Vol 41, No 7 (2016)

Nonperiodic vertical and temporal variations in wind direction in the lower 500-meter air layer related to synoptic conditions are studied using the long-term data of acoustic remote sensing by the MODOS sodar at Moscow State University. Average values of wind shear to the right (clockwise) with time as a result of the passage of atmospheric fronts are 55° for cold fronts, 40° for warm fronts, and 45° for occlusion fronts. In some cases the clockwise wind shear may reach 180° per 30 minutes and 720° per several hours. The wind shear to the left with time is usually observed if the northern periphery of anticyclones or the ridge axis pass by. It takes more time than the clockwise wind shear does. Dramatic variations in wind direction with height including synchronous opposite air flows at different heights are observed in the zones of fronts, axes of ridges and troughs (if they are inclined), and cols. The vertical wind shear may reach 250° in the lower 300-meter air layer. Thunderstorms in Moscow are usually accompanied by the average wind speed increase by 1 m/s during 30-40 minutes after their beginning.

The technology ofthe method of joint probabilities ofthe tidal and residual (de-tided) components developed to estimate the possible sea level fluctuations [1, 10] and modified to calculate rare extreme total sea current velocities [8], is applied to compute ice drift velocity on the northeastern shelf of Sakhalin Island. The initial data are the hourly series of the drift velocity vector obtained from radar observations at Odoptu coastal station (1986-1996, during the whole ice season) and at the Molikpaq drilling platform (in May in 1999, 2000, 2003, 2005, and 2006). The distribution of the tidal component was determined by the prediction of the corresponding series for 19 years that is possible due to the stability of characteristics of the tidal drift. The distribution of the residual component was estimated by combining all de-tided series for the entire time period. The obtained estimates of total ice drift velocities of rare occurrence are in good agreement with those presented in [8] and can be used for designing facilities for the extraction and transportation of hydrocarbons on the northeastern shelf of Sakhalin Island.

The results of the analysis of spatiotemporal variability of frost depth in the Volga River basin are presented. It is demonstrated that in the geographic zones of the basin the mean frost depth decreased in wide limits: from 10-20 to 90-100 cm and more. It was revealed that the frost depth decrease in the Volga River basin leads to the average increase in winter runoff by 17% (the variation range is from 3 to 42%).

The impact is assessed that the groundwater flow from the built-up areas on the left bank of the Don River in the Rostov oblast produces on the chemical composition and quality of surface water in the lower river reaches. It is demonstrated that the total average annual groundwater flow from the built-up areas on the left river bank is very small and equals 0.002 km3/year on average or 0.01% of the average annual water flow in the estuarine outlet. Despite the rather high degree of contamination of groundwater and the high content of principal ions, this causes the insignificant impact of groundwater runoff on water quality in the Lower Don. The average total mass of substances that annually come from the left-bank urbanized areas in the groundwater flow is about 4.9 x 10³ t or 0.04% of total mass of substances transported by the Don River to the Taganrog Bay.