The Köppen–Geiger climate classification made simpler (I hope so)

[Shaetano]

Hey,

I tried to apply your guide to my first map as well, but I think I am not very good with anything about wind and pressure systems. Would one of you (your work looks really awesome) maybe have a look at my different maps to tell me, where I'd have to adjust them?

Thanks in advance and kind regards

[Azélor]

It look pretty good that way. One thing I need to mention is that I based myself with the Earth map on the first place so it's supposed to look almost identical. You just did it backward.

[Charerg]

Well, you're right that the Robinson projection probably isn't ideal. Tbh, I'd recommend you to make an Equirectangular projection, because you're probably going to need it (it's easy to change an Equirectangular projection into another projection, but not vice versa). Also, the resolution is very low (1000x500 is very low res for a world map, you should ramp it up to 4000x2000 or something).

Anyway, here is the basic oceanic circulation:

Currents.png

For the most part it's similar to your version. The major addition is the Equatorial Countercurrents. Also, the southern pole shouldn't have a westerly flowing current (the winds there are the polar easterlies, resulting in easterly flowing currents). One area which is somewhat subjective is the narrow north-south oriented sea in the northeast corner of the map. I chose to essentially implement the circulation there as two separate gyres, but this is a little subjective. Areas like this are always very tricky, since no similar situation exists on Earth.

Next up, the location of the oceanic low and high pressure centers (semi-permanent, the exact location does fluctuate a little seasonally):

Currents_and_Pressures.png

This should demonstrate the relationship between the oceanic and atmospheric circulations. It should be noted that I've omitted the ITCZ here.

Then, the pressures by themselves, and pressures with the dominant winds:

Pressures.png

Pressures_and_Winds.png

Once again, the major caveat is that the ITCZ has been left out (it's simply assumed to be a continuous low pressure belt at the equator, in reality the location varies seasonally), and there is some seasonal fluctuation in the exact placement of the pressure centers. One major phenomenon to point out is that the location of the high pressure centers on the eastern margins of the oceans means that the the opposite shore of the oceans (the eastern coasts of continents) are hit by cyclones, and in general receive much more rain than the western coasts in tropical latitudes.

Also, I should note that I didn't include any continental pressure centers. Imo they're not strictly necessary, and it's often easier to get a good picture of what the global circulation looks like by leaving the continental centers out. Outside of the ITCZ, the only continental pressure centers that have a major effect occur if you have a situation like Asia, and you have a strong Monsoon effect. It's up to you if you want to include that, but imo it's a perfectly valid option to just roll with the basic circulation.

[Shaetano]

Hi and thanks for the reply. Wow.. I must say, that is way more than I expected. Thank you for your help.

Most of your points helf me very much, I even started to redo the map as an Equirectangular projection. It isn't THAT much work anyway..

There are just one thing I want to add and two questions about your work. First - the big blue blob in the north-east which you identified as a part of the ocean is in fact just a blue part of the cold climate of the climate map. But I don't think that would affect the currents too much, so I'd just let them travel around the bigger landmass.

One thing is a bit unclear for me. The pressure/wind maps you posted - do they follow the guide for one of the seasons, or did you just but them together ignoring the current month as a little "overview". The tip about not including the continental pressure systems is great. They just add to my confusion and if their influence isn't that big, I think I won't inclue them either.

The 2nd question - how the hell do you draw these nice arrows?

[Charerg]

Hi and thanks for the reply. Wow.. I must say, that is way more than I expected. Thank you for your help.

Most of your points helf me very much, I even started to redo the map as an Equirectangular projection. It isn't THAT much work anyway..

There are just one thing I want to add and two questions about your work. First - the big blue blob in the north-east which you identified as a part of the ocean is in fact just a blue part of the cold climate of the climate map. But I don't think that would affect the currents too much, so I'd just let them travel around the bigger landmass.

One thing is a bit unclear for me. The pressure/wind maps you posted - do they follow the guide for one of the seasons, or did you just but them together ignoring the current month as a little "overview". The tip about not including the continental pressure systems is great. They just add to my confusion and if their influence isn't that big, I think I won't inclue them either.

The 2nd question - how the hell do you draw these nice arrows?

The pressures and winds are just an overview, they're basically intended to demonstrate what the basic pattern should look like (like I mentioned, it does vary a bit between the seasons). As to the arrows, they're just hand drawn. In GIMP, you can use the "Smooth stroke" option and adjust the settings to draw nice and smooth lines.

[Shaetano]

Hey!

Like I said I started from the beginning again. With the help of your pictures I went through the guide again and hope I did a little bit better this time.

What I am unsure about are parts of the pressure systems. I followed the guide more or less, but don't know if it would be better / more realistic to change the size/position of the systems from season to season more than I did.

Here are my maps from step to step. The last one, after the climate script, isn't edited, as it takes really much time and I want to see if I have to change anything before I start with that.


General Map with heights & currents:
currents.png

Winds & pressure January:
wind_pressure_january.png

Winds & pressure July:
wind_pressure_july.png

Temperatures January:
climate_january.png

Temperatures July:
climate_july.png

Rain January:
rain_january.png

Rain July:
rain_july.png

Climates:
climate_zones.png

[Charerg]

A bit of news to revive this thread (btw, shouldn't this be in the tutorial section now that it's finished?):

I made a bit of a modification for Azelor's tutorial, ramping up the precipitation categories to 8 (from 6). Additionally, I changed the scheme for categorizing the climate types (precipitation-wise, the temperatures remain unchanged). As most who have used the tutorial are probably aware, the current version tends to have a few problems (namely relative lack of BS areas in some cases, and a tendency for Af->BW or Aw->BW transitions), although it is still by far the best and most advanced climate-generation tutorial available. I think I've managed to identify and largely eliminate these problems, although this solution does complicate the tutorial slightly due to a greater amount of precipitation categories.

But before I get into the modified version, let's take a look at the changes I made to the climate categorization scheme:

A) Defining the precipitation patterns of A climates separately from C and D
A climates use different criteria when determining their type (f, m, w or s) than C/D. For example, it's entirely possible for a climate that would otherwise be classified as 'Cf' to be classified as Aw or As. Meanwhile, only the very rainiest climates (no month with less than 60 mm rainfall) qualify as Af.

I used the following scheme to classify the climate types, differentiating Af, Am, Aw and As from C/D f, s and w:

Prec Combos.PNG

The table displays the different average precipitation values I used for the different precipitation categories, and the Mean Annual Precipitation (Pann) calculated for each combo (this is used to determine whether a climate is steppe or desert). Note that 's' or 'w' climates would qualify as Aw/As (but as you can see, some 'f' climates also qualify as Aw/As!).

B) Determining the aridity threshold
Köppen uses different aridity thresholds depending on Mean Annual Temperature (MAT), and whether 2/3 or more of the precipitation occur in winter or in summer. These classes are quite different from the climate categories s, w and f. So, I used a different table to determine which aridity threshold should be used:

Prec Values for PTh Calc.PNG

Here, areas below the purple line can never be arid (they are too rainy), areas below the yellow line can never be desert (they can still be steppe), and areas above the red line are always desert.

Finally, here is the table I used to determine the MAT value of the various temperature combinations (Tann=mean annual temperature), as well as the associated aridity thresholds (areas with Mean Annual Precipitation (MAP) below the threshold are classified as steppe, and areas with precipitation less than half of the threshold are desert):

Temp Values.PNG

The red lines denote the boundaries of different temperature-based climate types, the yellow line denotes the boundary between Da and Da2 (an extreme version of Da, this climate doesn't appear on Earth). Note that although I used 'f', 's' and 'w' here to signify the various aridity thresholds, these refer to the aridity category, not the actual climate category!

C) The Results
With that out of the way, let's get into the testing of the modded version. First of all, I used data from WorldClim to generate temperature and precipitation maps for Earth (these should be almost identical to those used by Azelor in his earlier post). The only major difference is that these are in the Equirectangular Projection, and the precipitation categories are different:

January Temp:
Temp Jan.png

July Temp:
Temp Jul.png

January Prec:
Prec Jan.png

July Prec:
Prec Jul.png


And then, the final result. This is in the more commonly used "wikipedia colour scheme". Note that as no data was available for Antarctica, it has just all been painted as EF (I think some tundra exists there as well):

KG Climates.png

This is completely "script-generated" (actually manually done as I use GIMP), although I did shuffle some categories around to make it match actual Köppen maps of Earth as closely as possible. In general, it matches extremely closely, though there are three major divergencies:

1): Equatorial Africa is a bit messed up. This is caused by the "data gap" from having data only from January and July. As a result, there are weird instances of BS and As popping up, and Af and Am do not cover quite as much area as they should.

2): I classified any B climate with Cool (0-10) winters or colder as BSk/BWk. As a result, some areas like Northern Arabia have Bk climates instead of Bh. However, as drawing the Bh/Bk boundary at Cold (-10 to 0) would classify large areas of Central Asia and the North American prairies as Bh, I decided that this was the lesser of two evils.

3): The third difference is of course the distribution of the Cc climates. An old issue, and it can't really be fixed with the temperature categories we have withouth eliminating Cc climates completely (as pointed out by Azelor previously).

That said, I have yet to test this on a fictional world. The good news is that while this probably does sound rather complicated, it doesn't actually make the tutorial much harder to implement (you just have to use those 8 precipitation categories instead of the original 6). The bad news is that as I don't have PhotoShop, there is no possibility of scripting this, so this will be strictly manual-implementation-only. I'll try to put a "supplement for Azelor's instructions" together detailing how to implement this, in case someone is interested in trying this out (though I'm mostly making this for my own use ). I should note that this is perhaps intended more for the "advanced user" who is already familiar with the tutorial (and has preferably already tried the manual implementation before), since otherwise the extra complication will probably be of little benefit.

[Azélor]

I'm not sure if I misunderstood but A climates are different of C because of the temperatures, not the precipitations.
I'm also unsure why you said that the precipitation categories should be different for A, C and D. What do you mean by that?

[Charerg]

I'm not sure if I misunderstood but A climates are different of C because of the temperatures, not the precipitations.
I'm also unsure why you said that the precipitation categories should be different for A, C and D. What do you mean by that?

I mean that Af has specific criteria (no month with less than 60 mm) that are different from Cf/Df, as do Am (annual precipitation more than 25*(100-Pmin), where Pmin is the precipitation of the driest month). Likewise Aw and As are determined based on whether the month with less than 60 mm occurs in summer or in winter.

These criteria are much looser (in the case of Aw and As) than the criteria used to define Cs/Ds (3 times as much rain in the rainiest winter month than the driest summer month) and Cw/Dw (10 times as much rain in the rainiest summer month than the driest winter month). This is particularly true in our case perhaps, since we only have data from two months (so, effectively 3* the rain in winter->s and 10* the rain in summer ->w). I'm not sure if you took these into account, but this does result in the possibility that some climates with the same precipitation pattern could be classified as either Aw/As or Cf/Df depending on which temperature group they belong to.

The "Prec Combos" table I posted demonstrates this quite well. You can see that some precipitation combinations are classified as "f OR Aw" or "f OR As". One fringe case is the W4+S4 (avg. 50mm + avg. 50mm), which results in an even precipitation pattern, but is nevertheless too dry to be classified as either Af or Am. In most cases, this would actually fall into BS (because of the relatively low overall precipitation), but not in all. I chose to classify this as Aw, since it's more common than As, but there isn't really a category within A that represents this particular climate well.

[Azélor]

I took these numbers in consideration but since you used more categories, you had to redo the process anyway.