Our recent stretch of weather has seen very comfortable dew point temperatures in the 60s. The featured graph is a climatology of dew point observations from the Des Moines Airport. The five lines shown represent the lower (0) and upper bound (100) of 1 PM observed dew points along with the 25th and 75th percentile and also the median value (50). The months of July and August are highlighted for their rather consistent daily values due in part to increased plant transpiration.

Voting:
Good = 22
Bad = 18

Tags:   dewpoint  

Continuing with the series of climate features, today a plot of when the highest dew point temperature for the local day occurs. First off, let us start by saying that dew points are much less diurnal in nature than air temperature and outside of sensor bias, dew point is not a function of air temperature. The featured plot shows two obvious extremes around midnight, this is due to air mass advection bringing in more or less moist air during most of the 24 hour period (excuse brevity of explanation please). The plot also shows maxima:

• in the mid morning during the growing season due to dew evaporation before drier air is mixed down due to boundary layer growth,
• the early evening in the late summer probably due to increased corn/soy plant evapotranspiration and thunderstorm/frontal activity,
• and mid afternoon in the winter perhaps due to evaporation(?).

As with the other features, let me know what you think and how you think this is explained incorrectly. :)

Voting:
Good = 26
Bad = 6

Tags:   climate   dewpoint  

The featured chart is a histogram of the percentage of years that a 75+ degree dew point was observed per day since 1973. The frequency is roughly 1 in every 5 years during the summer with July having the most days.

Voting:
Good = 17
Bad = 11

Tags:   summer   dewpoint