Land Surface Temperature
Vegetation & Land Surface Temperature
Temperature is one of the three major influences on global patterns of plant growth. Along with available sunlight and water, temperature determines whether the land will support dense forests, grassland, or nearly barren desert. Conversely, plants influence how hot the surface of the land can become. In areas where vegetation is dense, the land surface temperature never rises above 35 degrees Celsius. The hottest land surface temperatures on Earth are in plant-free desert landscapes.
On these maps, vegetation is pictured as a scale, or index, of greenness. Greenness is based on several factors: the number and type of plants, how leafy they are, and how healthy they are. In places where foliage is dense and plants are growing quickly, the index is high, represented in dark green. Regions where few plants grow have a low vegetation index, shown in tan. The index is based on measurements taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. Areas where the satellite did not collect data are gray.
Land surface temperature is a measurement of how hot the land is to the touch. It differs from air temperature (the temperature given in weather reports) because land heats and cools more quickly than air. This image depicts average monthly land surface temperature in degrees Celsius as measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. The warmest temperatures are pale yellow, while the coldest temperatures are dark blue. Moderate temperatures are depicted in shades of pink and purple. Regions where land surface temperature measurements were not possible are gray.
The most obvious pattern that the maps show is a global one: vegetation is abundant around the equator all year long, where temperatures are high. (Rainfall and sunlight are also abundant). Between the equator and the poles, the vegetation greenness rises and falls as the seasons change and temperatures warm and cool.
Regional patterns of temperature and vegetation also exist. For example, the land surface temperatures of southeastern Canada stay colder longer in the Northern Hemisphere spring than they do in Europe, even though they are at the same latitude. These differences in temperature mean that Europe “greens up” faster in the spring than southeastern Canada. Even during the height of summer, the warmer, high latitudes of Europe, such as Scandinavia, have more abundant vegetation than similar latitudes of eastern North America, which remain colder. As another example, the high-altitude Tibetan Plateau in central Asia is much colder (and drier) than eastern China at the same latitude, and vegetation is far less abundant there. On the other hand, Earth’s hottest places, such as the deserts of southwest Asia, have the least vegetation.