Climates are affected by a variety of factors. Some of these have major effects over a large area, and others can have micro-effects in very limited areas.
Essentially the earth’s climates are driven by the sun’s radiation. When the sun is higher in the sky it generates more heat, so the places which have the sun more or less overhead for much of the year will generally have hot climates.
Land and sea areas behave differently in response to heating and cooling. Continents heat up relatively quickly, whereas sea areas take much more time to accumulate heat. The reverse is also true, and land areas cool much more rapidly than seas.
Areas of high and low atmospheric pressure generate winds which blow in fairly regular patterns around the world. As these winds blow they carry with them the conditions of areas over which they have passed. For example winds crossing large oceans will collect amounts of moisture, whereas those crossing continents will generally be dry as there is little or no moisture for them to collect.
The sea moves in currents, again generated by the sun’s heat and the earth’s rotation, and as some currents are relatively warm whereas others are relatively cool, these can have an affect on the climates of the land areas they pass, particularly if winds carry those temperature effects onto the coastal regions.
In regions of high altitudes, where the atmosphere is thinner, temperatures will be lower. This, in turn, will cause condensation within moist air and generate precipitation in high level areas.
There are many different climatic zones on the earth, and they are all caused by a combination of some or all of the above factors. For examples it is easiest to begin at the equator. Here, where the sun is high in the sky every day, temperatures are high and these temperatures generate rapidly rising currents of air which can cause heavy rain, normally during the late afternoon. These are the main features of the Equatorial climate.
Slightly north and south of the equator, where the earth’s orbit and tilt cause the sun to appear to rise and fall in the sky during the year, there are hotter seasons when the sun is higher, and less hot seasons when it is lower. This also leads to a seasonal rain pattern as the rain will fall only during the hottest periods.
Moving further away from the equator there is therefore a series of climates which follow a largely latitudinal pattern – nearer the equator they are hotter, and further away they are cooler. However, other factors become more significant as latitudes become higher.
Coastal regions, with a wind which normally blows from the sea, will have a moist climate which will be warm or cool depending on the ambient temperature of the sea area off the coast. Regions in the centre of continents, well away from any maritime influence, will have dry climates, often with extremes of temperatures – the land heating quickly in summer and cooling quickly in winter. By contrast the coastal areas, moderated by the seas which heat and cool more slowly, will have more equable climates, with fewer extremes.
There are one or two special climate cases, each of which have unusual and distinct patterns. One of these is the monsoon climate, affecting south and south east Asia and northern Australia. This is essentially tropical, but the word monsoon means ‘changing winds’ and it is the winds which cause the most dramatic effects. When the winds blow offshore, that is to say from the land out to sea, land areas are dry. By contrast, when the winds blow onshore, they bring torrential rain. As the hottest season approaches, before the rains fall, the climate can cause unbearable periods of high humidity and incredible heat – a time called by Europeans in India ‘the monsoon madness season’.
So, in essence, whereas the main climates of the world form a latitudinal pattern, there are major differences relating to distance from the sea, direction of prevailing wind, the effect of ocean currents and the altitude of land areas. The main climate headings and descriptions relate to latitudes – equatorial and other tropical climates in lower latitudes, warm temperate climates as we move further away from the equator, cool temperature climates even further away and cold climates near to the poles. However, there are more local variations relating to coastal or inland areas, mountain ranges and other features of land, sea or local wind conditions.
