IEM Daily Feature
Friday, 31 July 2015

Dew Point Mystery

Posted: 31 Jul 2015 05:47 AM

The past two days have seen very large differences in dew point develop during the afternoon hours between the Ames and Des Moines airport weather stations. The tan bars on the featured chart show Ames 10+ degrees higher than Des Moines for each of the past two days, but not for the two days prior What could be happening to cause this difference? The blue line is calculated latent heat flux from a flux station nearby to Ames. This value is a proxy to evapotranspiration and magnitude of the values indicate significant amounts of surface/ground water were being transpired into the air. So a theory is that the Ames airport station, which is literally surrounded by corn and soybean fields has elevated humidity levels during the day while the Des Moines station was drier without the substancial nearby agricultural fields. Having said that, NWS Des Moines plans to visit the Des Moines weather station today to check the sensor for issues, so it will be interesting to see what they find out!

Voting:
Good = 38
Bad = 17
Abstain = 17

Tags:   dewpoint