Great Bend Tribune
Part I
Published October 29, 2017
Agriculture, like any endeavor, is bombarded with numbers and statistics. Percentages, averages, normal, total, ratings, and a variety of other terms are constantly reported and analyzed. While they may be useful, their real value is only apparent if you understand where they come from and how they are determined. One short column can hardly describe all this with adequate perspective. So today, let’s start discussing weather data but first some definitions.
- Average or mean: constituting the result obtained by adding together several quantities and then dividing this total by the number of quantities. In English, we have four people, three earn $5,000 per year and one earns $85,000 per year. The average salary is $25,000. That number poorly reflects what each actually makes.
- Median: The middle value in a distribution, above and below which lie an equal number of values. In English, half the values of a group lie above this value and half below. An example: you have four values (1, 2, 4, and 7). The average is (1+2+4+7/4) is 3.5, however, the mean is 3.
- Range: This is simply the “spread” of the values under consideration. In the previous example the range is 7-1 or 6.
- Extremes: In weather they will provide the record high, low and perhaps peak wind, highest rainfall and so on. These will matter in next week’s column.
- Frost or freeze: when the temperature drops bellows 32 degrees Fahrenheit (0 degrees Celsius). This is different from the next definition.
- Hard or killing freeze: the occurrence of temperatures cold enough to kill all but the hardiest vegetation, especially the last such occurrence in spring and the first in fall, events that limit the agricultural growing season. There are two ways of looking at this. One is for native vegetation and the other for crop and landscape plants. Normally, it is thought of as temperatures several degrees below freezing for several hours. And what is a killing frost for one plant may not be for another.
- Growing season: the length of time from the last killing frost in the spring until the first killing frost in the fall.
- Drought: there isn’t one totally accepted definition of drought. A drought is a period of below-average precipitation in a given region, that may result in prolonged shortages in the water supply, whether atmospheric, surface water or ground water. Some define it as less than seventy-five percent of normal precipitation.
These definitions provide a basis for next week’s discussion. What is normal as we look at our weather?
Part II
Published November 5, 2017
Last week’s column defined terms used in weather such as average, extreme, drought, etc. used in weather and climate. With several hard freezes, it is finally possible to say the growing season is over. Was that date of the average end of the growing season? Long-term data says to expect a freeze in Barton County from October 12 in the northern part of the county until the 22nd in the southern portion. So it is close to that range. But if you think back over the years the area has seen a “light” frost during the State Fair. And over the last several years the first real “hard” freeze didn’t occur until mid-November. Why does this matter? Optimum wheat planting dates in Kansas are based on trying to avoid Hessian fly infestations and that is based around the average date of the first hard freeze. If a warming climate causes the average date of this event to occur on average later, this effects planting recommendations and makes dealing with Hessian fly more challenging.
Example two involves variation of weather averages around the average and what that means to producers – precipitation. Our current normal for precipitation is the average of thirty years, 1981 – 2010, and for the year in Barton County is 27.5 inches. So far we are short 6.2 inches with two months to go and November and December are generally dry months. However, the important item for producers isn’t just how much precipitation is received but its distribution. Please keep in mind that the numbers here are for a one location and we all know that precipitation here is quite variable over a short distance due to the nature of much of our precipitation – convective thunderstorm activity.
Ask any producer how the year went in the field and while the area may overall be short of the average, they dealt with dry conditions, followed by excessively wet conditions with two and one-half months of little precipitation and then back to wet again. Thanks to the weather in January, the first quarter of 2017 was average but February and March were over 1.5 inches below normal, almost no precipation. April and May, two of the wetter months were almost 2.5 inches above normal which delayed planting and the problem was compounded by cooler than normal weather. June through August were 6.5 inches below normal while September was 1.5 inches above and October was 2 inches below an average of about two inches. The purpose here isn’t to see if you would read all that but that an average here tells you almost nothing. What mattered to wheat producers was the lack of late winter moisture. What mattered to summer row crop producers was delayed planting from excessively wet conditions followed by excessively dry conditions during the summer on a corn crop that was already behind.
While our State has always dealt with large swings in weather conditions, the last twenty or so years have evidenced extremes extreme even for here. So while averages may not change much, the numbers going into those averages have and the question that needs answering is simple and extremely complicated. Is this a part of normal climate variation alone or part of a normal variation exacerbated by man-made climate change?