Past IEM Features tagged: sdd
This year has certainly seen its share of hot weather as compared with recent years. The featured chart presents two measures of heat stress. The top panel is the number of hours where the temperature was at or above 93 based on data from the Des Moines Airport sensor. The bottom panel presents the traditional stress degree days, which is a measure of the exceedance of 86 by the daily high temperature. For both measures, this year has been the warmest since the drought year of 1988. The largest values, by a large margin, on the chart are from the dust bowl in the 1930s.
Stress Degree Days are an indicator of the stress plants may experience due to excessive heat. The statistic is computed by adding up the daily temperatures over 86 degrees. Since we have had very few really warm days, it is no wonder that our SDD value for this year is a mere 21 units compared with a long term mean of 78. The featured plot shows the yearly accumulation of SDDs for Ames up until the 19th of August.