On the Structure of Temperature Pulsations near the Surface under Convective Conditions

Abstract

Temperature pulsations are measured under conditions of summer hot weather in the near-surface air layer in a desert territory using wire sensors distributed spatially and in height with a recording frequency of 1000 Hz. For the power spectra, slopes with values from “–1” to “–1.35” (scales: 0.2‒2 m) are recorded for frequencies below the “–5/3” inertial interval region. At frequencies above the inertial interval (scales: 0.01‒0.1 m), slopes range from “–4.2” to “–5.8.” In some episodes at frequencies less than 0.1‒0.3 Hz, there are slopes from “–0.2” to “–0.85.” Based on the equations of motion in the Boussinesq approximation, estimates are obtained for the observed slopes of the spectra: “–1,” “–4/3,” and “–7/3” that are typical of a thermally stratified medium. Using a qualitative (visual) method at different signal averaging times (1, 10, 200 s), the emergence of thermoconvective ramp structures with a temporal length of 0.3‒1 s is revealed, which constitute a ramp with a length of 1‒10 s at larger averaging.