Texas Climate

After my recent visit to Texas, USA I was really fascinated by the climate of the state and decided to write up about the Texas Climate. Some of my old physical geography notes were able to be applied when researching!!

Introduction

Texas is located south central of the United States and is the second largest state by area (696,241 km2) and population in the states (27,469,114). Due to the large size of Texas, it has multiple climate zones which give the state highly variable weather. There are a number of variables which affect the weather which will be discussed in this paper. In addition, the influences and the extreme climate variability in Texas will be discussed and point out some of the effects of this on the future for water and the second largest amount of population in the United States.

Main Body

Firstly, the Rocky Mountains, or more broadly the North American Cordillera. These mountain ranges present a barrier for winds traveling east to west or west to east. This is shown in figure 1 stopping the polar jet stream until the Mexican Highlands where the subtropical jet stream and west winds send the polar jet stream through central Texas. The Rocky Mountains extend from Alaska, through Canada and the United States to Mexico. This is not the case for El Paso, which is in the cordillera, but has winds from North to South, which are more common in Texas (Nielsen-Gammon (2011)).

texas-climate-1
Figure 1 – The geographic location of Texas within North America and its interaction with seasonal air masses affets the state’s unique climate variablility (Digital elevation data for base map from USGS, 2000)

Secondly, two geographical features of Central America and the Gulf of Mexico. Both of these are a pathway for air moment around Texas but depend on the route taken. The Great Plains are a flat landmass from the Arctic Circle to Texas. The cold air appears on the eastern side of the North American Cordillera are channelled southwards. This travels a distance of a day and a half from the Canada to the US and Texas. The Gulf of Mexico is a source of moisture source for Texas, with most of the moisture crossing the coastline from the Caribbean Sea and the open Atlantic Ocean. There is also additional moisture picked up by the Gulf of Mexico. The Gulf of Mexico moderates the land surface as temperature surface do not change much from day to day or winter to summer.

According to Nielsen-Gammon p39 (2011), “the basic climate patterns in Texas are fairly simple” as annual mean temperatures from north to south and annual mean precipitation west to east increase. The salient of Texas has colder winters than North Texas, while the Gulf Coast has mild winters. Texas has wide variations in precipitation patterns. El Paso, on the western end of the state, averages 8.7 inches (220 mm) of annual rainfall, (El Paso weather (2016)) while parts of southeast Texas average as much as 64 inches (1,600 mm) per year. (Mauriceville weather (2016)) Dallas in the North Central region averages a more moderate 37 inches (940 mm) per year. Maximum temperatures in the summer months’ average from the 80s °F (26 °C) in the mountains of West Texas and on Galveston Island to around 100 °F (38 °C) in the Rio Grande Valley, but most areas of Texas see consistent summer high temperatures in the 90 °F (32 °C) range.

texas-climate-2
Figure 2 – Climate divisions of Texas with corresponding climographs (Source data from NCDC, 2011)

Snow falls multiple times each winter in the salient and mountainous areas of West Texas, once or twice a year in North Texas, and once every few years in Central and East Texas. Snow falls south of San Antonio or on the coast in rare circumstances only. Of note is the 2004 Christmas Eve snowstorm, when 6 inches (150 mm) of snow fell as far south as Kingsville, where the average high temperature in December is 65 °F (Wunderground.com 2008).

Texas Climate Influences

Texas climate is influenced by weather features such as the Bermuda High and the jet streams, which are influenced by cyclical changes in sea surface temperature patterns associated the El Niño Southern Oscillation, the Pacific Decadal Oscillation, the Atlantic Multidecadal Oscillation, and the atmospheric pressure patterns of the North Atlantic Oscillation.

The Bermuda High, a dominant high pressure system of the North Atlantic Oscillation, influences the formation and path of tropical cyclones as well as climate patterns across Texas and the eastern United States.  During periods of increased intensity of the Bermuda High system, precipitation extremes also tend to increase. The jet streams are narrow, high altitude, and fast-moving air   currents   with   meandering paths from west to east. They steer large air masses across the earth’s surface and their paths and locations generally determine the climatic state between drought and unusually wet conditions.

The El Niño Southern Oscillation (ENSO), a cyclical fluctuation of ocean surface temperature and air pressure in the tropical Pacific Ocean, affects Pacific moisture patterns and is responsible for long-term impacts on Texas precipitation, which have led to moderate to severe drought (Changnon 1999). During a weak or negative oscillation, known as a La Niña phase, precipitation will be below average in Texas and some degree of drought will occur. During a strong positive oscillation or El Niño phase, Texas will usually experience above average precipitation. In 2016 Texas has had a wet summer suggesting that the could have been a strong positive oscillation (TWDB 2012 & Trenberth 1997).

The Pacific Decadal Oscillation affects sea surface temperatures in the northern Pacific Ocean, while the Atlantic Multidecadal Oscillation affects the sea surface temperature gradient from the equator poleward (Nielson-Gammon, 2011). These two long-term oscillations can enhance or dampen the effects of the ENSO phases and therefore long-term patterns of wet and dry cycles of the climate. Generally, drought conditions are enhanced by cool sea surface temperatures of the Pacific    Decadal Oscillation and also warm sea surface temperatures of the Atlantic Multidecadal Oscillation (TWDB 2012).

Conclusion

The variability of Texas climate could present many future problems as it will be harder to determine what the exact effects. It can also be said that the influences on Texas climate, for instance El Niño could have more regular strong or negative oscillations, meaning more draughts or harsher storms. Moreover, these influences could start differing the weather patterns like stopping the amount of polar jet steam shown in figure 1.

Bibliography

Changnon, S.A., (1999). Impacts of 1997-98 El Niño-generated weather in the United States. Bulletin of the American Meteorological Society, 80(9), p.1819.

Nielsen-Gammon, J.W., (2011). The changing climate of Texas. The impact of global warming on Texas, pp.39-68.

Trenberth, K.E., (1997). The definition of el nino. Bulletin of the American Meteorological Society, 78(12), p.2771.

Texas Water Development Board (TWDB), (2011) 2012 State Water Plan, [online] Available at:  https://www.twdb.texas.gov/publications/state_water_plan/2012/2012_SWP.pdf pp. 145-153 (Accessed: 22 September 2016)

Weatherbase.com, (2016a), El Paso weather [online] Available at:  http://www.weatherbase.com/weather/weather.php3?s=7227&refer=&cityname=El-Paso-Texas-United-States-of-America (Accessed: 22 September 2016)

Weatherbase.com, (2016b), Mauriceville weather [online] Available at:  http://www.weatherbase.com/weather/weather.php3?s=86614&refer=&cityname=Mauriceville- Texas-United-States-of-America (Accessed: 22 September 2016)

Wunderground.com. (2008) “History: Weather Underground”. [online] Available at: https://www.wunderground.com/history/airport/KNQI////DailyHistory.html?req_city=Kingsville&req_statename=Texas  (Accessed: 22 September 2016)

 

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