Simulation of Extreme Surges in the Taganrog Bay with Atmosphere and Ocean Circulation Models

The simulation the most extreme surges over the period of instrumental observations in the Taganrog Bay since 1881, the surges occurred on March 24, 2013 and September 24, 2014. The objective of the simulation is to study surge formation features and to reveal requirements for the accuracy of simulating atmospheric and oceanic circulation in the Sea of Azov. For this purpose, the Institute of Numerical Mathematics Ocean Model (INMOM) with the spatial resolution of ~4 km and ~250 m was used. The atmospheric forcing over the Black Sea region was specified using ERA-Interim reanalysis data and WRF model data with the spatial resolution of 80 and 10 km, respectively. It is shown that the quality of simulation of extreme surges in the Sea of Azov is more dependent on the quality of the input atmospheric forcing than on the spatial resolution of the ocean circulation model. The usage of WRF data as atmospheric forcing allows the more accurate simulation of extreme surges. However, the simulation of the extreme surge of 2014 overestimates, and simulations for the 2013 surge underestimate the surge level. Evidently, as the used version of INMOM does not take into account the coastal zone flooding, the maximum surge value is overestimated.     

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.     

Specific features of ice conditions in the Sea of Azov and the Kerch Strait in the winter season of 2005/06

Peculiarities of the ice situation in the Sea of Azov and the Kerch Strait during the cold winter of 2005/06 are considered using a set of satellite images in the visible range, accumulated at the Southern Research Institute of Marine Fisheries and Oceanography (in Kerch). The ice conditions of the water area over the last years are examined and compared to the climatic data.     

Studying the Ionization of Atmospheric Surface Layer in Different Geophysical Conditions

The results of atmospheric electricity measurements are presented which were conducted at observation points of different types: at the urban point (Rostov-on-Don), at the point near the Sea of Azov (Taganrog and Primorka), and at the high-mountain point (Cheget Peak) near Elbrus. The patterns of spatiotemporal variations in electrical conductivity (concentration of light ions) of the atmospheric surface layer are revealed for different conditions. The impact of natural radioactivity and aerosol pollution on the concentration of light ions is assessed for observation points near the Taganrog Bay (the Sea of Azov). The results of the comparative analysis of urban and high-mountain data of atmospheric electricity observations are presented.     

Numerical modeling of ice drift in the Sea of Azov

Considered is the dependence of the evolution of the ice drift velocity field in the Sea of Azov on the direction and duration of the impact of wind of constant intensity based on the constructed two-dimensional mathematical model.     

Numerical modeling of the Sea of Azov dynamics during an atmospheric cyclone passage

Based on a hydrodynamic finite-element model, this work studies how the level surface and velocity field of wave currents in the Sea of Azov react to a change in storm conditions of November 14–16, 1992 due to cyclone passage.     

Present-day and future precipitation in the Baltic Sea region as simulated in a suite of regional climate models

Here we investigate simulated changes in the precipitation climate over the Baltic Sea and surrounding land areas for the period 2071–2100 as compared to 1961–1990. We analyze precipitation in 10 regional climate models taking part in the European PRUDENCE project. Forced by the same global driving climate model, the mean of the regional climate model simulations captures the observed climatological precipitation over the Baltic Sea runoff land area to within 15% in each month, while single regional models have errors up to 25%. In the future climate, the precipitation is projected to increase in the Baltic Sea area, especially during winter. During summer increased precipitation in the north is contrasted with a decrease in the south of this region. Over the Baltic Sea itself the future change in the seasonal cycle of precipitation is markedly different in the regional climate model simulations. We show that the sea surface temperatures have a profound impact on the simulated hydrological cycle over the Baltic Sea. The driving global climate model used in the common experiment projects a very strong regional increase in summertime sea surface temperature, leading to a significant increase in precipitation. In addition to the common experiment some regional models have been forced by either a different set of Baltic Sea surface temperatures, lateral boundary conditions from another global climate model, a different emission scenario, or different initial conditions. We make use of the large number of experiments in the PRUDENCE project, providing an ensemble consisting of more than 25 realizations of climate change, to illustrate sources of uncertainties in climate change projections.     

菲律宾海地区异常环流与长江中下游6月旱涝的关系

利用1951—2010年NCEP/NCAR逐月再分析资料和中国160站月降水总量资料,研究了菲律宾海地区大气环流异常与长江中下游6月旱涝的关系。结果表明,菲律宾海附近是影响长江中下游地区6月降水的关键区。菲律宾异常反气旋（气旋）在对流层低层明显,强度随高度衰减。且这种大气环流异常与长江中下游地区6月降水的相关关系在低层850hPa最显著,到高层相关性减弱。当出现菲律宾异常反气旋环流时,垂直速度和水汽输送等异常分布特征有利于降水发生,使得长江中下游地区偏涝,反之则偏旱。     

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.     

An ensemble forecast of the South China Sea monsoon

1.IntroductionThispaperexploresanensembleforecaststrategyforthelarge--scaletropicalpredictionproblem.Thisisgeneralizedfromarecentstudyontheuseofempiricalorthogonalfunction(EOF)--basedperturbationsforhurricanetrackensembleforecasts,(ZhangandKrishnamur...     

Interdecadal Change in Extreme Precipitation over South China and Its Mechanism

Based on the daily precipitation data taken from 17 stations over South China during the period of 1961--2003, a sudden change in summer extreme precipitation events over South China in the early 1990s along with the possible mechanism connected with the anomalies of the latent heat flux over the South China Sea and the sensible heat flux over the Indochina peninsula are examined. The results show that both the annual and summer extreme precipitation events have obvious interdecadal variations and have increased significantly since the early 1990s. Moreover, the latent heat flux over the South China Sea and the sensible heat flux over the Indochina peninsula also have obvious interdecadal variations consistent with that of the extreme precipitation, and influence different months' extreme precipitation, respectively. Their effects are achieved by the interdecadal increases of the strengthening convection over South China through the South China Sea Summer Monsoon.     

一次冬季江淮气旋逗点云区的雷达回波和气流结构分析

2016年2月12—13日,受冷空气和江淮气旋暖锋锋生影响,山东出现一次极端暴雨雪天气过程,全省有42个站的降水突破同期历史记录。采用多种观测以及WRF模式模拟的热力学变量,基于拉格朗日方法的气流轨迹模式(HYSPLIT v4.9),分析了气旋逗点云区云系的演变特征、降水不同阶段气旋逗点云区气流结构和轨迹特征。结果表明:(1)江淮气旋逗点云区由4条带状回波合并发展形成,气旋形成后降水回波呈气旋式旋转、拉长,形成多条中尺度强降水带。(2)降雨阶段气旋逗点头从下到上主要由来自东海、黄海、日本海或内陆的边界层气团,来自中国南海和中南半岛的暖湿气团以及来自西亚和东欧的干冷气团组成。气旋逗点头内有3个降水区:北部和南部暖湿气团浅薄、层结稳定,为层状云降水区;中部暖湿气团深厚,中高层有条件性不稳定发展,为深厚的对流云降水区。气旋逗点头中南部的干冷空气来自高层的西亚气团,而剖面北部有来自中层(即青藏高原东部气团)的干冷空气,气团明显变性,对降水贡献大。(3)降雪阶段气旋逗点头从下到上主要由西伯利亚气团、东海气团、南海气团和孟加拉湾气团叠置而成。气旋逗点头西部层状降水区分两部分:北部为降雪区,南部为降雨区。降雪与降雨阶段的明显差别是冷湿的东海气团下面是否有西伯利亚冷气团。降雪区西伯利亚气团上空东海气团深厚,南海气团浅薄;降雨区南海气团深厚,东海气团浅薄。      

Intraseasonal SST-precipitation relationship and its spatial variability over the tropical summer monsoon region

The SST-precipitation relationship in the intraseasonal variability (ISV) over the Asian monsoon region is examined using recent high quality satellite data and simulations from a state of the art coupled model, the climate forecast system version 2 (CFSv2). CFSv2 demonstrates high skill in reproducing the spatial distribution of the observed climatological mean summer monsoon precipitation along with its interannual variability, a task which has been a conundrum for many recent climate coupled models. The model also exhibits reasonable skill in simulating coherent northward propagating monsoon intraseasonal anomalies including SST and precipitation, which are generally consistent with observed ISV characteristics. Results from the observations and the model establish the existence of spatial variability in the atmospheric convective response to SST anomalies, over the Asian monsoon domain on intraseasonal timescales. The response is fast over the Arabian Sea, where precipitation lags SST by ~5 days; whereas it is slow over the Bay of Bengal and South China Sea, with a lag of ~12 days. The intraseasonal SST anomalies result in a similar atmospheric response across the basins, which consists of a destabilization of the bottom of the atmospheric column, as observed from the equivalent potential temperature anomalies near the surface. However, the presence of a relatively strong surface convergence over the Arabian Sea, due to the presence of a strong zonal gradient in SST, which accelerates the upward motion of the moist air, results in a relatively faster response in terms of the local precipitation anomalies over the Arabian Sea than over the Bay of Bengal and South China Sea. With respect to the observations, the ocean–atmosphere coupling is well simulated in the model, though with an overestimation of the intraseasonal SST anomalies, leading to an exaggerated SST-precipitation relationship. A detailed examination points to a systematic bias in the thickness of the mixed layer of the ocean model, which needs to be rectified. A too shallow (deep) mixed layer enhances (suppress) the amplitude of the intraseasonal SST anomalies, thereby amplifying (lessening) the ISV and the active-break phases of the monsoon in the model.     

Analysis of effects of constant wind on the velocity of currents and seiche oscillations in the Azov Sea level

Physical regularities of free oscillations of the Azov Sea level induced after the cessation of long-lasting action of wind are analyzed. Spatial characteristics of seiche oscillations, the position of nodal lines, and the velocity of induced currents are simulated with the three-dimensional nonlinear barotropic hydrodynamic model. It was found that in the coastal zone the maximum amplitude of these oscillations is comparable with the value of storm surges. It is demonstrated that seiches make essential contribution to the variability of velocity of currents.     

Analysis of the connection of ice cover parameters of the non-Arctic seas in the European part of Russia with global atmospheric processes

Criteria of winter severity for three non-Arctic European seas are determined from long time series of observations. Periods and dates of indices of macrocirculation epochs are estimated. Results of analysis of the connection of macrocirculation processes (E, W, and C forms of atmospheric circulation) with winter severity and with the ice concentration and thickness of the White Sea, the Gulf of Finland, and the Sea of Azov are presented. Some aspects of the ice cover evolution in the non-Arctic European seas are identified for various latitudinal zones from analysis of changes in global atmospheric processes over a large territory.     

Current Trends in Atmospheric Circulation in the Azov–Black Sea Region

The daily parameters characterizing the field of surface air pressure from 1960 to 2014 are used for assessing the current trends in atmospheric circulation over the Azov–Black Sea region. It was revealed that the decrease in mean air pressure and the weakening of northeastern air trans port which was typical of the atmospheric circulation in this region in the previous period (1960–1990), occurred from 1991–1993 to 2005–2007. In recent 7–8 years, the ongoing air pressure drop is accom panied by the intensification of northeastern air transport.     

中国西南地区5月降水与阿拉伯海季风关系的年代际变化

本文利用1960～2017年中国西南地区115个台站观测降水资料和日本气象厅发布的55年再分析资料集,研究了中国西南地区5月降水变异的主导模态及其与阿拉伯海季风的关系。结果显示,中国西南地区5月降水的第一主导模态主要表现为全区一致的变异特征;该模态与同期5月阿拉伯海季风强度异常关系密切,但两者的关系在20世纪70年代后期发生了显著的年代际变化。在1960～1976年,阿拉伯海季风异常所引起的低层大气环流和水汽输送异常主要集中在阿拉伯海到孟加拉湾一带;阿拉伯海季风异常所引起的大气环流不能到达中国西南地区,因此它对中国西南地区5月降水的影响偏弱。但在1981～2017年,阿拉伯海季风异常可以导致整个北印度洋到南海地区的大气环流异常,进而引起中国西南地区水汽和垂直运动的变化,最终对该地区5月降水产生显著的影响。进一步的研究显示,阿拉伯海季风与中国西南地区5月降水关系的变化可能与季风自身的年代际变率有关。阿拉伯海季风在20世纪70年代末之前变率偏弱,其引起的环流异常也偏弱;相反在20世纪70年代末之后,其变率增强,它引起的大气环流异常也偏强,可以延伸到中国西南地区,进而影响到西南地区的5月降水。因此,季风变率的强弱可能在季风对西南地区5月降水的影响中起着非常重要的作用。     

Regional-scale relationships between aerosol and summer monsoon circulation, and precipitation over northeast Asia

We investigated the regional-scale relationships between columnar aerosol loads and summer monsoon circulation, and also the precipitation over northeast Asia using aerosol optical depth (AOD) data obtained from the 8-year MODIS, AERONET Sun/sky radiometer, and precipitation data acquired under the Global Precipitation Climatology Project (GPCP). These high-quality data revealed the regional-scale link between AOD and summer monsoon circulation, precipitation in July over northeast Asian countries, and their distinct spatial and annual variabilities. Compared to the mean AOD for the entire period of 2001–2008, the increase of almost 40–50% in the AOD value in July 2005 and July 2007 was found over the downwind regions of China (Yellow Sea, Korean peninsula, and East Sea), with negative precipitation anomalies. This can be attributable to the strong westerly confluent flows, between cyclone flows by continental thermal low centered over the northern China and anticyclonic flows by the western North Pacific High, which transport anthropogenic pollution aerosols emitted from east China to aforementioned downwind high AOD regions along the rim of the Pacific marine airmass. In July 2002, however, the easterly flows transported anthropogenic aerosols from east China to the southwestern part of China in July 2002. As a result, the AOD off the coast of China was dramatically reduced in spite of decreasing rainfall. From the calculation of the cross-correlation coefficient between MODIS-derived AOD anomalies and GPCP precipitation anomalies in July over the period 2001–2008, we found negative correlations over the areas encompassed by 105–115°E and 30–35°N and by 120–140°E and 35–40°N (Yellow Sea, Korean peninsula, and East Sea). This suggests that aerosol loads over these regions are easily influenced by the Asian monsoon flow system and associated precipitation.     

Global warming impact on the dominant precipitation processes in the Middle East

In this study, the ability of a regional climate model, based on MM5, to simulate the climate of the Middle East at the beginning of the twenty-first century is assessed. The model is then used to simulate the changes due to global warming over the twenty-first century. The regional climate model displays a negative bias in temperature throughout the year and over most of the domain. It does a good job of simulating the precipitation for most of the domain, though it performs relatively poorly over the southeast Black Sea and southwest Caspian Sea. Using boundary conditions obtained from CCSM3, the model was run for the first and last 5 years of the twenty-first century. The results show widespread warming, with a maximum of ~10 K in interior Iran during summer. It also found some cooling in the southeast Black Sea region during spring and summer that is related to increases in snowfall in the region, a longer snowmelt season, and generally higher soil moisture and latent heating through the summer. The results also show widespread decreases in precipitation over the eastern Mediterranean and Turkey. Precipitation increases were found over the southeast Black Sea, southwest Caspian Sea, and Zagros mountain regions during all seasons except summer, while the Saudi desert region receives increases during summer and autumn. Changes in the dominant precipitation-triggering mechanisms were also investigated. The general trend in the dominant mechanism reflects a change away from the direct dependence on storm tracks and towards greater precipitation triggering by upslope flow of moist air masses. The increase in precipitation in the Saudi desert region is triggered by changes in atmospheric stability brought about by the intrusion of the intertropical convergence zone into the southernmost portion of the domain.     

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.