Do we get thermal above water?

[tocano]

I like to know if we have as much chance to get a thermal above water as land? We have few parks next to a river. The river is few miles wide like a size of a small lake. Some are suitable to fly glider.
I am getting back into glider, electric powered this time so I can fly in parks other than my glider club.

[ferincr]

According to what I read you are more likely to get a thermal over water or over a forest in the afternoon when the air is starting to cool down over land.
It makes sense, water takes longer to warm up than soil, but also takes longer to cool down.
So late afternoons are good times to fly over water or dense forests (someone said...).
Fernando

[tw126a]

Interesting observation Fernando. As a full scale pilot I avoid water, especially large bodies, like the plague. However, a few weeks ago, while camping, I observed some of our fine feathered friends obviously enjoying a thermal over the middle of a lake. It was late afternoon and a little overcast.
Another phenomonon I've noticed concerns our Lake Superior. Our climate is cold, -30 to -40C in the winter but before the lake freezes up, many times on a cold morning you can see wisps of condensation rising upwards. Its not as thick as fog but you can make out individual strands rising up. I'll try taking a picture of this in December. I wonder if there is some kind of convection occurring. I've never noticed birds soaring in this but then perhaps I was too far away.

Tom

[DLD]

Thermal activity happens in just about every environment. Any time the air close to the ground, or ground level, is warmed to a higher temperature than that above it enough to break it loose from the ground and rise, you have a thermal. Water can be warmed by the sun just like anything else. When it comes to a body of water, the depth of the water, the time of day, and whether or not the water is moving(and how fast) will determine the thermal activity. Knowing how quickly different things warm can be very important to the contest flyer. Plowed fields, pavement, or growing crops warm very quickly, freshly watered crops, bodies of water or grass warm more slowly.
I have found thermal activity strong enough to gain altitude in fog, rain, very high wind, over chicken houses, manufacturing facilities, water and many other places that initially might not seem to be the best place.

Good question, and happy thermalling.

David Layne

[nemonis]

One thought would be to pay attention to which way the wind is blowing. If the wind is blowing from the land to the water, the water should be warmer. If the other way, you will probably find sink there. One other thought: make sure you can make it back. I can't imagine water would be as forgiving as grass for a landing out.

God bless!
Wayne J.

[tocano]

Fernando, your observation makes good sense. I should get some thermal above the water in late afternoon.

I wonder if we get more thermal above water in winter or summer?
Where I live the temperature is between 5 C (winter morning) and 40C (the middle of summer usually late afternnon 4 -5 pm). I exclude extreme days.
Temperature difference between day and night is probably around 10 - 15C.

[dhamilton]

The Big Bear Solar Observatory BBSO (http://www.bbso.njit.edu/) was built by Cal Tech in 1969 on an artificial island in Big Bear Lake, California for the specific reason that the air over the water had a minimum of convective distortion.

I agree with the comments elsewhere in this thread that indicate the possibility of finding rising air due to temperature differences between a large body of water and the surrounding land, but classical thermals are very unlikely.

The winter photograph below shows "steam" over the lake, but also shows the stillness of the air.

Regards,

[tw126a]

Yes, that does look like steam and it is very uniform as fog would be. What I have observed is totally different, it looks like a ribbon or streamer and it rises in a continuous vapour for perhaps 500 hundred feet or so. This only happens when it is very cold, at least -25C and the water not frozen yet. There are literally thousands of these when observed across the bay and they are all rising at a perceptible rate.

Tom

[dhamilton]

Tom,

I believe you. If the lake is not yet frozen, then the water temperature must be very near 0C, and therefore much warmer than the -25C air over land, and therefore likely to be rising.

You have really stimulated my curiosity. I wonder if the air is rising rapidly enough to support sustained soaring by an RC model. You do not describe any cyclonic flow in the "ribbons." So, the lift is either not very strong :( , or it is over a very large area :o .

Actually testing the conditions almost sounds worth enduring the -25C.

Regards,

[terry.cx]

One of the places I slope faces a river. When a thermal comes through the wind changes direction and if you're too low you don't make it back to the top of the cliff!
Terry

[jkettu]

Another possible scenario: good preheating area over land and wind from land to water. The shoreline acts as a thermal treshold and cuts a prewarmed bubble free. It then drifts with wind over the water. Of course you will need some altitude to catch it.

[Thermalin]

Think seabreeze....

Air movement is very rare toward the water... living in west central florida we have seabreezes most every afternoon... air over land heats up during the day... rises... air over water moves in to fill the void (hence the breeze) and thunderstorms at 4:30 like clockwork (in the summer anyway) !!
Mike

[Thermalin]

Think seabreeze....

Air movement is very rare toward the water... living in west central florida we have seabreezes most every afternoon... air over land heats up during the day... rises... air over water moves in to fill the void (hence the breeze as the air over water is cooler for it takes more engery to heat water) and thunderstorms at 4:30 like clockwork (in the summer anyway) !!
Mike

[Whorges]

Minimum ground temperature usually accurs (baring fronts) right at day break. For a large body of water the daily temperature fluctuation is minimal. I would strongly suspect that your best luck over water would be in the fall after a cold front has moved into the area. This way the water is still warm from the summer but the air temperatures are descending. On the other hand I suspect you'd have no luck in the spring. In FL, buzzards and hawks are frequently seen thermaling and gaining altitude over the swamps in the morning. If you do try it, let us know if you have any luck :O).

[spudboy]

This past August I went on a water ski trip to Topaz Lake NV. Brought my trusty EZ400 to fool around with. I did catch a couple of thermals over the water about 200 yards off shore in the afternoon.

[histarter]

I found "house" thermals over a pond that was adjacent to our flying field in Denton Tx, that was quite effective. :D

But, the most fun in low launch occurs after a rain when the ground is still damp, and when the sun comes out, the water vapor starts to rise invisably to bouy a light slow tight spiralling sailplane up by a myriad of small thermals - that will exist (at a bit less frequency) in a overcast, that the high launchers think is unfruitfull. :D

[seeker]

I fly at a slope site on the shore of lake mead nv. I encounter huge thermals that will lift my 18 oz wing loading gliders. I believe the water provides the cold air "fill", and allows the 110 degree ground air to rise in a continuous thermal along the shore of the lake. Just my thoughts. Jon

[gliderstuff]

You can get help by email to learn to thermal...the video ,,, Ive seen it work...thats why its guaranteed also.. clik here www.rcgliders.blogspot.com