Filling in of Fraunhofer and gas-absorption lines in sky spectra as caused by rotational Raman scattering.

A line-by-line radiative-transfer model to quantify the Ring effect as caused by rotational Raman scattering has been developed for the 310-550-nm spectral interval. The solar zenith angle and the resolution are key input parameters, as is the sky spectrum (excluding inelastic atmospheric scattering), which was modeled with MODTRAN 3.5. The filling in is modeled for ground-based viewing geometry and includes surface reflection and single inelastic scattering. It is shown that O2 contributes half of the filling in of N2. A strong inverse relationship with wavelength is noted in the filling in. A comparison with observations shows moderate agreement. The largest filling in occurs in the Ca II K and H lines.

Laboratory technique for the measurement of thermal-emission spectra of greenhouse gases: CFC-12.

A new technique has been developed to make possible the laboratory study of the infrared-emission spectra of gases of atmospheric interest. The thermal-emission spectra are in local thermodynamic equilibrium, just as they are in the atmosphere, and are not chemiluminescent. Demonstration results obtained by the use of this new technique are presented for dichlorodifluoromethane (CFC-12) at a pressure of 0.5 Torr in a cell with a path length of 5 cm. The measured cell spectra have been compared with simulations with the FASCD3P radiation code. The measurements of the emission spectra of radiatively active gases may be important for the atmospheric greenhouse effect and global warming.

Least-squares error analysis of the 1985 N(2)O(5) observation: reply.

A least-squares fitting analysis of the original 1985 observed N(2)O(5) spectrum was conducted. By the method of random number noise enhancement, the error that is due to random noise was estimated to be 8.3%, consistent with the original published error estimate of 10%.

High resolution atmospheric transmission calculations down to 28.7 km in the 200-243-nm spectral range.

Decrease in stratospheric ozone absorption and increase in oxygen absorption with decreasing wavelength combine to produce a window of maximum atmospheric transmission near 210 nm. Since solar radiation in this spectral region dissociates molecular oxygen, the deep atmospheric penetration at this wavelength is of particular aeronomical interest. High resolution calculations of the transmittance down to 28.65 km were made for the 200-243-nm spectral range in this window region, in support of a stratospheric balloon flight from Fort Churchill in July 1974. The calculations were made by dividing the atmosphere into layers which were chosen so that each could be assumed homogeneous; optical depths were calculated separatelyfor each of these layers and then summed to obtain the over-all transmittance of the atmosphere. Absorptionby molecular oxygen (line and continuum) and by ozone was included, as well as extinction through Rayleigh scattering by air molecules. The calculated transmittances were combined with hig h altitude(above 100-km) rocket measurements of the sun-center spectrum and center-to-limb variations to give residual high resolution solar spectral flux for several altitudes and solar zenith angles.