IEM Daily Feature
Monday, 13 June 2016

Arridity Index

Posted: 13 Jun 2016 05:34 AM

The featured chart displays a time series of an Arridity Index computed for the central Iowa Climate District. There are a number of ways this index can be computed. For the purposes of this plot, it presents the standardized departure of average daily high temperature subtracted by the standardized departure of total precipitation over the past 31 days. The standardization is simply normalizing the departure by the standard deviation of departures for each of the same periods for the period of record years. The index is an attempt to express the additive effects of having anomalously hot and dry weather at the same time. Having either cool and/or wet weather decreases the index value. Rewording, wet weather can help mitigate warm weather. Anyway, no index is perfect and for central Iowa, this index shows the recent increase in June with the arrival of hot and mostly dry weather. Rain has been visiting the state recently, but just not widespread.

Good = 7
Bad = 2
Abstain = 2

Tags:   arridity