasa.gov.