Most pronouced air-surface temp difference

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Joseph S.
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Most pronouced air-surface temp difference

Post by Joseph S. »

Just curious what you guys have personally found.

It always shocks me that even when air temps are forecasted as cold-how quickly rocks/sand etc. heat up.
simus343
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Re: Most pronouced air-surface temp difference

Post by simus343 »

The rocks (and sand) absorb heat quickly from direct sunlight and retain it longer. Using a temp gun I have found that to determine "air temps" it must be pointed forward over un-obstructed long distances using a laser-temp gun. Pointing it into the sky, even when it is 81 degrees F out, results in a reading that says something like 27 degrees F. Pointing at the ground with this sky reading will in turn say 103 degrees F. The air its self doesn't hold or produce heat, the sun does. On ground level it feels warmer than a "sky'" reading because all of the plants and ground materials are radiating heat out from their surfaces.
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Kelly Mc
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Re: Most pronouced air-surface temp difference

Post by Kelly Mc »

simus343 wrote:The rocks (and sand) absorb heat quickly from direct sunlight and retain it longer. Using a temp gun I have found that to determine "air temps" it must be pointed forward over un-obstructed long distances using a laser-temp gun. Pointing it into the sky, even when it is 81 degrees F out, results in a reading that says something like 27 degrees F. Pointing at the ground with this sky reading will in turn say 103 degrees F. The air its self doesn't hold or produce heat, the sun does. On ground level it feels warmer than a "sky'" reading because all of the plants and ground materials are radiating heat out from their surfaces.

Nice :)
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Bryan Hamilton
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Re: Most pronouced air-surface temp difference

Post by Bryan Hamilton »

A couple weeks ago...

ambient temperature = 28C (82F)
substrate temperature = 47C (117F)

The ambient temperature was taken in the shade of a bush about 1.5 meters about the ground. The substrate temperature on the ground surface with the thermometer covered with a thin layer of soil.

It was far too hot for snakes in the sun and they were all sticking very close to the shade.
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Re: Most pronouced air-surface temp difference

Post by chris_mcmartin »

From the 5th annual Fort Leavenworth (Kansas) herp survey this past weekend:

We flipped a black rat snake and a prairie kingsnake sharing the same piece of tin. The air temperature was around 80 degrees. The surface of the tin was 108. It was 73 degrees beneath (it wasn't snug to the ground), but I'm surprised it wasn't hotter since usually the heat goes right through the tin. Plywood is a better insulator and seems to be used later into the season--not sure if it's because it stays cooler longer, or because it retains moisture better, or a combination of both factors.
simus343
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Re: Most pronouced air-surface temp difference

Post by simus343 »

I would think both. The herps can slip outside/top side for heat, slip under to cool off. Also the heat will result in the snakes and other herps requiring hydration and many can receive as much hydration as this requires from a very moist and damp micro-environment. Again, this is just what I think, haven't put more thought than 10 seconds into this for the time being.
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Chris Smith
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Re: Most pronouced air-surface temp difference

Post by Chris Smith »

We have had surface readings of over 140F in open sandy areas when air temps are around 80F.

-Chris
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Rich in Reptiles
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Re: Most pronouced air-surface temp difference

Post by Rich in Reptiles »

Chris Smith wrote:We have had surface readings of over 140F in open sandy areas when air temps are around 80F.
Interesting topic! ^That is amazing!
simus343
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Re: Most pronouced air-surface temp difference

Post by simus343 »

Something I have been thinking about is that it (whats active at what temps between air and ground) also comes to the species as well. With ground temps over 100 many Squamata still come out to bask though because mind that they will also loose heat passively just as the surfaces from which they are acquiring it, and the more moderate air temps, which end up evening the body temp of a given hot environment Squamata out. Eastern Hogs as an example are said to be most active with temps in mid 70s and are usually in the open. The ground temps of one I found the other day was 101.5 degrees F. Air temp 74 degrees F. Amphibians on the other hand are generally active when it is cooler out or at night because the ground temps are warm, not hot, and it helps keep them from desiccating as quickly. That's also why many road cruised animals are on paved roads in the evening, the pavement if cooling off as night approaches, which is why the animals were in the woods during the day, not on the road.
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Don Becker
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Re: Most pronouced air-surface temp difference

Post by Don Becker »

I've had rock temps in the 60s (F) when outdoor temp was in the low 30s.
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PNWHerper
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Re: Most pronouced air-surface temp difference

Post by PNWHerper »

Cool topic. Hellihooks and I recorded something around 60-65 degrees F and with ground temperature of 106+ degree F. This was on a day in March at some black lava beds. Jim, help correct me if I am wrong...
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Re: Most pronouced air-surface temp difference

Post by chris_mcmartin »

Reptiles Magazine recently published an online version of my "Weather for Herpers" article which appeared in print two years ago, albeit with some slight modifications for the web.

I hope this thread inspires more people to log weather information with their herp observations. I think with more such data, some interesting patterns in species activity may be seen.
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Joseph S.
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Re: Most pronouced air-surface temp difference

Post by Joseph S. »

I need to start carrying my temp gun in a holster or something-haven't brought it with me but am continually amazed that I and the air will be cold but undersides of rocks and particularly sheet metal can heat up greatly. Many things affect this however.

A neat little gadget a friend of mine picked up for her masters work.
http://www.kestrel-direct.com/shop/?gcl ... fgodu0YAQw

I think also that the plasticity of reptiles in surviving at suboptimum temperatures is underestimated-we all know cases in captivity of snakes being kept without hot spots for years and doing ok. But even with these two variables my suspicion is that the range of a species as determined by weather comes when keeping temperature within these restraints is too difficult for individuals to reproduce. For egglayers appropriate incubation temperatures could be a serious constraining factor. Same goes for livebearers-such as rubber boas being found in edge habitat-though I'm sure they could survive in the deep forest.
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chris_mcmartin
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Re: Most pronouced air-surface temp difference

Post by chris_mcmartin »

Joseph S. wrote:A neat little gadget a friend of mine picked up for her masters work.
http://www.kestrel-direct.com/shop/?gcl ... fgodu0YAQw
Pocket weather instruments are awesome. One word of caution--you need to turn them on and let them "settle in" on the spot readings for a minute or so...if you've had the instrument in your car or pocket, its readings will probably be affected by the different temperature and relative humidity in those environs.

Also, it is best to set the instrument to read "station pressure" for the barometric pressure--that means it will read the no-kidding pressure on-site vs. attempting to correct to sea level (when you see pressure readings on weather websites, they are all corrected to sea level for standardization between sites). If you try to read sea-level pressure, you need to know the exact elevation of your chosen site, and we herpers don't tend to stay put at a known location much, instead we hike, road cruise, etc. up and down hills.

Converting your field reading to sea-level pressure after your herping adventure is easy because you're taking GPS coordinates (right?), and you'll have the site elevation (needed for the correction) either from your GPS data or by pulling it off Google Earth. There are websites that automate the calculation for you; Google "convert pressure to sea level."

I use a WindMate 350. It's comparable to the Kestrel 4500 (the only thing it doesn't do that the Kestrel does is compute the heat index, but I don't use that for herp-related readings anyway), and it's cheaper. On Amazon, the Kestrel 4500 is $290 for the base model (no Bluetooth or NVG-compatibility) at the time of this post; WindMate 350 is $160.
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sjfriend
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Re: Most pronouced air-surface temp difference

Post by sjfriend »

I actually found some AZ snakes a few nights back when air temps were near 60 deg and road (black top) temps were over 80 degs. Dirt was still mid 70s. Guess they don't always hide when it's cold. The whole reason I was still looking was the substrate temps.
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chris_mcmartin
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Re: Most pronouced air-surface temp difference

Post by chris_mcmartin »

chris_mcmartin wrote:Converting your field reading to sea-level pressure after your herping adventure is easy because you're taking GPS coordinates (right?), and you'll have the site elevation (needed for the correction) either from your GPS data or by pulling it off Google Earth. There are websites that automate the calculation for you; Google "convert pressure to sea level."

One caution: Ensure you apply the correction the correct way (adding vs. subtracting). One web application I use to determine the correction, http://www.csgnetwork.com/barcorrecthcalc.html, appears to apply it the wrong way (i.e. you get a much lower sea-level pressure than actual; applying it the reverse direction gives the correct reading). You can "check your work" by comparing to the nearest weather station on a site like www.wunderground.com and looking at their almanac data for the date/time of your spot reading. It should be reasonably close (usually within 0.05 inches Hg).
mikez
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Re: Most pronouced air-surface temp difference

Post by mikez »

Very cool topic. Something I think about a lot, especially in early spring and late fall when some snakes will bask at den sites in weather most people, even herpers, would never believe.
Sadly, I'm ashamed to admit, I have only my own scrambled incomplete memories and no true data. Too bad, as I live in a cold climate and spend lots of time outside after the other herpers go inside. I've found dozens of dens over the years of 6 or 7 species. I've observed garters in all 12 months in Ma. [they hibernated in my house foundation, crawled on freak warm days], northern watersnakes as early as Feb as late as Thanksgiving, ribbons basking on sunbaked surface of beaver lodge while the swamp was frozen solid and a foot of old snow in the woods, even black racers out basking in mid March long before most people see them here. I even temporarily beat the ban on looking at and photographing two high profile protected herp species because the powers that be put a range of dates on their "Keep Out" signs. In both cases, a turtle and a rattler, the early dates weren't early enough and I was able to get in and "legally" observe these animals in unusually warm early spring weather.
[As a sad side note, I got caught at both places and chased away, public land in both cases. For the turtles, the feds ended up getting rid of the dated signs and shutting a whole huge swath of land to all public access even though we own it. I have no idea what they did at the timber den, I ain't been back :roll: but wouldn't be surprised if they changed the signs to cover my loophole.]

The thing that catches my attention in the field is micro-climates. That is why I have so successful finding dens. Besides the obvious visual, geographical clues we all recognize, I feel I can smell a difference in the air. Not as crazy as it sounds, such sites are usually sheltered from the cold crisp winter breeze, snow melt has exposed the dirt which is thawing and adding humidity and fragrance to the air, the leaves and vegetation are exposed doing the same. Sometimes I think you could blindfold me and lead through the woods on a sunny March day and I'd find such a spot. Not always a snake den there, but lot's a times there are.
Anyway I digress, what I need to do is get a meter and get reads on those March and November New England snakes.
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