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

[Charerg]

Ok now I understand we you said the letters could be confusing. Indeed using the same letters for

• At least 2/3 (or ~67%) of rain occurs in summer (W aridity group, use threshold T_ann*20+280)
• Between 1/3 to 2/3 (34-66%) of rain in summer (F aridity group, use threshold T_ann*20+140)
• Less than 1/3 (~33%) of rain falls in summer (S aridity group, use threshold T_ann*20)

as s,f,and w climates, doesn't make much sense since they are 2 different things.
I guess I'm just repeating you.

I personally don't really care how Koppen name them, if it's too confusing we should change the naming, assuming we keep them.

Arid
Average
Wet

West coast
Something (Faoofa?)
East coast (the dry summer is more prominent on east coasts, or the eastern sides of mountains in the case of Central Asia). it is the opposite for w pattern.
Now I remember I used to say precipitation pattern. For example, Brest in Brittany has a Cfb climate with a s pattern because the summer is drier than winter but not dry enough to qualify as a s climate.

I don't think they have been named as such, I just adopted the W/F/S terminology since it works for me (and kind of assumed everyone was "on the same page" as myself, I guess).

But essentially it's the percentage of total rainfall that falls in summer from 0-100% divided into even thirds. I guess you could call them the "winterwet third", "middle third" and "summerwet third", though tbh that could be even more confusing since "winterwet" is more or less the same same as "summer dry". But precipitation pattern sounds good, as long as you use capital letters when talking about the pattern, and lowercase when referring to the climate class, then at least I'll understand (not sure about anyone else though ).

[Azélor]

This if for the climates. the area in light colour belong to s and w respectively but should be f if we follow the strict criteria of the formula. Do you want to try the new ones or keep the old distribution?


This is for the threshold
the dark ones actually falls into the green zone but barely. I know when at look at the exact numbers, those are rounded.



This is the actual aridity table before I make the changes:

[Azélor]

It results generally in a increase in aridity



Sorry It's supposed to be like this instead. the 22% is in s climates but we considered iit was a bad idea since it made large areas in Europe with Cs climates.

[Charerg]

This is for the threshold
the dark ones actually falls into the green zone but barely. I know when at look at the exact numbers, those are rounded.

Overall looks good. Just one minor quibble: since the precipitation pattern is divided into even thirds, it should look like a "mirror image" on both sides of the central diagonal. Yet in this case the "S pattern" has an extra combo (32%) compared to "W pattern". A minor matter, but technically the green 68% should be a "W pattern", that way you'd have the expected mirror image.

Edit:
Oh, and a question about the Winter 75+Summer 37,5 combo (referring to the avg. precipitations).

From the threshold table we see that this combo is in the "green zone". So, assuming that it had the F threshold previously (or "middle third" threshold, if you prefer), it shouldn't change in terms of aridity, yet apparently it did become more arid. Why is that the case?

[Azélor]

Alright :



That cell is also going to become more arid.

[Charerg]

Sorry It's supposed to be like this instead. the 22% is in s climates but we considered iit was a bad idea since it made large areas in Europe with Cs climates.

Actually that was an f climate to begin with (assuming this was the previous table). The categories I shifted from s back to f for the script were 33% and 32%, so those weren't "technically s" to begin with. Also, I doubt the 22% would have an effect in Europe: it would be either BS or BW with the temperatures that occur in southern Europe. It might push some areas in Siberia or Canada from f to s, though. In any case, we haven't tested how the 22% would work as an s climate.

Edit:
Looking at the table for the 22% prec combo, it looks like you probably need it to be either ET/EF or at least a Cold winter for it to be something other than arid. I think we could include it as s (might be wrong about that, maybe half of Siberia will become Ds or something ).

Btw, maybe 90% should be a w climate? At 150 vs 17,5 it doesn't quite fulfill the 10x criterion, but it's not far off either.

[Azélor]

89% is not much farther.

Yea, 22% was a f climate.

[Azélor]

Supposing we decide to use more thresholds.

We use the % of precipitations falling during the summer.
W has the highest value, and s the lowest.
The difference between the maximum and the minimum is 280 mm at any given temperature.
so if
280 = 100%
and
0 = 0%
it means
2,8 = 1%

Every 1% increase in the share of precipitation for summer, increase the threshold by 2,8 ml.

We take the s threshold table as our base value

Base threshold + 2,8 (% of yearly precipitations falling in summer)
So if the precipitation is split evenly at 50%, I get the exact same value as the actual f threshold.

The table could look like this but I need to add the base threshold


There are 25 different thresholds instead of 3. Yet I have no idea what kind of impact to expect.

[Azélor]

The result

vs posted earlier

The version posted earlier still had that problem were increased precipitations resulted in increased aridity. The new version does not but it has 25 thresholds instead of 3.
Now I just need to find how to make this work without creating a bunch of complicated things.

[Azélor]

Using this new model, I get 22 precipitation categories (like old model) and 26 temperature categories (less than previous

22x26= 528 +2 total combinations
down from 574 if I recall correctly



Also, I inverted the January and July precipitation for the southern hemisphere. The next version will not mix s and w climates there.

Now the actual methodology to find the thershold in

Adding the base threshold which depend on the temperature (it's based on the old s thershold)
to another threshold that is based on the precipitations
so the the s climate in the bottom left doesn't increase
it increase gradually going to the top right, reaching the exact same value w had previously.
f that are exactly on the diagonal, will have the same value as before.

So to find the actual threshold, all I have to do is to addition the 2 values.