This thesis consists of 1-D and 2-D photochemical dynamical modeling in the upper atmospheres of outer planets. For 1-D modeling, a unified hydrocarbon photochemical model has been studied in Jupiter, Saturn, Uranus, Neptune, and Titan, by comparing with the Voyager observations, and the recent measurements of methyl radicals by ISO in Saturn and Neptune. The CH_3 observation implies a kinetically sensitive test to the measured and estimated hydrocarbon rate constants at low temperatures. We identify the key reactions that control the concentrations of CH_3 in the model, such as the three-body recombination reaction, CH_3 + CH_3 + M → C_(2)H_6 + M, and the recycling reaction H + CH_3 + M →CH_4 + M. The results show reasonable agreement with ISO values. In Chapter 4, the detection of PH_3 in the lower stratosphere and upper troposphere of Jupiter has provided a photochemical-dynamical coupling model to derive the eddy diffusion coefficient in the upper troposphere of Jupiter. Using a two-layers photochemical model with updated photodissociation cross-sections and chemical rate constants for NH_3 and PH_3, we find that the upper tropospheric eddy diffusion coefficient <10^5 cm^2 sec^(-1) and the deeper tropospheric value >10^6 cm^2 sec^(-1) are required to match the derived PH_3 vertical profile by the observation. The best-fit functional form derivation of eddy diffusion coefficient in the upper troposphere of Jupiter above 400 mbar is K = 2.0 x 10^4 (n/2.2 x 10^19)^(-0.5)cm^2 sec^(-1). On the other hand, Chapter 5 demonstrates a dynamical-only 2-D model of C_(2)H_6 providing a complete test for the current 2-D transport models in Jovian lower stratosphere and upper troposphere (270 to 0.1 mbar pressure levels). Different combinations of residual advection, horizontal eddy dispersion, and vertical eddy mixing are examined at different latitudes.
