Overview

Fields and observations can often contain missing values - it can be important to understand the implications of these, and also how to use them to remove unwanted data points. Using a mask of missing values can enable Metview to perform computations on a specific subset of points.

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There is another function, average(), to compute the mean value of a field. Find its documentation to see what the difference is. How different is the result?

Cheat: the integrate() function can accept an additional argument of a field of 1s and 0s, and will only compute the mean value where this field has 1s. Using this functionality, you can avoid using the bitmap functions altogether, at least in this particular computation! See Fieldset Functions.

The Land-sea mask

Write a line of macro code which will compute the number of land points in the lsm variable. There are two methods:

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