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I am trying to perform an analysis on weather and car collisions data of New York city. I have downloaded weather data from NOAA. But I am not able to understand the data provided in the precipitation column of the weather dataset. It has a numerical value followed by capital letter. Some of these letters are: A,B,C,G,I,H.

Example: 0.03G, 0.08A, 0.0H

Can anyone please help me understand what these letters mean here. I have provided a picture of this column. Also, the name of the column in the dataset is PRCP.

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    If you can provide a link to the dataset you are looking at, it would be helpful. There are quite a few weather datasets from NOAA. – Jeanne Holm Dec 9 '15 at 12:56
  • I'm going to agree with Jeanne on that one -- even if you don't know where it came from, the column headings might give us a clue. (and the time row -- is it hourly, daily, etc?). – Joe Dec 9 '15 at 15:46
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    And I should say -- I really hate it when people mix concepts like that in a single field. (I suspect it might be type of precipitation (rain, snow, hail, etc), but that's just a wild guess) – Joe Dec 9 '15 at 15:47
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This seems to be the same data mentioned at http://shallowsky.com/blog/programming/NOAA-weather.html .

In their write up, they also link to NOAA's documentation for the document.

Note that this is what's commonly called an 'ASCII table', in which it is not delimited, but contains a number of fixed-width columns.

As such, the field is not '0.00G' but actually two fields, '0.00' (columns 119 to 123) and 'G' (column 124).

Column 124 is a notation of how the value was measured at the given site:

  • A = 1 report of 6-hour precipitation amount.
  • B = Summation of 2 reports of 6-hour precipitation amount.
  • C = Summation of 3 reports of 6-hour precipitation amount.
  • D = Summation of 4 reports of 6-hour precipitation amount.
  • E = 1 report of 12-hour precipitation amount.
  • F = Summation of 2 reports of 12-hour precipitation amount.
  • G = 1 report of 24-hour precipitation amount.
  • H = Station reported '0' as the amount for the day (eg, from 6-hour reports), but also reported at least one occurrence of precipitation in hourly observations--this could indicate a trace occurred, but should be considered as incomplete data for the day.
  • I = Station did not report any precip data for the day and did not report any occurrences of precipitation in its hourly observations--it's still possible that precip occurred but was not reported.

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