Hey Pixie, you're clearly a perfectionist in your own way My work consists a bit in scientific vulgarization, so, I find your work here very interesting and quite complete.
Thanks for the compliments but save them for the end of the thread or I may well leave it half done.
In the meanwhile, if anyone is (has) tried this technique so far, I would like to know how difficult it was to apply and if there is anything unclear, overlooked, forgotten... This would be really helpful.
WIP (sort of tutorial to be) : Climates, applying Geoff's Cookbook at detail (some)
I attempted to use your ocean currents tutorial on my world map and posted my attempt in the thread "Another attempt at a world map" here in the regional maps subforum.
I would link to it but i cant figure out how to do that using the tapatalk app, but when i get to my computer ill edit this and link it if i remember.
Last edited by Pixie; 05-25-2014 at 09:31 AM.
Step 6 (part one), factors influencing temperature
Back at this.. It took me a while to find a perfect system I could share (and it probably ain't perfect or that easy to follow, but I'm hopeful).
This is the first part of steps towards creating a mean-temperature map for the extreme months of July and January. Along with the wetness maps for these months, we will then be able to determine the most likely climate for each region.
Temperature has a lot of conflicting influences, so we aren't just adding layers like we did for rain. The technique is somewhat different. We first map where each kind of influence is a factor to take into account. Then we generate a temperature map as if the continent was flat and waterless. And then we start adapting it.
So, first thing is mapping what will factor in. Create separate layers for each of these influences:
- Maritime influence / July and January
- Continental influence
- Cold ocean currents / July and January
- Warm ocean currents / July and January
- High humidity / July and January
- Medium elevation
- High elevation
- Very high elevation
(Overall it's 12 layers).
We'll look at one at the time.
1. Maritime influence:
Select all your oceans, seas and reasonably sized lakes (magic wand tool is your friend here). Expand that selection a fair number of pixels. Now, make your layer with dominant winds visible (for the corresponding month) and adjust your selection. Prolong it inland where the winds blow onshore, make it shorter where winds blow away from the coast. Lastly, check your topography. Areas behind mountains don't get maritime influence, except if winds can blow around them.
Paint your resulting selection in solid white and hide the layer.
Repeat for the opposing month.
This is an example where I made the white layer 50% transparent so you can see how the wind affects it.
2. Continental influence.
Select your land masses with the magic wand. Contract the selection a fair bit (in my 1000 pixels tall map, I contracted about 50 px). Check your topography and extend this selection to all areas cut away from the seas/lakes/oceans by mountain ranges.
Again paint in solid white (we'll always do this) and leave it.
3. Warm and cold currents, July and January.
All these four layers are done in the same way. Make winds and currents visible (for the appropriate month). Make a wide selection covering the arrows with the currents. Extend the selection in the direction of prevailing winds. Again, since this a maritime influence, the selection cannot pass over mountains, so check the topography before painting in plain solid white.
Taking winds and currents into account results in something along the lines of this (shown here is the area influenced by warm currents in july).
4. High humidity
Use your rain patterns map. Make a selection encompassing all areas that are Very Wet or Wet. That's it, it's your high humidity zones, which you paint as before.
We will cover three different elevation levels. Medium elevation is the selection encompassing everything above 1000m (roughly), High elevation covers areas above 2000/2500 m and Very high elevation will be for stuff above 5000m. These are aproximate levels, just use your judgement depending on your own elevation map.
Showing here is the area considered medium elevation (about 1000m high or above). As you can see this is quite a "tall" continent, and that will surely influence climate a lot...
Now, the influences are mapped. We will do the baseline temperature map which accounts only for solar radiation. Solar radiation depends mostly on the angle between the sun rays and the surface. In July, the Sun is stronger in the northen tropical line at 23º (equals the tilt of Earth, if you are doing a different tilt, adjust this); and in January same happens at 23º S.
Here's how I got this drawn:
1. First I defined a set of colors for "Very Hot", "Hot", "Warm", "Mild", "Cold", "Very Cold" and "Extremely Cold".
2. Then I drew a small 2 px line, East-West, halfway between the tropical line and the equator using the Very Hot color.
3. Then I measured the height North Pole to South Pole, in pixels and divided that by eleven. This gave me the width of each of the areas. Then, starting with the line I had drawn, I just kept expanding the selection by the number of pixels needed.
The result was this baseline "radiative" map. Note that I didn't take into account the curving of the latitude lines in the map associated with the projection. I took this liberty because I am only using the center of the map. You may have to devise alternative ways to create the baseline temperature if your map has a different projection. The point is to have this "striped" effect, ranging from Cold to Very Hot and back to Extremely Cold.
The pole facing the sun will start at Cold, whilst the other one will be Extremely Cold. In this case, the map is for January, since it's Summer in the souther hemisphere (that's the pole facing the Sun).
Time to take a rest before the second half....
EDIT: some spelling and grammar corrected
Last edited by Pixie; 07-17-2014 at 07:44 PM.
Step 6 (part two), shaping a mean-temperature map
Now we start shaping those straight lines from the baseline map. Start by putting the baseline map under all the layers which map influences and make all those layers 60% visible (opacity).
We will deal with one influence at a time. They may curve the lines in either direction. As a general rule I make the influence curve a temperature boundary only half way to the next boundary. I hope you get what I mean with help from the ilustrated examples.
Right, so let's jump in. You can ignore topography, winds, rain, and what not. All it matters now is the temperature map and each of the influences. So, turn everything off, except the baseline radiation map and...
1. Maritime Influence
This is a milding influence, which means it turns areas closer to mild/warm temperatures. Which means, bend the boundaries in a way that turns some "Very Hot" area into "Hot" area and "Hot" into "Warm", and on the opposite side, make "Extremely Cold" into "Very Cold", and so forth until "Cold" turns to "Mild".
As you can see, I use a dummy/draft layer to write the new boundaries, then adjust the temperature map. You have some liberty adjusting those boundaries, just try to keep the same criteria throughout.
2. Continental Influence
This is an extremes influence, basically working in the opposite direction to maritime influence. "Hot" turns to "Very Hot", "Warm" to "Hot" on the other end, "Cold" gets "Very Cold" and so forth. Mild is not affected.
Again, re-shape those boundaries like before.
In this particular case, you can see how the interior of this equatorial continent gets hotter. The original straight lines are disappearing already...
3. Cold/Warm currents
These have cooling or warming effects, obviously. However, they cannot take areas into extreme temperatures. Thus, they never influence an area into "Very Hot" or "Very Cold" into "Extremely Cold".
This is now showing the mean july temperatures after cold and warm currents are factored in. In the left side of the map I created a pocked of "Hot" in the middle of "Warm" as that area was under the influence of a warming factor and less than halfway to the next boundary - this can be done with any influence.
4. High humidity
This is a no-extremes effect. Water "soaks up" a lot of heat energy preventing temperatures from rising sharply and it also releases that heat energy should temperatures really drop. It changes every area closer to "Hot", "Warm" or "Mild". Areas already in these temperature range are not changed.
Keep reshaping the map. In this case, all the areas under this influence get affected, it's not a case of bending the boundary "half-way".
5. Medium Elevation
Well, the higher, the colder, that's a basic rule of thumb. Every temperature range will drop one level colder. However, compute this obeying the "only halfway to next boundary" rule... medium elevation isn't that high.
6. High Elevation and Very High elevation
On the other hand, these influences will make the temperature drop no matter at what latitude. Any area under this influence gets colder. I suggest you work this out from cold areas to warmer areas - if you do the other way around you will end up messing up the work.
So this is the final result. After every factor is computed in, I zoomed in on the details that didn't look right (like spikes, right angles, etc) and adjusted them slightly to get a more "natural" result. Then I used the sea mask to delete the over-the-ocean-clutter and end up with a mean-temperatures map of the land only.
But this is it, as computed by the method I just detailed.
It's a very mild Winter for most of the land south of the equator apart from the highlands where it gets Very Cold even at the tropics, while the Summer on the north is Hot, but not extremely except in some pockets. In January, on the other hand, things are different, Summer is scorching inland south of the equator. The very tall plateau in the northern hemisphere, however, even if almost tropical, gets freezing temperatures.
So glad to see the tutorial growing.
I finally got the guts to try out after being done with tectonics but I've a silly question before starting. In one of the first posts you recommend using Hammer projection, but I see for example Akubra did his currents on equirectangular projection, which I prefer too. So does the projection affect the results significantly? I don't mind using Hammer though, if necessary, in fact I'll get a Hammer version of my map to have it ready just in case.
Last edited by groovey; 07-15-2014 at 05:53 AM.
No, the projection doesn't matter at all. All you need to do, whatever the projection, is follow the latitude lines.
Yes but the latitudes are curved with the Hammer projection so you'd also need to curve your temperature zone (but the impact is minor if you only intend to make this continent)
I would like to know if your using a particular climate classification for this? It would be good to know how hot is the ''Very Hot'' area.
As a side note, your continent is small to have any real continental influence unless I'm missing something. Maybe there is but it's very small as you said in point 4.
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