Simulation of iceberg drift as a component of ice monitoring in the West Arctic

Discussed is the hydrodynamic model of iceberg drift. Presented are the examples ofits use in operational practice for predicting iceberg drift in the Kara Sea and for enhancing ice monitoring in the Barents Sea.     

Nonstationary time series prediction by incorporating external forces

Almost all climate time series have some degree of nonstationarity due to external forces of the observed system. Therefore, these external forces should be taken into account when reconstructing the climate dy- namics. This paper presents a novel technique in predicting nonstationary time series. The main difference of this new technique from some previous methods is that it incorporates the driving forces in the pre- diction model. To appraise its effectiveness, three prediction experiments were carried out using the data generated from some known classical dynamical models and a climate model with multiple external forces. Experimental results indicate that this technique is able to improve the prediction skill effectively.     

On the deterioration of icebergs in the marginal ice zone

Abstract

During the Labrador Ice Margin Experiment (LIMEX) of March‐April 1989, the International Ice Patrol (IIP) of the United States Coast Guard deployed two satellite‐tracked TIROS Arctic Drifter (TAD) platforms on two medium‐sized tabular icebergs. The icebergs were drifting in sea ice of about 9/10 concentration east of Newfoundland. These deployments were part of an experiment to examine differential sea‐ice/iceberg motion during spring conditions near the ice margin. Sea‐ice concentration and movement data were collected concurrently by other LIMEX investigators.

The TADs, deployed on 11 March 1989, were tracked using the ARGOS data collection and location system carried on two NOAA polar‐orbiting satellites of the TIROS family. For two months following the deployment, IIP periodically attempted to relocate the icebergs during routine aerial iceberg patrols. One of the TADs stopped transmitting on 23 April 1989 probably because of a major calving event that resulted in the TAD being crushed. As of 24 April the drift rate of the other TAD nearly doubled compared with its drift rate prior to that date, indicating that it had fallen off the iceberg and was floating on water. By 24 April there was no sea ice near either of the two icebergs.

The TAD data provide a unique datasetfor modelling the deterioration of icebergs while they emerge out of the marginal ice zone and travel in open water. It is shown that a good knowledge of the environmental conditions, pariicularly water temperature and sea state, are critical to model successfully the deterioration and calving of the two icebergs.     

Satellite Monitoring of Sea Ice Cover and Water Parameters for the Caspian Sea

A number of technologies have been developed in the Planeta Research Center for Space Hydrometeorology to provide the satellite monitoring of sea ice cover and water parameters for the Caspian Sea. These technologies produce maps of sea ice, sea ice drift, tracking of near-surface water fluxes, automated classification of ice and water objects, surface wind, and sea surface temperature. Satellite-based products are used for operational hydrometeorology and climate studies of the Caspian Sea environment. A specialized web service for the preparation and comprehensive analysis of satellite data on hydrometeorological and ice conditions in the Caspian Sea was developed to provide information on ice cover characteristics, surface wind, and sea surface temperature.     

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.     

Spatial interpolation of monthly and annual rainfall in northeast of Iran

Precipitation maps are the key input to many hydrological models. In this paper different univariate (inverse distance weighing and ordinary kriging) and multivariate (linear regression, ordinary cokriging, simple kriging with varying local mean and kriging with an external drift) interpolation methods are used to map monthly and annual rainfall from sparse data measurements. The study area is Golestan Province, located in northeast of Iran. A digital elevation model is used as complementary information for multivariate approaches. The prediction performance of each method is evaluated through cross-validation and visual examination of the precipitation maps produced. Results indicate that geostatistical algorithms clearly outperform inverse distance weighting and linear regression. Among multivariate techniques, ordinary cokriging or kriging with an external drift yields the smallest error of prediction for months April to October (autumn and winter) for which the correlation between rainfall and elevation is greater than 0.54. For all other months and annual rainfall, ordinary kriging provides the most accurate estimates.     

Non-Gaussian Lagrangian Stochastic Model for Wind Field Simulation in the Surface Layer

Wind field simulation in the surface layer is often used to manage natural resources in terms of air quality,gene flow(through pollen drift),and plant disease transmission(spore dispersion).Although Lagrangian stochastic(LS)models describe stochastic wind behaviors,such models assume that wind velocities follow Gaussian distributions.However,measured surface-layer wind velocities show a strong skewness and kurtosis.This paper presents an improved model,a non-Gaussian LS model,which incorporates controllable non-Gaussian random variables to simulate the targeted non-Gaussian velocity distribution with more accurate skewness and kurtosis.Wind velocity statistics generated by the non-Gaussian model are evaluated by using the field data from the Cooperative Atmospheric Surface Exchange Study,October 1999 experimental dataset and comparing the data with statistics from the original Gaussian model.Results show that the non-Gaussian model improves the wind trajectory simulation by stably producing precise skewness and kurtosis in simulated wind velocities without sacrificing other features of the traditional Gaussian LS model,such as the accuracy in the mean and variance of simulated velocities.This improvement also leads to better accuracy in friction velocity(i.e.,a coupling of three-dimensional velocities).The model can also accommodate various non-Gaussian wind fields and a wide range of skewness–kurtosis combinations.Moreover,improved skewness and kurtosis in the simulated velocity will result in a significantly different dispersion for wind/particle simulations.Thus,the non-Gaussian model is worth applying to wind field simulation in the surface layer.     

天津港气象水文综合预报系统

天津港气象水文综合预报系统是针对天津港安全生产特点和需求,集气象、水文要素监测实况和预报于一体、信息量大、获取及时、使用方便的一个具有行业特色的实用专业平台。该系统采用WRF大气模式和ECOM、ADI两种海洋模式以及计算浪高的半经验半理论的公式对海上大风、能见度、风暴潮、风浪进行了模拟计算,并依据自动站的观测数据进行了验证,从而实现了港口大雾、大风、风浪和风暴潮这四个方面的预报模拟,并提供了相关的可视化产品。     

Small icebergs and iceberg fragments off Newfoundland: Relationships to deterioration mechanisms and the regional iceberg population

Abstract

Several sets of previously compiled data on iceberg size distributions in areas between North America and Greenland are compared and analyzed. The obtained results indicate that populations of icebergs with lengths L ≥ 20 m are well‐described by log‐normal and gamma distributions together with statistical parameters which are compatible with existing understanding of regional iceberg deterioration and change processes. A lesser amount of data on size distributions in Newfoundland icebergs with L < 20 m show occurrence probabilities which increase exponentially with decreasing iceberg length. Evidence is presented to show that these data are most consistent with the dominance of fracture processes in determining iceberg occurrence versus length relationships. Physical arguments are presented to suggest that the key fracture events are initiated in the larger icebergs by coincidences of wave‐generated bending stress maxima and randomly distributed structural flaws. Similar considerations and use of a simple sequential fracture model imply that size distributions in icebergs (and iceberg fragments) with L < 20 m are more consistent with the presence of an alternative, spontaneous failure mechanism also acting at randomly distributed structural defects. The implications of these results for forecasting and monitoring populations of small icebergs are discussed.     

Potential hydrometeorological threshold values of the coastal hazard—an example from the Polish Southern Baltic coast

This paper analyses the spatiotemporal variability of extreme hydrometeorological events at the Polish coast of the Baltic Sea. Extreme precipitation events and storm surges determine to the largest extent the contemporary transformations of sea coastal geoecosystems and represent the major factors that disturb their functioning. The statistical characteristics of these values were computed from the data of six meteorological and tide-gage stations located at the Baltic seaside. Daily data on the amount of precipitation and the sea level for the period of 1966–2009 were used for the study. Annual and daily maximum values of precipitation and sea level are presented for the Southern Baltic coast. The threshold values of the hydrometeorological parameters considered in the study allow assessing the hazard caused by the disturbance of the functional stability of the sea coastal geoecosystems.     

GIS-Amur system of flood monitoring,forecasting, and early warning

GIS-Amur system offlood monitoring, forecasting, and early warning was developed at the Hydrometcenter of Russia and Planeta Research Center for Space Hydrometeorology for the effective surveill ance of hydrological conditions in the Amur River basin. The system is based on the use of hydrometeorological information, that is, observational data from weather and gaging stations, data from hydrological forecasts, and satellite data. The GIS- and web-based GIS-Amur system provides high reliability, safety, and operational speed. During the operational practice in the spring and summer 2015, the system demonstrated the forecast accuracy and reliability, the timely delivery of output products to end users, and the great variety of the output product types and formats. The system provides near-real time access to all available hydrometeorological data in the Amur River basin that favors correct and timely decision-making for flood risk reduction.     

水文气象研究进展

从面向流域的定量降水估测与预报、流域水文模型、水文气象耦合预报三个方面系统介绍水文气象研究进展。研究指出,融合天气雷达、卫星遥感及实况降水等多源信息是精细化定量降水估测产品的主要发展方向;采用多模式降水预报集成技术是提高定量降水预报精度的重要途径;分布式水文模型是流域水文模型的发展方向;引入定量降水预报的水文气象耦合预报模式可以延长洪水预报预见期,水文集合预报是水文预报方法的有效解决途径,而数值预报模式与水文模型的双向耦合模式是另一重要发展方向。     

On Heavy Particle Dispersion in Turbulent Shear Flows: 3-D Analysis of the Effects of Crossing Trajectories

In the approaches used to predict the dispersion of discrete particles moving in a turbulent flow, the effects of crossing trajectories due to gravity (or any other external force field) are generally accounted for by modifying the integral time scales according to the well-known analysis of Csanady (J Atmos Sci 20:201–208, 1963). Here, an alternative theoretical analysis of the time correlation of the fluid velocity fluctuations along a particle trajectory is presented and applied in a turbulent shear flow. The study is carried out in the frame of three-dimensional Langevin-type stochastic models, where the main unknowns are the drift tensor components rather than the conventional integral time scales of the fluid seen by the particles. Starting from a model for the space-time velocity covariance tensor of the turbulence under the assumption of homogeneous shear flow, the various components of the time correlation tensor of the fluid seen are expressed in the asymptotic case of large mean relative velocity (between the particles and the flow) compared to the particle velocity fluctuations. In order to provide comparison with the generally used expressions arising from isotropic turbulence assumption, we examine also the conventional integral time scales of the fluid seen in the directions parallel and perpendicular to the mean relative velocity. The most prominent deviations from isotropic turbulence are observed when the external force field is in the direction of the mean velocity gradient: in this case the loss of correlation in the mean flow direction is significantly lower than expected in a uniform flow, an observation that is in qualitative agreement with the few available data.     

A role for icebergs in the 8.2 ka climate event

We investigate the potential role of icebergs in the 8.2 ka climate event, using a coupled climate model equipped with an iceberg component. First, we evaluate the effect of a large iceberg discharge originating from the decaying Laurentide ice sheet on ocean circulation, compared to a release of an identical volume of freshwater alone. Our results show that, on top of the freshwater effect, a large iceberg discharge facilitates sea-ice growth as a result of lower sea-surface temperatures induced by latent heat of melting. This causes an 8% increased sea-ice cover, 5% stronger reduction in North Atlantic Deep Water production and 1°C lower temperature in Greenland. Second, we use the model to investigate the effect of a hypothetical two-stage lake drainage, which is suggested by several investigators to have triggered the 8.2 ka climate event. To account for the final collapse of the ice-dam holding the Laurentide Lakes we accompany the secondary freshwater pulse in one scenario with a fast 5-year iceberg discharge and in a second scenario with a slow 100-year iceberg discharge. Our experiments show that a two-stage lake drainage accompanied by the collapsing ice-dam could explain the anomalies observed around the 8.2 ka climate event in various climate records. In addition, they advocate a potential role for icebergs in the 8.2 ka climate event and illustrate the importance of latent heat of melting in the simulation of climate events that involve icebergs. Our two-stage lake drainage experiments provide a framework in the discussion of two-stage lake drainage and ice sheet collapse.     

Model simulation of the currents in the Barents Sea in connection with the development of the Shtokman gas condensate field

A three-dimensional nonstationary baroclinic model of the Barents Sea is under consideration. The simulation was performed with allowance for all basic factors influencing the current: wind, pressure, tides, inhomogeneous water density, and flows across the open boundaries. Stationary and nonstationary sea dynamics has been simulated. It is found that an instantaneous flow pattern is highly variable and does not coincide with the schemes of a general drift. The main contribution to variability is made by tidal oscillations. Periodically, the tide and wind form vortex structures in different parts of the Barents Sea. The model is developed and used for getting data on currents on open boundaries of local models of different sea sites for calculating the transport of suspended substances when laying the subwater gas pipeline from the Shtokman gas condensate field to Kola Peninsula. A brief review of measurement data and results of model simulation of the currents in the Barents Sea is prepared.     

CN05.1气象数据在流域水文模拟中的应用——以新疆开都河流域为例

为探讨中国再分析气象数据集CN05.1在流域水文模拟中的适用性潜力,以开都河流域为研究区,分别使用CN05.1数据集和传统气象站数据驱动SWAT水文模型,采用决定系数（R ²)、纳什效率系数（NSE）和相对误差（R_e）等评价指标对二者模拟效果进行对比分析,以确定CN05.1数据的适用性;最后采用两种数据订正方法对CN05.1降水数据进行了订正,并以水文模拟效果进行评价。研究结果表明:(1) CN05.1气象数据在开都河流域的水文气象模拟中具有较强的适用性;(2) 基于SWAT模型的水文模拟显示,CN05.1数据驱动的水文模拟精度高于传统气象站数据,其率定期（1995—2005年）和验证期（2006—2016年）的R ²分别为0.81和0.73,NSE分别为0.81和0.72,R_e分别为-0.97%和0.39%;(3)两种数据订正方法均能较好地再现流域径流变化过程,但基于空间关系订正法的径流模拟效果更好,R ²和NSE均在0.72以上,|R_e|＜1.7%。由此,订正后的CN05.1降水数据一方面弥补了传统气象站数据缺失的问题,另一方面补足了未订正CN05.1降水数据在径流模拟中峰值欠佳的问题。     

基于高分辨率数值天气模式的往返平飘式探空轨迹预测方法及初步评估

为了开展往返平飘式探空组网观测的仿真和模拟,以及评估组网观测对数值天气预报的影响,并实现往返平飘式探空在目标观测中的应用,本文提出了一种基于高分辨率数值天气模式的往返平飘式探空轨迹模拟和预报方法。基于我国自主研发的GRAPES区域高分辨率模式,初步建立了往返平飘式探空的轨迹预报系统。该系统将往返平飘式探空的上升段、平漂段和下降段的轨迹方程,以及下降段降落伞的动力学方程,直接嵌入到高分辨率数值天气模式中,实现对往返平飘式探空轨迹的模拟和预报。利用轨迹预测系统对63个往返平飘式探空轨迹进行轨迹预报试验和评估,试验结果表明,该系统的轨迹预测结果合理可信,6 h的轨迹预报平均误差小于40 km。     

The bases of data on hazardous hydrometeorological phenomena in Russia and results of statistical analysis

Main principles are considered of formation of special files on observed hazardous hydrometeorological phenomena (HHP) and adverse weather, along with experience of Roshydromet in standardization of registration and reports on their damaging effects. The first base is designed on the basis on hazardous phenomena registered by the hydrometeorological stations according to authorized criteria regardless the damaging effects on economy and population; these data are collected and stored in the State Data Foundation. These are special climatic data series on HHP from the stations; they are used in the studies of extreme and hazardous weather. The second base collects information on adverse and hazardous weather causing economic and social damage, irrespective of the HHP criteria reached or not. Distribution is presented of total case number of hazardous hydrometeorological phenomena causing social and economic damage during 1991–2008.     

Investigation of surges in marine estuaries (A case study for the Don River mouth)

Upsurges and downsurges in the Don River mouth are investigated using the observational data of the standard hydrometeorological network. The characteristics ofsurges are determined, andthe catalog of maximum annual dangerous surges is compiled for the observation points in the estuarine offshore zone and mouth reach of the Don River from the beginning of observations till 2014. The series of the maximum annual upsurges and downsurges at marine gaging stations in the Taganrog Bay are formed and statistically processed. The distribution of surges along the Taganrog Bay is analyzed. Catastrophic surges which cause adverse and severe events are identified as well as the qualitative and quaniiiaiive patterns of surge peneiraiion to the Don River mouth. The coefficients of upsurges and downsurges, the intensity of their attenuation, and water levels with the probability of 0.1, 1, and 50% at different river runoff are calculated at all gaging stations in the Don estuary for specific upsurges and downsurges. The results of test computations of surges for the specific point in the Taganrog Bay for 2013-2015 based on the numerical hydrodynamic model of the Sea of Azov are compared with observational data. The possibility was revealed of forecasting downsurges and upsurges based on synoptic conditions over the Sea of Azov with the lead time of three days using hydrodynamic models that allowed developing the prediction scheme of surge transformation calculation.     

Icebergs in the Southern Ocean and Factors Defining Their Distribution

Using the data of ~58 000 ship observations of Antarctic icebergs in 1947–2014, the map of average summertime concentration of icebergs (namely, of their number within a circle with the radius of 15 nautical miles) in the Southern Ocean was constructed. The main features of the iceberg distribution are revealed, and their possible reasons are investigated. It is shown that in the open ocean sea currents play a key role in the iceberg distribution. Wind effects are pronounced when ocean currents are weak or absent. According to the authors’ estimates, wind plays a decisive role only in the formation of one wide quasimeridional tongue of high iceberg concentration in the Weddell Sea. It is difficult to assess the impact of Antarctic glaciers’ productivity on the iceberg distribution, because currents, wind, and breaking and jamming of icebergs in shallow water areas cause their rapid redistribution. The clear physical explanation of the main features of iceberg concentration distribution on the constructed map indicates that it provides a rather real pattern.