Browsing by Author "Rastogi, P.K."
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Restricted Evaluation of effective eddy diffusive coefficients using radar observations of turbulence in the stratosphere(American Geophysical Union, 1984-03) Woodman Pollitt, Ronald Francisco; Rastogi, P.K.Radar observations show that thin persistent layers of turbulence occur sporadically in the troposphere and stratosphere. Two probabilistic approaches are used to show that the vertical eddy diffusivity due to such layers is of the order of 0.2-0.3 m²/sec in the lower stratosphere. An actual realization of turbulent layers, derived from the radar observations at Arecibo, is used in a numerical approach to obtain a profile of eddy diffusivity. It is suggested that turbulence plays a significant role in the vertical transport of trace constituents in the stratosphere.Item Restricted High-resolution VHF radar observations of turbulence structures in the mesosphere(American Geophysical Union, 1979-07) Röttger, J.; Rastogi, P.K.; Woodman Pollitt, Ronald FranciscoResults from a study of mesospheric turbulence, using a VHF radar with a height resolution of 150 m, are presented. Three types of turbulence structures have been identified: blobs, sheets and layers. Blobs and sheets occurred sporadically, predominahtly at heights of 60-70 km. Above 70 km, layers thicker than 1 km were dominant, which were advected with the background wind. Velocity fluctuations in these structures were proportional to their thickness. The role of partial or Fresnel reflections is discussed and possibility of diffuse reflections below 70 km is noted. Problems in estimating transport coefficients from radar data are outlined.Item Open Access Vertical transport in the tropo-stratosphere by intermittent turbulence: a simultation study(American Meteorological Society, 1983) Rastogi, P.K.; Woodman Pollitt, Ronald FranciscoThe possibility of a slow depletion of stratospheric ozone in reactions with pollutants inadvertently released in the lower atmosphere has received considerable attention over the past decade (see e.g. Kruger ad Setlow, 1982). Production and loss processes alone cannot be used to account for budgets of minor constituents in the stratosphere. Processes that effect their transport also need to be included. In the simplest and most widely employed one-dimensional (1-d) aeronomic models, transport coefficients are obtained from the observed profiles of a constituent whose chemistry id presumably well understood. In more sophisticated two and three dimensional models, transport by advection with atmospheric circulation is considered, but the effect of motions at scales smaller than some grid size are included only in a parametrized form, Estimates of transport coefficients, bases on direct observations of the underlying physical processes such as turbulence, are relatively scarse and have so far provided conflicting results.