ON THE ATMOSPHERIC HEATING EFFICIENCY IN THE OZONE TRIPLET CHANNEL

In recent studies on the photolysis of ozone the triplet channel has b een given much attention as a possible extra ozone source. The vibrati onally excited oxygen molecules produced can either be quenched to hea t the atmosphere or photolysed at longer wavelengths than normally pos sible for O-2. The latter potentially lowers the fraction of solar ene rgy that is converted to heat. Lack of experimental data to accurately estimate this fraction and the relatively small contribution to the t otal heating has been used to justify neglect of this effect. However, recent information on the quantum yield of excited oxygen as function of wavelength from ozone dissociation makes it possible to calculate the atmospheric heating efficiency in the ozone triplet channel in a m ore quantitative fashion. With the new quantum yield data the atmosphe ric heating efficiency in the triplet channel deviates from unity only above 80 km where the magnitude of the deviation is strongly dependen t on the quantum yield. However, the large yield into the singlet chan nel masks any deviations from unit in the triplet channel. Therefore t he current results indicate that previous work, which assumed unity he ating efficiency for the triplet channel in the whole altitude range, is within 4% of a detailed calculation. Below 80 km the current result s are consistent with previous work.