We recently had an unusual phenomenon, when a cold front dropped the temperature by 9° C in a matter of about two minutes. This was confirmed by both my Davis and Oregon stations. In both cases, Weather Display showed the drop over about five minutes, with a slight delay due to the thermal inertia of the sensors.
WeatherFlow took over an hour to respond to the change of temperature. I believe this to be due to the thermal inertia of AIR with the mass of the batteries.
The question is whether this slow response time to changes of temperature is significant. My guess is that it probably isn’t under most circumstances. How often do weather fronts proceed as rapidly as in the case that I’m citing?
For the anecdote, the sudden change of temperature created a significant mist as it was accompanied by an increase of relative humidity from about 50 percent to over 95 percent in the same timeframe, as shown on both legacy weather stations.
In the northeast we get frequent cold fronts of 10-15 degree drops in less than 30 minutes, sometimes in winter, in several minutes. While I only have an AcuRite prof. 5 in 1 at present - I can add to your alternative weather station observations that AcuRite does a good job of representing near real-time temperature decent. I do believe the housing unit itself needs to adjust to the rush of cooler air particularly if it is a summer time thunderstorm where the housing materials have absorbed and retained heat. I’d guess the more dense the materials under any sensor the longer it will take them (batteries) to cool down thus, perhaps, slowing down the actual rate of cooling from the new air mass.
I did some lab tests of Air response time a while ago. I instantaneously moved the Air from warm to cold (20 to 5C). The response time was highly dependent on airspeed.
Estimated 63% and 90% response times
“Static”air, T63=30min, T90=90min
0.5m/s, T63=12min, T90=50min
3m/s, T63=7min, T90=27min
I did not calculate the response time for RH but it appears to be faster.
Temperature changes are not rapid in my location, I concluded that the Air in a fan aspirated screen would closely track real air temperature.
Thanks @peter.jeffery.nz,
The air around my ‘bluff’ or headland is greatly influenced by temperature and humidity and of significant importance in the amount of lift for gliding. All other forecasts do not forecast the inversions we get during a sea breeze that cause a layer of calm air below the wind. It is the humidity that is a main key of the inversions existence. Just 2 days ago an incident occurred when the lift instantly vanished and a pilot made an emergency landing. It was very useful to be able to see the changes of humidity and temperatures at that time. Thermals lifting off (And sun behind cloud) change the temperature and so being able to see the changes I would like quicker response, so I think I will install a fan into my screen box. Here are the 2 graphs from different stations. Easy to see my Air is the smoother one, but we are in different locations.
cheers Ian
