A temperature gradient is the rate of change in temperature with respect to distance. Temperature gradients are important in many fields including atmospheric science, oceanography, and engineering. The most common unit of measure for a temperature gradient is degrees Celsius per meter (°C/m).
The Earth’s surface has a generally uniform temperatures because the Sun warms it evenly. However, there are some areas where the Sun’s energy is absorbed more or less than others. These areas have higher or lower temperatures than the surrounding area, creating a temperature gradient. The atmosphere also has layers where the air gets colder as you go higher up. The lowest layer of the atmosphere, where we live, is called the troposphere. Above that is the stratosphere, and then finally the exosphere. Each layer has a different average temperature.
The oceans have complex circulation patterns that cause variable mixing of cold and warm water masses at different depths. This results in interesting three-dimensional structures in oceanic temperature gradients known as thermoclines and pycnoclines. At depth, below around 1000 meters, there is very little mixing between water layers so deep waters remain near 4°C year-round while surface waters can vary widely from month to month and place to place (-2 to 30°C). In between these two extremes lies the thermocline: a region of rapid change in water temperature with depth caused by strong mixing between upper and lower layers. Finally, near coastlines currents can bring deep water up to shallower depths resulting in regions of very high verticalGradients know as pycnoclines