ASOS/AWOS Data

Grid data for daily maximum, minimum, and average temperature values have been estimated from hourly observations made at ASOS and AWOS stations in the vicinity of each cell in a grid covering the area of Minnesota and Wisconsin, using the following procedure:

First, hourly station (point) observations made with the ASOS/AWOS network in Wisconsin are spatially interpolated to a regular 2-dimensional grid using a technique known as objective analysis. To ensure quality, this interpolation technique ignores observations that are very different from other observations made nearby. The grid cell spacing used here is 0.4^O x 0.4^O, or approximately 30km longitude x 45km latitude at the latitude of Wisconsin.

Next, a time series of temperature estimates is extracted at the grid cell closest to location of interest. A maximum, minimum, and average temperature is determined from this day-long (midnight-to-midnight) time series. The process is similar for the reference ET values.