On the structure of temperature pulsations near the surface under convective conditions

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Measurements of temperature pulsations under conditions of summer hot weather in the near-surface air layer in a deserted area were carried out 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” (scale: 0.2–2 m) are noted 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, slopes from “–0.2” to “–0.85” are observed. Based on the equations of motion in the Boussinesq approximation, we obtained estimates for the observed slopes of the spectra: “–1”, “–4/3”, and “–7/3”, characteristic of a thermally stratified medium. Using a qualitative (visual) method at different signal averaging times (1, 10, 200 s), the occurrence of thermoconvective structures of “ramps” with a temporal length of 0.3–1 s was revealed, which constitute ramps with a length of 1–10 s at larger averaging.

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Sobre autores

Е. Malinovskaya

A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences

Autor responsável pela correspondência
Email: elen_am@inbox.ru
Rússia, Moscow

O. Chhetiani

A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences

Email: elen_am@inbox.ru
Rússia, Moscow

V. Azizyan

A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences

Email: elen_am@inbox.ru
Rússia, Moscow

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2. Fig. 1. Layout of 2-meter masts and installation of sensors of the wireless pulsation measuring complex (panorama, along the line, close-up, on a satellite image) and an illustration of the implementation of the second experiment with sensors at different heights.

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3. Fig. 2. Change in the angle of incidence of the sun's rays on the surface (scheme of the sun's movement).

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4. Fig. 3. Temperature pulsation spectra: (a) 22.07 at 12:00 points 1–3; (b) 22.07 at 13:00 points 1–3, (c) 28.07 at 12:00 at heights of 20 and 80 cm, (d) 29.07 at 13:00 at heights of 20 and 80 cm, (d) 28.07 at 10:00 at heights of 20 and 80 cm, (e) 29.07 at 11:00 at heights of 20 and 80 cm (ω is the frequency, u(20).

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5. Fig. 4. Dynamics of changes in the scales of structures (a - first inflection point, b - second inflection point) on a clear day 07/29/2022 and frequencies 07/28/2022 and 07/29/2022 at the inflection points, changes in slope coefficients during the day 07/28 and 07/29 (square areas - moments of time with cloudiness on 07/28).

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6. Fig. 5. Manifestation of self-similarity of structures with changes in the scale of visualization and averaging. (a) representation on an interval of 20 sec. with averaging of 1 sec., the selected structures have a length from 300 to 1000 ms, (b) representation on an interval of 50 sec. with a coefficient of x10, averaging of 10 sec., the selected structures have a length from 1 to 3 sec., (c) and (d) representation on intervals of 50 and 200 sec. with averaging of 100 sec., structures have a length from 1 to 10 sec.

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