Many years ago, when I first set out to write fantastic tales, I blundered through the intimidating task of designing a map by adding mountains, rivers, lakes, and deserts at random. Though I was aware that, in the northern hemisphere, the northern regions should be colder and the southern regions warmer on account of their nearness to the equator, this was the single solitary fact I could apply, and it left my creation stilted and strange. Even worse, my sense of different climates was formed from films, video games, and brief vacations, so that numerous impossibilities abounded - lush forests in eternal snowscapes, extensive deserts in temperate east coasts, or harsh winters on west coasts.
After making a personal study of climatology and geography over the past year, I can now offer some useful advice not only to those designing fantasy worlds, but also to those interested in determining what Robert Howard's Thurian or Hyborean lands might have looked like beyond simply invoking their counterparts in the modern age.
For reference, you may wish to check these threads:
Climatologists are often fond of elucidating the general principles of their science by sketching models of hypothetical climates, and few exercises could be so obviously useful to the fan of Howard's writing. Here is one such model based on the work of Arthur Strahler:
Note the brown areas of low rainfall extend slightly west of the actual continent, so that islands off the west coast of continents just at the border of the tropics will often experience low rainfall.
The reason deserts are found in the subtropics is that the air in the tropics is hottest of anywhere in the world; this hot air rises, cooling as it goes, forming clouds and rain along the equator. This dry air then moves poleward, bringing clear skies where it settles in the subtropics.
But deserts can also be formed by rain-shadows created by mountains in the temperate mid-latitudes near 45 degrees. As shown in the diagram, the Trade-winds close to the equator travel from the East, while winds in the temperate mid-latitudes travel from the West; if these winds are blocked by mountain ranges, then the air will be forced over these mountains in the same process, forming clouds and rain on the windward side of the mountains, leaving the far or leeward side with clear skies and dry ground.
The areas at the far north and south will also experience low precipitation, as the cold air tends to settle rather than rise over the poles; however, they are so cold that even a modest amount of precipitation, whether it falls as rain or snow, will not easily evaporate throughout the year. The so-called "arctic-desert" is therefore something of a misnomer; such frigid air is bone dry, but unable to hold moisture, leaving the areas wet even during times of thaw. The reverse is true near the equator, however, where even areas marked as "humid" in the diagram will experience seasonal droughts, as the sweltering tropical heat evaporates great quantities of water every day.
To understand the differences between eastern and western areas it is necessary to look not only at prevailing winds but also ocean gyres, or cycling currents which bring warm water to east coasts and cool water to west coasts. The warmer waters readily evaporate and warm the air, bringing rain and sultry heat to subtropical east coasts, while the cool water of west coasts allows deserts to extend even to the ocean.
An clear example of this phenomenon is the continent of Australia: Centered along the boundary of the Tropic of Capricorn, Australia is notoriously arid, and desert extends to the cooler waters on the west coast. However, the east coast shows much more greenery from clouds formed over the warmer waters of the east coast.
Surrounding this desert band on every continent are semihumid regions - steppes, savannahs, and sclerophyllous forests. At the eastern edges of the desert, such as Cross Plains, Texas (where Robert Howard grew up), rainfall is meager and sporadic across the seasons. But directly north and south of the deserts, precipitation follows highly seasonal patterns, which I will discuss in the next post.
Although it may seem reasonable to associate climate directly with geography, climate is driven by the sun, and the sun's relative position shifts throughout the year. This means that the hottest areas, where rising air brings rain, will move northward when the northern hemisphere is experiencing summer. But if so, then so, too, will the desert bands flanking the rain belts. Likewise in winter the rainy strip at the equator will move southward, and so, too, will the desert bands:
Moisture (blue) and aridity (white) shifting throughout the year; from Wikipedia
Climate by itself is not particularly useful for either authors or for fans of Robert Howard's work. It is rather the way in which the climate of an area expresses itself in the vegetation of an area that makes climate interesting. Although there are many subtle climactic phenomena we could discuss, I will move past all of these to focus on vegetation.
Trees and other vegetation thrive on two factors:
Typical forests require at least four months with average temperatures above 50 degrees F; with shorter growing seasons than this, most deciduous trees cannot survive, as it takes some time to regrow leaves lost to winter. Moving further into the cold, conifers and other hardy species such as birch trees become the only visible trees. Once we reach the point where even the warmest monthly temperature is below 50 F, no trees of any kind can grow, leaving moss and lichen in the few months without snow. Eventually, once no month's average temperature ever rises above freezing, no vegetation of any kind can be found.
Regarding moisture, the amount of rainfall trees require varies with numerous factors. But speaking very roughly, thriving forests require half the yearly average temperature in inches of rain. With less rain, trees thin out, leaning towards scrub and grass, until the grass gives way to sand and cacti, and ultimately, in the very driest regions, even the cacti cannot grow. However, lush growth can still be found near rivers flowing down from mountains which sweep the air upwards to form clouds and rain, or, surrounding oases where the terrain drops below the water table and groundwater becomes available for plants.
Putting everything together, any flat continent we find stretching from the equator to the arctic circle will look something like this:
In my next post, I'll conclude by looking at what these places are like, and discussing how you can tailor a fantasy world to your liking using coastlines and mountain ranges.
The overall feel of the locations above can be briefly described in this way:
Sweltering Jungles: Seasons run together with the only rhythms created by morning mist, sweltering afternoon sunbeams, and cool nights redolent with the tropical scents. Yet even these cycles are broken by showers as well as torrential downpours of a violence virtually unknown elsewhere in the world. Under these conditions, both a thick canopy as well as a lush understory teem with life, though when jungles are cut down or destroyed by cataclysms the soil is rapidly leeched of nutrients by the heavy rain. Travelers from afar will find the humidity creates a feeling of cloying closeness to the air, sharpening scents and subtle temperature fluctuations against the skin.
Hot, Winter Dry: These areas experience the weather of a jungle during the hotter portion of the year, with desert dryness during the cooler, low-sun period. Vast tracks of open grassland interspersed with tropical groves burst into lush greenery and flowers during the summer, which give way to yellow dryness during the winter. Where forests grow in these regions, the understory is either sparse or absent, but near water sources these areas can support jungles that remain verdant throughout the year.
Desert: In the absence of water, bare sand dominates the landscape, though cactus, scrub, and tumbleweed may thrive, particularly in the gullies where rain collects after a rare storm. The sun rules a cloudless sky, and afternoon temperatures soar; Mecca's daytime July high is a baking 110F on the average, but at night can drop to an average low of 66F in January - far from the freezing temperatures sometimes assumed to prevail by night, but cool in the dry air nevertheless. In the absence of vegetation, winds tear across the landscape; according to climatologist Glenn Trewartha: "In the desert the wind is almost the only element of life and movement in the domain of death... A journey in the desert is a continuous strife against the wind charged with sand." Sandstorms are rare, but when they strike, dust can cloud the air so thickly that men forced to breathe it sicken and die. As harsh as the desert may be, near oases and rivers numerous empires have arisen, and life sometimes finds surprising ways to survive - such as in coastal deserts, where fog provides enough moisture to sustain life of a peculiar and unsavory kind.
Warm, Summer Dry: These regions are a bridge between the deserts and temperate northwestern forests. Temperatures can be hot during the bone-dry summer, but seasonal extremes are low, particularly near the coast; San Diego's highest average high is a mere 76F (in August), while its coldest average low is 48F (in December). There are thus only three real seasons here: an early spring where green spreads explosively across the landscape, dusting the surfaces with pollen; a bright, cloudless summer of yellowed grass and scrub where every day is like the last, and a mild, wistful autumn where the westerlies bring rain to the parched soil. Agriculture thrives and fruit grows plentifully, though frequent droughts and wildfires remain a danger.
Subtropical Forest: A great variety of palms and conifers grow side by side in these regions, where abundant sun and rainfall provide good growing conditions year-round. As a general rule, the closer to the west coast and to the equator, the less seasonal fluctuation exists in temperature; the further towards the poles and deeper into continental interiors, the stronger the seasons. Thus, although the humid subtropical regions of South America or Oceania may have the same mild temperatures as the Summer Dry west coasts, much greater extremes can be found in the Southern United States or China, where brief snows blanket the countryside in winter, but summers can be crushingly hot; Guanghzhou averages only 10F on January nights, but with a sultry July high of 91F undiminished by the dryness of summer further west. In the southern hemisphere, however, the mild temperatures support delicate tropical growth.
Temperate Forest: Here we have the gloomy green hills and forests called to mind at once by Conan's Cimmerria and Solomon Kane's England. Though some locations, such as Seattle, Washington experience the sunshine of a summer dry locale, or others, like Hobart, Tasmania, are dryer and sunny throughout the year, these Temperate Forests are defined by the ocean breezes brought in by the Westerlies. Their temperatures are quite mild, with cool, pleasant summers and occasional winter snowfall that rarely survives a week. Though poisonous serpents and deadly spiders do lurk among the dripping boughs, the cool temperatures year-round make these the realms of wolves and deer which browse among the mossy standing-stones of bygone ages.
Continental Forest: Seen in our own Earth only in the large continents of the northern hemisphere, these regions are found far away from the western seas which moderate the winds from which their weather arises. The mild Westerlies passing through the Temperate Forests gradually lose their clouds, and, warmed by summer sun and cooled by winter nights until great seasonal extremes arise; though H.P. Lovecraft's beloved Providence has a latitude fully ten degrees south of London, the summer high in Providence is nine degrees hotter (83F), while the winter low is 8 degrees cooler (-6F). Great pine forests rise dark and forbidding against the sky, prowled by bears and moose. But poisonous snakes and spiders are unknown, for here no creature can survive except that which is prepared to outlast the winter. Not only are the seasons but the fluctuations in weather extreme; in few places on the earth can such pronounced cold spells, heat waves, or snow showers descend without warning. Indeed, snow blankets the earth for months at a time, so that continental locations such as Petersburg, Russia are famous across the world for their grim winters.
Harsh Winter Pine Forest: Better known as Boreal, these are the borderlands between the polar realms of endless day and night where no trees grow, and the populous realms to the south. It is absolutely wrong to imagine that the cold dominates these lands, for if that were the case than nothing could ever grow. Indeed, in summer the sun scarcely sets, flowers burst from every branch, vegetables grow huge and bright, and swarms of mosquitoes drone across the twilight. Yet summer does not last, and after a brief and early autumn, the cold sets in. Here cold takes on new meaning, deeper than mere winter, as temperatures regularly fall below -40 degrees. There, when the sun shines for only a handful of minutes a day, when the choking cold air cannot hold water, and electricity sparks across fabric, survival depends upon fuel provided by the thick pine forests which cover the landscape. Yet so cold does the winter air become that fingers freeze inside gloves, the iron ax becomes hard and brittle, and wet wood hardens until it is too strong to cut. Many a helpless wanderer, lost or hurt by a fall, has watched the aurora borealis streak across the lonely sky in the final moments before his frosty breath fell still.
Tundra: Now we have reached the very edge of habitable realms, where the summer sun spins around the horizon without setting, its rays too oblique to provide sufficient temperatures for trees to grow for fuel or construction, forcing tribesmen to construct their bows out of antlers or driftwood. Food is found by cutting holes through the ice for fishing, and in the brief summer months, foraged from the brush and moss that grows along the ground. Permafrost prevents the soil from draining, rendering the summer countryside a sodden marsh, and mud heaves up from the earth in autumn as the soil begins to freeze. Snowfall is rare and powdery, but water never leaves the climate, for it is too cold for evaporation.
Polar Wasteland: The same conditions prevailing in the Tundra winter are seen here throughout the year. Temperatures may be no colder than the pine forests during winter, but in the South Pole they average below -70 for half the year. The polar bears and penguins there survive by feeding off of fish from the surrounding oceans; in the interiors survival is virtually impossible.
So what can be made of all this?
Firstly, considering the climate of Hyboria, we have only rough maps provided by Howard and his contemporaries. Some more assertively colored maps have been made in recent days, but these are not always reasonable. Consider this map:
The extensive dry regions near the Vilayet Sea can be explained by the mountain ranges to the west, which force the rain to fall on the western lands. Hyrkania seems unusually dry, as we should expect the Westerlies to pull water from the Vilayet to the lands eastward. The Loulau Plateu of Pathenia begins to become quite strange, a highland surrounded on all sides by mountains and yet dry, only verging on snow. Most odd, however, is the climate of Vanaheim - modern day Norway, with its long coast, has extremely mild winters. Asgard's climate could very well be harsh, with its western mountains blocking the moderating influence of the ocean, but Vanaheim should more plausibly be a cool green expanse like the Pictish wilderness, receiving ample snowfall in winter without being anything like the harsh tundra depicted.
Finally, I'd like to conclude with some advice on designing maps for yourself. Although the pattern seen here may appear unforgiving to an aspiring author at first glance, it is possible to build strange and exotic maps through careful placement of highlands and rivers. Rivers should generally have their source in a mountain range, and these rivers can cut through otherwise inhospitable deserts, creating the context for a bustling, stone-walled city. Rivers even in greener lands provide reliable trade routes and water through dry spells, and can serve as natural boundaries between states. And highland areas can reduce temperatures wherever a cold climate is desired in the midst of a tropical or subtropical locale.
But even more, mountain ranges can divert winds. Commonly they will push winds upward, creating wet, rainy areas on the windward side, and drying the landscape to the leeward side. This is what we see in the northwestern United States, where the coasts receive extremely high rainfalls, but only a short distance to the east, the land in southern Ohio is quite arid. Additionally, large mountain ranges can divert winds north or south to provide radical changes to the weather nearby. Even a small change in rainfall can transform a small area within a desert into a lush paradise, and a slight deflection of winter winds could create a mild climate at otherwise high latitudes. By carefully inserting mountain ranges, it is possible to separate territories, provide sources for rivers, and mold the climate of your worlds to your liking.
Last Edit: Aug 14, 2019 10:53:38 GMT -5 by sorcerer: Confusing wording
This subject seized me with the force of a complete obsession, until I had rooted out its mysteries in their entirety. There's a great deal more, but in terms of understanding how to make a sensible map, the rectangular graphic I created really gives you what you need.
Poles are cold and dry, but the snow won't evaporate.
High latitude interiors have extreme seasonal swings and pine forests.
Mid latitudes are green, with wind mostly from the west.
Subtropics are dry, but green near the east coast.
The tropics are hot year-round, and extremely rainy.
Mistakes to avoid:
No forests in deserts, except near rivers or oases,
No trees of any kind in areas without at least a short summer,
No deserts touching east coasts, and
No harsh pine forests or icy wastelands touching west coasts.
Strategies to mold climates to your liking:
Mountain ranges in the mid latitudes can create dry areas to the east of them, and
Rivers and oases can create lush greenery in the desert.