Temperature and the way it is reported.

Ok, so this has been bugging me for quite some time now. It seems like every time we have either a heat wave or freezing temperatures, the media reports it grossly inaccurate.

For example, I live in Northern California near Sacramento. Currently we are experiencing a heat wave. Now yesterday the reported temps were right around 110F for the high. However my home thermometer never reached over 99F, the high being at 4:15pm last evening. I have verified the accuracy of my thermometers at home with SEVERAL others including digital and analog/dial probe thermometers. None of them were over 2 degrees in difference. All readings are taken in the shade away from buildings and wind. Just ambient air temps from several different locations. For years now I have never been able to get the readings that the media is supposedly able too. If it is hot out I get readings on average of 10-15 degrees cooler, on very cold days I get readings either very close to what is reported or just a bit warmer. I seriously doubt it is the 10-some-odd-number of thermometers I own, that are reading incorrectly. I just don’t buy that.

So why is it that websites such as The Weather Channel and AccuWeather, not to mention all televised weather media, all report much, MUCH higher temps?

Is there a conspiracy to make people believe that it is much hotter than it really is? Are we slowly being conditioned to believe that feeling an actual temp of 100F is 110F? What is the benefit from this kind of sensationalism? We’ve all seen how a light rain can be spun as STORM WATCH ’08 with some tool reporter in a rain slicker making us all feel like we should be buying stock in sand bags.

So what gives? Am I the only one here not buying into it?

Hi. I am not very familiar with Fahrenheit, but in the city i live in (not metropolis) there can be 3-4 degrees Celsius difference very easily. Height, wind , shade and area (asphalt cement and glass or grass and trees) all can change the readings.Qualified weather station has to comply with certain conditions to be more or less calibrated.
Also quality of thermometer is important.
This is what i know.

Most of the weather providers supply the temperature as an average over the hour. Data is collected every 10 minutes and averaged out. At (usually) the top of the hour. There are a lot of other factors involved as you know that weather is in a constant flux of change. Here are a few things I can think of.

-station elevation
-near a body of water
-heart of a city
-shade
-wind
-smog

Here in Canada our thermometers are tested and calibrated in a national laboratory and have a +/- acceptability of I believe one to 2 degrees of accuracy. Even less for the electronic ones. If the data is coming from an observer he may just be reading the thermometer a little off kilter as well or rounding up to the next decimal place.

etc.....the list can go on and on


there are so many variables to take into account but Im betting on the temperature averaging.

I always thought they took temp. readings from several different places in each area, and they average them out for a total average temp.

I know lots of highschools that have insterments that transmit data to certain places for weather forecast. I'm sure they have many different devices on many different buildings. I think they add them all together and average it out, and that is what they display.

I could be wrong.

Depends, Here in Vancouver the main station is at the Airport for the Vancouver area. They also give Temperatures of site specific areas like downtown, by the water, and in the valley from other stations located in those specific areas.

I dunno... I feel that I have a pretty good understanding of thermodynamics.

All I know is they have had consistently higher temp readings during heat waves then any home thermometer I have ever owned. I really think they hype things up during heat waves to get ratings.

After all, bad news is good business. I sense foul play.

Ok, maybe I can shed some light on this. Every city has an official recording station (ie will be the cities max temp and min temp for the day) as well as several minor stations in the area.

There are several factors that make official station more accurate than a household thermometer, no matter how well it is calibrated. First is the location. Where is it sitting? In direct sunlight/ shade/ both, is it exposed to a subtle air flow, is it exposed to moisture or rain?

The second most important factor is; is it sitting in a Stevenson screen? The stevenson screen is what we use at official recording stations, sheltering thermometers from outside interference. It is designed to create a near as possible uniform environment, relative to the air outside. Without a Stevenson screen, temperatures (in the meteorological world) are not considered accurate.

Hope this helps

en.wikipedia.org...

Ah stevenson screens.....I had to install one of those last week. They are a pain in the ass but do the job nicely. I believe we get prison inmates to build them here in BC

Originally posted by QBSneak000
Ah stevenson screens.....I had to install one of those last week. They are a pain in the ass but do the job nicely. I believe we get prison inmates to build them here in BC

Pffff, they're easy to install. We had to do it in training school even though its a techs job

Here are a few links to some of the equipment we use for digital Temperature data here in Canada.

Campbell Scientific HMP45c

Campbell Scientific 44212 probe

Most of the stations I am familiar with are on a platform as in the photo I sent you OZ, no Stevenson screen but we do use a gill shield.

More Temperature sensors

more 2

reply to post by OzWeatherman


For some reason I just don't like digging down 6 feet for the bases.....im just lazy.

So how is it that I consistently read lower than reported temps? I have my thermometer placed in as neutral an area as I can find. I also have noticed the only way I am able to get identical reading as what the weather stations report is to place my thermometer up against the house, which of course is only reading radiated heat from the brick. This rings as a false reading to me.

The only thing I can conclude is, store bought thermometers are unable to detect true atmospheric temps.

And for the record... what started all of this is, my wife was complaining about it being 110 degrees F outside and I was like, "Umm... no... the thermometer only read a high of 99F today." So I then had to prove to her that all of our thermometers all read identical temps... which they all did, something I verified years ago. So she reiterated to me, "Then WHY does the news always report much higher temps".

Here are a few photo's of some of the types of weather stations we have here in Canada.




This is a standard RCS compound with a stevenson screen at an airport with a wind profiler in the background.





And here is one of the RCS/OAN weather platforms at 3m height and a 10m winds tilt pole in the background.

Why so tall? Here's the same station buried under 9 ft of snow in the winter......a week later in one night they got over a meter of new snow.......it was fun digging it out.

Originally posted by Creedo
So how is it that I consistently read lower than reported temps?

Temperature is recorded not in a "neutral" place, but rather in a place which will record the more extreme temperatures. This means no shade, no trees, and a place where good wind readings can be taken.

I noticed that your thermometer is in the shade. Temperatures in the shade during the summer are 20+ degrees cooler (or more) than the temperature on your average mall parking lot or on the sidewalk at the pool.

A weather station temperature is a decent indicator of the OVERALL temp of the area. But the Earth's surface is not a single texture and material (rock, grass, trees, concrete, asphault, water, etc) and each one of those surfaces creates a different temperature.

Go outside and touch your thermometer against the Earth and other objects on the ground to get an idea of just how widely temperatures within a 30 foot area can vary.

I agree, its most likely because they are store bought thermometers. The ones that the weather agencies use around the world (WMO) are specifically calibrated and are very accurate which you won't find in any store bought one.

I believe this is where we get out thermometers from.


NRC

Oh, I don't think it has much to do with calibration etc.

When a weather network reports a "High" they will tend to report the hottest temperature recorded in the city.

Same goes for when they report their "Low", they will aim for the coldest temperature recorded in the city.


I see the same issues here in Canada. Especially in the winter.
They will tell you it's a low of -40 C when according you your thermometer, it never went below -35 C.
Same goes for summer. In the opposite direction.

I see... so they aren't necessarily looking to read just the air temps, but an average of several temps from several different locations under different circumstances. I guess it makes sense, but to me it just seemed more logical to take your reading from the actual air temp.

Thanks to everyone for their insight! =)

Originally posted by Creedo
I see... so they aren't necessarily looking to read just the air temps, but an average of several temps from several different locations under different circumstances. I guess it makes sense, but to me it just seemed more logical to take your reading from the actual air temp.

Thanks to everyone for their insight! =)

Actually, I dont know if it is the same in the US, but over here it is not an average taken of several temperatures, it is just the temp recorded at the official weather station for the location. I should know, I do work at one.....for Darwin, in the NT (Australia).

Taking an average of all the temperatures in one is considered to be not in quality control. Thats why we have offical manned stations, where quality control is constantly monitored, 24/7.

Most stations are either automatic weather stations (AWS's) which use thermometers run by an automated system. Offical manned stations use both AWS thermometers and human read thermometers. The human read being the one used for data from the max, min, dry bulb and wet bulb thermometers.

So its NOT an average....it just uses the offical recording station

Just to add, one must also take into account mirco weather systems such as elevation, as differences do occur frequently

reply to post by Creedo


Maybe the temperatures they are reporting in the winter include 'wind chill', similarly, the temperatures reported in the summer include humidity (higher temps)...?

I don't see a conspiracy with temperatures.

[edit on 7/9/2008 by porky1981]