Climate

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Climate variation factors

Climate

The main difference between weather and climate is a function of time. Where weather is defined by the meteorological variables (temperature, humidity, atmospheric pressure etc.) at a given point and time and changing in minutes or a matter of hours, climate describes the prevailing or average weather conditions of a region over a much longer period.

Climate is affected by various factors such as latitude, terrain, topography, altitude and nearby large water bodies. For example, a tall mountain range my block air currents carrying rain clouds, causing a much drier climate on the opposite side of the range or warm versus cold oceanic currents affecting their coastlines differently.

Classifying climates can approached using different classification schemes according to the average and typical ranges of of different variable, most commonly precipitation and average temperatures (e.g. an arid climate can be defined by very low annual rainfall and very high average temperatures).

Climate of Virginia

The climate of Virginia, a state on the east coast of the United States, is considered mild compared to other areas of the United States. Most of Virginia east of the Blue Ridge Mountains, the southern part of the Shenandoah Valley, and the Roanoke Valley, has a humid subtropical climate, typical of the American South. In the mountainous areas west of the Blue Ridge, the climate becomes humid continental and maritime temperate. Severe weather, in the form of tornadoes, tropical cyclones, and winter storms, impacts the state on a regular basis. Central Virginia received significant snowfall of 20 inches in December 2009.

A lot of variation occurs because of the state's significant relief. Elevations in Virginia vary from sea level to Mount Rogers at 5,729 ft (1,746 m) above sea level, with major gradations occurring at the edges of the Atlantic Ocean, the end of the Piedmont, and the Blue Ridge and Allegheny chains of the Appalachian Mountains. The moderating influence of the ocean from the east, powered by the Gulf Stream, also creates the potential for hurricanes near the mouth of Chesapeake Bay. Cold air masses arrive over the mountains, especially in winter, which can lead to significant snowfalls when coastal storms known as nor'easters move up the Atlantic coast. Much of central and southern Virginia however has not had over one foot of snow in a single storm since the Blizzard of February 5, 2010. The interaction of these elements with the state's topography create micro-climates in the Shenandoah Valley, the mountainous southwest, and the coastal plains that are slightly but noticeably distinct from each other The climate in the Appalachian region is temperate and humid, and it is approximately 10 degrees cooler than the surrounding lower elevations. The average high temperature in the summer is around the mid-80 degrees Fahrenheit and it can even go as high as the 90s, while the lows in winter can drop into the 20s.

Climate of South Africa

South Africa has a wide variety of climatic conditions. This variety is considerably greater than most countries on the continent, ranging from Mediterranean in the southwest to subtropical in the northeast and east. A desert climate prevails in a large region of the northwest corner while most of the interior of the country is temperate.

South Africa's climate and the differences to the climates of countries at similar latitudes (Australia), stems from a number of factors such as South Africa’s position between two oceans (the Atlantic and Indian oceans) as well as the topography as much of the country's interior is on a plateau at a significantly higher altitudes.

Climate Change

Climate change (often used interchangeably with “global warming”) refers to variation in global or regional climatic conditions over time. It describes changes in the variability or average state of the atmosphere over periods of time ranging from several decades to millions of years. These changes can be caused by processes internal to the Earth (e.g. supervolcanoes), external forces (e.g. variations in sunlight intensity or large meteorites) or, more recently, human activity.