Vol 41, No 6 (2016)

The Greenland ice sheet is a very important potential source of fresh water inflow to the World Ocean under warming climate conditions. Apparently, it was the same during the Last Interglacial 130-115 thousand years ago. In order to quantify input of the Greenland ice sheet to the rise of the global mean sea level in the past or in the future, we include a surface mass balance model block into the Earth System Model. The computational algorithm is based on the calculation of energy balance on the ice sheet surface. The key tuning parameter of the model is the daily amplitude of air surface temperature. It defines the area and the rate of snow or ice melting. The range of possible values of this parameter is determined during a series of numerical experiments. High sensitivity of meltwater runoff volume to surface air temperature amplitude is revealed.

The results are presented of the analysis of mean values and trends in precipitable water in the Arctic atmosphere determined from the data of 55 aerological stations located northwards of 60° N for 1972-2011. The regions with maximum and minimum mean values and trends are identified. It is demonstrated that the humidity increase took place almost over the whole latitudinal zone in summer. The comparison with similar characteristics obtained by other researchers from the reanalysis data demonstrates good agreement.

Empirical relationships between methane concentration and the rates of its oxidation and emission in the sediment-water-atmosphere system are computed using the experimental data and the data presented in the literature. For the Sea of Azov and the World Ocean the possibility is demonstrated of using the empirically derived formulae to compute the methane cycle elements in aquatic ecosystems. The comparability of methane volumes in the water column and bottom sediments as well as of those oxidized and released from water and sediments computed using these formulae, demonstrates the adequacy of the obtained formulae. It is shown that depending on morphological parameters of reservoirs of aquatic ecosystems and on their volume and area, the ratio of the amounts of methane that is oxidized and released to the atmosphere, changes as well as the rate of its turnover.

Numerical experiments based on the WRF model were conducted to analyze the structure and evolution of the polar mesoscale cyclone developed over the Kara Sea on September 29-30, 2008. It was found that baroclinic instability in the lower troposphere and convective instability (including that due to the wind-induced surface heat exchange) did not play a significant role. Significant contribution was made by the downward advection of potential vorticity from the upper troposphere and by the conditional instability of second kind. It is demonstrated that if water phase transitions are not taken into account, the mesocyclone intensity is reduced by 7-20% and the time of its development increases by 4 hours. The advection of potential vorticity was not the only process causing the intensification of the lower potential vorticity anomaly associated with cyclonic circulation.

The use of global Atmospheric Motion Vectors (AMV) satellite observations in the meteorological data assimilation system based on Local Ensemble Transform Kalman Filter (LETKF) algorithm is considered. The height assignment is the most crucial error source for AMV observations. To reduce its impact, the AMV height reassignment method is implemented; it is based on the consistency coefficient bet ween the observed and the background winds. The other way to improve the analysis quality is a more accurate specification of AMV observation errors. This necessitates the use of the nondiagonal observation-error covariance matrix R in the data assimilation scheme. The first results of these studies are presented. It is demonstrated that the use of AMV observations in the data assimilation system reduces the errors of forecasts computed from the initial data of this system.