共查询到19条相似文献,搜索用时 78 毫秒
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1引言每年秋末冬初,在江河封冻之前,江面有一段流冰时间,表现为大小不一的冰花在江面上流动,称为流凌。流凌期间虽短,但对船只威胁却很大,因为流动的冰花粘附在船只上,越积越多,将使船行受阻,进而可能导致船只无法及时返航,有被冻在江中的危险。因此,做好流凌日期的预报服务至关重要。松花江的流凌日期多年平均为11月10日。比该日期出现时间晚2~4d的定义为流凌偏晚,早2~4d的定义为偏早,偏晚或偏早5d以上的称之为特晚或特早。20世纪90年代以来,在全球气候转暖的大背景下,黑龙江省气温相应也较高,因此多为数年份流凌日期都较常年偏晚,但2002… 相似文献
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利用海温作山东半岛气温,降水预报的业务系统 总被引:1,自引:1,他引:1
通过分析太平洋海温与山东半岛气温和降水的相关性,找出了两者相关关系中的一些特点。用于制做月平均气温和月降水量的预报系统,在预报业务中取得了很好的预报效果和经济效益。 相似文献
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广西原料蔗产量大气环流因子预报模式研究 总被引:3,自引:0,他引:3
本文分析了我区代表性的15家糖厂及7个地区、3个市的原料蔗产量与大气环流因子的关系,并同时分析的大气环充因子与甘蔗产量关键期主要气象因子之间的关系,建立了有关糖厂、地的甘蔗产量大气环流因子预报模式,为进行原料蔗产量预报增加了一种新的方法。 相似文献
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河南省夏玉米产量预报方法 总被引:4,自引:0,他引:4
利用河南省农业气象产量预报业务系(WAPFOS),分析了夏玉米产量与光照、降水、气温等影响因子的关系,结果表明,旬降水量、旬日照时数和旬平均气温与夏玉米产量关系密切,是直接影响产量的重要因素。在此基础上,建立了预报模型。 相似文献
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Geometric and aerodynamic roughness of sea ice 总被引:2,自引:0,他引:2
The aerodynamic drag of Arctic sea ice is calculated using surface data, measured by an airborne laser altimeter and a digital camera in the marginal ice zone of Fram Strait. The influence of the surface morphology on the momentum transfer under neutral thermal stratification in the atmospheric boundary layer is derived with the aid of model concepts, based on the partitioning of the surface drag into a form drag and a skin drag. The drag partitioning concept pays attention to the probability density functions of the geometric surface parameters. We found for the marginal ice zone that the form drag, caused by floe edges, can amount to 140% of the skin drag, while the effect of pressure ridges never exceeded 40%. Due to the narrow spacing of obstacles, the skin drag is significantly reduced by shadowing effects on the leeward side of floe edges. For practical purposes, the fractional sea-ice coverage can be used to parameterize the drag coefficientC
dn, related to the 10 m-wind. C
dnincreases from 1.2 · 10-3 over open water to 2.8 · 10-3 for 55% ice coverage and decreases to 1.5 · 10-3 for 100% ice coverage.Aircraft turbulence measurements are used to compare the model values of C
dnwith measureents. The correlation between measured and modelled drag coefficients results in r
2 = 0.91, where r is the correlation coefficient. 相似文献
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Abstract Using satellite pictures of Baffin Bay and Davis Strait, ice‐floes were tracked in order to give weekly surface velocities for 1978–1979. The approximate location of the edge of the ice sheet was also determined. In winter the direction of travel was mainly southward in Davis Strait then, as the summer approached, the edge of the ice sheet retreated northward and floe motion became less clearly defined — even going north on occasion in Baffin Bay. Near shore speeds along Baffin Island exceeded 50 cm s‐1 in Davis Strait during November and February. Typical values in the winter/spring period were 10–15 cm s‐1 between Davis Strait and Hudson Strait. Wind records at nearby shore stations showed directions to be mainly from the northwest, roughly parallel to the Baffin Island coastline. The study confirms the usefulness of satellite pictures as a data source for modelling surface ice movement and for selecting navigation routes in these northern waters. 相似文献
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《大气与海洋》2013,51(3):169-183
Abstract Ice‐band characteristics for the region off East Queen Maud Land in Antarctica were examined and their relationship with the wind conditions was assessed using a large number of Marine Observation Satellite (MOS) Multispectral Electronic Self Scanning Radiometer (MESSR) images received at Syowa Station during the period 1989–93. Analyses from 43 examples of bands captured from August to December suggest that ice‐band formation and band scale are affected by both wind speed and direction over approximately the preceding four days (defined as the effective wind). Ice‐band width and spacing are significantly correlated with the effective wind speed and the maximum wind speed during that period. The long axis of ice bands tends to be oriented at 70°‐90° (mean of 75°) to the right of the effective wind direction. The band scales decrease from winter (August) to summer (December) with typical band spacing of 4–6 km in winter and 1–2 km in summer. This seems to be primarily due to a decrease in ice floe size and partly due to a decrease in the effective wind speed from winter to summer. Band scale decreases from the ice interior to the ice edge under conditions of off‐ice winds. 相似文献
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Although it is well known that sea-ice regions are important components of the Earth's climate system, the exchanges of energy between ocean, ice and atmosphere are not well understood. The majority of past observational and modelling studies of atmosphere-surface interactions over sea-ice regions were primarily concerned with airflow over a single, isolated area of open water. The more realistic situations of multiple polynyas within a sea-ice field and different areal concentrations of sea ice were studied here. Spatial structure of the atmospheric boundary layer in response to this surface was simulated using a high-resolution numerical model. A sea-ice concentration of 80%, typical of the Southern Ocean sea-ice zone, was maintained within a 100-km wide domain. The effects of three polynya characteristics were assessed: their horizontal extent; local concentration of sea ice (LCI); and their arrangement with ice floes. Over polynyas of all sizes distinct plumes of upward heat flux, their width and height closely linked to polynya width, resulted in mixed layers 600 to 1000 m deep over and downwind of the polynyas, their depth increasing with polynya width. Mean surface heat flux (MSHF) increased with size in polynyas less than 30 km wide. The air-to-ice MSHF over the first 10 km of sea-ice downwind of each polynya and the domain-average surface heat flux increased linearly with polynya width. Turbulent kinetic energy plumes occurred over all polynyas, their heights and widths increasing with polynya widths. Downward flux of high momentum air in the plumes caused increased wind speeds over polynyas in the layer from about 300–1000 m above the surface, the depth varying directly with polynya width. MSHFs decreased as LCIs increased. The arrangement of polynyas had relatively little effect on the overall depth of the modified layer but did influence the magnitude and spatial structure of vertical heat transfer. In the two-polynya case the MSHF over the polynyas was larger when they were closer together. Although the MSHF over the sea ice between the polynyas decreased in magnitude as their separation increased, the percentage of the polynya-to-air heat recaptured by this ice floe increased fivefold. 相似文献
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概述黄河下游凌汛,分析了气温时空差异与凌汛形成和凌情变化的关系,根据冬季气温变化过程特点,并结合1968-1969年度凌汛实例,分析讨论了气温变化过程对凌情的影响。 相似文献
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贺兰山地区大气冰核浓度的测量及初步分析 总被引:10,自引:2,他引:8
根据 1 994年在银川和阿拉善左旗观测得到的冰核资料 ,给出了两地不同天气条件下的大气冰核浓度 ,分析并讨论了冰核浓度与风、降水、天空状况等的关系 ,给出了飞机在空中测量冰核的结果。 相似文献
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