The Arridity Index is a handy means to combine the effects of temperature and precipitation departures. While it has been dry here lately, temperatures have been cool which helps to lessen water demand by the atmosphere and nascent plants. The index is computed by taking the standardized high temperature departure and subtracting the standardized precipitation departure, both of which are measured in sigma units. Positive values generally imply water stress and negative imply less water stress. The featured chart presents the index for Ames computed over three different trailing day periods since the beginning of last year. It is interesting to note that very little time over the past 365 days has been spent with any of these three metrics in negative territory. Our continued saving grace thus far this growing season has been the cool conditions. While rain is in the forecast, the heaviest amounts will stay off to our south and temperatures continue to look to plod along at seasonally cool levels.

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Tags:   arridity