Buddy check

Compares an observation against its neighbours (i.e. buddies) in a predefined square-box.

Parameters

The neighbourhood box is specified by radius, which is the half-width of the box in meters.

A minimum number of observations (buddies_min) is required to be available in the square-box and the range of elevations in the square-box must not exceed diff_elev_max metres.

The number of iterations is set by num_iterations.

The buddy check compares the value obs of the centroid observation against the averaged value in the square-box.

In the case of temperature, elevation differences should be taken into account because all observations are reported to the elevation of the centroid observation before averaging. A linear vertical rate of change of temperature can be set by elev_gradient. A recommended value is elev_gradient=-0.0065 degC/m as defined in the ICAO international standard atmosphere).

The observation is flagged as suspect if the (absolute value of the) difference between obs and avg normalized by the standard deviation in the square-box is greater than a predefined threshold thresholds.