CHAPTER 10

CLIMATOLOGY

MID-LATITUDE CLIMATES

The Mid-Latitude climates are divided into the mesothermal and microthermal climatic groups.

It is the degree of change that distinguishes one from another.

The mesothermal climates have long summers and mild winters that separate them from the microthermal climates that have shorter, cooler summers and longer, colder winters.

MESOTHERMAL CLIMATES

There are three distinct mesothermal climates. In all three, annual precipitation exceeds the annual potential evaporation.

• Mediterranean Climate

• Humid Subtropical Climate

• Marine West Coast

MEDITERRANEAN CLIMATE

The Mediterranean climate appears with remarkable regularity in the vicinity of 30° to 40° latitude along the west coasts of each landmass.

The alternative controls of subtropical high pressure in summer and westerly wind movement in winter cause this climate of warm, dry summers, mild, moist winters.

• Fog

HUMID SUBTROPICAL CLIMATES

The humid subtropical climate extends inland from continental east coasts between 20° to 40° North and South of the equator.

This climate is located at similar latitudes as the Mediterranean climates on the eastern side of continents.

Summers can be as hot and humid as the tropical areas.

MARINE WEST COAST CLIMATE

Proximity to the sea and prevailing onshore winds make the Marine West Coast climate one of the most temperate in the world.

Found between 40° and 65° and influenced by the westerlies, this climate receives ample precipitation throughout the year.

Unlike the Humid Subtropical Climate, the Marine West Coast Climate has mild to cool summers.

HUMID MICROTHERMAL (D) CLIMATES

The Humid Microthermal Climate Regions are found at high latitudes in the Northern Hemisphere between 35° and 75°N.

• No ocean modification.

They have cold winters and variable lengths of summer depending on latitude.

HUMID CONTINENTAL - HOT SUMMER (Dfa-Dwa)

This climate is found in large areas in North America, but in only limited areas of Europe and Asia. There are four distinct seasons.

• Precipitation decreases poleward and inland.

HUMID CONTINENTAL - MILD SUMMER (Dfb-Dwb)

This climate is found usually north of the Humid Continental – Hot Summer climate and generally is drier.

Winters are more severe and longer with greater amounts of snowfall.

HUMID CONTINENTAL - SUB-ARCTIC

The Sub-arctic Climate is the most extreme of the microthermal climates. It is not as extensive in North American as it is in Eurasia because:

· Eurasia is a larger landmass

· The large water surface of Hudson Bay provides a modifying marine influence.

This climate experiences short cool summers and long bitterly cold winters.

POLAR CLIMATES

There are two types of Polar climates:

Tundra (ET)

Warmest month between 32° to 50°F

Polar Ice Cap (EF)

No month above 32° F

HIGHLAND CLIMATES

Complexity is the hallmark of highland climate.

Every mountain range of significance is composed of a mosaic of climate that would be difficult to see on a small scale map.

EXPOSURE

Elevation is only one of several controls in Highland Climate; exposure is another. Exposure can have significant effects on the climate.

• Is the mountain facing the prevailing winds.

SLOPE ASPECT

Slope Aspect is the direction a mountain slope faces in respect to the sun’s rays.

• North – South

• East – West

HIGHLAND CLIMATES

Tree line is the line where trees no longer grow.

Snow line is where snow is on the ground all year-round.