Last week’s column focused on humidity. This week focuses on temperature measurements with emphasis on agriculture. However, instead of two parts devoted to this topic there will be three with next week’s focus on where the long-term data comes from and what it tells us. First we’ll briefly discuss the temperature measurements everyone is familiar with.
• Daily high and low temperature – This is just what it sounds like. What was the highest and lowest recorded temperature for the period starting at 12:01 a.m. and ending at midnight of that day. Even if that temperature only occurred for a second it counts. The official temperatures are recorded at specific sites designated by the National Weather Service. These are typically at airports such as Eisenhower in Wichita. There are other sites part of the NWS grid with some being automated and some, where information is gathered manually that you won’t see unless you dig for them. K-State has a network of sites as do many Groundwater management Districts. Also temperature is recorded at a specific height, 1.5 meters or about five feet and should be above a natural surface such as grass.
• Soil temperature – Producers planting summer crops in the spring are concerned about the soil temperature they are planting into, especially with more tropical crops such as cotton, sesame, grain sorghum, and soybean. Crops need a minimum soil temperature to germinate, emerge, and grow vigorously. Some such as cotton can be “shocked” with cool soil, and air temperatures, and while not dying never recover and have poor season long growth.
• Heat accumulation – While you won’t find this on your nightly forecast, you can find it at the K-State weather data library website. Crops such as corn and grain sorghum grow based on the accumulation of heat and their growth stage is determined by this accumulation. This accumulation is determined by adding together the daily high and low, dividing by two and subtracting a base temperature (50 degrees for corn). Various formulas may vary a bit from this.
• Cold accumulation – Winter wheat has to accumulate cold before it can go ahead and flower. Different varieties have differing amounts of cold they need to accumulate. This prevents the plant, along with the need for increasing day length, from flowering too early.
• Wind – Wind is measured at sites where temperatures are measured. Wind is described by how fast the air is moving and where it is coming from. Not where it is going. We care where it is coming from since that helps in understanding what the condition of the air is – hot or cold, moist or dry.
Next week – precipitation and long-term data.