In this guide we will be attempting to apply realistic climates to a map of our world, ending up with something like this, here each colour denotes a different climate. It won’t be 100% scientifically accurate but for the purposes of worldbuilding its close enough.

The primary resources involved in writing this are Geoff’s Climate Cookbook and Emma Lindhagen’s Ocean Currents Tutorial. This guide is a walk-through of both of these tutorials combined. I encourage you to check out these great resources for more information.

Use a program such as Photoshop or GIMP and do every step on a different layer as you will want to toggle visibility regularly throughout this process.

In The Beginning

We will need a map depicting our landmasses and mountains as our starting point.

Great Ocean Conveyor Belt

The first thing we need to work out is the location of our Great Ocean Conveyor Belt. This is the constantly moving circuit of system of water which flows around the planet. The exact reasons for the belt’s path are complex and so as long as you follow the basic rules you can place it where you want in your world and it can still be geologically correct within your world.

The GOCB carries cold water from the poles towards the equator , and warm water from the equator towards the pole

water from the poles , and water from the equator Geoff’s Climate Cookbook (depicted below) states that in the northern hemisphere that warm currents flow on the west of continents and cold, on the east

Our map is only for a section of the world so only part of the Great Ocean Conveyor Belt is depicted. When applied to our world, we get the following.

Surface Currents

The belt determines where our surface ocean currents flow from.

Currents north of the equator will turn clockwise.

Currents south of the equator will turn counterclockwise

Currents will change course when they run into land

Cold currents may overlap the cold GOCB (because it is deep-sea), but not the warm GOCB (as it flows nearer the surface)

Currents may change temperature as they near the equator/poles

Applied to our map we get this. You might notice we have some currents flowing anti-clockwise as a result of being deflected off landmasses.

High and Low Pressure

Next you want to work out your areas of high and low pressure.

In summer (left) , the cooling of the ocean causes high pressure , with low pressure areas over the pressure .

, the cooling of the causes , with areas over the . In winter (right), the cooling of the ground causes high pressure, with low pressure areas over the ocean.

Winds

Prevailing winds flow clockwise out of high pressure zones and anti-clockwise into low pressure zones.

Summer

Winter

Precipitation

This is where things begin to take shape. Remember here precipitation includes snow, so don’t get stumped if you have high precipitation in the regions you were expecting to be snowy wastelands.

Paint on two colours, representing high (darker colour) and low precipitation (high colour). These are relative terms and will be made more specific to the climate later on.

Mountains

First look to your mountains and the surrounding winds.

Mark high precipitation where the winds blow onto the mountains

precipitation where the Mark low precipitation in the rain shadow of the mountains

In summer, our map will look like this.

Ocean Currents

Warm currents will result in high precipitation

currents will result in precipitation Cold currents will result in low precipitation

Our summer map now looks like this

Winds

Onshore winds cause high precipitation

winds cause precipitation Offshore and parallel winds cause low precipitation

You might already have your coastlines accounted for from previous steps, so when applying this effect, you might be marking zones more inland than your currents. Don’t overlap your precipitation markings, apply next to them. After this step we will only have the interiors of our biggest landmasses still to define.

Our map now looks like this.

Interiors

There may not be loads of land left to cover, but interiors on our larger landmasses might still need looking at.

Mark extreme interiors as low precipitation

Near the equator mark low precipitation

the equator mark precipitation Away from the equator, mark high precipitation

from the equator, mark precipitation Western interiors are more likely to have high precipitation

Our Precipitation Maps

Once we have done this for both summer and winter, we have the following.

Latitude Guide

In order to work out what our climates are, we need to divide the map into equal sized horizontal strips based on degrees of latitude . For the northern hemisphere, make 10 strips, with each line up from the equator denoting 10 degrees. I decided to finish my map at 70 degrees north, to leave the arctic region an unknown area.

To do in GIMP,

Go Image -> Configure Grid

Set Width to something wider than your image, so its not cluttered

Divide the height of your image in pixels by how many strips you want

Set Height to the result

View -> Show Grid

You should also have a general idea of how a height map of your world would look. I am generally assuming there are hills around the mountains and flattens out towards the coast. You can make this up as you go along.

Discovering Your Climates

Toggle between your winter and summer precipitation layers to see the precipitation for each area.

between your to see the precipitation for each area. Compare the latitude

the Find the corresponding climate

Use a colour code to denote the climate

For example, once you know a strip of land is wet in summer and dry in winter, compare the latitude to the table and find the corresponding wet summer and dry winter climate.

Use the following table to figure out your climates. There is a simplified table further down.

Temperature Precipitation Location Name Summer Winter Summer Winter latitude in degrees Tropical rainforest Hot Hot Wet Wet 0-10 Tropical monsoon Hot Warm Very wet Short and dry 5-15; east and south-east coasts only Savannah Hot Warm Wet Long and dry 5-15 Hot desert Very hot Warm Dry Dry 10-30, especially on west coasts with cold currents Hot steppe Hot Warm Low to dry Low to dry 10-35; typically next to deserts Cold desert Hot Cold Dry Dry Interiors, rain shadow Cold steppe Warm Cold Low to dry Low to dry Interiors, rain shadow Maritime east coast Hot Warm to mild Wet Moderate 20-40; east coasts only Maritime west coast Warm to mild Cool to cold Wet Wet 40-60; west coasts only Mediterranean Hot Mild Dry Moderate 30-45, west coasts only Temperate monsoon Hot Mild to cold Wet Dry 20-40; east coasts only Laurentian Warm to mild Cold Moderate Low 40-60; not on west coasts Subarctic Mild to cold Very cold Moderate Very low 60-80; not on west coasts Manchurian Warm to mild Cold Moderate Dry 40-50; east coasts only Subarctic east Mild to cold Very cold Moderate Dry 45-70; east coasts only Tundra Cold Very cold Low Dry 60-80 Icecap Very cold Very cold Low Dry 75+

Simplified Table

If you are like me and find this table is a bit much. Consider using this simplified table below.

Temperature Precipitation Location Name Summer Winter Summer Winter Desert Hot Hot Dry (Low) Dry (Low) 0 – 30 Semi- Arid Desert Hot Hot Wet (High) Dry (Low) 0 – 15 Surrounds Desert Tropical Hot Hot Wet (High) Wet (High) 0-20 Savannah Hot Warm Wet (High) Long and Dry (Low) 15 – 30 Between Tropical and semi-Desert Steppe Warm Cold Low Dry (Low) 30 – 60 Temperate Grassland Warm to Mild Cold Moderate (High) Low (Low) 20 – 65 Temperate Forest Warm to Mild Cold Moderate (High) Low (Low) 20 – 65 Taiga Cold Very Cold Moderate (High) Dry (Low) 50 – 70 Tundra Cold Very Cold Low Dry (Low) 60 – 80 Icecap Very Cold Very Cold Low Dry (Low) 75+

So far

Applying this to a work-in-progress map we get the following.

These colours represent the following:

Grey: Tundra

Teal: Taiga

Dull Green: Steppe

Light Green: Temperate Grassland

Dark Green: Temperate Forest

Off-Green: Tropical Rainforest

Yellow: Savannah

Orange: Semi-Arid Desert

Red: Desert

Elevation and Tidy Up

As the environment rises in elevation it cools. For elevated areas look again at the table and see what climates the corresponding amounts of precipitation would result in if you looked at the cold row rather than warm.

For example, if we elevate a template grassland we get tundra. If we elevate savanna, we get steppe.

Apply this around your mountains and anywhere else you want to show elevation.

Thin strips would show steep gradient whereas larger blobs of colour would show a more gradual change, or even a plateau.

It wouldn’t make sense to have desert next to water, so if you have this in your map, go along the coast to replace it with semi-arid desert.

Apply this to our map and we get this!

Artistic Direction

The nice thing about worldbuilding like this is your result feels accurate and therefore real. But you don’t have to follow the rules, its your world remember! If you want to change things around, by all means go ahead, but you’ve got a realistic starting point here to add your own creativity if you wish.

Conclusion

So hopefully you enjoyed this and found it useful. Next time, I’ll be explaining a new type of map, Resource Maps! This will help determine how our nations grow and how trade will develop, which will greatly impact the fortunes of your nations.

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