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Llansadwrn (Anglesey) Weather

Atmospheric depositions code

Logo: Llansadwrn Weather - Melin Llynnon, Ynys Môn

Most weather stations have their equipment set into a short grass sward. While it has been normal practice to make observations of the state of the soil on a bared plot, not much use has been made of the grass. One use, put forward by Terence Meaden 1, is to observe the state of the grass as a means of recording the deposition of the various liquid and solid forms of water. Use is made of a 10-digit sequence for this purpose (Table 1).

I have been recording the state of the grass at Llansadwrn since 1996 and found it to be an informative addition to my observations. The grass code is a good discipline to adopt as it affords a means of accurately recording, in the weather diary, the types of water deposition observed. The code is simple to use and carried out over several years can form a valuable record at any weather station 2.

The grass code is not a substitute for the state of the ground code (Table 2) as different information is recorded. For example the ground may be frozen, or more than 50% covered with snow. I have added also a concrete surface (a road surface or some other surface would also be interesting) and suggest a modified code which I use (Table 3). Some interesting differences can occur throughout the year, and often within a day, due to contrasting thermal regimes.

Table 1 State of the grass code (from Meaden, 1996)

Table 2 MO State of the ground code

Table 3 State of a concrete surface (from Perkins, 1997)


1: MEADEN, G.T. (1996) An atmospheric deposition code using observations of the state of the grass. Weather 51, 68-71.
2: PERKINS, D. (1997) Use of a state of the grass code to record atmospheric depositions. Journal of Meteorology 22(218), 121-125.

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Updated: 22 July 1999

Last updated 23 April 2014

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