Part B: Regional Climate Drivers
Source: Prism Climate Group
When you look at a weather map, or listen to the weather report on the news, you probably wonder: What are the forces that control our daily, weekly, or monthly weather patterns? Weather forecasters use their understanding of these forces to predict the upcoming weather events, and with a little practice, so can you.
Over time these weather patterns become the averages that we know as climate. On the map to the right you can see the average annual precipitation patterns for the past 30 years in the United States. Areas colored blue receive more rainfall on average than areas colored orange or reddish brown. Can you predict why some areas might receive more rainfall than others?
In addition to the global circulation patterns that you reviewed in the first part of this lab, six continental- and regional-scale forces work together to control weather and climate in your part of the country. These forces, called "Synoptic-scale drivers," each contribute to the weather that we experience on any given day, week, or month. The region of their influence can be several hundreds to thousands of kilometers wide covering large sections of the continents. They occur on a timescale of days to weeks. Think of these climate drivers as the ones that you see on your local weather forecast maps. The six major regional weather drivers are listed below.
- Air masses
- Pressure systems
- Wind patterns
- Ocean surface currents
- Mountain ranges and topography
What are the predominant forces that are controlling your regional weather today, and ultimately your long-term climate?
As you work through the weather drivers described below, refer to your local region for each. Some questions to ask yourself: Do you live near a coast, or are you inland? Are you upwind or downwind of a mountainous region? And which type of air mass is over your region most often? Use the map (linked below) to help you record information as you work through these six drivers. Build a list of the drivers influencing your regional weather this week; number the list in order of size of influence (with 1 being the most influential). You will use this list, your maps, and a chart in a discussion of regional weather climate at the end of the activity.
Begin your study of the climate in the United States by downloading and analyzing maps of United States: Climate from Education Place.
- Click the link to access the United States: Climate map. (Note: your teacher may have already provided you with a copy of this map, in which case you do not need a second one.)
- Locate your state or region on the map.
- Record the average temperature and precipitation of your home state, notice how it compares to other states.
- Use the map of the USA: Average Precipitation and Temperature to record your notes and observations while completing this lab. Continue to use the organizing chart and World Climate map from Lab 3A as well.
Air masses are slow moving and relatively stable; they influence weather on a time scale of several days to a few weeks. As they move to a new region, they gradually are transformed by the characteristics of the new region. For example, an air mass that moves from the polar regions southward will gradually warm and lose its "punch."
- First, watch this short video to get a better understanding of air masses. Air Masses by Dan Guthrie
- Learn about the air mass classification scheme. The classification system is relatively simple: each air mass is represented by a two-letter classification scheme based on its moisture and temperature characteristics. This code tells its place of origin and type. The first letter in lowercase m (maritime) or c (continental) describes its moisture content. The second letter in uppercase E (Equatorial), T (Tropical), P (Polar), or A (Arctic) provides information about its temperature.
- Next, check your understanding of these symbols, and learn more about the characteristic of air masses with the following air mass characteristics table.