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Georgia's Climate: 

Georgia's Climate Produced by Pam Knox, Georgia Assistant State Climatologist Past, Present and Future

What is climate?: 

What is climate? A measure of the general environmental conditions and their variability over time and space Commonly described by temperature, precipitation, wind, humidity and other weather-related factors Includes averages, extremes and variability

What controls Georgia’s climates?: 

What controls Georgia’s climates? Where we are on the globe Where we are on the continent Landforms and water Local conditions

Georgia’s position on earth: 

Georgia’s position on earth Latitude 30-35 N Our position means that we experience winter in December, January and February, and summer in June, July and August, with transitional seasons in between, due to the sun’s position in the sky relative to earth.

Earth and sun positions at different seasons: 

Earth and sun positions at different seasons

Where we are on the continent: 

Where we are on the continent In mid-latitudes, prevailing wind is from the west Climate is directly affected by what is upwind In Georgia, prevailing wind varies with the season, so influences of climate also change

Slide7: 

Georgia is in the southeastern US Winds in winter tend to be from the NW from over the continent Winds in summer tend to be from the SW from the Gulf of Mexico Local conditions can affect the prevailing wind at any location!

Landforms and water: 

Landforms and water Variations in elevation cause variability in both temperature and precipitation The presence of water or mountains can create local circulations which affect local climate Ground fog in low-lying area

Slide9: 

Landforms of Georgia

Local conditions: 

Local conditions Vegetation type and land cover can also affect climate The presence of cities, irrigated land, or other human-induced changes can affect local conditions, too

Slide11: 

This false-color LANDSAT image shows the variation of land uses across the state. Dark green=mountain forests White=cropland Red=coastal forests Bright green= coastal estuaries

What does Georgia’s climate look like?: 

What does Georgia’s climate look like? Temperature Growing season Precipitation Wind Hazards

Slide13: 

Annual mean temperature ranges from about 54° F in the northeast to 68º F in the south. Temperature 65 70 60 55

Slide14: 

January mean temperature ranges from about 36º F in the north to 53º F in the south. Temperature 50 40 32

Slide15: 

July mean temperature ranges from about 70º F along the NC border to 84º F in the south. Temperature 80 70

Slide16: 

Statewide monthly temperatures vary smoothly from January (44.7º F) to July (79.5º F) and lag the seasonal solar radiation by about a month. Temperature

Slide17: 

Mean extreme high temperatures range from below 90º F in the northeast mountains to over 100º F in the coastal plain away from the coast. Temperature 100 95 90

Slide18: 

Mean extreme low temperatures range from below 0º F in the northeast mountains to over 20º F near the ocean. Temperature x 10 20 0

Slide19: 

The average number of days with temperatures above 90º F ranges from less than 15 in the northeast to over 90 in the south. Temperature x 90 60 45 30 15 <1

Slide20: 

The average number of days with temperatures below 32º F ranges from less than 30 along the coast to over 120 in a few isolated areas in the northeast mountains. Temperature x 30 60 90 120

Slide21: 

Temperature Records Highest temperature was 112º F Louisville 7/24/1952 Greenville 8/20/1983 Lowest temperature was –17º F CCC Camp F-16 1/27/1940 (in northwest Georgia)

Slide22: 

The median length of the growing season (based on 32º F) ranges from over 270 days along the southern coast to less than 180 days in the mountains. Growing season x 270 240 300 180

Slide23: 

The average date of last spring frost ranges from late February along the coast to early May for the mountains. Growing season x Mar 1 Apr 1 Apr 15 May 1

Slide24: 

The average date of first fall frost ranges from early October in the northeast to early December along the southern coast. Growing season x Nov 15 Dec 1 Nov 1 Oct 15 Oct 1

Slide25: 

The average annual rainfall in Georgia ranges from a low of about 45 inches near Mt. Vernon in Montgomery County (X) to a high of over 80 inches in isolated mountainous areas in the northeast. Precipitation 50 X 70

Slide26: 

The average annual snowfall for most of the state is less than 3 inches (green area). The far south does not usually experience snow. A few mountaintops in the northeast have more than a foot of snow each year. Precipitation x 0 3 12

Slide27: 

The average monthly precipitation ranges from 3.4 inches in November and April to 5.3 inches in July. Precipitation

Slide28: 

. Precipitation Records 24 hour rainfall: 21.10 inches Americus 7/5-6/1994 (Tropical Storm Alberto) Calendar year precipitation: 122.16 inches Flat Top 1959 24 hour snowfall: 19.3 inches Cedartown 3/2-3/1942 Seasonal snowfall: 39.0 inches Diamond 1894-95

Slide29: 

Prevailing winds change across the state from season to season. Average monthly wind speeds range from 5 to 9 mph. Wind Jan Apr Jul Oct White= 5 mph Light gray= 6 mph Dark gray= 7 mph Violet=8 mph Turquoise= 9 mph

Slide30: 

In the period from 1950-1995, Georgia experienced an average of 20 tornadoes per year, of which 6 were strong or violent tornadoes. Note that tornado reports are strongly biased by population, so cities tend to be over-reported compared to rural areas. Natural Hazards x

Natural Hazards: 

Natural Hazards The Gainesville tornado of April 6, 1936, was one of the country’s deadliest, with 203 killed and about 1600 injured. Photo from Carl Vinson Institute of Government

Slide32: 

In the period from 1980-1995, Georgia experienced an average of 65 hail reports per year for hail larger than ¾ inch. Hail reports, like tornado reports, are strongly biased by population, so cities tend to be over-reported compared to rural areas. Natural Hazards

Slide33: 

The number of days with thunder ranges from over 70 per year in the far southwest to about 40 near the northeast border with South Carolina. Natural Hazards 3 40 70 60 50 40

Slide34: 

The number of days with heavy fog (visibility of less than ¼ mile) ranges from about 20 in west central Georgia to over 35 in the NE mountains. Natural Hazards 20 25 30 35 40

Natural Hazards: 

Natural Hazards Hurricanes occasionally move across Georgia, although they are usually downgraded to a tropical storm by the time they enter the state. This map only shows storms that reached hurricane force at some point. Dark Red=Strong Huricane. Red= Weak Hurricane Yellow=Tropical Storm Green=Tropical Depression Black=Tropical Low

Climate variability: 

Climate variability Georgia’s climate varies on many different time scales, from seasonal to multi-decadal. These variations are due to a number of factors, including ocean temperatures, land use changes, and weather and climate events happening elsewhere in the US and the world.

Climate variability: 

Climate variability One factor that can cause climate to vary is El Niño. El Niño is one phase of an oscillation in ocean temperatures and atmospheric pressure in the eastern Pacific Ocean that can steer weather systems in the southeastern US and elsewhere. El Niño is considered the warm phase of the oscillation. However, El Niño tends to affect Southern Georgia in winter more than any other part of Georgia or any other season. La Niña (sometimes known as El Viejo) is the opposite atmospheric pattern from El Niño.

Climate variability: 

Climate variability In an El Niño winter, the average precipitation in the southern half of Georgia is about 2 inches above the precipitation expected in a neutral year. In a La Niña year, precipitation is about 2 inches lower than in a neutral year. Northern Georgia does not show this statistical relationship. However, there is quite a bit of variability from one event to the next. Green=South Central Red=North Central

Georgia’s past climate: 

Georgia’s past climate During the last Ice Age, Georgia probably experienced a climate somewhat wetter and cooler than we have today. Models indicate that the average annual rainfall was about 63 inches and the annual average temperature was 56.3º F, compared with modern values of 51 inches and 63.5º F.

Georgia climate trends: 

Georgia climate trends Since 1895, Georgia’s climate has cooled slightly (black line on chart). This may be due to reforestation of Georgia over the last century or for other reasons. However, the current trend (since 1965) is toward warmer temperatures.

Georgia climate trends: 

Georgia climate trends Since 1895, Georgia’s rainfall has varied from one year to the next, but there is only a very slight trend towards higher precipitation over the last century.

Thank You!: 

Thank You! We hope that you have enjoyed this look at Georgia’s climate. If you have questions or comments, please feel free to contact us at: Climate@engr.uga.edu Or visit our web site at: http://climate.engr.uga.edu

Credits: 

Credits Many of the charts in this presentation were obtained from the Climate Atlas of the United States, published by the National Climatic Data Center, NOAA, in September 2000 on CD-ROM. You can access their web site at: www.ncdc.noaa.gov

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