The characteristics of acoustic-gravity waves (waveforms, time durations, amplitudes, azimuths and horizontal phase speeds) from the eruption of the Hunga-Tonga-Hunga-Hapai volcano detected at ...different infrasound stations of the Infrasound Monitoring System and at a network of low-frequency microbarographs in the Moscow region are studied. Using the correlation analysis of the signals at different locations, six arrivals of signals from the volcano, which made up to two revolutions around the Earth, were detected. The Lamb mode of acoustic gravity waves from the volcano eruption is identified and the effect of this mode on generation of tsunami waves and variation of aerosol concentration is studied. The energy released from an underwater volcano into the atmosphere is estimated from the parameters of the Lamb wave and compared with the energy released from the most powerful nuclear bomb of 58 Mt TNT.
Using the measurement data in a wind–sand flux on the desertified areas of Astrakhan oblast and Kalmykia, it has been established that the time variability of saltating and dust aerosol particle ...concentrations, the electric characteristics of the wind–sand flux, including electric currents of saltation, the volume charge of dust aerosol particles, and the electric field intensity in the near-surface layer of the atmosphere within a range of ~30 s to 30 min are determined by the low-frequency variations in the horizontal component of the wind velocity. According to the data of measurements, over the desertified area, the electric charge surface density reaches +25 nC/m
2
. The empirical probability distribution of a specific charge for sand grains under the condition of quasi-continuous saltation is obtained. A saltation initiation mechanism by electric discharges on the underlayer surface is proposed. An analytical model of particle liftoff to the near-surface layer of the atmosphere by electric discharges on the underlayer surface is presented. It is shown that, during the electric (corona) discharge, the saltating particle launch velocity can exceed 1 m/s.
The vertical turbulent dust aerosol (DA) and heat fluxes are determined on the basis of measured fluctuations of the components of the wind speed, air temperature, and concentration of aerosol ...particles on a desertified territory of Astrakhan oblast during intermittent DA emission. The temporal variability of the horizontal and vertical components of the wind speed, air temperature, and concentration of aerosol particles is characterized using spectral analysis. It is shown that the intermittent DA emission is caused by low-frequency convective-related variations in the horizontal component of wind speed if the threshold saltation speed is exceeded. The significant differences in the spatiotemporal variability of vertical heat and DA flux are revealed. The 30-min average values of heat (90‒158 W/m
2
) and DA (7.2‒27.5 cm
–2
cm
–1
) fluxes, as well as the rates of heat (14‒21 cm/s) and DA (10‒16 cm/s) removal, are calculated.
The saltating particle aleurite mode has been discovered in the wind–sand flux over a desertified area. The approximation of the measured saltating particle distribution was found using two lognormal ...distribution functions. In the wind–sand flux, the countable concentrations of aleurite and sand particles depend differently on the wind velocity in the atmospheric surface layer.
Vertical turbulent and convective fluxes and corresponding velocities of the dust aerosol particle uplift under conditions of quasiperiodic emission have been determined by the measurements of the ...dust aerosol particle concentrations and the turbulent fluctuations of the wind speed components in a desertified area in the Astrakhan region. It is shown that convective fluxes are caused by the combined action of both regular upward motions (updrafts) in the convective coherent structure of the atmospheric boundary layer and turbulent diffusion. In the surface layer of the atmosphere at heights from 0.3 to 6.0 m, the vertical profiles of the dust aerosol concentration are approximated by power functions. It is demonstrated that the vertical turbulent and convective fluxes of dust aerosol can be estimated by the gradient method using the scales of turbulent and convective vertical motions in the atmospheric boundary layer.
Vertical Turbulent Dust-Aerosol Fluxes Karpov, A. V.; Gorchakov, G. I.; Gushchin, R. A. ...
Izvestiya. Atmospheric and oceanic physics,
09/2021, Letnik:
57, Številka:
5
Journal Article
Recenzirano
Vertical turbulent dust-aerosol fluxes over a desertificated area in Astrakhan oblast under almost quasicontinuous saltation conditions have been calculated based on measurements (with a resolution ...of 1 s) of fluctuations in aerosol-particle concentrations and the vertical wind velocity component. It is shown that the time variability of the density of vertical turbulent dust-aerosol fluxes within a scale range of 30 s to 1 h is determined by convectively caused variations in both horizontal and vertical wind velocity components in the atmospheric surface layer. The normalized turbulent flux or the rate of dust-aerosol removal reaches 4–5 cm/s. The daily variations in vertical turbulent aerosol fluxes are in agreement with those in turbulent heat fluxes. Particle-size dependences of the mass turbulent dust-aerosol flux have been obtained. The method of estimating low-frequency variations in the density of turbulent dust-aerosol fluxes over a desertificated area has been proposed based on measurement data on the wind velocity components and the saltation threshold velocity.
According to the monitoring data of the optical and microphysical characteristics of smoke aerosol at AERONET stations during forest fires in the summer of 2019 in Alaska, the anomalous selective ...absorption of smoke aerosol has been detected in the visible and near-infrared spectral range from 440 to 1020 nm. With anomalous selective absorption, the imaginary part of the refractive index of smoke aerosol reached 0.315 at a wavelength of 1020 nm. A power-law approximation of the spectral dependence of the imaginary part of the refractive index with an exponent from 0.26 to 2.35 is proposed. It is shown that, for anomalous selective absorption, power-law approximations of the spectral dependences of the aerosol optical extinction and absorption depths are applicable with an Ångström exponent from 0.96 to 1.65 for the aerosol optical extinction depth and from 0.97 to –0.89 for the aerosol optical absorption depth, which reached 0.72. Single scattering albedo varied from 0.62 to 0.96. In the size distribution of smoke aerosol particles with anomalous selective absorption, the fine fraction of particles of condensation origin dominated. The similarity of the fraction of particles distinguished by anomalous selective absorption with the fraction of tar balls (TBs) detected by electron microscopy in smoke aerosol, which, apparently, arise during the condensation of terpenes and their oxygen-containing derivatives, is noted.
Vertical profiles of the total saltating particle concentration have been constructed for a range of wind speed changes in the surface layer of the atmosphere from 5.5 to 10.5 m/s, and the profiles ...of the concentration of aleurite (silt) and sandy particles according to measurements in a desertified area in the Astrakhan Region under conditions of quasi-continuous saltation have been found. In the saltation layer from 0 to 15 cm, the concentration of silty particles with a size of 47 μm decreases two times more slowly than the concentration of sand particles with a size of 156 μm. In the lower saltation layer about 9 cm thick, the logarithmic gradient of the total concentration does not depend on the wind speed, and in the upper saltation layer it changes from –0.40 to –0.21 cm
–1
with an increase in the wind speed in the atmospheric surface layer from 5.5 to 10.5 m/s. It is shown that, in contrast to the lower saltation layer at heights of 11 and 15 cm, the dependences of the particle concentration on the wind speed turned out to be nonlinear. For the lower and upper layers of saltation, approximations of the concentration of saltation particles are obtained as a function of height, wind speed, and the threshold speed of saltation.
Anomalous absorption of finely dispersed smoke aerosol was recorded in large-scale smoke haze during mass fires in the boreal forests of Alaska in July 2019 in the visible and near-infrared regions ...of the spectrum (440‒1020 nm) according to the data of monitoring of the spectral dependences in the refractive index imaginary part on the network of AERONET stations. The variations in the spectral dependences of the aerosol optical depths (extinction and absorption), as well as the size distribution function of aerosol particles, are analyzed. During the anomalous absorption, the imaginary part of the refractive index increased by a factor of 1.8‒7.2 with an increasing optical wavelength from 440 to 1020 nm, reaching a value of 0.315 for the wavelength of 1020 nm. A power approximation is proposed for the spectral dependence of the imaginary part of the refractive index with indices of power approximately from 0.7 to 2.3.
