Climate help needed!

[Qwynegold]

I'm working with this map:
[IMG]On second thought, check the thumbnail at the bottom of the page instead, the page got too wide when I posted the full-size image.[/IMG]
I know it's full of mistakes and **** (like way too many hotspots), but it's like a practice map I'm making before I start working on a real conworld map. The next thing I need to work on is the climate. On this map, the water currents are already marked with arrows (blue for cold water, red for hot), but I think I need to mark the wind pattersn, like in these maps:


I guess I need to mark the low and high pressure areas first, because the winds depend on them. But I have no idea how to go about doing that. I mean, where should these different pressure areas be? Can anyone help? The planet is just slightly smaller than Earth, I don't remember the exact size and can't seem to find my notes, but it's like 39,980 km across the Equator or something. It's similar to Earth in all other aspects as well. Um, I don't know what else you need to know about the cosmology in order to answer my questions, but just ask me whatever you need to know. Though, I haven't really decided much about the planet.

I tried searching for "climate" on this site, but couldn't find anything relevant. I also looked through a few pages of the tutorials section, but it was just too much to look through everything.

[Jeff_Wilson63]

On this map, the water currents are already marked with arrows (blue for cold water, red for hot), but I think I need to mark the wind pattersn, like in these maps:

OK. First on currents.

On a spherical rotating world ocean currents are driven by the world's rotation. The explanation for this gets rather technical, dealing with inertia and relative rotations, but the effect the easy: All else being equal, currents flow clockwise in the northern hemisphere and counterclockwise in the southern hemisphere. An ocean straddling the equator will have a major current at the equator heading from east to west and currents on its north and south boundaries heading from west to east.

Of course "all else being equal" is rarely the case. To accurately map currents you should begin with the largest water distance along a line of latitude. Keep in mind that once all that water starts flowing it has to go somewhere and you can map the lines of flow.

Your existing map looks pretty good. I might change some things, but currents can do some really strange things. (Particularly, that eastern flow above your western equatorial continent doesn't look right to me. I'd think the equatorial current to the west would tend to "pull" water out of that sea.)

[Jeff_Wilson63]

In dealing with wind patterns as a mapper or world creator, you first have to realize that the way meteorologists look at the world isn't helpful. Maps intended to convey information to a meteorologist need to be reinterpreted to be useful to a world creator.

As with ocean currents, air on a spherical rotating world tends to flow clockwise in the northern hemisphere and counter-clockwise in the southern hemisphere. Those patterns are disrupted as water evaporates and condenses. On a world scale, evaporation encourages evaporation and condensation encourages condensation. An area of evaporation brings air in along the surface then pushes it up and out high in the atmosphere (a high pressure zone). An area of condensation pulls air in from high in the atmosphere and pulls it down and then out along the world's surface (a low pressure zone).

Now, while the flow of air high in the atmosphere holds fairly constant, the effects near the surface are subject to effects from the ground, particularly mountain ranges. (Individual mountains don't have much affect on their own.) Mountains won't block the flow of the air, but they will distort and slow it.

To place global wind / weather patterns, you first need to be sure of your ocean currents and mountains ranges. Once you are sure of those aspects, create 4 maps, one for each equinox and solstice. Start with the map representing summer in the hemisphere you make your make your home, and place your major areas of evaporation. These areas will center the winds which match the natural deosil movement of the air in that hemisphere. Having placed your major evaporation zones you can place your major condensation zones. Winds around these zones will flow widdershins (counterclockwise in the northern hemisphere, clockwise in the southern hemisphere). Repeat for your other maps in seasonal order.

I hope this (and the previous) helped. It's a very complicated subject, but I hope I supplied enough information to get you started.

[Qwynegold]

An ocean straddling the equator will have a major current at the equator heading from east to west and currents on its north and south boundaries heading from west to east.

On a map I have, it seems to be exactly the opposite in the Pacific Ocean.

I'll make some changes, at least to my currents on the northern polar sea, and then reply to the rest of the stuff...

Your existing map looks pretty good. I might change some things, but currents can do some really strange things. (Particularly, that eastern flow above your western equatorial continent doesn't look right to me. I'd think the equatorial current to the west would tend to "pull" water out of that sea.)

The two red arrows going from NE to SW that are between the two equtorial currents?

[Jeff_Wilson63]

Er, you've reversed directions. East is on your right looking at the map, west is on the left. It's even labeled that way on your map.

I have problems with directions myself, so I know how this can happen.

[Qwynegold]

Er, you've reversed directions. East is on your right looking at the map, west is on the left. It's even labeled that way on your map.

I have problems with directions myself, so I know how this can happen.

Wait, wait, wait, wait, what? Isn't it like this?:

(sorry about the crappy quality, my scanner doesn't work with this computer I'm using, so I just took a quick photo).

[Jeff_Wilson63]

Interesting. What book is that from?

Countercurrents exist everywhere. (There's actually a quite important one running directly east of the Gulf Stream.) However, from a climatological standpoint they're insignificant. Even if you plan to deal with sea travel or fishing economies, it's easier to just assume that countercurrents are just there than to indicate them on your map. That countercurrents exist doesn't change the main mass of the water flow.

Stuff like the northern Indian Ocean and the arctic currents are why you need to map your largest masses of water first.

[Qwynegold]

Interesting. What book is that from?

It's from a big-ass atlas called Geographica.

Countercurrents exist everywhere. (There's actually a quite important one running directly east of the Gulf Stream.) However, from a climatological standpoint they're insignificant. Even if you plan to deal with sea travel or fishing economies, it's easier to just assume that countercurrents are just there than to indicate them on your map. That countercurrents exist doesn't change the main mass of the water flow.

Stuff like the northern Indian Ocean and the arctic currents are why you need to map your largest masses of water first.

Oh, now I see. I didn't even know there was a difference between regular currents and counter-currents. So around the Equator, the important currents just go from east to west?

[Qwynegold]

OK, how does this look like? At some places it may look odd with red and blue arrows crossing, but I've been told that warm water floats on top of cold water, so it should be okay. And where the big island by the north pole is, a current is branched off, with one branch going north. This current goes under the packed ice (I read on Wikipedia that the ice cap on the North Pole is like at max 30 m thick or something like that, so the current should be able to cross under it). It makes almost a u-turn around the north pole (it's following the clockwise direction of rotation when doing that) and re-emerges near the right edge of the map.

[Jeff_Wilson63]

Oh, now I see. I didn't even know there was a difference between regular currents and counter-currents. So around the Equator, the important currents just go from east to west?

For purposes of general world mapping, yes. Now, if you were mapping sea travel lanes or fishing resources noting counter-currents would be a good idea. Certain counter-currents can also have a disproportionate affect on local weather, but that can only be discussed individually.

(A side note: I think the Pacific counter-current occurs on so many maps because of the number of Americans who have served on naval vessels in the Pacific. If you're in the middle the Pacific and want to head home, you want to locate that counter-current in order to make the best time. Thus it looms large in people's experience, even if it isn't particularly important on a global scale. I would expect it to be much reduced on Japanese maps.)

Your new map looks really good. The only place that looks odd to me is the sea north of your eastern equatorial continent. At first glance I would expect some circular motion there. Looking a bit more deeply, however, what you have is probably as good at anything else. I really don't have a clue how that would turn out in reality.