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Techniques for extraction of boundary layer parameters from measurements of a short pulse (≈0.4 μs) CO2 Doppler lidar (λ = 10.6 μm) are described. The lidar is operated by the National Oceanic and Atmospheric Administration (NOAA) Wave Propagation Laboratory (WPL). The measurements are those collected during the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE). The recorded radial velocity measurements have a range resolution of 150 m. With a pulse repetition rate of 20 Hz it is possible to perform scannings in two perpendicular vertical planes (x–z and y–z) in approximately 72 s. By continuously operating the lidar for about an hour, one can extract stable statistics of the radial velocities. Assuming that the turbulence is horizontally homogeneous, we have estimated the mean wind, its standard deviations, and the momentum fluxes. We have estimated the first, second, and, third moments of the vertical velocity from the vertically pointing beam. Spectral analysis of the radial velocities is also performed, from which (by examining the amplitude of the power spectrum at the inertial range) we have deduced the kinetic energy dissipation. Finally, using the statistical form of the Navier‐Stokes equations, the surface heat flux is derived as the residual balance between the vertical gradient of the third moment of the vertical velocity and the kinetic energy dissipation. With the exception of the vertically pointing beam an individual radial velocity estimate is accurate only to ±0.7 m s−1. Combining many measurements would normally reduce the error, provided that it is unbiased and uncorrelated. The nature of some of the algorithms, however, is such that biased and correlated errors may be generated even though the “raw” measurements are not. We have developed data processing procedures that eliminate bias and minimize error correlation. Once bias and error correlations are accounted for, the large sample size is shown to reduce the errors substantially. We show, for instance, that a single momentum flux estimate has an accuracy of ±2m2s−2, but when combined with other measurements, the error can be reduced to ±0.10 m2 s−2. The principal features of the derived turbulence statistics for two case studies (July 11, 1987, 1611–1710 UTC and 1729–1810 UTC) are as follows: The mean surface wind is from the south and has a speed of approximately 15 m s−1. There is a southerly jet 1 km above the surface. The wind in the direction normal to the surface wind becomes more westerly with height. The derived momentum fluxes in the mixed layer agree with the unfiltered airplane measurements. They are of the order of approximately 0.5 m2 s−2 near the surface and are retarding the southerly wind. At the stable layer, the momentum fluxes are countergradient; they remain negative even though the southerlies are diminishing with height and are concentrated in thin layers. By spectrally analyzing the vertical beam, we have identified the Brunt‐Väisälä frequency as the dominated frequency in...

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Two semiempirical climate models are formulated as time‐dependent problems in order to study the stability of their asymptotic steady state equilibrium solutions to perturbations in internal (in this case, initial) conditions. Whereas these models have shown dramatic sensitivity to slight changes in external parameters (e.g., solar constant), here they are found to be relatively stable to perturbations in initial conditions. For fixed external conditions our time‐dependent versions of these models exhibit fully transitive behavior to positive perturbations in initial conditions, slight intransivity to negative perturbations up to −18°K, and an ice‐covered earth regime is obtained for extremely large negative perturbations in initial temperatures (below −18°K). The parameterization found to be most critical in these models is the albedo‐temperature coupling, especially in tropical regions. The temperature albedo parameterization from an intransitive climate model used in a time‐dependent form of one of the preceding models is found to be highly sensitive to negative perturbations in both internal and external conditions. Numerical experimentation with these semiempirical models shows the important role of the tropics in maintaining the equilibrium climate and suggests that the radiation balance in equatorial latitudes might have a controlling influence on the equatorward extent of the polar ice cap. The major assumptions and approximations of semiempirical climate models are discussed critically.

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