Radiative flux measurements in the troposphere

The results of radiative flux-density measurements in the troposphere, made using an especially designed radiometer mounted on a Cessna 402B aircraft, are reported. The radiometer incorporates several well-known principles that result in highly accurate determinations of radiative fluxes in the atmosphere. Heating rates for gases and for aerosols are calculated, using measurements and radiosonde data. Instrument performance is verified by calculating the solar constant at the top of the atmosphere, using the radiative flux densities measured in the troposphere. Total heating rates of 0.175 and 0.377 K h(-1) are determined for hazy and foggy atmospheres, respectively. Aerosol heating rates of 0.065 and 0.235 K h(-1) are deduced from the total heating rates. Environmental noise measurements during data acquisition are presented. The solar constant value of 1387 +/- 21 W m(-2) derived from the experiments agrees within 4% of the standard value.