不同环境温度下冰云粒子的单次散射参量

本文提出了直接Stokes参量变换的射线追踪方案,优化了作者过去建立的求解六角冰晶粒子散射的射线追踪模式.在冰晶有吸收(折射指数为复数)的情况下,新模式采用了有效折射指数处理粒子内的非单色折射波.其次,新模式还引入了有效单次散射参量,消除了来自几何透射线的前向δ散射效应.最后,根据不同环境温度下的冰云中冰晶粒子的粒径谱分布,本文计算了粒径谱积分平均的3D随机取向六角冰晶粒子的单次散射参量.文中给出的冰晶粒子单次散射参量的数值,对研究冰云辐射特性将有一定参考价值.     

A year-round monitoring of sea ice properties from the AMSU satellite microwave radiometer data

A new approach to the year-round daily monitoring of sea ice properties based on the multispectral measurements of the AMSU satellite radiometer is considered. It is revealed that the increase in the values of the sea ice scattering index and its anomalously high variability are observed during the warm period of the year. The analysis of main reasons influencing the variations of the sea ice scattering index in different seasons is carried out. The recommendations are proposed on the identification of ice properties on the maps of the sea ice scattering index plotted for the warm, cold, and transition periods.     

Hydrometeorological conditions in the Barents Sea during El Niño of 1997–1998

Interadapted fields of main hydrophysical characteristics in the vicinity of hydrological sections carried out in 1997–1998 in the Barents Sea are obtained on the basis of model computations. The complex analysis of these materials and atmospheric situation in the region during 1997–1998 enabled to estimate quantitatively the variations of significant hydrodynamic conditions: the decrease in the inflow of rather warm and salty North Atlantic waters and the compensation inflow of polar waters, the decrease in total heat content and the weakening of water dynamics in the system of the general cyclonic circulation, and the increase in the ice coverage of the Barents Sea in anomalously cold winter 1997/98. It is revealed with a high degree of the confidence probability that the significant deviations from the normal conditions occur in response to the global El Niño disturbance which took place in the same years with the maximum values of the Southern Oscillation Index in January–March 1998.     

Investigation of parameterization effect on the methane flux estimation from the regional climate model of the main geophysical observatory for the territory of Russia

An effect is studied of parameterization method of the methane flux from the wetlands of Siberia on the results of model estimates carried out using the one-dimensional model of heat transfer in the soils. The results of computations of the regional climate model of the Main Geophysical Laboratory are used as the input data of this model. The computation estimates of seasonal methane flux variations at certain observation points are compared with the measured values of the methane flux. It is shown that the optimal choice of methane flux parameterization at the use of the grid climate model data as the forcing should correspond to the conditions of prevailing subgrid natural complex of one or another type of wetlands. A spatial distribution of methane emission intensity under conditions of the present-day climate and at the end of the 21st century is obtained. The analysis revealed that the methane fluxes in Western Siberia will increase by 1.5–2.5 times by the end of the 21st century.     

Simulation of Formation and Melting of Ice in the Kerch Strait

The optimized (all iterative procedures are excluded) local one-dimensional thermody-namic model of the formation and melting of ice is proposed. The numerical computation of ice cover evolution in the Kerch Strait under the influence of thermodynamic factors for the period of 5 months is carried out for the real conditions of winter of 2011/12. Thec results agree well with the available obser-vational data on the timing of ice formation and on ice thickness in the southern part of the Sea of Azov and in the Taman Bay. In combination with the full three-dimensional hydrodynamic model and taking into account diurnal variations in external factors, the model simulates the spatial distribution of ice cover formation.     

CICE海冰模式中反照率相关参数对北极海冰模拟的影响

国家气候中心气候系统模式BCC_CSM2.0最新耦合了美国Los Alamos国家实验室发展的海冰模式CICE5.0,为试验模式中与反照率相关参数的敏感性及其对模拟结果的影响,提高模式对北极海冰的模拟能力,选取海冰模式中3个主要参数进行了敏感性试验。利用以BCC_CSM2.0耦合框架为基础建立的海冰-海洋耦合模式,选取CORE资料为大气强迫场开展试验,试验的3个参数分别为冰/雪表面反射率、雪粒半径和雪粒半径参考温度。结果表明,参数取值的不同对北极海冰的模拟有显著的影响,优化后的取值组合极大提高了模式的模拟能力,主要表现在:（1）改善了对北极冬季海冰厚度的模拟,海冰厚度增大,与观测资料更为吻合;（2）显著提高了对北极夏季海冰密集度的模拟能力,从而模拟的北极海冰范围年际循环与观测更为一致。参数取值的优化改进了模式对海冰反照率的模拟,进而影响了冰面短波辐射的吸收和海冰表层的融化,最终提高了模式对海冰密集度和厚度的模拟效果。      

Tide-induced ice cover deformations on the northeastern shelf of Sakhalin Island

The ice drift data obtained with the Furuno radar using a special methodology simultaneously at seven fixed points around the Molikpaq oil-drilling platform on the northeastern shelf of Sakhalin Island in the period from May 14 to 28, 2003 are analyzed. It is shown that at different distances from the shore significant variations are observed both in the alongshore and, especially, transverse components of the tidal seaice drift, which are responsible for the ice cover deformation, whose indices are of a substantial magnitude. The divergence has the maximum positive values (the ice opening is observed) at comparatively low drift velocities of southern bearings soon after the tidal flow direction changed. The ice cover compression was accordingly observed under opposite conditions. The dependence of deformation indices on the tidal cycle phase is well agreed with the results earlier obtained at the coastal Odoptu radar station (RS), where the measurements were carried out using a similar methodology under alike physico-geographic conditions. A steady character of the results obtained allows forecasting the tide-induced ice cover extension and compression, which is of a practical value for providing the ship operations in the region of the Molikpaq platform in the ice season.     

Complex studies of hydrometeorological and ice conditions on the northwestern shelf of the Caspian Sea based on satellite and expedition observational data and model calculations

In accordance with the contract of the LUKOIL Oil Company, a cooperation of the Roshydromet organizations (Planeta Research Center for Space Hydrometeorology, a main contractor, Hydrometeorological Research Center of the Russian Federation, Arctic and Antarctic Research Institute, and State Oceanographic Institute) carried out in 2008 complex studies of the hydrometeorological and ice conditions for the Filanovskii oil- and gas-field facility construction on the northwestern shelf of the Caspian Sea. Three expeditions were organized and conducted within that project: a helicopter ice research expedition (specialists from the Arctic and Antarctic Research Institute carried out a huge volume of measurements of physicomechanic properties of level, rafted and hummocked ice, and morphometric characteristics of ice piling, hummocks, and stamukhas); specialists from the State Oceanographic Institute organized a ship expedition on studying sea ground exaration formed due to impacts of ice formations (hummocks and stamukhas) using hydro-radar and echo-sounder surveys as well as a complex hydrometeorological and hydrochemical expedition with five autonomous buoy stations mounted in two months. From the moment of ice formation to the end of the expedition activity, an operational space monitoring of the northwestern Caspian Sea was carried out at the Planeta Research Center for Space Hydrometeorology. Based on the NOAA, TERRA, and AQUA satellite data, corrected and geographically fixed satellite images of the area of activity were issued with a periodicity of 6 times per day; index maps on the ice situation (twice a week) and ice situation forecasts (lead-time of 1–7 days). Besides, long-term series of satellite data on the northwestern Caspian Sea are collected and processed: their results are used for estimating seasonal and interannual variability of the drift ice and fast ice. Specialists of the Hydrometeorological Research Center of the Russian Federation completed the work on processing and analysis of library materials, research/technical reports, handbooks, expedition observational data, and on hydrodynamic and probability modeling of long-term series of hydrological, meteorological, and partly ice data. In particular, basic characteristics of the hydrological regime (sea level, currents, and waving) are calculated for the place of the oil platform location and along the pipeline routing. Tentative local specifications on the hydrometeorological regime in the Filanovskii field are worked out based on the results of the work performed.     

Methodology of evaluation of forecasts of the reservoir ice cover thickness (the Votkinsk reservoir case study)

Relationships between the ice cover thickness alimentation and negative temperatures sums are defined for several ice profiles in the Votkinsk reservoir. Possibility of their using for the ice cover thickness forecasting is considered. Criteria of the acceptable errors of the ice cover forecasts and computations are studied. A new way of their improvement is proposed.     

Thinner Sea Ice Contribution to the Remarkable Polynya Formation North of Greenland in August 2018

In August 2018, a remarkable polynya was observed off the north coast of Greenland, a perennial ice zone where thick sea ice cover persists. In order to investigate the formation process of this polynya, satellite observations, a coupled iceocean model, ocean profiling data, and atmosphere reanalysis data were applied. We found that the thinnest sea ice cover in August since 1978(mean value of 1.1 m, compared to the average value of 2.8 m during 1978-2017) and the modest southerly wind caused by a positive North Atlantic Oscillation(mean value of 0.82, compared to the climatological value of-0.02) were responsible for the formation and maintenance of this polynya. The opening mechanism of this polynya differs from the one formed in February 2018 in the same area caused by persistent anomalously high wind. Sea ice drift patterns have become more responsive to the atmospheric forcing due to thinning of sea ice cover in this region.     

Simulation of the atmospheric circulation in the Weddell Sea region using the limited-area model REMO

Summary ?To analyse the applicability of a limited-area atmosphere model to the Southern Ocean, a one-year simulation for 1985 is performed using the REgional MOdel REMO at 55-km horizontal grid-spacing implemented for the Antarctic regions of the Weddell, Bellingshausen and Amundsen Seas. To evaluate the performance of REMO, a comparison of model results to observations and to reanalysis/analysis data sets is carried out. REMO is initialized and driven at the lateral and lower boundaries by data of the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA15). Overall, REMO is an appropriate tool for further climate studies in Antarctic regions. It reproduces reasonably well basic spatial patterns and the seasonal cycle of the atmospheric circulation. However, the simulated mean sea level pressure (MSLP) is predominantly lower than the MSLP provided by observations and by ERA. Considerable temperature differences in the lower troposphere over sea ice in winter cause discrepancies between the REMO and ERA pressure fields in the mid-troposphere too. The precipitation rate P of the REMO simulation agrees qualitatively well with main features of the observed climatological spatial distribution described in literature. The seasonal cycle of P in the inner Weddell Sea reflects the Antarctic semi-annual oscillation. Concerning the forcing fields, the ERA sea ice surface temperatures in winter are generally higher than satellite derived surface temperatures. Although the differences are 10 to 15 K in the southern Weddell Sea, this deficiency of the ERA data hardly influences the mean large-scale circulation. Received October 10, 2001; revised April 22, 2002; accepted May 12, 2002     

Investigation of effects of spatially and temporally variable wind on currents, surges, and admixture spread in the Sea of Azov

The analysis of surges in the Sea of Azov is carried out on the basis of three-dimensional nonlinear model using the prognostic fields of near-water wind and atmospheric pressure. Carried out is the comparison of the results of numerical computations with the data of direct measurements of the sea level at a number of coastal stations. Studied is an effect of atmospheric impact intensity variations on the maximum values of sea level deviations and current velocities, as well as on the admixture transformation features. The analysis of results of numeric computations enabled to make a conclusion on the dependence of the pollution dissipation time on the wind speed and on the location of pollution areas.     

Changes of cloud microphysical properties during the transition from supercooled to mixed-phase conditions during CIME

A ground-based seeding experiment using carbon dioxide and propane sprayed from pressurized bottles was carried out under supercooled cloud conditions on a small spatial and short time scale. Water vapor deposition on the artificially generated dry ice and propane ice germs as the main ice formation process (nucleation and growth) is consistent with the experimental results. After nucleation, diffusional growth of the ice particles, partly at the expense of evaporating small droplets, was identified during the mixing of the seeding line with the ambient supercooled cloud. Within the seeding plume, ice water contents up to 80% of the total condensed water are observed, although the size of the formed ice particles did not exceed 25 μm. From the changes of the ice and supercooled liquid phase with time under mixed-phase conditions, liquid water content (LWC) evaporation, ice water content (IWC) formation, and ice crystal growth rates are estimated, which are not affected by the artificial nucleation process. Thus, these rates are assessed to be applicable for a growing ice phase of small ice particles in a young mixed-phase cloud, where other growth mechanisms, like riming or aggregation, are negligible.     

Modeling of fast ice evolution in the Arctic seas

A one-dimensional model of fast ice wind-induced break-up developed before was adapted for two-dimensional case that enabled to explain many regularities of this phenomenon. A numerical scheme is proposed of the integration of the acting stresses and potential resistivity by the fast ice area as well as the method for taking into account the correlation between the wind direction and prevailing coastline orientation that enables to simulate practically any combination of tensile and shearing stresses in the basins of arbitrary shape. The seasonal variability of strengthening ice properties is taken into account. All numerical tests carried out within the frameworks of this investigation demonstrated the qualitative and, partly, quantitative similarity of computation results and regularities observed in nature. The model sensitivity to the variation of some parameters is studied. The limits of model applicability are discussed and the directions of further research are proposed.     

Simulation of sea ice and ocean variability in the arctic during 1955–2002 with an intermediate complexity model

Abstract

A number of recent sea‐ice and ocean changes in the Arctic and subarctic regions are simulated using the global University of Victoria (UVic) Earth System Climate Model version 2.6. This is an intermediate complexity model which includes a three‐dimensional ocean model (MOM 2.2), an energy‐moisture balance model for the atmosphere with heat and moisture transport, and a dynamic‐thermodynamic sea‐ice model with elastic‐viscous‐plastic rheology. The model is first spun up for 1800 years with monthly wind stress forcing derived from the National Centers for Environmental Prediction (NCEP) climatology winds and a pre‐industrial atmospheric CO₂ concentration of 280 ppm. After a second spin‐up for the period 1800–1947 with daily climatology winds‐tress forcing, and a linearly increasing atmospheric CO₂ concentration, the model is run with interannually varying wind stresses for the period 1948–2002 with an average forcing interval of 2.5 days and an exponentially increasing atmospheric CO₂ concentration varying from 315 to 365 ppm. However, the analysis of the model output is only carried out for the years 1955–2002.

The simulated maximum and minimum sea‐ice areas for the Arctic are within 6% of the observed climatologies for the years 1978–2001. The model output also shows a small downward trend in sea‐ice extent, which, however, is smaller than has been observed during the past few decades. In addition, the model simulates a decrease in sea‐ice thickness in the SCICEX (SCientific ICe EXpeditions) measurement area in the central Arctic that is consistent with, but smaller than, that observed from submarine sonar profiling data.

The observed variability and magnitude of the export of sea ice through Fram Strait is quite well captured in the simulation. The change in correlation between the North Atlantic Oscillation (NAO) index and the sea‐ice export around 1977 as found in a data study by Hilmer and Jung (2000) is also reproduced. Within the Arctic basin the model simulates well the patterns and the timing of the two major regimes of wind‐forced sea‐ice drift circulation (cyclonic and anticyclonic) as found earlier by Proshutinsky and Johnson (1997). The influence of variations in the Fram Strait ice export on the strength of the North Atlantic thermohaline circulation and surface air temperature are also determined. In particular, it is shown that 3–4 years after a large ice export, the maximum meridional overturning streamfunction decreases by more than 10%.

The temperature and salinity increase at depths of 200–300 m, as observed in the eastern Arctic by Morison et al. (1998), between the USS Pargo cruise in 1993 and the Environmental Working Group (EWG) Joint USRussian Arctic Atlas climatology for the years 1948–87, are just visible in the model simulation. The increases are more noticeable, however, when the ocean model data are averaged over the pentade 1995–2000 and compared with model data averaged over the pentade 1955–60. The fact that these, and some of the other modelled changes, are smaller than the observed changes can likely be attributed to the relatively coarse resolution of the UVic Earth System Climate Model (3.6°E‐W and 1.8°N‐S). Nevertheless, the fact that the model captures qualitatively many of the recent sea‐ice and ocean changes in the Arctic suggests that it can be successfully used to investigate other Arctic‐North Atlantic Ocean climate interactions during past and future eras.     

Wave attenuation in the marginal ice zone during LIMEX

Abstract

During the Labrador Ice Margin Experiments, LIMEX ‘87 in March 1987 and LIMEX ‘89 in March and April 1989, the Canada Centre for Remote Sensing (CCRS) CV‐580 aircraft collected synthetic aperture radar (SAR) image data over the marginal ice zone off the east coast of Newfoundland, Canada. One aspect of these experimental programs was the observation of ocean waves penetrating into the marginal ice zone (MIZ). Based upon directional wavenumber spectra derived from SAR image data, the wave attenuation rate is estimated using SAR image spectra and compared with predictions from a model developed by Liu and Mollo‐Christensen (1988). The wave and ice conditions were considerably different in LIMEX ‘87 and LIMEX ‘89. However, the model‐data comparisons are very good for all ice conditions observed. Both the model and the SAR‐derived wave attenuation rates show a characteristic roll‐over at high wavenumbers. A model for the eddy viscosity is proposed, using dimensional analysis, as a simple function of ice roughness and wave‐induced velocity. Eddy viscosities derived from SAR and wave buoy data for the wave attenuation rate show a trend that is consistent with the proposed model.     

A Laboratory and Theoretical Study on the Uptake of SO2 Gas by Large and Small Water Drops Containing Heavy Metal Ions

Laboratory experiments have been carried out to investigate the uptake of sulfur dioxide by water drops containing heavy metal ions where the metal ions serve as catalysts to oxidise the taken up S(IV) into S(VI). During the gas uptake the drops were freely suspended at their terminal velocity in the airstream of the Mainz vertical wind tunnel. Two series of experiments were carried out, one with large millimeter size water drops containing manganese or iron ions, and the other with small water drops containing manganese ions and having radii in hundreds of micron size range. The experimental results were compared against model computations using the Kronig–Brink model and the fully mixed model, modified for the case that heavy metal ions present in the liquid phase act as catalysts for the oxidising process. The results of the model calculations show that there are only small differences between the predicted gas uptake according to the two models. In addition it was found that the experimental obtained results from the uptake of SO₂ by water drops containing heavy metal ions for both, large and small water drops did agree with the model results.     

Estimates of intensity and formation frequency of ice pile-up on the northwestern coast of the Caspian Sea from the results of model computations

The technique and results of computations of statistical parameters of ice pile-up formation on the western coast of the northern Caspian Sea are presented. The dynamic model of ice pile-up formation on the shores is described. The main ice, meteorological, and morphologic factors influencing the shore pile-up formation are analyzed. The test computation enabling to estimate the model adequacy is described. The estimation principle of the probability of the formation of the ice pile-up of certain size is given and the distribution functions of geometrical parameters of the pile-ups on the western coast of the northern Caspian Sea are obtained. The limits of the proposed model are specially stipulated.     

A tide in the operational model for short-range forecast of current velocity and sea level in the Barents and White seas

The operational model for the short-range forecast of velocity of currents and the sea level of the Barents and White seas is introduced into the automatic system of operational data processing of Hydrometcenter of Russia and works in the operational mode. The tidal block of the model is verified using eight major harmonics of the tide in the Barents and White seas. It is revealed that the model simulates adequately the large-scale features of tidal circulation in the Barents Sea. The model verification is based on the comparison between the diagnostic computation of the total sea level and the observational data on the sea level from the automatic buoy station. Demonstrated is a good agreement between the total sea level computations and the observations in the area of Teriberka settlement. The model takes account of the ice presence and simulates the ice effects on the currents. It is established that the ice presence affects significantly the amplitude and phase of tidal waves, especially in coastal regions.