Synoptic-scale Waves Research Articles

PROPAGATION OF SYSTEMATIC ERRORS IN A ONE LAYER PRIMITIVE-EQUATION MODEL FOR SYNOPTIC SCALE MOTION

Abstract A one-layer, mid-latitude, beta-plane channel model of an incompressible homogeneous fluid is constructed to study the propagation of systematic errors on a nearly stationary synoptic scale wave. A time- and space-centered difference scheme is used to evaluate the governing primitive equations. Data fields resulting from height field perturbations injected at various locations in the synoptic wave are compared to the unperturbed synoptic wave at 3-hr intervals for 5 model days. Results show that the low-frequency or quasi-geostrophic component of the error tends to move toward the core of maximum velocity in the basic state and that, after 5 days, these maximum height errors are in the core regardless of the location of the initial perturbation.

SOME REMARKS ON AFRICAN DISTURBANCES AND THEIR PROGRESS OVER THE TROPICAL ATLANTIC

Abstract A daily analysis of the 2,000- and 10,000-ft streamlines over West Africa was made for a 3½-mo period beginning in July 1968. With the aid of satellite photographs and auxiliary sea-level pressure data, a total of 33 synoptic scale wave perturbations were observed to move across West Africa and the tropical Atlantic Ocean during this period. Some general features of these disturbances are summarized, including facts on their origin, speed, intensity, distribution of sea-level pressure, appearance on the satellite photographs, and movement over the Atlantic Ocean. The effects of the large-scale circulation and the influence of sea-surface temperatures on the movement and intensity of disturbances are also discussed.

Observational Evidence of Kelvin Waves in the Tropical Stratosphere

Abstract This study of synoptic-scale wave motions in the equatorial stratosphere is based on the analysis of six months of radiosonde data from three tropical stations. Fluctuations in the zonal wind with an average period of 15 days, and amplitudes in the order of 8–12 m sec−1 are noted. Corresponding fluctuations are found in the temperature field with amplitudes of 3–5C and a phase lead of ¼ cycle with respect to the zonal wind. These wave motions which propagate phase downward do not appear to involve the meridional wind component. The observed fluctuations resemble Kelvin waves, which represent one of the solutions of the wave equation on an equatorial beta plane. One of the notable features of this type of wave is that it produces an upward flux of westerly momentum. The observations indicate that this flux is large enough to account for the westerly accelerations associated with the quasi-biennial oscillation.