Turbopause

Abstract: A detailed theoretical model with measured values of solar flux, absorption cross sections, and chemical rate constants for input data is used to study the diurnal variation of [NO] in the upper atmosphere. Two models for sources of N(2D) are considered: in model 1 all NO+ recombinations result in N(2D) production and in model 2 photoelectron dissociation of N2 and ion-atom interchange of N2+ and O are the sources. Results are compared with the recent rocket measurements reported by L. G. Meira, Jr. (1970), and very good agreement is obtained for both models. For the D region, where Lyman α is the source of ionization, a decrease in electron density for model 1 and an increase for model 2 is predicted for increasing solar activity. D-region electron density measurements may be helpful in selecting the appropriate model. Below 150 km the distribution of [NO] is nearly time independent. Above 150 km the diurnal variation of [NO] is small and never exceeds a factor of 4 in the model. The sensitivity of the solutions to the eddy diffusion coefficient K is studied, and below the turbopause the NO density increases as K decreases.

Abstract: Turbulence parameters in the tropo-stratosphere are analyzed using high-resolution balloon temperature mea- surements collected during the MUTSI (MU radar, Temper- ature sheets and Interferometry) campaign which took place near the Middle and Upper atmosphere (MU) radar (Japan, 35 N, 136 E) in May 2000. Vertical profiles of the spe- cific dissipation rate of turbulent kinetic energy, ", and tur- bulent diffusivity, K, are estimated from the Thorpe length- scale, LT . The last is obtained by using two methods. The first one consists of measuring directly LT by reordering the potential temperature profiles. The second method is based on estimates of the temperature structure constant, C 2 T. A relationship between LT and C 2 can be found by assum- ing either adiabatic vertical displacements or a model based on turbulent energy balance consideration. Analysis shows that the adiabatic assumption gives indirect estimates of LT more consistent with direct measurements. We also found that vertical profiles of analyzed turbulence characteristics show substantial intermittency, leading to substantial scatter of the local, median and average values. General trends cor- respond to a decrease in " and K from the boundary layer up to altitudes 20-25 km. Layers of increased turbulence are systematically observed in the tropo-stratosphere, which may be produced by instabilities of temperature and wind profiles. These maxima may substantially increase local values of tur- bulence diffusivity. ergy by turbulence and increased heat conduction by turbu- lent diffusion are important for a full understanding of at- mospheric energetic and dynamic processes. Turbulent mix- ing and diffusion of natural and anthropogenetic gas species control atmospheric composition below the turbopause (nor-