Weather
The hydrologic cycle plays a very important role in Earth's weather cycle! As noted earlier, nearly all of Earth's weather takes place in the Troposphere, which is where most of Earth's clouds and water vapor resides.
Weather vs. Climate
- Weather is the short-term, day-to-day condition of the atmosphere. Weather is a 'snapshot' of current atmospheric conditions.
- Weather differs from climate, which is the long-term average of weather conditions and extremes in a region, measured over decades.
Dr. Marshall Shepherd Links to an external site., an atmospheric scientist at the University of Georgia, says that "Weather is like your mood, climate is like your personality." Your mood can change a lot day-to-day, but your personality stays relatively stable over time. Similarly, weather is highly variable day to day; you can't necessarily say that climate change isn't happening just because one day is colder than average.
The scientific study of Earth's atmosphere - and, by extension, its weather and climate - is known as meteorology. Meteorologists study the physical characteristics and movements of the atmosphere, the complex linkages of atmospheric systems, and its related chemical, physical, and geologic processes.
Meteorologists also forecast weather - but unfortunately, this is often all people think meteorologists do! The next time you see a meteorologist on the news, keep in mind that they have gone through a lot of scientific training. (Other than Punxsutawney Phil Links to an external site., the groundhog who 'predicts' the weather every February 2 in Punxsutawney, Pennsylvania, U.S. He is not a trained meteorologist, sadly.)
Weather Systems
As you may recall from the Biosphere module, a system is is any set of ordered, interrelated components that are connected by flows of energy and matter. Systems can be open or closed, dynamic or steady-state.
Weather is no different. Weather is driven by complex, interlinked atmospheric systems. At the global scale, weather is driven by Earth's biosphere, atmosphere, hydrosphere, and lithosphere. At regional scales, weather is composed of systems like air masses and atmospheric circulations. Systems exist at the scale of a storm and even a single cloud.
Satellite images of the ten costliest Atlantic hurricane systems as of January 2025: Katrina (2005), Harvey (2017), Helene (2024), Ian (2022), Maria (2017), Milton (2024), Irma (2017), Ida (2021), Sandy (2012), and Ike (2008)
If systems are connected by flows of energy and matter, what energy and matter drive weather systems? You will find out on the next page!