Latitude refers to the distance of a location of a place on the earth surface from the equator; while altitude describes how high a place is located above the sea level. Latitude and altitude are two primary factors known to affect variations in temperature on the earth surface because of unequal heating of the earth’s atmosphere.
Variation in Altitude
For every 100-meter rise in altitude, temperature decreases by about 1 degree Celsius. Regions in high altitudes, such as mountainous places, experience low temperatures. The earth’s surface absorbs heat energy from the sun and when it warms up, the heat diffuses into the atmosphere, warms it and in turn transfers some of the heat to the upper layers of the atmosphere. Therefore the layers of atmosphere closest to the earth's surface receive the most heat compared to the high-altitude areas.
Although typically higher altitudes experience low temperatures, this may not always be true. At times, temperature decreases with altitude (what is referred to as lapse rate) in some layers of the atmosphere (such as the troposphere). This occurs during cold winter nights when the sky is clear and the air is dry so the heat from the earth's surface radiates and cools faster than atmospheric air. It then warms the low-lying atmospheric air that rises rapidly into the sky. Consequently, places located in high altitudes, such as mountainous regions, get to experience high temperatures. Usually, the average lapse rate in the troposphere is 2 degrees Celsius per 1,000 feet.
Angle of Incidence
Angle of incidence on the earth's surface depends on the region’s latitude (distance from the equator). It refers to the angle at which the sun's rays strike the earth's surface so that when the sun is positioned directly above the earth's surface at 90 degrees, the solar radiations strike the surface of the earth at right angles, making these regions experience high temperatures. However, if the sun is 45 degrees above the horizon, the solar radiations strike the earth's surface at an angle that spreads out rays over a larger surface area with less intensity, making these regions experience lower temperatures. Such regions are located further from the equator, therefore the further you go from the equator, the cooler it becomes. In essence, regions at the equator experience higher temperatures than those in the North and South poles.
Diurnal variation is the change in temperature from day to night and often depends on latitude and the earth’s rotation on its axis. Normally, the earth receives heat during the day by solar radiation and loses heat through terrestrial radiation at night. During the day the sun’s radiation heats the earth's surface, but the intensity would depend on the length of the day, as some days are shorter than others. Regions with longer days will experience more intense heat. In this case, during polar winter when the sun is below the horizon for 24 hours, no solar radiation is felt and these regions remain cold. Solar radiation intensity on the earth's surface would hence depend on the latitude, the sun’s altitude and the time of the year (season), ranging from no solar radiation during polar winter to maximum solar radiation of about 400 watts per square meters during summer.
- Aviation Weather: Temperature Variations
- Seasonal Variation and the Earth’s Heat Budget
- Earth-Sun Relationships and Insolation
- National Snow and Ice Data Center: Solar Radiation
- Missoula Fire Sciences Laboratory: Seasonal and Diurnal Variations in Air Temperature
- Encyclopedia Britannica: Temperature Inversion
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