climate confusion - so where are the subtropics and what is ultratropical?

[Mike T]

Everyone pretty well knows the zonal system and koppen climate classification. There are easy ways to figure how much climate cools with altitude or is moderated by oceans and even water temperatures of nearby seas. Just where the equator is, the  tropics lies and where the temperate zones are is pretty straight forward.
I do notice when reading threads that people talk about the sub tropics and warm temperate areas a fair bit and also refer to ultra tropicals and people seem to have different meanings for these areas so I thought Id just draw attention to it.

Subtropics is in the Temperate Zone and relates to the warmer half from about latitude 23 to 33.While koppen never used this term his modified classification includes humid subtropics as Cfa and Cwa climates. Warm temperate really means the same thing.

Ultratropical is really outside of the tropics or being even hotter than the tropics. I think most of the time on the forum people are referring to equatorial areas and plants from around about 5 degrees latitude either side of the equator.

[Mike T]

I left out the bit about classification of subtropics by temperature.In the Trewartha climate classification which is a modified Koppen classification, a subtropical region should have at least eight months with a mean temperature greater than 10 °C and at least one month with a mean temperature under 18 °C. In most regions in this zone the coldest month has a mean temperature of above 7 C. Most of these climates are located in the portions of the temperate zone closest to the tropics.

[SeaWalnut]

Another important aspect its how long the sun shines during the day.
On tropics its 12 hours daylight all year while where i live on 45N i get up to 16 hours of light during the summer.
Sun in my area can fry tropical plants.In winter on the otther hand we get up to 16 hours of night  but usually fruits rippen during the summer.
Because of more hours during the summer,australian and japanese greenhouse mangos are more reddish than tropical ones.

[Mike T]

Only right on the equator is daylength pretty stable at 12 hours all year and the equatorial region is just a small portion of the tropics. Seasons are fairly pronounced and daylength varies quite a bit even at 10 latitude. The sun is much milder in the temperate zone even if daylength is longer in summer. Mangoes are not really grown in green houses in Australia or many places really.

[pineislander]

Sun in my area can fry tropical plants.In winter on the otther hand we get up to 16 hours of night  but usually fruits rippen during the summer.

Plants which have to deal with such a variance of sunshine probably can't adapt to the change. Plants which grow in full tropical sun and get adapted to that don't have trouble. When I lived in the tropics we could always tell the tourists who had come down from up north and got burned up like lobsters. After a year or two the skin gets used to it. 

[Finca La Isla]

There are many complications to consider. I live at 9N and have a climate very similar to Perak, Malaysia. Also at a similar latitude to me on the other side of CR they have at least six months of dry accompanied by strong winds. We aren’t growing the same things. The daylight is the same but it’s hotter over there. We get more clouds and a good distribution of rainfall.
I never say ‘ultra’ but equatorial wet and, depending, that zone easily passes 10 degrees.
Peter

[SeaWalnut]

Only right on the equator is daylength pretty stable at 12 hours all year and the equatorial region is just a small portion of the tropics. Seasons are fairly pronounced and daylength varies quite a bit even at 10 latitude. The sun is much milder in the temperate zone even if daylength is longer in summer. Mangoes are not really grown in green houses in Australia or many places really.

Only on the Equator is the daylight 12 hours every day of the year and further you go from the equator it gets slightly longer in the summer and shorter in the winter until you get to the North pole where during the summer peak there is sun shining 24 hours and theres no night.
Sun shines a lot more during the sumer where i am on 45 North paralel,you would get a lot more severe sunburns than in the tropics here  and because there is a lot of light during the summer,thats why the japanese mangoes are  more red than any otther mangoes ,because they are blasted by more light.
And they grow these mangoes in the greenhouse because in Japan on such northern latitude its too cold for mango to survive outdoor.

[pineislander]

The Japanese mango color is a function of variety. They grow Irwin which has the desired blush color for cultural reasons.
If you grew a yellow ripening mango in Japan it would not ripen red due to the sun.
Sunburn is a factor of UVB intensity which is always higher at higher altitudes and lower latitudes due to one reason, the sun's elevation, not due to daylength. Since the sun is always higher in the sky at lower latitudes UVB exposure is always higher on a daily and an average annual basis. Annual insolation, the measurement of total solar energy received, is also always higher at lower latitudes despite summer solstice daylength being longer at higher latitudes.

Note the area under the curves(taken on the summer solstice) to see the total dose of UVB is higher at lower latitudes:


Note the area under the curves to see that total insolation is higher at lower latitudes:
 

[SeaWalnut]

Thats Irwin mango but in Florida doesnt become that red because it gets less sun during the growing season than in the more northern Japan.
Irvin is less red colored in Florida ,more red in Australia( because Australia gets more sun than Florida) and brightest red in Japan where it gets more light than in Australia.
On 45 N you get direct sun light in the middle of the summer day just like on the Equator just that it lasts consideeavly longer and sunburns are worst here thats why people go closest to the equator to sunbath in summer ,because the sun its lighter and lighter.
Probably if you never get that much northern ,you would have a shock to see how strong the sun is during the summer.
2 days of sun here in the summer=3 days of sun on the Equator.


And again,im talking only about the summer not anual because most fruits rippen during the summer.
Its obvious that we get here 8 hours of night during summer and 8 hours of daylight during the winter.
This means that on 45 N ,during the summer we get a lot more light than any tropical place .

[spaugh]

Thats Irwin mango but in Florida doesnt become that red because it gets less sun during the growing season than in the more northern Japan.
Irvin is less red colored in Florida ,more red in Australia( because Australia gets more sun than Florida) and brightest red in Japan where it gets more light than in Australia.
On 45 N you get direct sun light in the middle of the summer day just like on the Equator just that it lasts consideeavly longer and sunburns are worst here thats why people go closest to the equator to sunbath in summer ,because the sun its lighter and lighter.
Probably if you never get that much northern ,you would have a shock to see how strong the sun is during the summer.
2 days of sun here in the summer=3 days of sun on the Equator.


And again,im talking only about the summer not anual because most fruits rippen during the summer.
Its obvious that we get here 8 hours of night during summer and 8 hours of daylight during the winter.
This means that on 45 N ,during the summer we get a lot more light than any tropical place .

You dont get more intense light at 45N than they do at 23.5N in the middle of summer.  The north pole get 24hrs of light 6 months a year but its still frozen because the angle of the sun is low in the horizen.  The earth only tilts 23.5 degrees so anywhere north of there is never getting direct sunlight. 

[SeaWalnut]

Not more intense but much longer time,more photons hit the soil here and its direct enough like there is no shadow mid day.
Its all the light we lost during the winter,we get it in plus during the summer,that simple it is .

[pineislander]

This is a forum about tropical fruit and most of us know the difference between the sun at 45 degrees and 25 degrees latitude. Those who know are laughing.

[SeaWalnut]

This is a forum about tropical fruit and most of us know the difference between the sun at 45 degrees and 25 degrees latitude. Those who know are laughing.

Im laughing too having this in mind all the time i comented on this subject. https://youtu.be/G_YM9cCtwz4

[brian]

So far everything I am growing in my greenhouse at 40N latitude is doing fine.  My citrus and guavas got huge, mango tripled in size.  This year I got a ton of “true tropicals”, ill see how they do over winter.  I dont give any supplemental lighting, just heat

[Mike T]

It is a bit hard to compare a continent spanning over 30 degrees of latitude with smaller areas like japan or florida because comparisons of solar intensity or day length should be done comparing specific point locations.
http://www.bom.gov.au/jsp/ncc/climate_averages/uv-index/index.jsp?period=nov#maps
If you look at solar uv index average for November in Australia there is a clear pattern and extreme values in the north.

[brian]

How much light intensity is actually required for these plants, though?  UV index where I am at is just 6 midsummer and 1-2 midwinter.  Everything is growing great, maybe simply less in winter.  Ivve always assumed the important part of subtropical/tropical description for plants is cold tolerance

[spaugh]

How much light intensity is actually required for these plants, though?  UV index where I am at is just 6 midsummer and 1-2 midwinter.  Everything is growing great, maybe simply less in winter.  Ivve always assumed the important part of subtropical/tropical description for plants is cold tolerance

I am surprised a mango for instance doesnt have issues with such short days and weak light levels in winter.  There was a member here working on the giant greenhouse project in greenland.  He was quite knowledgeable about photo requirements of various plants and had it all in a spread sheet.  They were going to have to run supplemental lighting to keep the plants alive.

[brian]

The mango has been in the greenhouse for one winter with no issues, now I have a lot more tropicals that will have their first winter.  If the jackfruit and purple mangosteen do okay I would think anything will.

[sahai1]

My place in Thailand in 8 degrees N, we have a monsoon season, the sky and be predominantly blocked out for a month at a time, the clouds hovering even if not raining.  Most plants are dormant at this period, including grass.