Essay:

Mesan - an Operational Mesoscale Analysis System

Mesan (www.smhi.se/sgn0106/if/meteorologi/mesan.htm)

SMHI has access to many different types of observations such as manual observations (called synop or metar), automatic station data, satellite and radar imagery. The best estimate of a meteorological parameter is given by combining all available observations of that variable in an analysis. The analysis is made on a grid where every value represents the mean for a grid square. In that process the quality and the representativety of each observation is taken into account. That means that an observation at a large distance from the square will have less influence on the value than an observation close to it.