Air temps, water temps, and radiational cooling

Merrymeeting · 10-21-2008, 09:34 AM

I've been tracking the nighttime temps VERY closely this week. Normally we close up our foundationless, unheated camp on Columbus Day weekend. But for many reasons were unable to finish this year and will be completing the job this weekend.

When I saw the forecast for some nights in the mid-20's this week, I began fretting about pipes freezing. But I consoled myself by reasoning that this cold would be short in duration, that the inside of the house would remain warmer from residual daytime heat (though several pipes are exposed underneath), and most importantly, the radiated heat from the lake would keep localized temps higher.

I am surprised to see the low recordings on the Black Cat Weather site. Despite being surrounded by water in the high-50's, the nighttime temps have still gone into the high 20's. Not what I would have expected with all that "heat" around it.

I know these clear, cool nights result in radiational cooling where the cold drops from above. But it is still surprising that it has such a dramatic effect so close to the water.

CLA, can you give us a lesson on the interaction between all these conflicting micro-layers during this season of change?

Thanks!

CanisLupusArctos · 10-22-2008, 03:16 PM

Quote:

Originally Posted by Merrymeeting

CLA, can you give us a lesson on the interaction between all these conflicting micro-layers during this season of change?

Thanks!

I've been noticing that too. The tomatoes are still growing - no frost on them yet, but my car has had frost on the same mornings when only dew formed on the tomatoes. My first guess would be presence or absence of wind. In spring, the difference of warm air/ice water often generates a lake breeze that forces the water-cooled air upon the land. The water is much better acting as a heat sink than a heat source. At this time of year, it's in the process of giving up heat to the air, and the coldest nights usually occur when there is no wind (radiational cooling.) Lake fog rises straight up, indicating heat rising into the cold air. But there is no fog in the yard, where the instruments are. I would have to wait for a breeze to blow some of the water-warmed air onto the land, and usually by the time that happens, the sun has warmed things up anyway.

Let me think about this some more, while I do a brake job on my car (today's priority.)

In the meantime, take a look at the WeatherCam's comparison of 10/22 last year and this year... in the "Yuki" thread.

Sunrise Point · 10-22-2008, 07:05 PM

I checked out the photos and other than the clouds in the 2008 photo, the only other difference I could see was the lack of leaves on the tree on the left.

It seems colder, earlier to me. My tomatoes didn't survive, but as of last Sat. I still had geraniums and impatiens blooming in front of our camp.

We usually drain and winterize over the Veteran's Day weekend, but I think that we will be doing it a bit earlier this year.

I hope that the brake job went well...

CanisLupusArctos · 10-22-2008, 07:27 PM

Quote:

Originally Posted by Sunrise Point

I checked out the photos and other than the clouds in the 2008 photo, the only other difference I could see was the lack of leaves on the tree on the left.

That's what I was getting at -- leaves vs. no leaves. The fall weather has been ahead of schedule since mid-summer, which itself was very short this year. But then again, I don't need to say that - I think everyone noticed.

Check out the other thread for another photo I took today.

secondcurve · 10-23-2008, 07:29 PM

Merrymeeting:

Don't worry about pipes freezing. You need to be in the single digits for a few days. Standing water is clearly freezing at night now. However, you need to have some very cold weather to not only freeze water, but to freeze water inside pipes to the point that it is able to expand and blow out the pipes. That's not going to happen for a time yet.

DickR · 10-24-2008, 12:59 PM

About the pipes freezing, it really depends on whether the wind blows. A brief overnight dip into the 20s typically won't cause a problem with exposed pipes under a camp if the air is calm. Calm air and clear skies overhead and the resultant pronounced radiational cooling can be the reason for the temp dipping into the 20s in the first place. The relatively warm ground under the pipes and the building above them will radiate heat back to the piping to prevent freezing

But if there is a cold air mass coming in, with a breeze behind that cold, then the pipes can freeze. I had this happen to me at the first camp, a few days before Halloween. When I went up to blow the pipes and shut down for the winter two days later, the damage had been done in a single night.

hazelnut · 10-24-2008, 02:24 PM

I did a semi-winterization last time I was up. I knew I wasn't going to be at the camp for a couple of weeks so I drained all the pipes down and filled the traps with non-tox. When I finally shut down I'll blow the pipes out with compressed air.

10-21-2008, 09:34 AM	#1
Merrymeeting Senior Member Join Date: Mar 2003 Location: Merrymeeting Lake, New Durham Posts: 2,217 Thanks: 299 Thanked 795 Times in 365 Posts	Air temps, water temps, and radiational cooling I've been tracking the nighttime temps VERY closely this week. Normally we close up our foundationless, unheated camp on Columbus Day weekend. But for many reasons were unable to finish this year and will be completing the job this weekend. When I saw the forecast for some nights in the mid-20's this week, I began fretting about pipes freezing. But I consoled myself by reasoning that this cold would be short in duration, that the inside of the house would remain warmer from residual daytime heat (though several pipes are exposed underneath), and most importantly, the radiated heat from the lake would keep localized temps higher. I am surprised to see the low recordings on the Black Cat Weather site. Despite being surrounded by water in the high-50's, the nighttime temps have still gone into the high 20's. Not what I would have expected with all that "heat" around it. I know these clear, cool nights result in radiational cooling where the cold drops from above. But it is still surprising that it has such a dramatic effect so close to the water. CLA, can you give us a lesson on the interaction between all these conflicting micro-layers during this season of change? Thanks!

10-22-2008, 07:05 PM	#3
Sunrise Point Senior Member Join Date: Jan 2007 Location: Meredith Center / Winnisquam Posts: 250 Thanks: 87 Thanked 34 Times in 21 Posts	Yuki may be ready, but I'm not. I checked out the photos and other than the clouds in the 2008 photo, the only other difference I could see was the lack of leaves on the tree on the left. It seems colder, earlier to me. My tomatoes didn't survive, but as of last Sat. I still had geraniums and impatiens blooming in front of our camp. We usually drain and winterize over the Veteran's Day weekend, but I think that we will be doing it a bit earlier this year. I hope that the brake job went well... Last edited by Sunrise Point; 10-22-2008 at 07:09 PM. Reason: addition

10-24-2008, 02:24 PM	#7
hazelnut Senior Member Join Date: Oct 2003 Posts: 1,348 Blog Entries: 3 Thanks: 508 Thanked 462 Times in 162 Posts	Semi-Winterization I did a semi-winterization last time I was up. I knew I wasn't going to be at the camp for a couple of weeks so I drained all the pipes down and filled the traps with non-tox. When I finally shut down I'll blow the pipes out with compressed air.

10-23-2008, 07:29 PM	#5
secondcurve Senior Member Join Date: Jan 2005 Posts: 2,084 Thanks: 1,267 Thanked 557 Times in 286 Posts	Merrymeeting: Don't worry about pipes freezing. You need to be in the single digits for a few days. Standing water is clearly freezing at night now. However, you need to have some very cold weather to not only freeze water, but to freeze water inside pipes to the point that it is able to expand and blow out the pipes. That's not going to happen for a time yet.

10-24-2008, 12:59 PM	#6
DickR Senior Member Join Date: Apr 2008 Location: Moultonborough Posts: 735 Thanks: 4 Thanked 254 Times in 166 Posts	About the pipes freezing, it really depends on whether the wind blows. A brief overnight dip into the 20s typically won't cause a problem with exposed pipes under a camp if the air is calm. Calm air and clear skies overhead and the resultant pronounced radiational cooling can be the reason for the temp dipping into the 20s in the first place. The relatively warm ground under the pipes and the building above them will radiate heat back to the piping to prevent freezing But if there is a cold air mass coming in, with a breeze behind that cold, then the pipes can freeze. I had this happen to me at the first camp, a few days before Halloween. When I went up to blow the pipes and shut down for the winter two days later, the damage had been done in a single night.