Mhc's minimalist approach on Climate Classification (place, world, America, most)

[FirebirdCamaro1220]

Originally Posted by Klimaforscher

I can understand why you might enjoy having many designations, but, Köppen already divides climates into more types than genuinely exist. Going further than that invents unreal distinctions.

By way of example, what is the difference between moderate deserts, dry deserts, and ultra dry deserts? One could easily create precipitation thresholds separating each "type" from the others. But:

• Sun control will dominate the temperature patterns at moderate, dry, and ultra dry deserts.
• All three deserts will be subject to descending air masses at the subtropical end of the Hadley cell, and what precipitation falls in each type will be unpredictable.
• Wind speeds will be high due to diurnal temperature swings and lack of forest cover to serve as windbreaks; sandstorms unknown to other climates will threaten all three deserts.
• Biomass and biodiversity in all three deserts will be low, and what life is visible will cluster around streams originating from elsewhere, or be heavily adapted to conditions of perpetual drought.
• Agricultural potential in each type will be the same: with reliable irrigation and soil enrichment, heat-tolerant crops will grow rapidly due to predictably high insolation.
• If you find yourself cut off from civilization in any one of the three deserts, your chances for survival are low, and will depend on your using strategies to avoid water loss during the day, staying warm at night, locating a stream, oasis, or some other water source, and signalling passing aircraft for help.

So if Köppen feels too simple, you should probably just do as Joe90 does and read the numbers directly. (Or read up on Thornthwaite's "rational" climate system, which highlights just how pointless a system is when no attempt is made to minimize complexity, and type boundaries are drawn arbitrarily rather than carefully aligned to genuine distinctions provided by nature.)

Per the bolded, moderate=Tucson, dry=Phoenix, ultra dry=Yuma.

Just look at pictures from the outskirts of all 3 places, you'll notice an obvious visual difference

[Klimaforscher]

Tucson isn't a desert; Phoenix and Yuma might be examples of the moderate and dry deserts, while Sabha, Libya is a pretty good example of the ultradry.

But any distinctions we draw between three, five, or twelve classes of humidity within deserts will all be as arbitrary as between three, five, or twelves classes of humidity in humid subtropical climates. Such lines are imaginary.

On the other hand, there is a clear type difference between deserts which are always dry, Mediterranean which is fully humid for some of the year and desert dry for the rest, and Humid Subtropical, which is humid all year. Those are three objectively distinct types of climate.

[grega94]

Originally Posted by Klimaforscher

Tucson isn't a desert; Phoenix and Yuma might be examples of the moderate and dry deserts, while Sabha, Libya is a pretty good example of the ultradry.

But any distinctions we draw between three, five, or twelve classes of humidity within deserts will all be as arbitrary as between three, five, or twelves classes of humidity in humid subtropical climates. Such lines are imaginary.

On the other hand, there is a clear type difference between deserts which are always dry, Mediterranean which is fully humid for some of the year and desert dry for the rest, and Humid Subtropical, which is humid all year. Those are three objectively distinct types of climate.

There are also climates that are dry in the winter and wet in the summer.

Borzya
Beijing
Patna
Xi'an

[FirebirdCamaro1220]

Originally Posted by Klimaforscher

Tucson isn't a desert; Phoenix and Yuma might be examples of the moderate and dry deserts, while Sabha, Libya is a pretty good example of the ultradry.

But any distinctions we draw between three, five, or twelve classes of humidity within deserts will all be as arbitrary as between three, five, or twelves classes of humidity in humid subtropical climates. Such lines are imaginary.

On the other hand, there is a clear type difference between deserts which are always dry, Mediterranean which is fully humid for some of the year and desert dry for the rest, and Humid Subtropical, which is humid all year. Those are three objectively distinct types of climate.

Tucson is most certainly desert, Koppen gets Tucson wrong. It does grade to semi arid as you go almost immediately south or east of town, but in town and to the immediate north and west, it IS desert

[Ethereal]

I like the distinction between continental and subcontinental.

[Klimaforscher]

Originally Posted by grega94

There are also climates that are dry in the winter and wet in the summer.

Borzya
Beijing
Patna
Xi'an

True, although they are found in similar locations to humid subtropical climates on a hypothetical continent, and they are treated by Köppen, Trewartha, and Strahler as humid subtropical. Maybe the tradition is wrong; can you explain why?

Originally Posted by FirebirdCamaro1220

Tucson is most certainly desert, Koppen gets Tucson wrong. It does grade to semi arid as you go almost immediately south or east of town, but in town and to the immediate north and west, it IS desert

If you define that as desert, then OK; you can say there are two kinds of desert. When I gave my example of three deserts, I was writing of deserts as usually envisioned, and/or as defined by published thresholds. Looking at images of both the city of Tucson and the surrounds, I don't recognize it as unambiguously a desert; it looks more like a peripheral zone that fits into "(summer) Dry Subtropical" or "Dry Subtropical + Subcontinental."

[FirebirdCamaro1220]

Originally Posted by Klimaforscher

True, although they are found in similar locations to humid subtropical climates on a hypothetical continent, and they are treated by Köppen, Trewartha, and Strahler as humid subtropical. Maybe the tradition is wrong; can you explain why?




If you define that as desert, then OK; you can say there are two kinds of desert. When I gave my example of three deserts, I was writing of deserts as usually envisioned, and/or as defined by published thresholds. Looking at images of both the city of Tucson and the surrounds, I don't recognize it as unambiguously a desert; it looks more like a peripheral zone that fits into "(summer) Dry Subtropical" or "Dry Subtropical + Subcontinental."

Saguaro and Cholla cacti are abundant in Tucson, and they are desert plants, not semi arid plants. Plus there is no native grass in Tucson, unaltered zones only have bare sand/dirt with brush and cacti

[grega94]

Originally Posted by Klimaforscher

True, although they are found in similar locations to humid subtropical climates on a hypothetical continent, and they are treated by Köppen, Trewartha, and Strahler as humid subtropical. Maybe the tradition is wrong; can you explain why?"

Well the w climates usually exist between the arid/semi arid climates in the west and the f climates to the east. I kinda understand why w climates are lumped in with the f, considering their vegetation is very similar since winter is the dormant season so rainfall amounts don’t really effect them, and the summers are just as wet and humid as the f climates if not more so, so in summer the landscapes will be pretty much the same. That being said the Am monsoonal climates get to have their own designation and I could be wrong, but aren’t the w climates essentially a temperate version of the Am monsoonal climate.

[Klimaforscher]

Originally Posted by Ethereal

I like the distinction between continental and subcontinental.

(So do I - I've been using something like it for a while. Interestingly "subcontinental" as I define it only exists in the northern hemisphere, just like continental.)

Originally Posted by grega94

Well the w climates usually exist between the arid/semi arid climates in the west and the f climates to the east. I kinda understand why w climates are lumped in with the f, considering their vegetation is very similar since winter is the dormant season so rainfall amounts don’t really effect them, and the summers are just as wet and humid as the f climates if not more so, so in summer the landscapes will be pretty much the same. That being said the Am monsoonal climates get to have their own designation and I could be wrong, but aren’t the w climates essentially a temperate version of the Am monsoonal climate.

Trewartha gets by without Am at all; in fact neither my chart or the OP's includes any monsoonal tropical climate. You can have a monsoonal tropical climate, but savannah and rainforest are enough.

As for Cw, my understanding is that it is a result of highlands (the Himalayas) redirecting the Westerlies south during low sun and north during high sun. It wouldn't exist on a flat hypothetical continent, which is why it, too, doesn't exist on either my chart, or the OP's.

Originally Posted by FirebirdCamaro1220

Saguaro and Cholla cacti are abundant in Tucson, and they are desert plants, not semi arid plants. Plus there is no native grass in Tucson, unaltered zones only have bare sand/dirt with brush and cacti

One man's desert is another's dry subtropical climate. Yes, there are cacti, but cacti and tumbleweed are found in classic Mediterranean climates too, and some of those photos for Tucson are pretty green.

But to take a more scientific approach, using the most sophisticated corrections that I can, taking the data to 3 significant figures, and carefully accounting for the fact that Tucson is not quite aseasonal in its precipitation pattern, I built the following graph. Several other cities are also given for comparison, also with precipitation levels corrected for degree of summer dryness (bonus) vs winter dryness (penalty).



Annual Average Precipitation (cm) vs Average Annual Temperature (degrees C)
Green Line: Steppe/Humid boundary
Red Line: Steppe/Desert boundary

Some interesting features:

• The correction that is usually given for receiving rainfall in the summer rather than the winter was quite extreme for Sabha, increasing its effective precipitation by a factor of 8. If Sabha's minescule precipitation were shifted towards the winter, the correction would effectively give it negative precipitation. That's ridiculous, but the formula only needs to classify climates correctly near those boundaries.
• Classic Mediterranean climates are near the subhumid boundary in a way that suggests they do blend into other dry subtropical climates.
• I was going to include Seattle, but its corrected precipitation was 100cm and it's nowhere near the steppe boundary. People who insist Seattle is straightforwardly Mediterranean are free to do so, but Seattle gets quite a lot of rain.

And of course Tuscon is precisely on the boundary. These equations are never as exact as people like to pretend, so it's anyone's guess what Tucson really is. If you say it's a desert, then whatever, there are four categories of desert. Oh and all of four them have essentially the same genetics, diurnal temperature swings, unpredictable rainfall, reduced biodiversity, agricultural profile, and survival strategies.

[Mhc1985]

Originally Posted by grega94

Cool diagram, but without thresholds it’s not applicable. I understand that thresholds are a bit limiting when it comes to transitionary climates that have features of two or more climates, but I don’t really how else one is able to apply climate classifications.

I agree… any ideas on where to set some thresholds? I guess good old Köppen is a necessary point of reference to begin with.

The general idea is adapting a system and base it on the global circulation without neglecting the consequences on the biosphere. Köppen unveiled some weather/climatological patterns just by trying to represent an association between biomes and climate, but many others kept obscure. Granted, he had the obvious limitations due to the availability of information in the time he lived, but what if we took the opposite approach?

Originally Posted by InchingWest

When it comes to climate classification the last thing I want to be is a minimalist.

Both the Koppen and the Trewartha systems have too few designations and are not specific enough.

This is a discussion I have already had, and I tend to think the opposite. A classification is supposed to tidy up something untidy. If we have too many designations, we are at risk of keeping everything as a mess, and therefore failing in our goal. This is what I’ve seen in several personal schemes presented on this site, in which the excess of combinations (plus sometimes loosely linked to the natural processes of the planet) make them very impractical.