Estimation of the height of the mixing layer from the altitude-time distributions of the dissipation rate of turbulent energy and the Richardson number

Estimating the height of the turbulent mixing layer from height-time distributions of the Richardson number

“…The threshold was set equal to Thr  = 10 -4 m 2 /s 3 and was chosen from its compliance with the lower boundary of moderate turbulence, when turbulent mixing becomes insignificant. The same threshold for estimation of mix h was set in [7] and in [9,10].…”

“…When estimating diurnal variations of the height of the turbulent mixing layer from the height-time distributions of the Richardson number , we assumed that the turbulent mixing takes place in the same periods and at the same heights , when and where the Richardson number Ri < 0.5. The height of the turbulent mixing layer at the chosen time was taken to be the minimal height, starting from which the Richardson number becomes greater than 0.5 [9,10]. The Richardson number was used for estimation of the turbulent mixing layer height, in particular, in [11][12][13].…”

“…There are different technical facilities that are widely used for turbulent parameters estimation in the atmospheric boundary layer (ABL) and determining the mixing layer height [1][2][3][4][5][6][7][8]. The results of determining the height of the turbulent air mixing layer from height-time distributions of the turbulent energy dissipation rate and from height-time distributions of the Richardson number Ri obtained from measurements of a pulsed coherent Doppler lidar (PCDL) and a temperature spectroradiometer are compared in [9,10]. Comparative experiments in [9,10] were conducted under the conditions of diurnal alternation of stratification in the atmospheric boundary layer from stable at night to unstable in daytime which is typical for summertime.…”

“…The results of determining the height of the turbulent air mixing layer from height-time distributions of the turbulent energy dissipation rate and from height-time distributions of the Richardson number Ri obtained from measurements of a pulsed coherent Doppler lidar (PCDL) and a temperature spectroradiometer are compared in [9,10]. Comparative experiments in [9,10] were conducted under the conditions of diurnal alternation of stratification in the atmospheric boundary layer from stable at night to unstable in daytime which is typical for summertime. It was shown that the temporal profiles of the height of the turbulent mixing layer calculated by the threshold value of the dissipation rate Thr  = 10 -4 m 2 /s 3 and by the criterion Ri < 0.5 are in a qualitative agreement.…”

Об Оценивании Высоты Слоя Турбулентного Перемешивания Из Высотно-Временных Распределений Числа Ричардсона

“…В работах [1,2] проведено сравнение результатов определения высоты слоя турбулентного перемешивания воздуха из высотно-временных распределений скорости диссипации турбулентной энергии и из высотно-временных распределений числа Ричардсона Ri , получаемых из данных измерений импульсного когерентного доплеровского лидара (ИКДЛ) и температурного спектрорадиометра. Сравнительные эксперименты в [1,2] Расхождение данных о стратификации в ночное время в нижнем 150 метровом слое по градиенту и по числу Ричардсона объясняется тем, что в это время на этих высотах существовали низкоструйные течения (см. верхнее распределение слева на рисунке 4), в области которых число Ричардсона принимает пониженные значения [3].…”