Format for University of Wisconsin GOES Effective Cloud Amount (i.e., Sky-Cover) data


Each line (record) contains 83 characters and is a complete "report" in the folllowing ASCII format:


1X,I4,I3,1X,I2.2,I2.2,I2.2,1X,F8.4,1X,F9.4,3X,F6.2,3X,F6.2,2X,F7.2,1X,I2,A1,2X,F7.2,3X,F6.2

Parameters are as follows:

I4     -- GOES image year (YYYY)
I3     -- GOES image day of year (JJJ)
I2.2  -- GOES image hour (HH)
I2.2  -- GOES image minute (mm)
I2.2  -- GOES image second (ss)
F8.4 -- GOES field-of-view latitude (to nearest 0.0001 degree -- N+, S-)
F9.4 -- GOES image field-of-view longitude [to nearest 0.0001 degree -- either 0-360 W or W+, E- (cannot tell because observations appear only in Western Hemisphere)]
F6.2 -- Pixel-averaged (see *) IR cloud emissivity (effective cloud amount) centered on the GOES field-of-view (to nearest 0.01 %)
F6.2 -- GOES field-of-view IR cloud emissivity (effective cloud amount) (to nearest 0.01 %)
F7.2 -- GOES field-of-view cloud top pressure (to nearest 0.01 mb)
I2     -- GOES satellite number (currently either "13" or "15")
A1   -- hardwired to "i" (GOES imager)
F7.2 -- Pixel-averaged (see *) cloud top pressure centered on the GOES field-of-view (to nearest 0.01 mb)
F6.2 -- GOES field-of-view visible cloud transmission (albedo) (to nearest 0.01 %)

* - Take a given GOES Imager pixel somewhere, and call it location (Y,X), where Y = a line (N-S) coordinate,
      and X = an element (E-W) coordinate.   For a given image, there can be literally millions of these pixels,
      as you can imagine.   Then for that pixel, we determine the # of pixels (using great circle distance) one must
      travel N, E, S and W to arrive at a location 25km distant from pixel (Y,X).  This forms essentially a 4-sided
      polygon surrounding pixel (Y,X).  In other words, we will have a 2-d matrix of pixels that surround pixel (Y,X).
      Then for each pixel that lies within this polygon/matrix, the great circle distance gets computed, and ONLY those pixels
      whose great circle distance is  <= 25.0km  get used to compute the quantities FINAL_AVG_CLOUD_EMISSIVITY
      and AVG_CLOUDTOP_PRESSURE.   The point here is that we are attempting to only include those pixels in the
      computations of these two quantities that an earth-based observer would see if they were looking up and around
      in all directions  (the  "celestial dome").


For example:

-- start of file contents --
 2015160 010000  19.9312   69.1336    67.26    91.00   894.00 13i   868.06   100.00
 2015160 010000  19.9312   69.0883    69.07    91.00   896.00 13i   878.92   100.00
 2015160 010000  19.9312   69.0429    66.55    92.00   902.00 13i   886.83   100.00
 2015160 010000  19.9312   68.9990    62.67    93.00   906.00 13i   894.39   100.00
 2015160 010000  19.9312   68.9550    55.88    93.00   905.00 13i   899.53   100.00
 2015160 010000  19.9305   68.9097    52.52    93.00   908.00 13i   903.01   100.00
 2015160 010000  19.9298   68.8644    49.32     0.00     0.00 13i   905.25   100.00
 2015160 010000  19.9291   68.8205    44.63     0.00     0.00 13i   906.10   100.00
 2015160 010000  19.9284   68.7765    38.90     0.00     0.00 13i   901.26   100.00
 2015160 010000  19.9312   68.7312    36.29     0.00     0.00 13i   892.37   100.00
 2015160 010000  19.9339   68.6859    33.95    94.00   895.00 13i   843.36   100.00
 2015160 010000  19.9442   68.6378    33.43    93.00   909.00 13i   760.11   100.00
 2015160 010000  19.9545   68.5897    36.74     7.00   216.00 13i   707.20   100.00
 2015160 010000  19.9669   68.5403    35.88     0.00   196.00 13i   648.80   100.00
 2015160 010000  19.9792   68.4909    30.83    15.00   228.00 13i   546.00   100.00
 2015160 010000  19.9772   68.4483    24.93    20.00   247.00 13i   409.89   100.00
 2015160 010000  19.9751   68.4057    21.11    24.00   262.00 13i   270.81   100.00

      <snip>
-- end of file contents --