Horizontal wavenumber spectra of winds, temperature, and trace gases
during the Pacific exploratory missions: 1. Climatology
Aircraft-based meteorological and chemical measurements from NASA's
Pacific Exploratory Missions (PEM) provide a suitable data base 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 deg
S to 60 deg N in latitude. The spectra were averaged according to
altitude and latitude regions. The wavelength range covered was
typically about 0.5 to 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 deg compared to latitudes lower than 30 deg.
This latitudinal trend confirms the earlier results of the Global
Atmospheric Sampling Program.
Send e-mail to
j y n c @ m i t . e d u for a copy of
the complete article.
href="../publications.html">Return to publications list.