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In this paper we analyze distinct layers seen in the tropospheric ozone and water vapor profiles taken during NASA's Global Tropospheric Experiment (GTE) Pacific Exploratory Mission in the Tropical Pacific (PEM-Tropics) Phase B campaign. In summary, fewer layers were observed in this campaign than during the PEM-Tropics A campaign. However, of those layers found, there were relatively more ozone-rich-water-vapor-poor layers (68% versus 52%). The percentage of the sampled troposphere occupied by layers during PEM-Tropics B was less than half of that found during PEM-Tropics A (8% versus 20%). The differences between these two campaigns suggest a seasonal variation in the occurrence of layers. This is confirmed using measurements made by the Southern Hemisphere Additional Ozonesondes (SHADOZ) network., United States. National Aeronautics and Space Administration (Grant NAG1-2173), National Science Foundation (U.S.) (Grant ATM 9910244)

With aircraft-mounted in situ and remote sensing instruments for dynamical, thermal, and chemical measurements we studied two cases of tropopause folding. In both folds we found Kelvin-Helmholtz billows with horizontal wavelength of ∼900 m and thickness of ∼120 m. In one case the instability was effectively mixing the bottomside of the fold, leading to the transfer of stratospheric air into the troposphere. Also, we discovered in both cases small-scale secondary ozone maxima shortly after the aircraft ascended past the topside of the fold that corresponded to regions of convective instability. We interpreted this phenomenon as convectively breaking gravity waves. Therefore we posit that convectively breaking gravity waves acting on tropopause folds must be added to the list of important irreversible mixing mechanisms leading to stratosphere-troposphere exchange., United States. National Aeronautics and Space Administration (Grant NAG2-1105), United States. National Aeronautics and Space Administration (Grant NAGl-1758), United States. National Aeronautics and Space Administration (Grant NAGl-1901)

Water vapor fluctuations are measured and analyzed at an unprecedented 10-m resolution throughout the troposphere. Computation of structure functions shows that specific humidity variations observed by research aircraft over the Pacific Ocean exhibit anomalous scaling from about 50 m to 100 km in horizontal range. The scaling laws show different characteristics for the marine boundary layer, the tropical free troposphere, and the extratropical free troposphere. More specifically, boundary-layer humidity fluctuations are less smooth and more stationary than those in the free troposphere, while the extratropical free tropospheric variations are less intermittent than those in the other two regions. The anomalous scaling results argue against passive advection by a spatially smooth flow (chaotic advection) at these scales., United States. National Aeronautics and Space Administration (Grant NAG1-2173), United States. National Aeronautics and Space Administration (Grant NAG1-1901)

Aircraft-based meteorological and chemical measurements from NASA's Pacific Exploratory Missions provide a suitable database for studying the climatology of horizontal wavenumber spectra in the troposphere overlying an ocean. The wavenumber spectra of trace gas and meteorological quantities aid in identifying the physical processes producing atmospheric structures as well as provide diagnostics for general circulation models. Flight segments were distributed over altitudes ranging from about ∼50 m to 13 km and 70°S to 60°N in latitude. The spectra were averaged according to altitude and latitude regions. The wavelength range covered was typically ∼0.5–100 km. Quantities processed in this way were horizontal velocity, potential temperature, specific humidity, and the mixing ratios of ozone, methane, carbon monoxide, and carbon dioxide. Spectral power and slope (in log-log coordinates) corresponding to the wavelength regime of 6–60 km were tabulated for those measured quantities. The spectral slopes of horizontal velocity and potential temperature were generally close to −5/3 with no transition to a steeper slope at short wavelengths as seen in some other studies. Spectral slopes of the tracer species also ranged around −5/3. This agreement in form of the dynamical and tracer spectra is consistent with both the gravity-wave advection and quasi two-dimensional turbulence models. In the upper troposphere the spectral power for all quantities except specific humidity tended to be greater at latitudes higher than 30° compared to latitudes lower than 30°. This latitudinal trend confirms the earlier results of the Global Atmospheric Sampling Program., United States. National Aeronautics and Space Administration (Grant NAG1-1758), United States. National Aeronautics and Space Administration (Grant NAG1-1901)