What a difference a few days make in latitudes farther from the Equator; in Guatemala (14 deg N.) our longest day is 13 hours; and our shortest day is 11.

-Tom

Nothing like being on the upswing!

After snowmageddon in the East, Mid Atlantic homes will be even brighter!

Last year we were inundated with snow and it was a lot lighter in my house.

two weeks ago it was still cold in the huge greenhouse near my house with all doors closed on a sunny day in the 30's....Today it was hot in there and the sun felt like it was burning me. How quickly it comes back and I love it.

Last week my greenhouse would get no warmer than 70 at noon on a sunny day. It got to 80 in there today at noon. ..Just loving it!

bumped for 2017 ;)

I was looking for this thread. Thanks

Perfect time to resurrect this thread. We've had two days of foggy, overcast, rainy, nasty weather....and tomorrow and Monday will be the same. Spring can't come fast enough!

We seem to have so many cloudy days this winter I decided to look to see what the average number of clear days would be. Below is a link to a list of clear days by state:

https://www.currentresults.com/Weather/US/average-annual-state-sunshine.php

This is when I feel I need a greenhouse where you can take advantage of increasing light. In my "sun porch" initially it is great since the Sun is still low and can throw the light deep in the room. Plants start being happy and new buds show up like crazy. But over time the Sun becomes steeper and less and less light reaches inside (except near the windows). To compensate I add some extra lights and increase the duration.

This is what I tell gardeners. It is much more important to start your plants extra early to get the jump on food production when you have sun but no warmth than it is to extend the season when there is no warmth or sun. Cover up early. The same goes with citrus when you still need warmth and sun in fall to ripen your fruit. I will provide extra light in spring to push my kumquats into bloom so there is enough sun to ripen the fruits this late summer /early fall. Once the fruits of many citrus are ripe they can store on the tree for months till when you are ready to pick.

6b Steve

James, my pomegranate seedling is doing the same thing. My strawberry roots were tucked away in the dark corner, they started to leaf out too.

We have fog advisory for the next couple of days, tomorrow is going to be +5C outside.

bump for 2019!

Spring cant come soon enough. I hate seeing my lemon putting out so much new growth and then dropping most of it. My mylar-lined CFL bulb chamber works well for maintaining existing growth but not for supporting new growth. At least nothing is turning yellow or losing leaves.

I hope that in another month the sun will be strong enough that they'll be able to spend some days outside in an unheated greenhouse.

In Seattle the shortest day has 8 hours and 25 minutes of daylight, while the longest day has almost 16 hours of total daylight.

The difference between the Summer solstice vs the Winter solstice is it getting dark at 10:40 compared to getting dark at 4:20.

Yuzu can manage to grow out here. (Different type of climate from the East Coast, citrus would never be able to grow at this latitude on the East Coast)

My indoor grow chamber works fairly well for supporting growth. I think the secret is having it all sealed up, which helps hold in humidity and some of the heat. I also have a clear plastic one that doesn't seem to do very well, probably because it doesn't hold in heat very well, whereas the mylar coated one is better at that.

Did you know that Northern latitudes actually get a bit more total solar energy in the Summer due to longer day lengths than the equator?

Tom's graph near the beginning of this thread actually illustrates that northern latitudes get more solar insolation per day compared to equator - the poles being the highest but for a short duration.

More fun facts: Over a year all latitudes get about the same solar energy. The average day length over a year is exactly 12 hrs no matter where you are.

That’s hilarious, I was just saying that it was finally starting to get brighter outside. I can tell you where the sun will come up from my back porch based on what seasonit is. I love tracking these kind of things! Winter always gets me feeling funky and grumpy bc of the darkness. You don’t appreciate the summer sun without the winter loss though.

By the middle of February I feel it around here thank God!!! I can actually stand against a warm wall in 0 degrees weather at the beach and still get a sunburn. Can't wait!

"More fun facts: Over a year all latitudes get about the same solar energy."

That part isn't true. Maybe you meant to say 'over a year all latitudes get about the same length of daylight'.

Even during the height of the Summer, the strength of sunlight is still weaker at far Northern latitudes due to the angle of the sun. It's just the day will last longer, so overall you will end up getting more solar energy during that day.

(Actually, right on the day of the Summer solstice, 45 N latitude will be at about the same angle to the sun at high noon as the equator is, with the tropic of cancer getting the most direct angle)

socal: You are absolutely right if you are considering solar energy incident on a horizontal surface on the earth at different latitudes. No question about that.

In the back of my mind, I was thinking how greenhouses/solar-panels are designed to maximize input from Sun and left out some details. If hold a meter directly pointed at the Sun (that is a surface perpendicular to Sun) then it will measure about the same at all latitudes over a year (minus some extra loses through the atmosphere at higher latitudes).

For more detail this may be useful: http://www.powerfromthesun.net/Book/chapter02/chapter02.html. The articles addresses both the scenarios.

Greenhouses/solar-panels are specifically angled facing the Sun. If it is at a fixed angle then the optimal angle is determined by Sun's angle during Equinox. Solar panels that can track Sun will obviously get the max benefit. In this case the difference between latitudes over a year is lot less. The actual loses are the dispersion loses due to the distance it has to travel through the atmosphere at higher latitudes.

The total energy received at the poles is definitely less.

That's not entirely true either. If the sun is coming in at an extreme angle, it has to pass through more atmosphere. That's why the sun in the winter in far northern latitudes is such a golden color.

socal: I just looked up the effect of air mass on solar energy and you are right. At the peak of summer the poles would get at least 30% less compared to the equator - assuming the measurement is done directly facing the Sun. Tapers off pretty rapidly in other months. And yet I clearly remember reading that solar panels can produce close to 100% of their power even close to the poles during the peak summer months. At one point I was looking up info on solar panels for our house but never got around to installing. Now I cannot find a decent article on studies how solar panels fare close to the poles. May be I read or interpreted wrong. I will have to keep trying to find info to reconcile this discrepancy.

Edited a bit above for clarity.

The poles don't have a lot of clouds, pretty clear skies, that's probably why.

And plus all the ice reflecting back sunlight actually makes the ambient light reflecting back from the sky brighter.

Found this again - forgot which thread to post to.

I did think about those factors but still it does not explain the discrepancy. I have not found any good article regarding that either. At least it is not convincing enough. Another possibility could be temperature. At low temperatures solar panels (or for that matter anything electronics) work more efficiently. The effect can be quite substantial. But again I do not have a good sense of the scale.

It's all about the angle. At the poles, the same angled surface area will intercept nearly the same intensity of light as at the equator (minus radiation lost to Mie/Rayleigh scattering from the longer atmospheric path). You'll just cast a huge shadow, unlike at the equator.

I really worded this wrong. I meant to State that the length of time lost from solstice to solstice we have gained about 13% back. There is no way I could do the Calculations needed to deal with the quality of light gained. Your points made are of interest and a GREAT addition to bring up.

Steve

Very interesting thread... Even in the second sunniest state, winter still pretty much sucks. The dependable sunshine is a lifesaver, and great for greenhouses, but being outside is still unpleasant, and I groan at all of the things I can’t grow in the garden because of the winter cold! I’m very excited to see the days lengthening, just started loads of seeds in the greenhouse yesterday!

I am going to start today with Kale.

Steve

I'm a little late bumping this, so maybe we've gained back around 15% by now. ;)

Here's my lemon tree, grown from seed in 2016, outside on a warm day last month when temps got near 60 degrees. It's not often you see a lemon tree next to a snowbank in January.

Happy to hear that report! We gained something like 40% more sun because the neighbours chopped down a few big trees. We'll take every minute we can get lol. There is lots to get started, seed wise too.