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Why A giant jurassic sequoia forest doesn't fix with the mediterranean word and historic concept at all. Redwoods forests have cool hiperoceanic (C3ch) climate in my system.
I reverse the premise to you: Just because a place has a reverse Pp pattern, doesn't disqualify it from the possibility of not being Mediterranean climate. Redwood's environment is just too wet to be labeled "mediterranean" as well as cooler than most med climates out there.
Redwoods are adapted to long periods of drought though. Their seeds in fact are regenerated by fire. Different Mediterranean regions have different plant species adapted to live there depending on local evolutionary conditions.
In my opinion, as long as the climate meets Trewartha's Subtropical classification and has more than 3 times more precip in wettest month vs. driest month then it is Mediterranean. San Francisco meets these requirements easily.
Even San Francisco much further south has large redwood forests just north of the city in Muir Woods. Just because a place has tall trees and heavily forested, doesn't disqualify it from having a Mediterranean climate.
The reason there are large redwood forests is because the winter rainy season produces copious amounts of rain (some places north of SF see 60" of rain in the winter) and then the "fog season" produces morning and evening fog in the summer. The redwood trees basically absorb the fog, on the other side of the redwood forests there is no fog and redwood trees can't grow without irrigation.
So, November to April there is ample rain to support the redwoods. From June to August there is ample fog.
May is still moist, all the creeks are usually flowing so there's ample residual moisture. Only September and October are stressful times for the redwoods as there is no fog and winds blow from the east. This is also fire season. But the trees are tough enough to last out the two month drought period.
The reason there are large redwood forests is because the winter rainy season produces copious amounts of rain (some places north of SF see 60" of rain in the winter) and then the "fog season" produces morning and evening fog in the summer. The redwood trees basically absorb the fog, on the other side of the redwood forests there is no fog and redwood trees can't grow without irrigation.
So, November to April there is ample rain to support the redwoods. From June to August there is ample fog.
May is still moist, all the creeks are usually flowing so there's ample residual moisture. Only September and October are stressful times for the redwoods as there is no fog and winds blow from the east. This is also fire season. But the trees are tough enough to last out the two month drought period.
All of this is true. The fog that is produced during the fog season doesn't disqualify the area from being a Mediterranean climate though. The amount of moisture that the fog produces doesn't amount to that much if we compare the equivalent precipitation amount.
All of this is true. The fog that is produced during the fog season doesn't disqualify the area from being a Mediterranean climate though. The amount of moisture that the fog produces doesn't amount to that much if we compare the equivalent precipitation amount.
True because the fog isn't precipitation (it produces dew but not rain) so it doesn't add significantly to the rain total in the summer (maybe 0.1" max for the month). The redwood trees are just very good at absorbing that moisture. Most other plants and trees can't process fog.
Most of the Cs climate zone in South Africa is Csb including all of the coastal parts. Csa only exists in a smaller area away from the coast. Cape Town is often given as an example of a mediterranean climate outside the Mediterranean region. Summers aren't hot enough to qualify as Csa as the highest daily mean is 20.4 C in Jan and Feb. But the rainfall pattern has a very strong winter peak and summer minimum. Practically two thirds of the rain falls in May-Aug and just over 12% in Nov-Feb. Native vegetation types are typically mediterranean being dominated by evergreen shrubs with small, hard leaves adapted to periodic fire. Many bulbous plants are endemic and grow over winter, flower in the spring and then die down during the summer drought. There is not enough summer rainfall for natural forests to grow.
I haven't been to Portland or anywhere like that, but the summer dry season seems too short (three months under 40 mm/two months under 30 mm as opposed to 6/5 months in Cape Town) to be typically mediterranean. The vegetation doesn't look typically mediterranean either, it seems too forested and typical of a wetter climate.
Many places in the northern part of the Mediterranean Basin actually have a shorter dry season than Portland. Nice, Barcelona, and Genoa all have very short dry seasons - even Rome has only one month below 30mm. The length of the dry season doesn’t matter, just the reason for it - which in almost every Mediterranean climate, if not every one, is summer high pressure causing a lack of rain.
I feel like Koppen works best with the US West and Europe in mind. Trewartha made his system with the US East in mind.
Also, to the “Seattle is Mediterranean” argument, Csb and Csa are different things. Csb is literally just an oceanic climate with a dry summer. Csa is “true” Med climates - subtropical climates occuring in the Mediterranean Basin, California, parts of Australia, parts of Chile, and South Africa.
Csb interestingly isn’t very common - only really occuring in the PNW/NorCal and northern Portugal. Maybe it has to do with the subtropical high pressure system bringing heat? Many Csb climates also have consistent summer warmth with Portland being only 1°C from Csa in the warmest month and Porto being fairly warm too.
Genuine cool summer climates with Med precip patterns like the Oregon Coast seem to be fairly rare. Puget Sound area Olympia-Seattle has cool summers (Everett north is Cfb) but they warm once you get into SW WA and no longer have the 55 degree pool of water.
Isn't most of South America's dry-summer/Mediterranean climate region Csb? Seattle summers aren't nearly as cool as on the Pacific coast, daytime highs there are almost always 5-10 F warmer (but often cooler than Portland by 5-10 F as well).
Many places in the northern part of the Mediterranean Basin actually have a shorter dry season than Portland. Nice, Barcelona, and Genoa all have very short dry seasons - even Rome has only one month below 30mm. The length of the dry season doesn’t matter, just the reason for it - which in almost every Mediterranean climate, if not every one, is summer high pressure causing a lack of rain.
Thanks for correcting me on Csb regions though.
I'm not saying that Portland and climates like it aren't mediterranean, just that there there are Csb climates that I think have stronger mediterranean features. The Mediterranean Basin actually has quite a variety of climates and some of them are only marginally mediterranean or not mediterranean at all. Eg Barcelona's rainfall pattern is only marginally mediterranean with its main peak in autumn and a secondary one in spring and main minimum in summer and secondary minimum in winter.
But back to Koppen. I'm not really asking why he grouped climates into such broad categories, because that's inevitable without creating a lot more categories. What I want to know is what reasoning he had for his boundaries.
I'm not saying that Portland and climates like it aren't mediterranean, just that there there are Csb climates that I think have stronger mediterranean features. The Mediterranean Basin actually has quite a variety of climates and some of them are only marginally mediterranean or not mediterranean at all. Eg Barcelona's rainfall pattern is only marginally mediterranean with its main peak in autumn and a secondary one in spring and main minimum in summer and secondary minimum in winter.
But back to Koppen. I'm not really asking why he grouped climates into such broad categories, because that's inevitable without creating a lot more categories. What I want to know is what reasoning he had for his boundaries.
I think -3C for the coldest month was chosen as a boundary between C and D climates as that corresponds to the limit of permanent snow cover. The other temp/precip limits I am not sure about.
Duh..... pretty much all of Western Europe is oceanic climate
There's plenty of Continental Climates and Mediterranean Climates too. Take for example the Humid Subtropical Climate, that's a good example of the classification working in Europe.
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I wanted to add that I think that one requirement for a clinate to be considered "subtropical" is having 4 to 11 months with a mean 18°C or higher.
I came to that conclusion as their are tropical climates that have all 12 months between 18°C and 22°C, like Brasilia; and there are climates like San Diego where all 12 months are below 22°C, but they are clearly more subtropical than they are oceanic.
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A giant jurassic sequoia forest doesn't fix with the mediterranean word and historic concept at all. Redwoods forests have cool hiperoceanic (C3ch) climate in my system.
