Suchergebnisse

A new version of 1D thermodynamic and hydrodynamic model LAKE 2.1 is presented. The model is supplemented with description of dynamics and vertical distribution of salinity in ice layer. Simulation results are compared to in situ and satellite data on water temperature and ice cover at Lake Uvs (Mongolia) from 2000 to 2015. We demonstrate that underestimation of mixed-layer depth by the model with standard k–ε closure during summer and autumn leads to significant shift of ice-on to earlier dates. If the effects of water salinity are neglected in the model, ice cover establishes 16–17 before the observed dates. This error is removed, if influence of salinity on water density and freezing point is included, still assuming the fresh ice. However, in this case, LAKE model underestimates the maximal winter ice thickness on average by ≈0.2 m. In turn, this discrepancy decreases an order of magnitude if dynamics and vertical distribution of salinity in ice are reproduced. Such an effect does not take place when using constant salinity value in ice.

We study the conditions for the occurrence of "the voice of the sea" in the infrasound range can occur and determine its parameters from infrasound measurements in the Black Sea water area conducted in 2011 and 2016 and in the water area of the Sea of Okhotsk in 2017. To this end, we compared the observations of different parameters (mean correlation, spectra of acoustic arrivals, direction and phase velocity) of the high-frequency infrasound (1–10 Hz), recorded in Katsiveli (Crimea) in 2011 and 2016. We performed a detailed study of the wind conditions in the Black Sea water area during the measurement period, as well as the conditions for the propagation of acoustic waves along the direction of their arrivals.
In both cases the atmospheric vortices in the direction of the arrival of infrasound were detected, which caused changes in wind velocity vector above the sea surface. The infrasound recorded in 2011 was caused by the interaction of two differently rotating atmospheric vortices over the sea. In 2016, a vortex was observed to the West from the registration point. The possibility of generating "the voice of the sea" due to the rotation of the wind velocity, which causes a nonlinear interaction of surface waves propagating in opposite directions to each other, and the formation of their 2nd harmonic in the form of a standing surface wave is discussed.
From the analysis of the wind speed and wind direction profiles along the infrasound arrival path, as well as the acoustic pressure fields calculated by the parabolic equation method for the effective sound speed profiles in the direction of infrasound propagation, the most probable areas of infrasound generation were determined. In both cases these areas coincided with the zones in which the wind speed drops to zero, and the direction of the wind changes to the opposite.
An example of simultaneous detection from one direction of the microbaroms with frequencies 0.2–0.3 Hz and "the voice of the sea" with a higher frequency of 5.5 Hz is given.

This work is devoted to testing the hypothesis about the presence of a diagnostic connection between the second and third moments of the hydrodynamic quantities \({{c}_{1}}\) and \({{c}_{2}}\) in the atmospheric boundary layer above a geometrically complex surface: \(\overline {w{\kern 1pt} 'c_{1}^{'}c_{2}^{'}} = C{{S}_{{{{c}_{1}}}}}{{\sigma }_{{{{c}_{1}}}}}\overline {w{\kern 1pt} 'c_{2}^{'}} .\) To test this ratio, a seven-month series of high-frequency measurements on an eddy covariance tower installed at the Meteorological Observatory of Lomonosov Moscow State University was used. Based on the statistical distribution of the third moments, the optimal methods for analyzing the reliability of the dependence under study were determined. For the first time on a large series of data, a statistically valid assessment of the validity of the tested hypothesis was obtained in the conditions of the urban underlying surface. The influence of stratification conditions and the nature of the underlying surface in the area of flux formation on the fulfillment of ratio second and third moments is studied. It is established that for the third moments \(\overline {w{\kern 1pt} 'w{\kern 1pt} 'T{\kern 1pt} '} ,\) \(\overline {w{\kern 1pt} 'T{\kern 1pt} 'T{\kern 1pt} '} ,\) \(\overline {w{\kern 1pt} 'u{\kern 1pt} 'u{\kern 1pt} '} ,\) and \(\overline {w{\kern 1pt} 'v{\kern 1pt} 'v{\kern 1pt} '} \) relation second and third moments is valid in 80% of cases.

Using the example of an analysis of an extreme lowering of temperature in Moscow in January 2017, the horizontal and vertical extent of the urban heat island against the background of a strong stable stratification of the atmospheric boundary layer is studied. The possibilities of measuring and monitoring the vertical structure of the atmosphere by means of ground-based remote sensing are investigated. The capabilities of the mesoscale model WRF, adapted for a detailed description of mixing processes in the atmospheric boundary layer, in reproducing the spatial dynamics of the temperature anomaly are demonstrated. The numerical estimates of the amplitude and vertical extent of the urban heat island are compared with the measurement accuracy and the total errors of the numerical predictions. Comparison of measurement data and numerical simulation results on the WRF model, using the example of a winter urban heat island in January 2017, showed that mesoscale synoptic models so far only capture the main features of the urban heat island. But deviations between model and observed temperature fields can reach 5 C.

The results of recording of internal gravity waves (IGWs) and infrasound waves from the warm and cold fronts associated with the atmospheric storm passing through Moscow on May 29, 2017 are presented. The waves were recorded by a network of 4 microbarographs IFA–MGU–MSR–ZNS located in Moscow and Moscow region, and compared with the data of measurements of the parameters of infrasound waves at infrasound station IS43 in Dubna. We study the temporal changes in the characteristics of IGWs and infrasound waves (coherence, direction of propagation,phase velocities, characteristic periods and frequency spectra) with the passage of warm and cold fronts through the network. The transition from the gravity to the acoustic dispersive branch of acoustic-gravity waves due to an increase in frequency and the temporal modulation of the phase velocity of infrasound waves caused by IGWs are also studied. The measurement data for PM10 aerosol concentrations and NO2 gas concentrations at various locations in Moscow during a passage of atmospheric storm are presented. The possibility of detecting wave precursors of atmospheric storms simultaneously in variations of atmospheric pressure, wind velocity and aerosol concentrations is studied.