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1.
全球变暖的背景下,北极航线的常规通航甚至商业运营有望实现,而海雾会严重影响航道上船只的航行安全。海冰的存在使海气之间相互作用变得更为复杂,是研究北极海雾不可忽略的因素。船载观测发现,与中纬度常见平流冷却雾形成时气温下降速度往往超过海水降温速度不同,北极海雾发生时海冰的存在还会使海水降温速度超过空气降温速度。然而目前海冰分布是否会影响模式模拟海雾的准确性还不得而知,因此本文利用Polar WRF（Polar Weather Research and Forecasting）模式模拟了中国第七次北极考察中观测到的一次海雾过程,并进行海冰密集度敏感性试验。通过与船载观测和欧洲中期天气预报中心再分析数据比对发现,在低浮冰区内（海冰密集度小于50%）考虑海冰分布时可以更加准确地刻画潜热通量与水汽通量,模拟出与观测事实相符的表层空气降温与增湿过程以及相对湿度的变化,因此能够更好地刻画海雾的三维结构及其生消演变。 相似文献
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Meteorological observation by a helicopter was carried out to investigate the structure of sea breezes over the coastal area of Tosa Bay in Shikoku island, Japan. Several groups of wave trains were found over the sea during a flight made on 25 November 1992. Not only the terrain barrier but the remaining cold air pools formed in valleys hindered further advance of the sea breeze inland, so that the presence of such wave trains may appear to be due to the effect of the secondary flow which supplies moister and cooler air from behind the sea breeze front. 相似文献
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J. Körper I. Höschel J. A. Lowe C. D. Hewitt D. Salas y Melia E. Roeckner H. Huebener J.-F. Royer J.-L. Dufresne A. Pardaens M. A. Giorgetta M. G. Sanderson O. H. Otterå J. Tjiputra S. Denvil 《Climate Dynamics》2013,40(3-4):531-550
With an increasing political focus on limiting global warming to less than 2 °C above pre-industrial levels it is vital to understand the consequences of these targets on key parts of the climate system. Here, we focus on changes in sea level and sea ice, comparing twenty-first century projections with increased greenhouse gas concentrations (using the mid-range IPCC A1B emissions scenario) with those under a mitigation scenario with large reductions in emissions (the E1 scenario). At the end of the twenty-first century, the global mean steric sea level rise is reduced by about a third in the mitigation scenario compared with the A1B scenario. Changes in surface air temperature are found to be poorly correlated with steric sea level changes. While the projected decreases in sea ice extent during the first half of the twenty-first century are independent of the season or scenario, especially in the Arctic, the seasonal cycle of sea ice extent is amplified. By the end of the century the Arctic becomes sea ice free in September in the A1B scenario in most models. In the mitigation scenario the ice does not disappear in the majority of models, but is reduced by 42 % of the present September extent. Results for Antarctic sea ice changes reveal large initial biases in the models and a significant correlation between projected changes and the initial extent. This latter result highlights the necessity for further refinements in Antarctic sea ice modelling for more reliable projections of future sea ice. 相似文献
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Monitoring sea level changes 总被引：3，自引：0，他引：3
Vivien Gornitz 《Climatic change》1995,31(2-4):515-544
Future sea level rise arouses concern because of potentially deleterious impacts to coastal regions. These will stem not only from the loss of land through inundation and erosion, but also from increased frequency of storm floods, with a rising base level, even with no change in storm climatology, and from saltwater intrusion and greater amounts of waterlogging. Current sea level trends are important in formulating an accurate baseline for future projections. Sea level, furthermore, is an important parameter which integrates a number of oceanic and atmospheric processes. The ocean surface demonstrates considerable variability on diurnal, seasonal, and interannual time scales, induced by winds, storm waves, coastal upwelling, and geostrophic currents. Secular trends in sea level arise from changes in global mean temperature and also from crustal deformation on local to regional scales. The challenge facing researchers is how best to extract the climate signal from this noise.This paper re-examines recent estimates of sea level rise, discusses causes of variability in the sea level records, and describes methods employed to filter out some of these contaminating signals. Evidence for trends in long-term sea level records and in extreme events is investigated. Application of satellite geodesy to sea level research is briefly reviewed. 相似文献
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利用2013年1月—2014年12月山东近海的8个浮标站、海岛站和自动站资料与ASCAT近岸风速和风向进行对比,以分析ASCAT反演风场在山东沿海的适用性。研究发现：总体上看,ASCAT近岸风速与代表站实况风速正相关,ASCAT近岸风速在山东沿海误差较小,风向有明显的偏离。ASCAT近岸风在渤海、渤海海峡和黄海北部的适用性优于黄海中部。风力不同时,ASCAT近岸风速与实况偏差有明显差别,表现为当实况出现6级及以上的大风,ASCAT近岸风速小于实况;当实况出现6级以下的风,ASCAT近岸风速大于实况。就ASCAT风速偏差而言,6级以下的风速偏差小于6级及以上风。ASCAT近岸风向与实况偏差也有明显差别,当实况出现6级及以上的大风,ASCAT近岸风向与实况的偏离变小;当实况出现6级以下的风,ASCAT近岸风向与实况的偏离变大。因此,ASCAT近岸风速在山东沿海有较好的适用性,6级以下风更优;ASCAT近岸风向也有一定的适用性,6级及以上风向可用性比6级以下强。 相似文献
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《大气与海洋》2013,51(2):141-143
Abstract The fluctuation of remotely sensed sea radiance is investigated and comparatively simple expressions for the average value and the variance of radiance are derived. Possible causes for this fluctuation are sea waves and the angular gradient of sky radiation. The influence of oil films on the average radiance is also estimated. 相似文献
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In an attempt to estimate accurate local sea level change, “sea level trend” modes are identified and separated from natural variability via cyclostationary empirical orthogonal function (CSEOF) analysis applied to both the tide gauge data (1965–2013) and the reconstruction data (1950–2010) around the Korean Peninsula. For the tide gauge data, ensemble empirical mode decomposition (EEMD) method is also used to estimate sea level trend to understand an uncertainty from different analysis tools. The three trend models—linear, quadratic, and exponential—are fitted to the amplitude time series of the trend mode so that future projection of sea level can be made. Based on a quadratic model, the rate of local sea level rise (SLR) is expected to be 4.63?±?1.1 mm year?1 during 2010–2060. The estimates of “local” sea level trend vary up to ～30%. It should be noted that, although the three trend models estimate similar sea level trends during the observational period, the projected sea level trend and subsequent SLR differ significantly from one model to another and between the tide gauge data and the reconstruction data; this results in a substantial uncertainty in the future SLR around the Korean Peninsula. 相似文献
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Drag of the sea surface 总被引：6，自引：1，他引：6
It is shown how the drag of the sea surface can be computed from the wind speed and the sea state. The approach, applicable both for fully developed and for developing seas, is based on conservation of momentum in the boundary layer above the sea, which allows one to relate the drag to the properties of the momentum exchange between the sea waves and the atmosphere.The total stress is split into two parts: a turbulent part and a wave-induced part. The former is parameterized in terms of mixing-length theory. The latter is calculated by integration of the wave-induced stress over all wave numbers. Usually, the effective roughness is given in terms of the empirical Charnock relation. Here, it is shown how this relation can be derived from the dynamical balance between turbulent and wave-induced stress. To this end, the non-slip boundary conditions is assigned to the wave surface, and the local roughness parameter is determined by the scale of the molecular sublayer.The formation of the sea drag is then described for fully developed and developing seas and for light to high winds.For the Charnock constant, a value of about 0.018–0.030 is obtained, depending on the wind input, which is well within the range of experimental data.It is shown that gravity-capillary waves with a wavelength less than 5 cm play a minor role in the momentum transfer from wind to waves. Most of the momentum is transferred to decimeter and meter waves, so that the drag of developing seas depends crucially on the form of the wave spectrum in the corresponding high wavenumber range.The dependence of the drag on wave age depends sensitively on the dependence of this high wavenumbertail on wave age. If the tail is wave-age independent, the sea drag appears to be virtually independent of wave age. If the tail depends on wave age, the drag also does. There is contradictory evidence as to the actual dependence. Therefore, additional experiments are needed.The investigation was in part supported by the Netherlands Geosciences Foundation (GOA) with financial aid from the Netherlands Organization for Scientific Research (NWO). 相似文献
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Virginie Guemas Francisco J. Doblas-Reyes Kristian Mogensen Sarah Keeley Yongming Tang 《Climate Dynamics》2014,43(9-10):2813-2829
Polar climate studies are severely hampered by the sparseness of the sea ice observations. We aim at filling this critical gap by producing two 5-member sea ice historical simulations strongly constrained by ocean and atmosphere observational data and covering the 1958–2006 and 1979–2012 periods. This is the first multi-member sea ice reconstruction covering more than 50 years. The obtained sea ice conditions are in reasonable agreement with the few available observations. These best estimates of sea ice conditions serve subsequently as initial sea ice conditions for a set of 28 3-year-long retrospective climate predictions. We compare it to a set in which the sea ice initial conditions are taken from a single-member sea ice historical simulation constrained by atmosphere observations only. We find an improved skill in predicting the Arctic sea ice area and Arctic near surface temperature but a slightly degraded skill in predicting the Antarctic sea ice area. We also obtain a larger spread between the members for the sea ice variables, thus more representative of the forecast error. 相似文献
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The response of the polar atmosphere to the reduction of sea ice area in the Arctic and the rise of sea surface temperature is considered using the atmospheric general circulation model with prescribed boundary conditions on the ocean surface. Boundary conditions include the observed sea ice concentration and the sea surface temperature in recent three decades. The study demonstrates that the reduction of sea ice extent is the major factor contributing to the amplification of the warming in the Arctic. However, the spatiotemporal distribution of the warming is not uniform. It is mostly pronounced in autumn and winter and extends up to the height of about 1 km in the areas of large reduction of sea ice concentration or of its complete disappearance. It is demonstrated that the rise of the sea surface temperature also provides some contribution to the warming in the Arctic. Due to the global warming in recent decades statistically significant changes occurred in the distribution of the sea-level pres sure and geopotential heights in the polar region and at mid-latitudes in autumn, winter, and spring. However, these changes are mainly associated with the increase in the sea surface temperature but not with the reduction of sea ice extent. The study has not revealed any significant ret ationships between ice cover anomalies in the Arctic and the evolution of pressure patterns of the synoptic scale that could contribute to the development of cold weather episodes over Eurasia in winter. 相似文献
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The risk of sea level rise 总被引：3，自引：1，他引：2
The United Nations Framework Convention on Climate Change requires nations to implement measures for adapting to rising sea level and other effects of changing climate. To decide upon an appropriate response, coastal planners and engineers must weigh the cost of these measures against the likely cost of failing to prepare, which depends on the probability of the sea rising a particular amount.This study estimates such a probability distribution, using models employed by previous assessments, as well as the subjective assessments of twenty climate and glaciology reviewers about the values of particular model coefficients. The reviewer assumptions imply a 50 percent chance that the average global temperature will rise 2 °C, as well as a 5 percent chance that temperatures will rise 4.7 °C by 2100. The resulting impact of climate change on sea level has a 50 percent chance of exceeding 34 cm and a 1% chance of exceeding one meter by the year 2100, as well as a 3 percent chance of a 2 meter rise and a 1 percent chance of a 4 meter rise by the year 2200.The models and assumptions employed by this study suggest that greenhouse gases have contributed 0.5 mm/yr to sea level over the last century. Tidal gauges suggest that sea level is rising about 1.8 mm/yr worldwide, and 2.5–3.0 mm/yr along most of the U.S. Coast. It is reasonable to expect that sea level in most locations will continue to rise more rapidly than the contribution from climate change alone.We provide a set of normalized projections which express the extent to which climate change is likely to accelerate the rate of sea level rise. Those projections suggest that there is a 65 percent chance that sea level will rise 1 mm/yr more rapidly in the next 30 years than it has been rising in the last century. Assuming that nonclimatic factors do not change, there is a 50 percent chance that global sea level will rise 45 cm, and a 1 percent chance of a 112 cm rise by the year 2100; the corresponding estimates for New York City are 55 and 122 cm.Climate change impact assessments concerning agriculture, forests, water resources, and other noncoastal resources should also employ probability-based projections of regional climate change. Results from general circulation models usually provide neither the most likely scenario nor the full range of possible outcomes; probabilistic projections do convey this information. Moreover, probabilistic projections can make use of all the available knowledge, including the views of skeptics; the opinions of those who study ice cores, fossils, and other empirical evidence; and the insights of climate modelers, which may be as useful as the model results themselves.The U.S. Government right to retain a non-exclusive royalty-free license in and to any copyright is acknowledged. 相似文献
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A. S. Zapevalov 《Russian Meteorology and Hydrology》2011,36(9):624-629
The variability of cumulants of the fifth and sixth orders of the sea surface elevations is studied. The investigations are
carried out on the basis of the data of direct wave measurements carried out in the field conditions. It is demonstrated that
the cumulants of the fifth order are weakly correlated with the variations of the mean sea surface slope generated by the
dominant waves. The variations of the cumulant of the sixth order are not correlated with the mean slope variations. The errors
of the sea surface elevation probability density approximated by the models based on the use of Gram-Charlier series are analyzed.
The analysis is carried out for the models including various numbers of terms of the Gram-Charlier series. 相似文献
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Abstract Monthly mean sea‐level pressure (SLP) data from the Northern Hemisphere for the period January 1952‐December 1987 are analysed. Fluctuations in this field over the Arctic on interannual time‐scales and their statistical association with fluctuations farther south are determined. The standard deviation of the interannual variability is largest compared with that of the annual cycle along the seaboards of the major land masses. The SLP anomalies are generally in phase over the entire Arctic Basin and extend south over the northern Russia and Canada, but tend to be out of phase with fluctuations at mid‐latitudes. The anomalies are most closely associated with fluctuations over the North Atlantic and Europe except near the Chukchi Sea to the north of Bering Strait. The associations with the North Pacific fluctuations become increasingly more prominent at most Arctic sites (e.g. the Canadian Arctic Archipelago) as the time‐scale increases. Associations between the SLP fluctuations and atmospheric indices that represent processes affecting sea‐ice drift (wind stress and wind stress curl) are determined. In every case local associations dominate, but some remote ones are also evident. For example, changes in the magnitude of the wind stress curl over the Beaufort Sea are increased if the atmospheric circulation over the North Pacific is intensified; wind stress over the region where sea ice is exchanged between the Beaufort Gyre and the Transpolar Drift Stream is modulated by both the Southern and North Atlantic Oscillations. Severe sea‐ice conditions in the Greenland Sea (as measured by the Koch Ice Index) coincide with a weakened atmospheric circulation over the North Atlantic. 相似文献
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Xiaoli Guo Lars n Vladimir K. Makin Ann-Sofi Smedman 《Journal of Atmospheric & Ocean Science》2003,9(3):97-120
Measurements from the Baltic Sea and a wind-over-wave coupled model are used to study the wave impact on the sea drag. The study has been carried out for different wave conditions, namely a pure wind-sea, following-swell/ mixed sea and cross-swell/ mixed sea. Measurements reveal the fact that the sea drag is dependent on the sea-state. In stationary conditions and in the absence of severe cross-swell, swell reduces drag compared to wind-sea at the same wind speed. The cross-swell enhances the drag as compared to the following-swell case and the magnitude of the drag coefficient is increased with increasing the angle of swell propagation to the wind. It is shown that the agreement between the model results and measurements is good for pure wind-sea and stationary mixed-sea cases. Discrepancies occur at light winds, where most of the data represent pure swell conditions. During these pure swell conditions the data are characterized by a large variation of the drag coefficient. The variation is caused by mesoscale variability in the stress co-spectra, wind-cross-swell effects and nonstationarity in the wave and wind fields not represented in the model. 相似文献
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A. N. Chetyrbotskii 《Russian Meteorology and Hydrology》2016,41(4):276-284
Data on sampling long-term monthly mean distributions of Antarctic sea ice extent are analyzed for the period of 1974-2013. In the framework of propositions on the nature of variations in the components of limited-area system, the numerical model of sea ice extent dynamics was developed. It is demonstrated that in 1974-2013 the variations in monthly mean sea ice extent were defined by semiannual, annual, 30-year, and 60-year periodic components. The interpolation of the obtained results is presented. The forecast of Antarctic sea ice conditions for 2015-2135 is given. 相似文献
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Pasquill stability categories or similar classifications can be used to estimate dispersion of airborne material. Such categories are defined in terms of synoptic surface-layer variables. In order to transpose experience gained over land to sea, the different boundary conditions over land and sea must be considered. Using the assumption that the turbulence intensity and hence diffusion will be the same over land and sea if the boundary conditions expressed by sensible heat flux and shear stress are equal, a conversion is derived. With a reasonable degree of accuracy, synoptic parameters, mean wind speed and air sea temperature difference can be used at sea to specify stability categories.During the course of this research, it was found that Golder's relation between stability categories and Monin-Obukhov length can not be used at sea, since this relationship must depend on the Bowen ratio and albedo. 相似文献
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A large nuclear war could produce massive quantities of smoke from burning cities and industries. A portion of this smoke would fall out on Arctic sea ice, thus lowering its albedo and potentially increasing the solar energy absorbed by the ice and the snow that covers it. We use a one-dimensional thermodynamic sea ice model to examine the effect of smokefall on the seasonal variation of sea ice. In particular, we test the sensitivity of the model results to the time of year, duration, and latitude of smokefall.Sea ice thickness variations and the period of summer ice-free conditions are sensitive to the season of smokefall. The largest sea ice perturbations are generated by smokefall in spring. In this case the period of ice-free conditions during the summer can increase by 2 – 3.5 months between 67.5° N and 82.5° N. In any given season, the annual cycle of sea ice is not very sensitive to the duration of smokefall. The equilibrium annual cycle of sea ice variation is restored within a few years of smokefall when the smoke is flushed out of the ice/snow system.Since the sea ice model used here is not a comprehensive global climate model, it is difficult to predict the mid-latitude climate effects of the massive, but temporary, Arctic sea ice changes. However, our results suggest that future global climate model simulations of the effects of nuclear war smoke include interactive sea ice calculations.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献