Introductory Meteorology

Lesson 3. Global and Local Controllers of Temperature


a close-up view of a galileo thermometer
The Galileo thermometer measures temperature by detecting small changes in fluid density. The change in density causes glass floats to rise and sink within the column of liquid.

"What's the temperature going to be today?" Have you ever been asked that question? I have (occupational hazard, I guess). It's the second most popular weather question that I hear after, "Do you think it's going to rain today/tomorrow?

You might be tempted to think that this most basic of all meteorological variables would be easily determined by a few simple factors, but it isn't.  Temperature is affected by many processes at several different scales, both temporal and spatial. Some of these factors are well understood (and very predictable, like the seasons), others... not so much.

Many factors that affect the surface temperature must first themselves be understood and forecasted correctly. Clouds are one example. In Lesson 2, we learned that one of the factors for determining temperature on a local scale was the surface's energy "checking account." However, if you played with the interactive energy budget tool, you likely discovered that clouds have a great influence on surface temperature during both the day and night. Therefore, in order to properly predict surface temperatures, you must get the cloud prediction correct first. The same goes for wind direction and speed - which affects mixing (from Lesson 2) and advection (which we'll learn about in this lesson). Then there's precipitation, ground cover, urban versus rural effects... Yikes! Needless to say, simply predicting the temperature can be a real challenge, even for the professionals.

Well, rest assured, there is a lot to learn about temperature. You'd better just dive right in. Before you get started reading the text, make sure that you read (and print off) the learning objectives. They are very useful in helping you organize the information that you need to learn.