Diurnal Variation of Wind, Pressure, and Temperature in the Troposphere and Stratosphere over the Azores

Abstract

The diurnal and semidiurnal variations of wind, pressure, and temperature at Lajes Field, Terceira, Azores, were computed for each month of the year for 30 levels between the surface and 10 mb. The semidiurnal variations were found to agree fairly closely with those at Washington, D.C., where data for the troposphere during the summer months are available for comparison. However, the diurnal variations of pressure and wind at the two stations are quite dissimilar. In order to check the consistency of the wind and pressure variations at Lajes Field, the diurnal and semidiurnal height variations were computed from the wind variation at each isobaric surface by the use of a model based on a linearized form of the equations of motion, frictionless flow, and the assumption that the oscillations are simple progressive waves. Results of the analysis indicate that the radiosonde observations contain diurnal, and smaller semidiurnal, temperature errors which superimpose fictitious pressure variations on the true pressure oscillations in the stratosphere, causing the phase of the latter to be moved toward noon. These results are supported by a similar analysis of rawinsonde data for Ft. Worth, Texas. The diurnal and semidiurnal temperature variations implied by the wind-derived height changes in the stratosphere are in general agreement with the results of determinations based on radiation theory. The diurnal error of the radiosonde temperature observations (observed minus computed temperature change) shows a maximum near noon at levels between 12 and 27 km, the diurnal range increasing from about 1C at the lower to about 2.5C at the upper level.