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Luppy

Definition of a rainday

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I'm currently analysing weather records at a location in Yorkshire dating back to the the early 1970's.

My query is regarding rainfall, should a day that only records 'trace' as rainfall be included in the  'number.of raindays' in a monthly total ?

Thanks in anticipation.

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A day is only counted as a rain day if it records 0.2 mm or more. Days with 0.1 mm are not counted as rain days but the 0.1 mm is still added to the monthly total.

The reason 0.2 mm was adopted as the lower limit was to try and differentiate between small amounts of precipitation resulting from dew or fog ( often trace or 0.1 mm ) and days with actual rain. It is possible for 0.2 mm or more to result from condensation or fog, though quite rare, and in this case the day is counted as a rain day even if no actual rain has fallen. One of the anomalies of meteorological statistics I'm afraid but if everyone sticks to the same rules at least the readings are comparable.

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Many thanks for the info, it will help in my analysis.

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Trace is where rain is observed to fall but isn't enough to measure.

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