The urban heat island of San Antonio, Texas (USA)

摘要

A study of the urban heat island effect was carried out comparing 45-year daily temperature records (1946-1990) of San Antonio, Texas (USA), with three small surrounding towns; New Braunfels, Poteet, and Boerne, These towns are all within 40 kilometers of San Antonio and were chosen because they form a nearly equilateral triangle around the city from northeast to south to northwest, respectively. The study shows that, on average, the minimum temperatures at the San Antonio International Airport (the location of the weather station) are increasing at an average rate of about 0.3℃ per decade relative to surrounding small towns with similar elevation. The difference in minimum temperatures is most pronounced during the summer months. The summer temperature minimum differences relative to New Braunfels indicated the largest increase at 0.4 +- 0.1℃ per decade and an increase of 0.2 +- 0.1℃ per decade relative to Poteet. In 1947, the minimum temperatures in New Braunfels were on average about 0.2℃ warmer than San Antonio and they were about equal between San Antonio and Poteet. In 1990, summer minimum temperatures were more than 1.7℃ cooler in New Braunfels and more than 1.0℃ cooler in Poteet. A similar trend in the minimum summer temperatures is seen in comparisons with Boerne but the magnitudes are smaller and there are larger temperature fluctuations in the data. This may be due to the higher elevation of Boerne (about 700 meters above sea level) whereas San Antonio, New Braunfels, and Poteet all have similar elevations (about 200 meters above sea level). The same effects are found in the maximum temperatures in the winter months for New Braunfels and Poteet. They are increasing at average rates of about 0.8℃ per decade compared to New Braunfels and 0.5℃ per decade compared to Poteet in the winter months. No statistical change in the winter maximum temperatures between San Antonio and Boerne was found. Despite many mitigating influences (e.g., much vegetation, little polluting industry), it has been shown that San Antonio has an increasing urban heat island effect.