A relationship has been obtained and experimentally confirmed that relates the structural constant of turbulent temperature fluctuations and the turbulent energy dissipation rate through vertical gradients of the average wind speed and average potential temperature and the turbulent Prandtl number.
It is demonstrated how the energy is redistributed and the law of conservation of energy is fulfilled when optical radiation reflecting in a turbulent atmosphere. It is found that the mean intensity of an optical beam, scattered by a point reflector or by an ensemble of point reflectors in a turbulent atmosphere, increases in the strictly backward direction (backscatter amplification (BSA) effect) at the expense of overflow of the energy from a huge area several orders of magnitude exceeding the BSA effect localization area.
It is shown that zones of clear air turbulence can be indicated remotely both from the variance of radial velocity measured by a coherent Doppler wind lidar and from the structure constant of turbulent fluctuations of the refractive index measured by the lidar capable of determining the intensity of optical turbulence.
It is shown that in the absence of developed convective turbulence, estimating the mixing layer height from height-time distribution of the Richardson number not always provides correct results. The more correct way is to estimate the mixing layer height from height-time distributions of the turbulence kinetic energy (TKE) dissipation rate by the threshold criterion.
A comparison is made of the time variations in the height of the turbulent mixing layer, which is determined from the
altitude-time distributions of the dissipation rate of the kinetic energy of turbulence and from the distributions of the
Richardson number Ri . It is shown that qualitatively the time series of the height of the turbulent mixing layer,
calculated according to the threshold value of the dissipation rate Thrɛ= 10-4 м2/с3 and according to the criterion
Ri <0.5, agree with each other.
The results of experimental investigation of the atmospheric boundary layer using coherent Doppler wind lidar Stream Line and temperature profiler MTP-5 are presented. Measurements were carried out in Tomsk and in the coastal zone at the western coast of Lake Baikal near the village Listvyanka. Found that on Baikal stable thermal stratification with the formation of low-level jets almost always was realized, regardless of the time of day. The Richardson number becomes less than the critical number in the area of jet streams and its value can be close to zero. During measurements in Tomsk there was a periodic change of thermal stratification in the boundary layer from stable at night to neutral and weakly unstable during daylight hours.
The results of a numerical analysis of the manifestation of the backscatter amplification effect in the regime of weak optical turbulence in dependence on diffractive size of the transmitting aperture are presented. It is shown that the magnitude and localization of the amplification of the average power of the radiation back scattered in a turbulent atmosphere depends on the Fresnel number of the transmitting aperture. Since the Fresnel number changes with changes in the distance from which the lidar signal arrives, this must be taken into account when profiling the intensity of optical turbulence from the lidar data on the amplification of the average power of scattered radiation.
Data are presented about the variations in the average power of lidar echo signals with coherent and incoherent receiving over wide range of variations of the refractive turbulence strength in the atmosphere. It is established that in the case of incoherent receiving the backscatter amplification coefficient first increases with increase of the turbulence strength, then saturates at a certain level in the regime of strong turbulence on the probing path and decreases with further refractive turbulence strength increase. The maximum value of the amplification coefficient achievable at a given distance depends on the refractive turbulence strength at the moment of measurement. The time course of the backscattering amplification coefficient is in a good agreement with the temporal changes of the structural constant of turbulent fluctuations of the air refractive index, determined from independent measurements.
The formulae and results of calculation of the spatiotemporal structure function of intensity in the optical image of a topographic object in a turbulent atmosphere are presented. The results can be used in development of algorithms for estimation of the crosswind velocity from optical images of natural scene.
The function of mutual coherence of the field and the mean intensity of partially coherent pulsed optical radiation scattered by an atmospheric layer have been calculated. It is shown that as the pulse duration decreases, the spatial coherence of backscattered radiation improves in comparison with the coherence of scattered continuous-wave (cw) radiation. In contrast to cw radiation, which scatters uniformly in the backward direction, the backscattering of pulsed radiation becomes nonuniform for shorter pulses, and for ultrashort pulse durations the backscattered radiation is localized near the strictly backward direction in the zone with transverse dimensions comparable with the initial size of the sensing beam.
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