Map assignment

LECTURE 10: CLIMATE REGIONS

Patterns of climate are important for geographers to examine. For our definitions, climate is the annual pattern of temperature and precipitation. In other words, weather on an annual basis. Climatic classifications are based upon the temperature and precipitation levels which exist in predictable patterns across the earth's surface. For example, an Af (Tropical Rainforest) climate is located along the equator (see page 14-15 atlas- 21st edition).

As noted on the climate map in the Goode’s World Atlas (p. 14-15), the letter A identifies a climate whose temperatures are above 64.4 degrees F throughout the year. The small letter f identifies a climate who receives precipitation on a daily basis, and is constantly moist. The climographs at the bottom of the atlas page is a good quick reference.

Notice the line which reflects annual temperature, and the bar graph represents rainfall for each month of the year. Singapore is definitely a prime example of a Tropical (Af) climate.

When we merge patterns of temperature and precipitation, recognizing from exam one and discussion of pressure patterns and the hydrologic cycle, we can see that climatic patterns are extremely predictable. What I want you to concentrate upon is the predictable type of weather that exists in each region.

Tropical climates: Af

Dominated by low pressure (ITCZ), areas in the tropics experience convectional precipitation. On a daily basis, warm air evaporates warm water, rising in the atmosphere, cooling by the average lapse rate and by around 4 pm, as the atmosphere begins to cool (LW radiation), precipitation occurs. These regions can receive more than 150 inches of rain a year, and experience a small fluctuation in temperature.

Use the climate graphs for each region to help you identify the precipitation pattern and temperature pattern for this climate type. Examine page 264 text (9th ed) or page 256 (10th ed), looking at ​Uaupes, Brazil​. It’s latitude is along the Equator, O degrees. Uaupes receives over 114.8 inches of precipitation a year, including over 10 inches a month. Its temperature is constant at 77 degrees F, as you see the ITCZ dominating this region yearlong. There will be daily evaporation, with clouds forming as the heat increases during the day. As large cumulus clouds form vertically all day, precipitation will occur after 4 pm each day, as the sun starts to set, and the temperature of the atmosphere cools.

Other examples demonstrate a clear relationship with high precipitation when the region is dominated by the ITCZ. See the next page​, Yangon, Myanmar’s climate graph ​clearly shows high precip (54.7 inches to 60.2 inches) in months where the low pressure of the ITCZ is overhead.

This can also occur in the midlatitudes. Climates with such rainfall are usually classified as Cfa or Cfb climates. Similarly, looking at ​Nagasaki, Japan (p. 268, 9th ed or p. 260, 10th ed)​, we can see high precipitation during the summer months (June and July receiving 11-12 inches of rain each month! Chengdu, China ​(page 269, 9th ed, or p. 261, 10th ed) and ​Bluefield, West Virginia ​(page 270, 9th ed or page 262, 10th ed) also show increased precipitation during their summers. Recall this is a great example of absolute humidity---warmer

air can hold more water, creating more precipitation during summer months, especially in regions with warm currents.

Subtropical climates: BS/BW

Areas between 20 and 40 degrees in latitude which are dominated by the subtropical highs. These are

desert regions, due to the limited amount of humidity carried in relatively cool air (when compared to the tropics) and stable air masses. Aswan is a great example of the BW climate (W stems from the German word “wuste” which means desert). Desert climates receive less than 10 inches of rain per year. BS climates are considered semi-arid regions. These areas, such as the ​Central Valley, ​receive between 10-20 inches of rain per year. The zone of interface between A climates and BW climates is represented by the BS climate (see map). This area experiences a little more precipitation due to the meandering of the ITCZ. Frontal lifting dominates the type of precipitation in North American Steppe zones, such as the Great Basin. Yet, due to the inland location of these areas, little precipitation occurs (continentality).

Examine the climate graph for ​Ar Riyad, Saudi Arabia ​on page 280, 9th ed or page 271, 10th ed. Here you will see the temperature goes off the graph during the summer solstice, July and August. These areas have the highest recorded temperatures on Earth, as you can see July and August are well over 100 degrees F. Precipitation is less than 3.2 inches a year, and occurs during the cooler times of the year enabling condensation and precipitation (October through May). These are as are dominated by subtropical high pressures which limit any upward movement of air, and are continental, limiting water availability.

Midlatitude climates: Cs/Cf/Cw

(Mesothermal) Regions in the midlatitudes, between 40 to 60 degrees in latitude experience seasonal variations in temperature and precipitation, having a cool season, a warm season, and a dry season and wet season. Frontal lifting is the cause of precipitation in these areas, mostly stimulated by the jet stream (Cf climates along west coasts in the northern Hemisphere, and east coasts in southern hemisphere). Precipitation usually occurs in the winters in these locations, as low pressures dominate adjacent oceanic regions, and the land surface cools the atmosphere stimulating condensation and precipitation. Other Cs/Cw climates experience rainfall throughout the year and reflect the poleward movement of mT air masses causing summer rains (Florida, China) and are associated with large continental masses.

This is our climate region, so the images on page 271, 9th ed or page 262, 10th ed, should look familiar to you. Both ​San Francisco and Seville, Spain ​are dominated by Cs climates. In the photos you can see that these regions are natural grasslands. Both receive between approximately 10-20 inches of precipitation, mostly in the winter months as the atmosphere cools. Because these regions are 37 degrees N, we know that they are affected by frontal lifting. Air masses from the ocean moved over land by the jet stream. Our precipitation is associated with low pressure over the oceans (winter months), and we experience drought as the land warms up and low pressure moves over land. During the summer, high pressures sit on the ocean limiting evaporation (see page 18-19 atlas 21st edition).

Subpolar Climates: Dfa/Dfb ​(Microthermal)

Microthermal climates are similar to mesothermal climates as frontal lifting and polar fronts dominate their precipitation patterns. Yet, they experience cooler climates throughout the year. This may be due to the high albedo rates which snow covered landscapes create, as well as the limited amount of solar

radiation they receive due to the angle of incidence and circle of illumination (Siberia and Northern Canada). Low pressure systems they may experience are much cooler than midlatitude regions, which limits the amount of moisture the air can carry.

Examine the climate graph for ​Churchill, Canada ​and ​Verkhoyansk, Russia ​on page 275, 9th ed or page 267, 10th ed. Here you can see that most months fall below 32 degrees F. Precipitation is associated with warm temperature months (warm air holds more water), as the temperature only rises above freezing from May to October.

Polar Climates: ET/EF ​Polar climates are cold deserts. They receive less than 10 inches of precipitation each year, and their warmest months are below 50 degrees F. ET climates have a warm season, experiencing temperatures between 32 degrees F and 50 degrees F (Northern Canada, the rim of Greenland), while the temperature in EF climate remains below 32 degrees F year round (Iceland, Antarctica). We tend to have alot of misperceptions concerning polar climates. Most Americans have the perception of regions dominated by heavy precipitation. I think this stems from all of our visions of Santa Claus and the North Pole. But these areas are deserts, they may be snow covered throughout the year, due to high albedo rates and temperatures below freezing. See map inset on page 276, 9th ed or page 268, 10th ed for specific locations.

Overall, climate patterns reflect a latitudinal zonation. Similar to temperature regions from the first exam, we find that temperatures fall as we move poleward. Precipitation patterns also decrease as we move to the poles, due to the inability of cool air to hold much humidity (both patterns reflect pressure regions). Secondly, climates reflect changes in elevation, such as the Sierras and Atlas mountains in North Africa. This is due to orographic precipitation patterns causing rainshadows. And lastly, climate patterns reflect continentality, both in temperature variation and precipitation patterns. Along the west coasts of North America and Europe we see frontal lifting causing precipitation (Cs climates) and as these air masses are pulled across the continent by the Jet Stream, the amount of precipitation they offer is reduced. In North America, the Sierras, Cascades and the Rockies wring out moisture much more rapidly than in Europe (having no great mountain barriers running North/South).