Pat Shingleton: "Frost and Clearing the Land..."
We are projecting a start temperature of 37 degrees Monday morning. Barbara Tufty's book, 1001 Questions About Hurricanes, Tornadoes and Other Natural Air Disasters mentions that frost usually occurs on clear, calm nights during the autumn when the air up top is moist. In South Louisiana frost occurs closer to the beginning of winter. When tender plants aren't affected, it's an example of light frost. Heavy frost contains crystallized water and doesn't kill sturdy vegetation. The most destructive frost to vegetation is killing frost while black frost or hard frost hits northern areas in late autumn when temperatures are consistently below freezing. A hard or black frost will cause leaf edges and plant tips to turn black as if they were burnt. Meteorologically, a freeze is defined as a period of time when the surface temperature of a whole air mass remains below freezing. That could occur for us in mid-January. Last year, our first freeze was November 21st with the first freeze of 2015 on November 23rd. In closing, in the late 1700s, many scholars were debating whether human activities were changing the earth’s climate. Thomas Jefferson and his colleague, Harvard professor Samuel Williams, wrote, ”A change in our climate is taking place…both heats and colds are much more moderate within the memory of the middle-aged. When settlers enter a township their first business is to cut down trees, clear lands and sow grains.” It was their belief that the surface of the earth became warm and dry and as settlements increased, the effects are more extensive. Dr. Noah Webster believed that the clearing of lands welcomed more sun, thus the changeover from forest to field changes the heat balance. Webster’s reflections were noted by Helmut Landsberg 170 years later.