Hummocks near the North Pole 35 drifting station

Study of hummocks is a very important applied and scientific problem. The main objective of this work is representing new information on structure of hummocks that were studied in the spring time at the North Pole 35 drifting station. In this paper, methodology and results of studying several hummocks with different morphology are considered. The maximum hummock keel draft varied from 3.5 to 14 m, while the maximum sail height was between 2.5 and 3.9 m. The hummock porosity and porosity of the unconsolidated part of its keel varied in the range of 6–18 and 4–26%, respectively. The average thickness of the hummock consolidated layer stayed in the range from 1.8 to 2.4 m. It was found that relatively small sail heights do not affect the consolidated layer thickness, however higher sails influence on the consolidated layer size. The higher the hummock sail, the less its consolidated layer thickness is.     

Modeling of freezing and melting hummocks on shelf of Sakhalin Island

In this paper, results of numerical experiments based on the one-dimensional thermodynamic model of hummock formations evolution, which has been developed by the authors, are analysed. This model has been used for computation of relative rates of freezing and melting of hummocks in typical conditions of the northeastern shelf of Sakhalin Island; then obtained values were compared with the plain sea ice cover parameters simulated by using climate and actual meteorological data. It is shown that obtained results well comply with observational data collected during expeditions in this region.     

The use of one-dimensional thermodynamic model for computing the level ice thickness and hummock freezing intensity in the Northern Caspian Sea

The results are analyzed of numerical experiments obtained using a one-dimensional thermodynamic model of the sea ice developed by the authors. The computations of the level-ice (fast-ice) evolution and ice hummock consolidation layer formation in different climatic situations (anomalously cold and anomalously warm winters) are carried out within the frameworks of the proposed model for the conditions being typical of the Northern Caspian Sea. The results of model computations are compared with the data of field researches carried out by the specialists of the Arctic and Antarctic Research Institute in 2003–2008. A good correspondence is demonstrated between the model computations and expeditionary data. A conclusion is made on the prospectivity of using the model for design engineering.     

Method of investigation of internal structure of ice hummocks and stamukhas using the thermal drilling technique

Computer recording of thermal drilling rate of ice hummocks and stamukhas gives the objective information on their internal structure and basic morphometric characteristics. Methods of determination of the consolidation layer of ice hummocks and stamukhas and the thermal drilling data processing technique are considered in the paper. The reliability of determination of consolidated layer boundaries on the basis of the thermal drilling rate should be corroborated by the temperature measurements. To estimate the time spent for the ice hummock temperature measurement using the polyethylene tubes which are put into the boreholes and filled with the antifreeze, the experimental study of the borehole freezing rate was carried out depending on the temperature and salinity of ice. The results of experiments corroborating the existence of convection in the antifreeze are given. The used methods of ice hummock temperature measurement are discussed. The method of investigation of ice formations combining the thermal drilling technique and ice temperature measurement on the borehole wall enables to obtain the accurate data on the position of the lower boundary of consolidated layer, although it results in a smaller number of the boreholes.     

On the problem of determination of hummocky formation albedo

It is demonstrated within the frameworks of the analysis of determination methods of snowice cover reflectance that the problem of the measurement technique of hummocky formation albedo has not been studied enough. The results of in situ experiments carried out on the Arctic sea ice are presented. The results of ice hummock albedo measurements using different techniques are discussed. The need to organize the special experimental research for the development of practical recommendations for estimating the hummocky formation albedo is declared.     

Formation and consolidation of hummocks on the Arctic seas’ one-year ice cover as a result of laboratory and field researches

Structural-genetic types of hummocks formed on the Arctic seas’ ice cover are considered. A method of the laboratory physical modeling was used for understanding kinematic schemes of the hummocks’ formation processes. A methodology of computation of the hummock consolidation intensity for different hummocks’ structural types was proposed. The performed computations showed good coherence of the laboratory experiments results and field studies of hummocks’ structure in the Barents and Kara seas.     

Future vegetation changes in thawing subarctic mires and implications for greenhouse gas exchange—a regional assessment

One of the major concerns regarding climate change in high latitudes is the potential feedback from greenhouse gases (GHG) being released from thawing peat soils. In this paper we show how vegetational patterns and associated GHG fluxes in subarctic palsa (peat mounds with a permanently frozen core) mires can be linked to climate, based on field observations from fifteen palsa sites distributed in northern Fennoscandia. Fine resolution (100?m) land cover data are combined with projections of future climate for the 21st century in order to model the potential future distribution of palsa vegetation in northern Fennoscandia. Site scale climate-vegetational relationships for two vegetation types are described by a climate suitability index computed from the field observations. Our results indicate drastic changes in the palsa vegetational patterns over the coming decades with a 97?% reduction in dry hummock areas by 2041?C2060 compared to the 1961?C1990 areal coverage. The impact of these changes on the carbon balance is a decrease in the efflux of CO₂ from 130 kilotonnes C y^?1 to a net uptake of 11 kilotonnes C y^?1 and a threefold increase in the efflux of CH₄ from 6 to 18 kilotonnes C y^?1 over the same period and over the 5,520?km² area of palsa mires. The combined effect is equivalent to a slight decrease in CO₂-C emissions, from 182 to 152 kilotonnes C y^?1. Main uncertainties involve the ability of the vegetation community to adapt to new conditions, and long-term changes in hydrology due to absence of ice and frost heaving.     

The Parameterisation of Scalar Transfer over Rough Ice

We test a surface renewal model that is widely used over snow and ice surfaces to calculate the scalar roughness length (z _s ), one of the key parameters in the bulk aerodynamic method. For the first time, the model is tested against observations that cover a wide range of aerodynamic roughness lengths (z ₀). During the experiments, performed in the ablation areas of the Greenland ice sheet and the Vatnajökull ice cap in Iceland, the surface varied from smooth snow to very rough hummocky ice. Over relatively smooth snow and ice with z ₀ below a threshold value of approximately 10^?3 m, the model performs well and in accord with earlier studies. However, with growing hummock size, z ₀ increases well above the threshold and the bulk aerodynamic flux becomes significantly smaller than the eddy-correlation flux (e.g. for z ₀ = 0.01 m, the bulk aerodynamic flux is about 50% smaller). Apparently, the model severely underpredicts z _s over hummocky ice. We argue that the surface renewal model does not account for the deep inhomogeneous roughness sublayer (RSL) that is generated by the hummocks. As a consequence, the homogeneous substrate ice grain cover becomes more efficiently ‘ventilated’. Calculations with an alternative model that includes the RSL and was adapted for use over hummocky ice, qualitatively confirms our observations. We suggest that, whenever exceedance of the threshold occurs (z ₀  >  10^?3 m, i.e., an ice surface covered with at least 0.3-m high hummocks), the following relation should be used to calculate scalar roughness lengths, ln (z _s /z ₀)  =  1.5  ? 0.2 ln (Re _*)  ? 0.11(ln (Re _*))².     

一种粒子——烟团扩散模型的应用研究

本文运用随机游动模拟方法改进建立一种粒子—烟团模式，成功地模拟了对流边界层条件下污染物扩散，粒子—烟团模式的模拟结果与水槽试验的结果吻合较好。数值模拟试验结果表明粒子—烟团模式能在施放粒子数较少，从而运行时间很短的情况下，得到优于一般随机游动模式的模拟性能。用KNRC的资料对模式的模拟性能作一验证，表明模式也能很好地模拟实际大气中不同稳定度情况下的扩散。     

沙尘暴天气数值预报系统及其预报效果检验

沙尘暴天气数值预报系统包括区域大气模式、陆面过程模式、风沙模式(包括风蚀、输送和沉降模式)和地理信息系统。用该系统对2002年3月20日和4月7日2次沙尘天气进行了预报试验,利用地面观测资料和卫星观测资料对模式输出的主要沙尘天气预报产品进行了对比分析。分析结果认为,沙尘暴天气数值预报系统对沙通量、尘通量和垂直积分质量有很好的预报能力,但仍需改进陆面参数和沙尘气溶胶的初始值。     

区域模式和GCM对青藏高原和西北地区气候模拟结果的对比分析

使用一个区域模式与大气环流模式（ＧＣＭ）嵌套,模拟了我国西北及青藏高原地区夏季气候的平均状态。将区域模式与ＧＣＭ嵌套的模拟结果和ＧＣＭ单独使用时的模拟结果与观测场进行了对比分析和相关分析。结果表明：ＧＣＭ模式拟出了我国西北和青藏高原地区夏季大尺度气候的基本特征,对降水的模拟也基本合理,但无法分辨出较小系统。区域模式与ＧＣＭ嵌套拟结果有明显改善,它可成功地再现西北及青藏高原地区夏季的区域气候特征（包     

Comparisons of modelled and observed climate for impact assessments

Summary Comparisons between observed and modelled values of surface temperature, surface precipitation and 500 hPa height for the current climate were made for the southeast United States. Daily values and analyses pertinent to impact assessment, were emphasized. For the model, the time-independent 10-year series of values developed by the Geophysical Fluid Dynamics Laboratory general circulation model were used. Observations were drawn from records for various stations and decades within the model grid-cell. Cumulative frequency distributions of temperature indicated both more clustering close to the mean and greater extremes for the model. The model reproduced the seasonal cycle of day-to-day temperature variability, but introduced a phase shift of about four months. One result was an apparent overabundance of hot spells in the model results. For precipitation the model indicated twice as many raindays as were observed, about the same number of days when precipitation exceeded 5 mm, and fewer days with amounts exceeding 10 mm, effectively decreasing the probability of heavy precipitation while enhancing annual totals. In winter the model appeared to represent the results from an aggregation of stations within the grid-cell, but in summer it was closer to individual station results. The model reproduced the seasonal cycle in the height and standard deviation of the 500 hPa surface, with a damped amplitude in both cases.With 9 Figures     

RegCM-Dust模式对东亚一次沙尘暴天气过程模拟的效果检验

为检验区域气候模式与沙尘模式耦合模式RegCM Dust的性能,以2006年东亚地区一次沙尘暴过程为例,将模拟结果与观测资料进行对比,以检验模式对沙尘天气过程的模拟能力。结果表明：模式对沙尘暴过程的地面风场特征模拟效果较好,总体上重现了大风区的分布;地面沙尘浓度和沙尘光学厚度模拟结果与观测分布总体吻合。模式虽然是区域气候模式与沙尘模式耦合模式,但由于其内核是建立在中尺度数值模式MM4基础上,因此对天气过程尤其是沙尘天气过程具备较好的把握能力,对于沙尘天气过程预测具有良好的应用前景。     

复杂下垫面地域边界层结构的三维细网格数值模拟

建立了一个可供复杂下垫面地域使用的非静力的三维细网格边界层模式，就复杂下垫面条件下的边界层结构和湍流特征作了以实例为对照的数值模拟试验，模式采用能量闭合方案，舍弃了静力近似。以实测资料为初台输入，同时还做了一些数值试验，分别获得了采用静力与非静力模式和不同闭合方案对ＰＢＬ模型的结果。     

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.     

考虑降水时间相关性的地面观测-雷达-卫星遥感逐时降水融合方法研究

以广东省北部山区2018年汛期强降水时段4月23—28日龙舟水、5月7—11日龙舟水和9月16—17日台风“山竹”3次典型暴雨过程的逐时降水为研究对象,研究基于XGBoost算法与地统计学理论的地面观测-前两个时刻逐时降水-雷达-卫星遥感的多源逐时降水融合模型,充分考虑相邻时刻降水的时间相关性,得到空间分辨率为1 km的逐时降水融合数据。此外,分别利用XGBoost与随机森林(RF)算法进行不考虑降水时间相关性的地面观测-雷达-卫星遥感逐时降水融合对比试验,并对试验结果进行精度评价。结果表明：(1) 在3次暴雨过程中,三种融合模型的逐时降水融合结果具有类似的空间分布;(2) 与XGBoost和RF逐时降水融合结果相比,融合了降水时间相关性的逐时降水融合结果在不同暴雨过程的准确性均有明显改进,3次暴雨过程的决定系数(R2)平均提高了7.89%和23.27%;(3) XGBoost逐时降水融合模型的精度整体上优于RF逐时降水融合模型,3次暴雨过程的R2分别提高了7.1%、4.3%和31.4%。     

Lagrangian Estimations of Ozone Loss in the Core and Edge Region of the Arctic Polar Vortex 1995/1996: Model Results and Observations

Ozone evolution and diabatic descent in the Arctic polar vortex in winter 1995/1996 was studied with a newly developed diabatic trajectory–chemistry model (DTCM). To study the chemical and dynamic evolution of the species in the polar vortex, 400 diabatic trajectories were calculated in the vortex core and edge region by using three-dimensional (3-D) wind data provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). The averaged diabatic descending motion and ozone behavior were obtained for particles started from the core and from the edge region of the vortex. The difference in ozone-loss rates as well as the difference in descending rates between the vortex core and the vortex-edge region was not statistically significant. The average cumulative ozone loss of 65 ± 16% in the vortex core obtained from the model calculations was consistent with the estimates obtained with a different method (Match experiment). The model results for the vortex core were compared with those obtained using trajectories with the vertical winds calculated on the basis of radiative cooling rates as used by the SLIMCAT 3-D chemical transport model. Although the trajectories based on cooling rates exhibited lower descending rates than those based on 3-D analyzed wind data, the ozone behavior was similar for both types of trajectory. Ozonesonde data from two stations (Ny-Alesund in the vortex core and Yakutsk in the vortex edge) were compared with the model results. For Lagrangian estimation of the ozone loss at these stations, the descending rates obtained by the diabatic trajectory calculations were used. Good agreements were obtained between the model results and observations for both the vortex core and edge region. These results suggest that strong ozone depletion occurred not only in the core, but also in the edge region of the vortex, and that air masses from the mid-latitudes did not appreciably affect the degree of ozone depletion in this winter–spring period. The sensitivity of the model to different descending rates and to the presence of large nitric acid trihydrate (NAT) particles was also examined.     

变网格一体化模式的研究进展

作者介绍了近年来在数值天气预报领域的一个新动向－变网格一体化模式的进展。这种模式可以替代目前业务数值天气预报的有限区模式和全球谱模式，降低业务数值天气预报的计算成本。网格距离的可变性，以及采用半隐式－半拉格朗日式时间差分方案是该模式的主要特点。法国的变网格一体化模式自１９９２年已投入业务使用，其可行性已得到了预报检验的初步证实。     

海-气耦合距平滤波模式的月、季数值预报

本文用海—气耦合三层距平滤波模式(AFM)作了1976—1977以及1982—1983两个EINino事件年冬季八个月预报个例实验。其结果表明,该模式成功地预报了大尺度月地表温度距平场,预报与实况的相关系数基本上都超过了惯性预报。与距平大气环流模式(AGCM)相比,两者的结果相差不大,但AFM可节省近一百倍的计算时间。与此同时,我们还作了季节预报试验,即提前三个月作月预报,完成了1977年2月、3月和1983年2月、3月四个试验例子。结果表明,用该模式作大尺度环流的季节异常预报的潜力是存在的。最后,结合本文的结果,我们把提出距平滤波模式以来近十年的工作作了小结,对模式的预报能力作了评价。