Donal P. Murtagh

Simultaneous retrievals of temperature and volume mixing ratio constituents from nonoxygen Odin submillimeter radiometer bands

We present the retrieval of temperature and O(3) volume mixing ratio profiles in the middle atmosphere from a single strong O(3) line. We performed the study using simulated limb-sounding measurements in the frame of the submillimeter radiometer (SMR) instrument that will be carried by the Odin satellite that is due to be launched in early 2001. This study is interesting for the Odin SMR data analysis because we first provide additional temperature measurements, and second reduce significantly the O(3) retrieval error that is due to the temperature and pressure uncertainties. Nonlinear retrievals are performed to retrieve the O(3), CO, H(2)O, and temperature profiles simultaneously from the spectral band 576.27-576.67 GHz. The pressure profile is deduced from the hydrostatic equilibrium equation after each iteration. Temperature and O(3) can be retrieved throughout the stratosphere from 15-50 and 20-50 km, respectively, with a vertical resolution of 3 km. The altitude domain corresponds to the parts of the atmosphere where the signal intensity saturates in some spectrometer channels. A total error of 4-6 K has been found in the temperature profile, mainly because of the instrumental thermal noise and to a lesser extent the calibration. The total error in the O(3) profile is 5-10% and is dominated by the O(3) line-broadening parameter. The total error on the retrieved pressure profile is 2-10% because of the errors in calibration and reference pressure.

Ozone photodissociation in the Hartley band: A statistical description of the ground state decomposition channel O2(X 3Σ−g)+O(3P)

Ozone photodissociation in the Hartley band O3+hν→O(3P)+O2(Xu20093Σ−g) is simulated with a statistical model. In the model, energy is partitioned at a decoupling distance which is located at a position with nonzero potential energy on a repulsive and dissociative potential energy surface. Introduction of the repulsive potential on which dissociation takes place, and the choice of decoupling distance is shown to be of crucial importance for the final energy distributions, and in particular it determines the amount of energy left in translation. The model is shown to give good agreement with experimental vibrational and translational energy distributions, while the rotational distributions predicted by the model seem less peaked than experimental data. Vibrational state distributions are calculated for different dissociation wavelengths in the Hartley band (200–310 nm), and they are concluded to deviate substantially from distributions previously used in atmospheric modeling. The statistical approach is compare...