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1.
Observations of downward radiative flux at the sea surface generally contain uncertainty due to limited numbers of observations and limitations of auxiliary equipment. The lack of shading from direct solar radiation and ventilation systems causes bias or random errors. To evaluate the error of radiation measurements at buoys, downward shortwave and longwave radiative fluxes are compared with International Satellite Cloud Climatology Project (ISCCP), Japanese 55-year Reanalysis (JRA55), and Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved model calculations of 3-h and daytime averages. Cloud masking is evaluated by a combination of MTSAT-1R and in situ observations. Coincident observations from a land-surface station located near the buoy observatories are compared with satellite and reanalysis products. The bias at buoys, compared with retrievals, approximately over- and under-estimate for longwave and shortwave fluxes, respectively. The bias at buoys is larger and smaller than the land by 23–34 W m?2 for longwave and 13–51 W m?2 for shortwave radiation using 3-h averages under clear-sky conditions. The differences in bias decrease when using daytime averages for longwave, but the difference for shortwave increases with daytime averages. To evaluate the effect of environmental factors on buoy observations, we compared rainfall, wind speed, and solar zenith angle with the biases. We found that rainfall and wind speed affect buoy pyrgeometers such that they overestimate the longwave flux. The cosine of solar zenith angle does not cause overestimation for longwave flux, and the effect of dome heating is small. The strong wind causes underestimation of the shortwave radiative flux due to tilting. The effect of wind is reduced when daily averages are used.  相似文献   

2.
北极冰海耦合模式对两种不同大气再分析资料响应的分析   总被引：2，自引：2，他引：0  
牟龙江  赵进平 《海洋学报》2015,37(11):79-91
本文中我们比较了Climate Forecast System Reanalysis(CFSR)高分辨率的再分析数据集和低分辨率的Japanese 25-year Reanalysis Project(JRA25)再分析数据集在向下短波辐射、向下长波辐射、10m风场、近地面气温、降水、湿度上的不同,发现二者差异最大的为降水数据,其次为向下短波辐射数据、向下长波辐射数据。用这两个数据集驱动同一冰海耦合模式,CFSR强迫的海冰、北冰洋中层水和加拿大海盆温盐结构与实测相比有很大差距,等密度面上的地转流速在加拿大海盆和欧亚海盆比JRA25强迫的结果高20%,同时等密度面的深度偏深、位温偏高,在弗拉姆海峡的流通量也比海洋再分析数据Simple Ocean Data Assimilation(SODA)偏多。CFSR的向下辐射数据更加接近实测,采用此数据的敏感性实验模拟结果与实测符合的更好。对于海冰的模拟,云量起着至关重要的作用,降水带来的淡水通量通过影响大西洋入流水携带的热量进而影响到冰区。此外,CFSR过量的降水也是二者对于北冰洋温盐结构、弗拉姆海峡流通量以及地转流强度模拟产生偏差的主要原因。尽管风场的分辨率不同,在海盆尺度上对于海冰和海水温盐结构的影响并不大。  相似文献   

3.
The atmospheric forcing of the Bering Sea over its eastern shelf is estimated using the 40-year record of daily data from the NCEP/NCAR Reanalysis. This data set includes estimates of the processes responsible for the atmospheric forcing, namely the surface fluxes of momentum, sensible and latent heat, and longwave and shortwave radiation, and therefore permits quantifying effects that previously could be inferred only from the large-scale nature of the flow. The forcing in 1995–1999 is described in detail using daily time series; historical context for these results is provided with seasonal averages for the years 1959–1999.The analysis for winter concentrates on aspects related to the formation and advection of sea ice. Results indicate that the presence of sea ice is strongly related to the net surface-heat fluxes as well as the cross-shelf component of the wind. The 40-year record lacks any discernible long-term trend in the winter forcing and response. There was a notably cold period in the early to middle 1970s, and a warm period from the late 1970s into the early 1980s, but conditions during the 1990s are similar to those in the late 1950s and 1960s.The analysis for the warm season focuses on the mechanisms responsible for the variability in SST warming. Much of the intraseasonal and interannual variability in this warming can be attributed to variations in the downward shortwave radiation (solar heating). The 40-year record does indicate a long-term trend toward increased solar heating, and reduced surface latent-heat fluxes (evaporative cooling). These changes have led to August SSTs in the 1990s that are roughly 1°C warmer than in the 1960s.  相似文献   

4.
Over the past decades, sea ice in the polar regions has been significantly affecting local and even hemispheric climate through a positive ice albedo feedback mechanism. The role of fast ice, as opposed to drift ice, has not been well-studied due to its relatively small coverage over the earth. In this paper, the optical properties and surface energy balance of land fast ice in spring are studied using in situ observations in Barrow, Alaska. The results show that the albedo of the fast ice varied between 0.57 and 0.85 while the transmittance increased from 1.3×10?3 to 4.1×10?3 during the observation period. Snowfall and air temperature affected the albedo and absorbance of sea ice, but the transmittance had no obvious relationship with precipitation or snow cover. Net solar shortwave radiation contributes to the surface energy balance with a positive 99.2% of the incident flux, with sensible heat flux for the remaining 0.8%. Meanwhile, the ice surface loses energy through the net longwave radiation by 18.7% of the total emission, while the latent heat flux accounts for only 0.1%. Heat conduction is also an important factor in the overall energy budget of sea ice, contributing 81.2% of the energy loss. Results of the radiative transfer model reveal that the spectral transmittance of the fast ice is determined by the thickness of snow and sea ice as well as the amount of inclusions. As major inclusions, the ice biota and particulates have a significant influence on the magnitude and distribution of the spectral transmittance. Based on the radiative transfer model, concentrations of chlorophyll and particulate in the fast ice are estimated at 5.51 mg/m2 and 95.79 g/m2, which are typical values in the spring in Barrow.  相似文献   

5.
CICE5.0与BCC_CSM2.0模式的耦合及对北极海冰的模拟评估   总被引：2，自引：1，他引：1  
本文将美国Los Alamos国家实验室发展的最新海冰模式CICE5.0引入国家气候中心气候系统模式BCC_CSM2.0,替代原有的海冰模式SIS,形成一个新的耦合模式。在此基础上,评估新耦合模式对1985-2009年北极海冰的模拟性能,检验引入CICE5.0后对耦合模式中北极海冰、海洋和大气模拟结果的改进。结果表明,引入CICE5.0后,模式能较好地模拟出北极海冰的空间分布、季节以及年际变化特征。相比于旧版本耦合模式,新耦合模式模拟的北极多年冰增多、一年冰减少,同时,海冰增厚、海冰流速减慢,模拟效果得到显著改进,对波弗特涡流模拟的改善尤为明显。进一步分析发现,相比于SIS,CICE5.0对北极海冰特别是海冰厚度模拟性能的提升,在耦合进入BCC_CSM2.0后,会触发冰-温的正反馈机制,改进了模式对海平面气压场、表层气温和海表温度的模拟,由此进一步提高了模式对北极海冰的模拟能力。  相似文献   

6.
This study quantifies uncertainties in closing the seasonal cycle of diabatic heat storage (DHS) over the Pacific Ocean from 20°S to 60°N through the synthesis of World Ocean Circulation Experiment (WOCE) reanalysis products from 1993 to 1999. These products are DHS from Scripps Institution of Oceanography (SIO); near-surface geostrophic and Ekman currents from Earth and Space Research (ESR); and air-sea heat fluxes from Comprehensive Ocean-Atmosphere Data Set (COADS), National Centers for Environmental Prediction (NCEP), and European Center for Mid-Range Weather Forecasts (ECMWF). With these products, we compute residual heat budget components by differencing long-term monthly means from the long-term annual mean. This allows the seasonal cycle of the DHS tendency to be modeled. Everywhere latent heat flux residuals dominate sensible heat flux residuals, shortwave heat flux residuals dominate longwave heat flux residuals, and residual Ekman heat advection dominates residual geostrophic heat advection, with residual dissipation significant only in the Kuroshio-Oyashio current extension. The root-mean-square (RMS) of the differences between observed and model residual DHS tendencies (averaged over 10° latitude-by-20° longitude boxes) is <20 W m−2 in the interior ocean and <100 W m−2 in the Kuroshio-Oyashio current extension. This reveals that the residual DHS tendency is driven everywhere by some mix of residual latent heat flux, shortwave heat flux, and Ekman heat advection. Suppressing bias errors in residual air-sea turbulent heat fluxes and Ekman heat advection through minimization of the RMS differences reduces the latter to <10 W m−2 over the interior ocean and <25 W m−2 in the Kuroshio-Oyashio current extension. This reveals air-sea temperature and specific humidity differences from in situ surface marine weather observations to be a principal source of bias error, overestimated over most of ocean but underestimated near the Intertropical Convergence Zone.  相似文献   

7.
海表短波辐射收支是海–气界面能量交换的重要物理过程。本研究利用2019年南海北部夏季科考航次的走航观测数据,评估了ERA5再分析数据的海表短波辐射通量收支。结果表明,ERA5的向下短波辐射相比观测偏小,11时和15时(北京时间)的偏差最大,可达-100 W/m2。与此同时,ERA5的海表反照率整体偏低,其中高太阳高度角时段偏差较小,约为-0.03,低太阳高度角时段偏差较大,约为-0.15。向下短波辐射和反照率的偏差共同造成ERA5白天平均海表净短波辐射通量比观测偏小约25.4 W/m2;其中,反照率低估抵消了约50%向下短波辐射偏差的贡献。研究表明,在不同大气透射率情况下,ERA5的海表辐射收支偏差存在不同表现。ERA5海表反照率的低估可能与其采用的参数化方案在南海北部的适用性不足有关。基于观测本研究也给出了一个简单的参数优化方案。  相似文献   

8.
海冰消融背景下北极增温的季节差异及其原因探讨   总被引：7，自引：2，他引：5  
运用哈德莱中心第一套海冰覆盖率(HadISST1)、欧洲中心(ERA_Interim)的温度以及NCEP第一套地表感热通量、潜热通量等资料,研究了1979—2011年33a来北极海冰消融的季节特点和空间特征,并从反照率——温度正反馈与地表感热通量、潜热通量等方面分析了海冰减少对北极增温影响的季节差异。结果表明,北极海冰在秋季和夏季的减少范围明显大于冬季和春季,而北极地表升温却在秋季和冬季最显著,夏季最为微弱,且夏季的增温趋势廓线也与秋冬季显著不同。这主要是因为夏季是融冰季,海冰融化将吸收潜热。且此时北极低空大气温度高于海表温度,海水相当于大气的冷源。随着海冰的消融,更多的热量由大气传入海洋用于融冰和加热上层海水,这使得夏季的低空大气不能显著升温。而在秋冬季,海冰凝结释放潜热,且此时低空大气温度远低于海水温度,海冰的减少使得海水将更多热量释放到大气中导致低空大气显著增暖。海水对大气的这种延迟放热机制是北极低空在夏季增温不显著而在秋冬季增温显著的主要原因。此外,秋冬季的海冰减少与北极近地面升温具有非常一致的空间分布,北冰洋东南边缘和巴伦支海北部分别是秋季和冬季海气相互作用的关键区域。  相似文献   

9.
《Ocean Modelling》2010,35(3-4):137-149
Passive microwave satellite observations of ice extent and concentration form the foundation of sea ice model evaluations, due to their wide spatial coverage and decades-long availability. Observations related to other model quantities are somewhat more limited but increasing as interest in high-latitude processes intensifies. Sea ice thickness, long judged a critical quantity in the physical system, is now being scrutinized more closely in sea ice model simulations as more expansive measurements become available. While albedo is often the first parameter chosen by modelers to adjust simulated ice thickness, this paper explores a set of less prominent parameters to which thickness is also quite sensitive. These include parameters associated with sea ice conductivity, mechanical redistribution, oceanic heat flux, and ice–ocean dynamic stress, in addition to shortwave radiation. Multiple combinations of parameter values can produce the same mean ice thickness using the Los Alamos Sea Ice Model, CICE. One of these “tuned” simulations is compared with a variety of observational data sets in both hemispheres. While deformed ice area compares well with the limited observations available for ridged ice, thickness measurements differ such that the model cannot agree with all of them simultaneously. Albedo and ice–ocean dynamic parameters that affect the turning of the ice relative to the ocean currents have the largest effect on ice thickness, of the parameters tested here. That is, sea ice thickness is highly sensitive to changes in external forcing by the atmosphere or ocean, and therefore serves as a sensitive diagnostic for high-latitude change.  相似文献   

10.
We have constructed ocean surface data sets using mainly satellite data and called them Japanese Ocean Flux data sets with Use of Remote sensing Observations (J-OFURO). The data sets include shortwave radiation, longwave radiation, latent heat flux, sensible heat flux, and momentum flux etc. This article introduces J-OFURO and compares it with other global flux data sets such as European Centre for Medium Range Weather Forecasting (ECMWF) and National Center for Environmental Prediction (NCEP) reanalysis data and da Silva et al. (1994). The usual ECMWF data are used for comparison of zonal wind. The comparison is carried out for a meridional profile along the dateline for January and July 1993. Although the overall spatial variation is common for all the products, there is a large difference between them in places. J-OFURO shortwave radiation in July shows larger meridional contrast than other data sets. On the other hand, J-OFURO underestimates longwave radiation flux at low- and mid-latitudes in the Southern Hemisphere. J-OFURO latent heat flux in January overestimates at 10°N–20°N and underestimates at 25°N–40°N. Finally, J-OFURO shows a larger oceanic net heat loss at 10°N–20°N and a smaller loss north of 20°N in January. The data of da Silva et al. in July show small net heat loss around 20°S and large gain around 20°N, while the NCEP reanalysis (NRA) data show the opposite. The da Silva et al. zonal wind speed overestimates at low-latitudes in January, while ECMWF wind data seem to underestimate the easterlies. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

11.
Using the observations from ICOADS datasets and contemporaneous NCEP/NCAR reanalysis datasets during 1960-2002, the study classifies the airflows in favor of sea fog over the Huanghai (Yellow) Sea in boreal spring (April-May) with the method of trajectory analysis, and analyzes the changes of proportions of warm and cold sea fogs along different paths of airflow. According to the heat balance equation, we investigate the relationships between the marine meteorological conditions and the proportion of warm and cold sea fog along different airflow paths. The major results are summarized as follows. (1) Sea fogs over the Huanghai Sea in spring are not only warm fog but also cold fog. The proportion of warm fog only accounts for 44% in April, while increases as high as 57% in May. (2) Four primary airflow paths leading to spring sea fog are identified. They are originated from the northwest, east, southeast and southwest of the Huanghai Sea, respectively. The occurrence ratios of the warm sea fog along the east and southeast airflow paths are high of 55% and 70%, while these along the southwest and northwest airflow paths are merely 17.9% and 50%. (3) The key physical processes governing the warm/cold sea fog are heat advection transport, longwave radiation cooling at fog top, solar shortwave warming and latent heat flux between airsea interfaces. (4) The characteristics of sea fog along the four airflow paths relate closely to the conditions of water vapor advection, and the vertical distribution of relative humidity.  相似文献   

12.
BCC_CSM对北极海冰的模拟:CMIP5和CMIP6历史试验比较   总被引：1，自引：1，他引：0  
王松  苏洁  储敏  史学丽 《海洋学报》2020,42(5):49-64
本文利用北京气候中心气候系统模式(BCC_CSM)在最近两个耦合模式比较计划(CMIP5和CMIP6)的历史试验模拟结果，对北极海冰范围和冰厚的模拟性能进行了比较，结果表明:(1) CMIP6改善了CMIP5模拟海冰范围季节变化过大的问题，总体上更接近观测结果；(2)两个CMIP试验阶段中BCC_CSM模拟的海冰厚度都偏小，但CMIP6试验对夏季海冰厚度过薄问题有所改进。通过对影响海冰生消过程的冰面和冰底热收支的分析，我们探讨了上述模拟偏差以及CMIP6模拟结果改善的成因。分析表明，8?9月海洋热通量、向下短波辐射和反照率对模拟结果的误差影响较大，CMIP6试验在这些方面有较大改善；而12月至翌年2月，CMIP5模拟的北极海冰范围偏大主要是海洋热通量偏低所导致，CMIP6模拟的海洋热通量较CMIP5大，但北大西洋表层海流的改善才是巴芬湾附近海冰外缘线位置改善的主要原因。CMIP试验模拟的夏季海冰厚度偏薄主要是因为6?8月海洋热通量和冰面热收支都偏大，而CMIP6试验模拟的夏季海冰厚度有所改善主要是由于海洋热通量和净短波辐射的改善。海冰模拟结果的改善与CMIP6海冰模块和大气模块参数化的改进有直接和间接的关系，通过改变短波辐射、冰面反照率和海洋热通量，使BCC_CSM模式对北极海冰的模拟性能也得到有效提高。  相似文献   

13.
This study investigates the long-term changes of monthly sea surface wind speeds over the China seas from 1988 to 2015. The 10-meter wind speeds products from four major global reanalysis datasets with high resolution are used: Cross-Calibrated Multi-Platform data set(CCMP), NCEP climate forecast system reanalysis data set(CFSR),ERA-interim reanalysis data set(ERA-int) and Japanese 55-year reanalysis data set(JRA55). The monthly sea surface wind speeds of four major reanalysis data sets have been investigated through comparisons with the longterm and homogeneous observation wind speeds data recorded at ten stations. The results reveal that(1) the wind speeds bias of CCMP, CFSR, ERA-int and JRA55 are 0.91 m/s, 1.22 m/s, 0.62 m/s and 0.22 m/s, respectively.The wind speeds RMSE of CCMP, CFSR, ERA-int and JRA55 are 1.38 m/s, 1.59 m/s, 1.01 m/s and 0.96 m/s,respectively;(2) JRA55 and ERA-int provides a realistic representation of monthly wind speeds, while CCMP and CFSR tend to overestimate observed wind speeds. And all the four data sets tend to underestimate observed wind speeds in Bohai Sea and Yellow Sea;(3) Comparing the annual wind speeds trends between observation and the four data sets at ten stations for 1988-1997, 1988–2007 and 1988–2015, the result show that ERA-int is superior to represent homogeneity monthly wind speeds over the China seaes.  相似文献   

14.
2016年南极中山站固定冰冰厚观测分析   总被引：1，自引：1，他引：0  
极区海冰是全球气候系统的重要组成部分，南极的固定冰普遍存在于其沿海地区，中山站周边固定冰一般在11月中下旬达到最厚。海冰厚度是海冰的重要参数之一，2016年在南极中山站附近3个站点(S1、S2、S3站点)共布放了4套温度链浮标，包括1套SIMBA (Snow and Ice Mass Balance Array)温度链浮标和3套太原理工大学温度链浮标(TY温度链浮标)，SIMBA温度链浮标每天观测4次，TY温度链浮标每小时观测1次。利用浮标观测的温度剖面以及海冰和海水间不同介质温度差异计算得到海冰厚度。在S3站点，同时布放了SIMBA温度链浮标和TY温度链浮标。温度链浮标计算冰厚和人工钻孔观测冰厚比较结果显示，S1站点TY温度链浮标计算的海冰厚度平均误差和均方根误差分别为3.3 cm和14.7 cm，S2站点和S3站点分别为6.6 cm、6.9 cm以及4.0 cm、4.8 cm。S3站点的SIMBA温度链浮标计算冰厚和人工观测冰厚的平均误差和均方根误差为8.2 cm和9.7 cm。因而S3站点TY温度链浮标计算的海冰厚度更接近人工观测的结果。进一步对Stefan定律海冰生长模型进行对比，模型计算得到的海冰生长率为0.1～0.8 cm/d，生长率快于TY温度链浮标的结果，且受积雪影响明显。相比于卫星遥感反演冰厚的误差和观测时段的限制以及有限的人工观测，2种温度链浮标未来对于中山站附近海冰的长期监测均有重要的应用价值。  相似文献   

15.
北极海冰变化影响着全球物质平衡、能量交换和气候变化。本文基于CryoSat-2测高数据和OSI SAF海冰密集度及海冰类型产品，分析了2010-2017年北极海冰面积、厚度和体积的季节和年际变化特征，结合NCEP再分析资料探讨了融冰期北极气温异常和夏季风异常对海冰变化的影响。结果表明，结冰期海冰面积的增加量波动较大，海冰厚度的增加量呈明显下降趋势。融冰期海冰厚度的减小量波动较大，2013年以后融冰期海冰面积的减小量逐年增加。海冰体积的变化趋势和面积变化更相似，融冰期的减小速率大于结冰期的增加速率。融冰期北极海表面大气温度异常与海冰融化量正相关。夏季风影响海冰的辐合和辐散，在弗拉姆海峡海冰的输运过程中起关键作用，促进了北冰洋表层水向大洋深层的传输。  相似文献   

16.
Based on a coupled ocean-sea ice model, this study investigates how changes in the mean state of the atmosphere in different CO_2 emission scenarios(RCP 8.5, 6.0, 4.5 and 2.6) may affect the sea ice in the Bohai Sea, China,especially in the Liaodong Bay, the largest bay in the Bohai Sea. In the RCP 8.5 scenario, an abrupt change of the atmospheric state happens around 2070. Due to the abrupt change, wintertime sea ice of the Liaodong Bay can be divided into 3 periods: a mild decreasing period(2021–2060), in which the sea ice severity weakens at a nearconstant rate; a rapid decreasing period(2061–2080), in which the sea ice severity drops dramatically; and a stabilized period(2081–2100). During 2021–2060, the dates of first ice are approximately unchanged, suggesting that the onset of sea ice is probably determined by a cold-air event and is not sensitive to the mean state of the atmosphere. The mean and maximum sea ice thickness in the Liaodong Bay is relatively stable before 2060, and then drops rapidly in the following decade. Different from the RCP 8.5 scenario, atmospheric state changes smoothly in the RCP 6.0, 4.5 and 2.6 scenarios. In the RCP 6.0 scenario, the sea ice severity in the Bohai Sea weakens with time to the end of the twenty-first century. In the RCP 4.5 scenario, the sea ice severity weakens with time until reaching a stable state around the 2070 s. In the RCP 2.6 scenario, the sea ice severity weakens until the2040 s, stabilizes from then, and starts intensifying after the 2080 s. The sea ice condition in the other bays of the Bohai Sea is also discussed under the four CO_2 emissions scenarios. Among atmospheric factors, air temperature is the leading one for the decline of the sea ice extent. Specific humidity also plays an important role in the four scenarios. The surface downward shortwave/longwave radiation and meridional wind only matter in certain scenarios, while effects from the zonal wind and precipitation are negligible.  相似文献   

17.
CICE海冰模式中融池参数化方案的比较研究   总被引：1，自引：1，他引：0  
王传印  苏洁 《海洋学报》2015,37(11):41-56
冰面融池的反照率介于海水和海冰之间,获得较准确的融池覆盖率对认识极区气冰海耦合系统的热量收支有重要意义。在数值模式中,融池覆盖率的模拟结果直接影响到冰面反照率计算的准确性,本文对CICE5.0中的3种融池参数化方案进行了较系统的比较分析,结果显示3种方案各有优缺点,模拟结果都存在一些问题。cesm方案中判断融池冻结的条件更为合理。比较而言,融池冻结条件更改后的topo方案模拟的北冰洋区域平均融池覆盖率的年际变化幅度、融池覆盖范围、融池发展盛期持续时间与MODIS数据最接近。通过修改CICE5.0中的代码漏洞,研究了融池水的垂向渗透效应,这一效应会带来一些负面影响,如lvl方案中多年冰上几乎没有融池,说明目前的CICE模式中对于海冰渗透性演化或其他物理机制的处理仍有待改进。最后,着重讨论了topo方案的改进思路。  相似文献   

18.
利用"中国近海海洋综合调查与评价"2007年北黄海春季航次的资料,综合分析了短波、长波辐射及海面短波、长波反射辐射特征及与云量、气温、水汽压、海面红外温度等的对应关系。结果显示海面太阳入射辐射远大于海面反射辐射,二者相差约1个量级;海面长波辐射总体上大于大气逆辐射,二者相差约40 W/m2,平均净辐射为153.1 W/m2。观测期间大气透射率约为0.45,并据此分析探讨了云对太阳辐射传输的影响,建立了考虑总云量、低云量及水汽压等因素的海面太阳短波辐射经验估算公式,计算结果与实测结果具有较好一致性,均方根误差为11.3 W/m2。最后讨论了太阳辐射船基观测由于船体晃动可能造成的误差影响。  相似文献   

19.
林龙  赵进平 《海洋学报》2018,40(11):23-32
雪热传导系数是海冰质量平衡过程中的重要物理参数，决定了穿透海冰的热传导通量。北冰洋海冰质量平衡浮标观测获得多年冰上冬季温度链剖面可以明显地区分冰雪界面。本文考虑到冰雪界面处温度随时间变化，再根据冰雪界面热传导通量连续假定，提出了新的雪热传导系数计算方法。受不同环境因素影响，多年冰上各个浮标的雪热传导系数在0.23~0.41 W/（m·K）之间，均值为（0.32±0.08） W/（m·K）。北冰洋多年冰上冬季穿过海冰的热传导通量最大发生在11月至翌年3月，约14~16 W/m2。结冰季节，来自海冰自身降温的热量对穿过海冰向大气传输的热量贡献逐月减少，从9月100%减小到12月的35%，翌年的1月至3月稳定在10%左右。夏季，短波辐射通能量通过热传导自上而下加热海冰，海冰上层温度高于下层，热量传播方向与冬季反向，往海冰内部传递。直到9月短波辐射完全消失，气温下降，热量再次转变为自下往上传递。从冰底热传导来看，夏季出现海冰向冰水界面传递热量现象。由于雪较好的绝热性，冰上覆雪极大地削弱了海冰上层热传导通量，从而减缓了秋冬季节的结冰速度。尽管受雪厚影响，多年冰上层热传导通量与气温依旧具有很好的线性关系，气温每降低1℃，热传导通量增加约0.59 W/m2。  相似文献   

20.
The seasonal variabilities of a latent-heat flux (LHF), a sensible-heat flux (SHF) and net surface heat flux are examined in the northern South China Sea (NSCS), including their spatial characteristics, using the in situ data collected by ship from 2006 to 2007. The spatial distribution of LHF in the NSCS is mostly controlled by wind in summer and autumn owing to the lower vertical gradient of air humidity, but is influenced by both wind and near-surface air humidity vertical gradient in spring and winter. The largest area-averaged LHF is in autumn, with the value of 197.25 W/m 2 , followed by that in winter; the third and the forth are in summer and spring, respectively. The net heat flux is positive in spring and summer, so the NSCS absorbs heat; and the solar shortwave radiation plays the most important role in the surface heat budget. In autumn and winter, the net heat flux is negative in most of the observation region, so the NSCS loses heat; and the LHF plays the most important role in the surface heat budget. The net heating is mainly a result of the offsetting between heating due to the shortwave radiation and cooling due to the LHF and the upward (outgoing) long wave radiation, since the role of SHF is negligible. The ratio of the magnitudes of the three terms (shortwave radiation to LHF to long-wave radiation) averaged over the entire year is roughly 3:2:1, and the role of SHF is the smallest.  相似文献   

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