THE ENERGY BUDGET AT THE EARTH'S SURFACE: A STUDY OF THE CARBON DIOXIDE CONCENTRATION MONITORED OVER AN AGRICULTURAL FIELD NEAR ITHACA, N.Y.
AGRICULTURAL RESEARCH SERVICE ITHACA NY SOIL AND WATER CONSERVATION RESEARCH DIV
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Carbon dioxide concentration was monitored from July to December 1962, and from January to June 1964 over an agricultural field using an infrared CO2 analyzer. Supporting micrometeorological data, including windspeed, incident shortwave radiation, net radiation, air temperature, and soil temperature were taken during part of the monitoring program. The CO2 concentration showed an annual cycling much stronger than has been observed over oceans or at high altitudes. The computed average annual daytime CO2 concentration near the earths surface was 312 ppm. Diurnal cycles in concentration during the summer months frequently showed ranges in excess of 200 ppm. During July, August, and September 1962, the daytime average CO2 concentration at the top of the vegetation corn was about 291 ppm. In the diurnal cycle of CO2 concentration the daytime average CO2 concentration was very steady over an individual day, with little or no decrease during the course of a day after the nocturnal build-up had been dispersed or consumed. Incident shortwave radiation had a relatively small effect on CO2 concentration. Nighttime CO2 build-up was found to be directly proportional to mean temperature, soil-to-air temperature difference, and inversely proportional to windspeed. After harvest of the 1962 crop corn, the diurnal cycle was altered, with a more gradual drawdown of CO2 occurring throughout the daylight period. After snow-cover, diurnal variations became quite small, the typical maximum range being 22 ppm.
- Agricultural Engineering