Monday, August 8, 2016

How "Dry" Is This Summer?

Brown, the official color of summer
Some of you have commented about how dry it is this summer.  Let's have a look at some data, focusing on the Salt Lake City area.

In Salt Lake City, the total precipitation so far this summer (1 June – 7 August) is 0.59 inches, making it the 19th driest since 1874.

Source: NOAA Regional Climate Centers
Most of that precipitation fell in June, however.  The total precipitation since July 1 is only 0.07", good for 10th driest.

Source: NOAA Regional Climate Centers
However, "dryness" reflects not only precipitation, but also evapotranspiration.  Evapotranspiration is the transfer of water from the soil to the atmosphere through evaporation and transpiration.  Many factors effect evapotranspiration, including humidity, wind speed, and temperature.  I don't have access to historical humidity or wind records, so I'm going to ignore them here.  For temperature, however, the summer so far is the warmest on record, with an average temperature of 80.6ºF.

Source: NOAA Regional Climate Centers
Since July 1, we're in 4th place (not shown), so it has been an exceptionally hot summer too, and that is a major driver of the extreme dryness, increased irrigation demand, and stress on plants.  

Elsewhere in northern Utah, a few places may have benefited from showers and thunderstorms the past couple of days, but for the most part, it's been a dry and hot summer regionally.  

Summertime precipitation shows a great deal of variability spatially and from year-to-year.  Remember that last year was remarkably wet.  Temperature also exhibits year-to-year variations, but the trend is clearly up, with heat waves becoming stronger and more persistent.  It is because of these temperature trends that we expect summers to become increasingly arid over northern Utah in the coming decades.  

No comments:

Post a Comment