ИСТИНА

The detailed hydrodynamic modelling of meteorological parameters during the last 30 years (1985 – 2014) was performed for the Okhotsk Sea and the Sakhalin island regions. The regional non-hydrostatic atmospheric model COSMO-CLM used for this long-term simulation with ~13.2, ~6.6 and ~2.2 km horizontal resolutions. The main objective of creation this dataset was the out-look of the investigation of statistical characteristics and the physical mechanisms of extreme weather events (primarily, wind speed extremes) formation on the small spatio-temporal scales. The detailed meteorological information is also important since it allows to take into account sea and islands coast configuration, mountain systems and other mesoscale features of surface terrain. This work suggests and describes the downscaling technology for the long-term simulations using three consequent “nesting domain”, shows the results of obtained archive verification, as well as extreme wind velocities estimation. The COSMO-CLM model (v. 5.0) used as main tool for creation of this long-term meteoro-logical archive. COSMO-CLM is the climate version of the well-known mesoscale COSMO mod-el, including some modifications and extensions adapting to the long-term numerical experiments. The downscaling technique was realized and developed for the long-term simulations with three consequent nesting domains and standard configuration of COSMO-CLM model. ERA-Interim reanalysis (~0.750 degrees resolution) used as global forcing data for the starting domain (~13.2 km horizontal resolution), then these simulation data used as initial and boundary conditions for the next model runs over the domain with ~6.6 km resolution, and similarly, for the next step to ~2.2 km domain. Besides, the COSMO-CLM model configuration for ~13.2 km run included the ‘spectral nudging’ technique, i.e. an additional assimilation of reanalysis data not only at bounda-ries, but also inside the whole domain. Fig.1 and Table 1 shows the boundaries and main character-istics of used domains. Practically, this computational scheme realized on the SGI Altix 4700 su-percomputer system in the Main Computer Center of Roshydromet and used ~2,400 hours of CPU time total. More than 20 meteorological fields were obtained finally over these three domains with 1-hour temporal resolution throughout 30 years. According to modelling results, the verification of the obtained dataset was performed on the observation data, obtained from “Hydrometcenter database” and www.rp5.ru archive. Estima-tions for the whole period, all domains and different seasons showed the mean error -0.5 0C, up to 2 – 3 0C RMSE in temperature (error maxima was during spring and autumn), and overestimation of inland wind speed (RMSE is up to 2 m/s). It’s noteworthy that wind gusts were reproduced by model notably good (ME was up to 1 m/s, RMSE was 2 – 3,5 m/s, correlation coefficients were 0,8 and more), despite to a fairly simple algorithm [5]. Overall, analysis showed that the used downscaling technique with applying the COSMO-CLM model reproduced the meteorological conditions, spatial distribution, seasonal and synoptic variability of temperature and extreme wind speed for the study area with approximately the same adequate quality. The dependencies between reproduction quality of mesoscale atmospheric circulation features and the horizontal resolution of the model were revealed. In particular, it was shown that ~6.6 km resolution does not give any significant improvement comparing to ~13 km resolution, whereas ~2.2 km resolution provides an appreciable quality enhancement. Detailed synoptic analysis of extreme wind speed situations identified the two main types of favorable to their genesis. The first one (more frequent) was associated with developing of cy-clones over the Japan Islands or the Primorsky Kray of Russia, the subsequent moving the Sakha-lin Island, crossing it and coming in the Okhotsk Sea. The second one characterized by penetration of intensified cyclones from Pacific Ocean through the Kamchatka peninsula, Kuril or Japan Is-lands. Next, the deepening cyclones crossed the Okhotsk Sea and got close to the Sakhalin Island, causing extreme winds offshore. The obtained high-resolution dataset will continue to be used for a fully and comprehensive analysis of physical mechanisms of extreme weather events, the reproduction quality of hydrome-teorological fields, their statistical estimates, climatological trends, using this information for the detailed environment state assessment and many other objectives.