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1.
M. M. Arzhanov P. F. Demchenko A. V. Eliseev I. I. Mokhov 《Izvestiya Atmospheric and Oceanic Physics》2008,44(5):548-566
The IAP RAS CM (Institute of Atmospheric Physics, Russian Academy of Sciences, climate model) has been extended to include a comprehensive scheme of thermal and hydrologic soil processes. In equilibrium numerical experiments with specified preindustrial and current concentrations of atmospheric carbon dioxide, the coupled model successfully reproduces thermal characteristics of soil, including the temperature of its surface, and seasonal thawing and freezing characteristics. On the whole, the model also reproduces soil hydrology, including the winter snow water equivalent and river runoff from large watersheds. Evapotranspiration from the soil surface and soil moisture are simulated somewhat worse. The equilibrium response of the model to a doubling of atmospheric carbon dioxide shows a considerable warming of the soil surface, a reduction in the extent of permanently frozen soils, and the general growth of evaporation from continents. River runoff increases at high latitudes and decreases in the subtropics. The results are in qualitative agreement with observational data for the 20th century and with climate model simulations for the 21st century. 相似文献
2.
Changes in climatic characteristics of Northern Hemisphere extratropical land in the 21st century: Assessments with the IAP RAS climate model 总被引：1，自引：0，他引：1
A. V. Eliseev M. M. Arzhanov P. F. Demchenko I. I. Mokhov 《Izvestiya Atmospheric and Oceanic Physics》2009,45(3):271-283
Assessments of future changes in the climate of Northern Hemisphere extratropical land regions have been made with the IAP RAS climate model (CM) of intermediate complexity (which includes a detailed scheme of thermo- and hydrophysical soil processes) under prescribed greenhouse and sulfate anthropogenic forcing from observational data for the 19th and 20th centuries and from the SRES B1, A1B, and A2 scenarios for the 21st century. The annual mean warming of the extratropical land surface has been found to reach 2–5 K (3–10 K) by the middle (end) of the 21st century relative to 1961–1990, depending on the anthropogenic forcing scenario, with larger values in North America than in Europe. Winter warming is greater than summer warming. This is expressed in a decrease of 1–4 K (or more) in the amplitude of the annual harmonic of soil-surface temperature in the middle and high latitudes of Eurasia and North America. The total area extent of perennially frozen ground S p in the IAP RAS CM changes only slightly until the late 20th century, reaching about 21 million km2, and then decreases to 11–12 million km2 in 2036–2065 and 4–8 million km2 in 2071–2100. In the late 21st century, near-surface permafrost is expected to remain only in Tibet and in central and eastern Siberia. In these regions, depths of seasonal thaw exceed 1 m (2 m) under the SRES B1 (A1B or A2) scenario. The total land area with seasonal thaw or cooling is expected to decrease from the current value of 54–55 million km2 to 38–42 in the late 21st century. The area of Northern Hemisphere snow cover in February is also reduced from the current value of 45–49 million km2 to 31–37 million km2. For the basins of major rivers in the extratropical latitudes of the Northern Hemisphere, runoff is expected to increase in central and eastern Siberia. In European Russia and in southern Europe, runoff is projected to decrease. In western Siberia (the Ob watershed), runoff would increase under the SRES A1B and A2 scenarios until the 2050s–2070s, then it would decrease to values close to present-day ones; under the anthropogenic forcing scenario SRES B1, the increase in runoff will continue up to the late 21st century. Total runoff from Eurasian rivers into the Arctic Ocean in the IAP RAS CM in the 21st century will increase by 8–9% depending on the scenario. Runoff from the North American rivers into the Arctic Ocean has not changed much throughout numerical experiments with the IAP RAS CM. 相似文献
3.
Observations of the spatial distribution of salinity and tidal salinity fluctuations along the length of the Fleet are presented and different structures are identified with different freshwater runoff conditions. The salinity distribution appears to be the result of a balance between weak tidal flushing and a small freshwater input. A tidal exchange box model is developed to represent this weak balance and is able to reproduce the semidiurnal, fortnightly and seasonal fluctuations of salinity. By use of the tuned model, estimates are made of the flushing times of different segments of the lagoon, the distribution of water from particular stream inputs, and hence their polluting potential, and the likely effect on the salinity structure of changes in the tidal regime which could result from sediment deposition. 相似文献
4.
A dataset of continental river discharge based on JRA-55 for use in a global ocean circulation model
Tatsuo Suzuki Dai Yamazaki Hiroyuki Tsujino Yoshiki Komuro Hideyuki Nakano Shogo Urakawa 《Journal of Oceanography》2018,74(4):421-429
A dataset of historical river discharge into oceans was created using the CaMa-Flood global river routing model and adjusted runoff from the land component of JRA-55. The major rivers were well resolved with a 0.25° horizontal resolution. The total runoff on each drainage basin exhibits a distinctive bias on decadal time scales. The input runoff data were modified using 5-year low-pass-filtered multiplicative factors to fit the annual mean climatology and decadal variations in the reference dataset. The model incorporated data from 1958 to 2016. The yearly and seasonal variations of the major rivers are well represented by the model. 相似文献
5.
Reverberation measurements made by the SACLANT Undersea Research Centre at three shallow-water sites (130-190-m depth) are compared with each other and with estimates from the DREA normal-mode reverberation model OGOPOGO. The experiments over silt-clay and sand seabeds were conducted at slightly bistatic geometries (0.7-6.0-km source-receiver separation), using explosive sources detonated at mid-water depths. The signals were received on hydrophones of either a vertical or horizontal array and analyzed in one-tenth-decade frequency bands from 25 to 1000 Hz. The data are compared with each other to investigate the site differences and frequency dependencies, and with the estimates from the reverberation model OGOPOGO to interpret the data and to obtain a qualitative measure of the scattering. For modeling purposes, geoacoustic models of the seabed were assumed, and the reverberation data were fitted by adjusting the Lambert bottom scattering coefficients. Good model agreement was obtained with both individual hydrophone and data. Though somewhat sensitive to the geoacoustic the Lambert coefficients give a measure of the frequency dependence of the scattering. For the silt-clay bottom, the scattering is weak but is independent of frequency; for the sand bottoms, the scattering is stronger and increases with frequency. These results are compared with estimates from other experiments 相似文献
6.
利用LEVITUS温盐资料、HOAPS降水及蒸发资料以及OFES模式资料等分析加里曼丹岛西北侧表层低盐水的季节变化规律,并使用盐度平衡模式诊断了海面淡水通量、径流、卷挟作用以及平流作用对低盐水变化的贡献.分析表明:加里曼丹西北侧全年均存在1个低盐水团,其季节变化具有"双峰"特征,3月至4月以及10月至11月会发生2次低... 相似文献
7.
长江口、钱塘江口和珠江口是受咸潮影响较为严重的区域。本文利用全国沿海海平面变化影响调查、沿海水文观测等数据,分析了近十年长江口、珠江口和钱塘江口咸潮入侵的变化特征及影响。分析结果表明:(1) 2009-2018年,长江口咸潮入侵次数和持续时间均呈减少趋势,该时段长江口共监测到约48次咸潮入侵过程,发生时间集中在9-10月至翌年5月,其中3月和11月入侵次数较多,分别为12次和7次。(2)钱塘江口咸潮入侵过程受沿海季节性海平面影响显著,12月至翌年3月为钱塘江口季节性低海平面期,4-7月上旬径流量较大,上述两个时期钱塘江口受咸潮入侵的影响均较小,7月下旬至11月上旬,钱塘江口处于季节性高海平面期,是咸潮影响的集中时段。(3) 2009-2018年,珠江口共监测到约57次咸潮入侵过程,发生时间集中在9-10月至翌年3-4月,其中1月、2月和10月咸潮入侵次数较多,均超过10次,2015年至今咸潮持续时间明显增加。(4)咸潮入侵次数和持续时间与基础海面和径流量等密切相关,咸潮入侵影响三大河口沿线水厂供水以及工农业生产取水,给沿岸城市的居民生活、工农业生产和渔业养殖等造成一定不利影响。 相似文献
8.
对于径流变化明显的大型河口,其入射潮波受到径流季节性变化的显著影响。以往多关注洪枯季的特征对比,对年内变化过程的讨论还不充分。本文以长江河口潮波为例,基于潮区界以下多站位年内连续的实测逐时潮位资料,分析了潮差及其衰减速率、涨落潮历时等参数的时空变化特征,认识到长江河口潮波沿程特征除洪枯季差异外,还存在显著的逐月变化差异,重点关注镇江到江阴的过渡段,认识到三江营到魏村闸段在低径流月份的平均潮差衰减速率远低于其相邻上下段,仅为其三分之一。涨潮历时从河口段向近口段的递减存在拐点,到了江阴附近后,不再线性减小。并从典型径流量、沿程差异、河宽束窄等角度分析原因。 相似文献
9.
A. V. Eliseev I. I. Mokhov M. M. Arzhanov P. F. Demchenko S. N. Denisov 《Izvestiya Atmospheric and Oceanic Physics》2008,44(2):139-152
The climate model of the Institute of Atmospheric Physics of the Russian Academy of Sciences (IAP RAS CM) has been supplemented with a module of soil thermal physics and the methane cycle, which takes into account the response of methane emissions from wetland ecosystems to climate changes. Methane emissions are allowed only from unfrozen top layers of the soil, with an additional constraint in the depth of the simulated layer. All wetland ecosystems are assumed to be water-saturated. The molar amount of the methane oxidized in the atmosphere is added to the simulated atmospheric concentration of CO2. A control preindustrial experiment and a series of numerical experiments for the 17th–21st centuries were conducted with the model forced by greenhouse gases and tropospheric sulfate aerosols. It is shown that the IAP RAS CM generally reproduces preindustrial and current characteristics of both seasonal thawing/freezing of the soil and the methane cycle. During global warming in the 21st century, the permafrost area is reduced by four million square kilometers. By the end of the 21st century, methane emissions from wetland ecosystems amount to 130–140 Mt CH4/year for the preindustrial and current period increase to 170–200 MtCH4/year. In the aggressive anthropogenic forcing scenario A2, the atmospheric methane concentration grows steadily to ≈3900 ppb. In more moderate scenarios A1B and B1, the methane concentration increases until the mid-21st century, reaching ≈2100–2400 ppb, and then decreases. Methane oxidation in air results in a slight additional growth of the atmospheric concentration of carbon dioxide. Allowance for the interaction between processes in wetland ecosystems and the methane cycle in the IAP RAS CM leads to an additional atmospheric methane increase of 10–20% depending on the anthropogenic forcing scenario and the time. The causes of this additional increase are the temperature dependence of integral methane production and the longer duration of a warm period in the soil. However, the resulting enhancement of the instantaneous greenhouse radiative forcing of atmospheric methane and an increase in the mean surface air temperature are small (globally < 0.1 W/m2 and 0.05 K, respectively). 相似文献
10.
利用渤海湾和莱州湾现场实测的悬浮物含量和光谱数据,建立了基于555和670nm波段遥感反射率的悬浮物含量遥感反演模型。经检验,模型平均相对误差优于20%,对输入端误差不敏感。基于该模型,利用ENVISAT MERIS遥感数据,从空间分布格局、大风过程的短期扰动以及季节性差异等方面分析了渤海悬浮物的时空分布特征。(1)渤海悬浮物含量的高值区集中分布在莱州湾(尤其是黄河口和莱州湾湾底)和渤海湾沿岸,此外在辽东湾沿岸海域悬浮物含量也相对较高,而在渤海大部水体悬浮物含量较低。(2)大风过程可在短期内(约1~3d)显著改变全渤海的悬浮物空间分布格局,其中渤海湾和莱州湾响应最为强烈,辽东湾响应相对较弱,这与其各自的水深条件、底质类型和悬浮物粒径等因素有关。(3)渤海悬浮物含量总体上呈春夏低、秋冬高的分布特征;季节性差异最显著的区域是渤海湾、莱州湾和辽东湾,差异性最小的是秦皇岛近岸海域;风力等气候因素是悬浮物分布呈现季节性差异的主要原因,入海径流是另一重要因素。 相似文献
11.
The hydrographic fields in the Arctic region are calculated with a three-dimensional nonlinear model of the general circulation
in the World Ocean using climatic databases on temperature, salinity, and wind stress. The calculation results show that the
seasonal variability of the fields is negligible. The salinity distribution almost does not change from season to season,
and slight temperature differences are found only in the upper layer. In the winter period, a moderate intensification of
the currents is observed. The formation of an intermediate low-salinity layer is revealed at the Subantarctic front, where
the intensive turbulence and transverse circulation in the Antarctic Circumpolar Current near the front result in the sinking
of the surface low-salinity waters down to intermediate depths. The low-salinity water propagates in the oceans at intermediate
depths northward from the front by advection. The integral values of the seasonal transport of mass, heat, and salt in various
sections are presented in tables, and the distributions of appropriate characteristics in these sections are shown in figures.
According to the calculations, the highest seasonal variations of heat, salt, and mass exchange in the Antarctic region and
adjacent oceans are found in the Atlantic sector. 相似文献
12.
Seasonal variations in primary production, phytoplankton biomass, chlorophyll-a, dissolved inorganic phosphorus and nitrogen concentrations in the upper 10 m of the Kattegat were analysed by means of monitoring data from 1993–1997. Spatial optimal analysis, based on a stochastic model, was used to reconstruct weekly constituent fields onto a spatial grid. The reconstructed fields were spatially integrated, resulting in a relatively smooth seasonal variability of the average variables. A simple dynamical model, set up as a periodical boundary problem, is suggested for the average phytoplankton concentration, dissolved inorganic nitrogen and entrainment depth as state variables. The model is forced by the solar radiation, nitrogen load from the land sources and atmosphere as well as by nitrogen supply from the lower nutrient-rich layer. The latter process is modelled proportional to the water entrainment into the upper euphotic layer and is driven by atmospheric forcing, river runoff and the Baltic water inflow. Four model coefficient values were fitted by minimising the root mean square difference between the integrated monitoring data and the model output. The suggested diagnostic model reflects the main features in seasonal variability of phytoplankton and nitrogen concentrations by average values, including the magnitude and timing of such dynamic events as the spring and late summer phytoplankton blooms. The importance of different forcing factors is quantified and estimates of unobserved components such as new primary production can be computed. 相似文献
13.
渤海海温与叶绿素季节空间变化特征分析 总被引：4，自引：0，他引：4
以2003年MODIS数据为数据源，在图像处理、空间插值的基础上作海温与叶绿素浓度的空间相关分析。结果表明，整个海域的叶绿素浓度和海温的分布具有明显的区域和季节变化特征。基本规律是叶绿素浓度从近岸向渤海中央递减；温度则随季节发生变化，随着温度升高，近海叶绿素浓度增高，而渤海中央区域叶绿素浓度降低。渤海叶绿素浓度的分布与河口径流、季节等因素有关。从空间关系看，海温与叶绿素浓度不存在很明显的空间分布相关性，但不同季节有不同的相关性。上述研究可用于估算海洋初级生产力。 相似文献
14.
菲律宾海的声速剖面结构特征及季节性变化 总被引：3，自引：0，他引：3
应用Argo资料研究了菲律宾海的声速剖面结构特征。通过统计分析选取了合理的跃层标准，分析了主跃层、季节性跃层和表面正梯度层的区域性分布及季节性变化。结果表明，菲律宾海主要受赤道流系和北太平洋西边界流系的支配，其环流结构和水团配置对声场结构影响很大；主跃层的经向差异显著，但季节性变化较小，其平均位置由南向北逐渐加深，强度逐渐减弱；季节性跃层的分布及变化主要受混合层的季节性变化以及北部海区冬季温跃层通风过程的影响，夏季较强较厚，冬季较弱较薄；深海声道轴季节性变化较小，南极中层水和北太平洋中层水的温盐差异是其经向分布差异的主要原因。综合考虑海区声速结构区域性和季节性特征，将其归纳为6种典型结构，得出了各类声速剖面的模态特征及垂直结构参数的统计特征值。 相似文献
15.
Analysis of characteristics of time-frequency correlations between runoff, tidal range and salinity in the Changjiang Estuary 总被引：2，自引：0，他引：2
Power spectrum and cross-wavelet transform analysis was adopted to study the time-frequency characteristics and multiscale correlations between runoff, tidal range and salinity in the Changjiang Estuary based on the runoff data collected at the Datong Station, the tidal range measured at the Baozhen Station, and the salinity at the Baogang Station from 2008 to 2009. The variations of the salinity showed significant periodicity at scales of 2-3, 7-8, 14-15 and 26-30 d. The correlation between the salinity and the runoff and the tidal range were found to be significantly related to shock at scales of 5-7, 14-15, 26-30 d and 0.5 a. The correlation between the runoff and the salinity was mainly in the same phase, while the correlation between the tidal range and the salinity was in the antiphase. Different frequency bands were related to different degrees, and their relevance increased as the resonance frequency decreased. In addition, changes of the seasonal runoff were obvious. Specifically, a point of discontinuity was reached in early June with a cycle of 7-8 d, which coincided with the periodicity of plum rains in the Changjiang-Huaihe region. High-frequency changes (8-16 d period) of the salinity corresponded to the time domain in January-April 2008, February-April 2009 and October-December 2009 and exhibited an approximately 0.5 a (184 d) long frequency oscillation. Short-period changes were found to be stronger than long-period changes. Cross-wavelet transforms for the salinity, the runoff and the tidal range revealed local features in the time domain, while the significant levels of different periodic oscillations were observed in the frequency domain. The correlation characteristics of the salinity and the runoff were significant in the 80-90 d frequency domain, indicating that the major impact of the runoff on the salinity was reflected in seasonal changes. The tidal range on the small scale of 14-15 and 30-32 d was more obvious than the runoff. 相似文献
16.
17.
A climate shift in seasonal values of meteorological and hydrological parameters for Northeastern Asia 总被引：1，自引：0，他引：1
N. I. Savelieva I. P. Semiletov L. N. Vasilevskaya S. P. Pugach 《Progress in Oceanography》2000,47(2-4)
The well-known climate shift that occurred around 1976/1977 in the marine ecosystem of North Pacific Ocean was preceded by changes in the early 1970s over Northeastern Asia. In this paper long-term variability of Siberian High and Aleutian Low parameters, seasonal discharge of Siberian rivers and air temperature and precipitation regime in their watersheds are examined in data sets covering 1945–1995. It was found that the change in seasonal values of Siberian river discharges is a consequence of an atmospheric climatic shift that occurred in the early 1970s over North Asia. This shift was induced by a change in atmospheric circulation pattern in the Eurasian sector and Pacific sector of the Northern Hemisphere after 1970. It resulted in changes in position and intensity of the Siberian High and Aleutian Low before and after the 1970s, which induced a different pattern of precipitation in West and East Siberia. There was an increase in winter precipitation over West Siberia but a decrease over East Siberia. The period after 1970s is characterized by higher amplitude of all parameters and increases in the year-to-year variability. 相似文献
18.
On the use of discrete seasonal and directional models for the estimation of extreme wave conditions
Extreme value theory is commonly used in offshore engineering to estimate extreme significant wave height. To justify the use of extreme value models it is of critical importance either to verify that the assumptions made by the models are satisfied by the data or to examine the effect violating model assumptions. An important assumption made in the derivation of extreme value models is that the data come from a stationary distribution. The distribution of significant wave height varies with both the direction of origin of a storm and the season it occurs in, violating the assumption of a stationary distribution. Extreme value models can be applied to analyse the data in discrete seasons or directional sectors over which the distribution can be considered approximately stationary. Previous studies have suggested that models which ignore seasonality or directionality are less accurate and will underestimate extremes. This study shows that in fact the opposite is true. Using realistic case studies, it is shown that estimates of extremes from non-seasonal models have a lower bias and variance than estimates from discrete seasonal models and that estimates from discrete seasonal models tend to be biased high. The results are also applicable to discrete directional models. 相似文献
19.
For the Black-Sea region, we perform the dynamic reanalysis of the data on atmospheric circulation for the period 1958–2001
by using the HadRM3P model with a space resolution of 25 km. We estimate the mean climatic atmospheric fields of vorticity and divergence of the
wind velocity and study their space structure and seasonal variability. The climatic estimates of the annual course of vorticity
of the wind velocity over the sea are presented. The obtained large annual average values of vorticity of the velocity reveal
the predominant role played by the wind action in the generation not only of the seasonal variability but also of the mean
cyclonic circulation of waters in the Black Sea. 相似文献
20.
The flow-structure interaction in an ocean environment, for a pile placed in an erodible bed where currents and waves are of prime concern, changes the bed elevation due to scour in the vicinity of the obstruction. There are certain difficulties in predicting the scour depth, as the particulate movement of sediments due to scour is time-dependent. Considering the complexity of the problem, an instrumentation system has been developed for measuring scour depth with time. This paper outlines the experimental laboratory techniques used to measure scour around pile foundations in silty-clay sediments. Detailed laboratory testing on model piles having a diameter of 50-110 mm was carried out in a wave flume having a length of 30 m and a width of 2.0 m. The motivation of these studies is to obtain observational experience of scour rate in silty-clay soil. Scour depths were monitored continuously for different combinations of wave characteristics and current velocities, and scour-time history is measured. Based on the measurements, a relationship for the scour depth in terms of duration of flow, soil properties, model characteristics, and fluid parameters is presented. 相似文献