Heat island effects, anyone?

[mnealtx 0]

Ran across this blog today... interesting info!

I'm having a bit of trouble seeing how they can effectively adjust for heat island effects for some of the places shown...maybe it's time to find other places to put the measurement stations?

Also, a pro/con story from the Father of Scientific Meteorology, Reid Bryson.

Mike
I love you, Shannon and Jim.
POPS 9708 , SCR 14706

[billvon 3,132]

>I'm having a bit of trouble seeing how they can effectively adjust for
>heat island effects for some of the places shown...

Same way they adjust for the artificial cooling effects of placing temperature sensors in irrigated city parks (which are cooler than the surrounding areas) near artificial lakes (same thing) near the exits of air conditioned buildings, car washes etc. You could create a similar "How not to measure temperature parts 1-10" for them.

Which is to say, they don't. The erroneous signals tend to cancel (since they go in both directions) and the parts that don't cancel get lost in the noise. As evidence of this, note that the low-tropospheric (lower atmosphere) temperatures are rising more rapidly than ground temperatures here in the US. If the heat island effect was a big issue, you'd see the opposite happen. As further evidence, rural temperatures are still rising faster than urban temperatures. Again, if rapidly growing cities were skewing the temperatures, you'd see urban temps rise, not rural ones.

Edited to add - take a good look at the one they claim is a "correct" measuring station. It shows a downward trend! Surely this indicates that the rest of them are heat islands showing erroneous increases, and that NASA is just ignoring the 'true' readings.

Now look closely at the picture. It's on a green lawn. Use Google Earth to take a look at the location of this sensor (Orland, CA.) It's north of SFO behind a mountain range that blocks sea moisture, so all the unirrigated fields are brown, as you'd expect in a semi-arid climate like that.

How did that lawn get green? Perhaps they irrigate it; that's what you'd have to do to keep a lawn green there.

Now look at the time scale. Around the 1900's it starts dropping. Might someone have started watering the lawn as people moved there? It also drops significantly around 1940, around the time that sprinklers started becoming popular. Since then, temps seem to be on the rise.

See below for Mapquest picture of the monitoring station; it's on the pad just to the SW of the red star. Note how it's between two lawns, most likely irrigated by a timer based sprinkler system.

[mnealtx 0]

I'd like to see more information on how they adjust for the heat island effect. They'd have to figure in reflection off of pavement, air conditioner exhaust effects, etc for various times of year and weather conditions for each individual station in order to get a 'true' reading.

It seems like the isolated (non-urban) stations are reporting more "honest" info, in my (admittedly) non-meteorological opinion.

Re: low-tropospheric temperature... is there a way to determine if the temps are higher over the cities?

Mike
I love you, Shannon and Jim.
POPS 9708 , SCR 14706

[billvon 3,132]

> I'd like to see more information on how they adjust for the heat island effect.

They don't. It's a pretty insignificant effect, for the reasons I listed.

>It seems like the isolated (non-urban) stations are reporting
>more "honest" info, in my (admittedly) non-meteorological opinion.

Right - and they are reporting basically the same thing. The trends in urban stations for 1951 to 1989 was 0.10°C/decade; trends in rural stations were 0.09°C/decade.

Further reading:

http://lwf.ncdc.noaa.gov/oa/climate/research/population/article2abstract.pdf

http://www.nature.com/nature/journal/v432/n7015/abs/432290a.html

[mnealtx 0]

They seem to be saying that the heat island effect is only viable at night - am I reading that correctly?? It seems as if the skew in temperature between the urban and rural stations would be equally viable during the day, would it not?

Mike
I love you, Shannon and Jim.
POPS 9708 , SCR 14706

[billvon 3,132]

> They seem to be saying that the heat island effect is only viable
>at night - am I reading that correctly??

They're saying it is most noticeable at night and least noticeable in windy conditions, when the local heat is dissipated more rapidly. If the overall temperature record was being influenced by this effect, then we would see a significant difference between windy nights and still nights in the temperature record. No such difference has been observed. From the articles conclusion:

This analysis demonstrates that urban
warming has not introduced significant biases
into estimates of recent global warming.
The reality and magnitude of global-scale
warming is supported by the near-equality of
temperature trends on windy nights with
trends based on all data.

>It seems as if the skew in temperature between the urban and rural
>stations would be equally viable during the day, would it not?

Yes, but to a lesser extent, since traditionally temperature differences are not as great during that time.

[mnealtx 0]

I appreciate the additional info...thanks!

Looking at some of the recording stations...wow! I'll be interested to see what happens as other stations are 'checked out'.

Mike
I love you, Shannon and Jim.
POPS 9708 , SCR 14706