• Growing-Degree Units For Selected Agricultural Locations In Alaska

      Branton, C. Ivan; Shaw, Robert H. (University of Alaska, Institute of Agricultural Sciences, 1973-06)
      It is well known that the rate at which a plant grows is influenced by air temperature. The problem is to define this relationship in a quantitative manner so that the information can be applied to agricultural problems. In places where growth of a particular crop is limited by the length of the growing season, an evaluation of the "heat-units" available is particularly important. Many heat-unit systems have evolved over the years, with certain advantages claimed for each. In crop production, heat unit systems are used to estimate the time required for a crop to go from one stage of development to another, usually from planting to harvest. Each heat-unit system produces a particular set of values, the values being determined by the relationship between temperature and growth that is assumed in the calculations. This paper lists heat-units available in six areas in Alaska, all having agricultural potential. The system used measures temperature in "growing-degree units" and is described in detail. Recent comparative studies of growing season and growing degree days leads to the conclusion that the temperature records taken at Big Delta may have been favorably affected by the nearness of the weather recording station to an extensive coated runway. The "flywheel" effect of this large heat sink appear to have reduced the occurrence of 32°F. night temperatures in both the spring and fall, making the growing degree accumulation unrealistic.
    • Solar and Net Radiation At Palmer, Alaska 1960-71

      Branton, C. Ivan; Shaw, Robert H.; Allen, Lee D. (University of Alaska, Institute of Agricultural Sciences, 1972-06)
      Solar and net radiation received at Palmer, Alaska (61 ° 3 6 ’ N. lat., 1 49° 0 6 ’ W. long.) have been observed fo r m ore than ten years. On a yearly basis, the daily average incoming global short wave radiation has been 219.1 langleys, and net radiation has been 70.0 langleys. From May 3 thru August 1, net radiation averages 221 .2 langleys. This is 2.571 kilowatt hours per square meter, or 8 15 .2 Btu per square foot (English units). From November 1 thru January 3 0, net radiation is negative, showing an energy loss of 54.2 langleys per day. This is equivalent to 0.63 0 kilowatt hours per square meter or 199.8 Btu per square foot.