共查询到20条相似文献，搜索用时 15 毫秒
1.
Preliminary validation of SMOS sea surface salinity measurements in the South China Sea 总被引：1，自引：0，他引：1
The SMOS(soil moisture and ocean salinity) mission undertaken by the European Space Agency(ESA) has provided sea surface salinity(SSS) measurements at global scale since 2009.Validation of SSS values retrieved from SMOS data has been done globally and regionally.However,the accuracy of SSS measurements by SMOS in the China seas has not been examined in detail.In this study,we compared retrieved SSS values from SMOS data with in situ measurements from a South China Sea(SCS) expedition during autumn 2011.The comparison shows that the retrieved SSS values using ascending pass data have much better agreement with in situ measurements than the result derived from descending pass data.Accuracy in terms of bias and root mean square error(RMS) of the SSS retrieved using three different sea surface roughness models is very consistent,regardless of ascending or descending orbits.When ascending and descending measurements are combined for comparison,the retrieved SSS using a semi-empirical model shows the best agreement with in situ measurements,with bias-0.33 practical salinity units and RMS 0.74.We also investigated the impact of environmental conditions of sea surface wind and sea surface temperature on accuracy of the retrieved SSS.The SCS is a semi-closed basin where radio frequencies transmitted from the mainland strongly interfere with SMOS measurements.Therefore,accuracy of retrieved SSS shows a relationship with distance between the validation sites and land. 相似文献
2.
Analysis of cost functions for retrieving sea surface salinity 总被引：1，自引：0，他引：1
Two kinds of Bayesian-based cost functions (i.e., the unconstrained cost function and parameter-constrained cost function) are investigated for retrieving the sea surface salinity (SSS). In low SSS regions, we have analyzed the sensitivity of the two cost functions to geophysical parameters. The results show that the unconstrained cost function is valid for retrieving several parameters (including SSS, wind speed and significant wave height), and the constrained cost function, which largely depends on the accuracy of reference values, may lead to large retrieval biases. Furthermore, as a retrieval parameter, the sea surface temperature (SST) can re-sult in the divergence of other geophysical parameters in an unconstrained cost function due to the strong sensitivity of brightness temperature to SST. By using the unconstrained cost function and the simulated brightness temperature TB with white noises, the retrieval biases of SSS are discussed with the following two procedures. Procedure a): the simulated TB values are first averaged, and then SSS is retrieved. Procedure b): the SSS is directly retrieved from the simulated TB , and then the retrieved SSS values are aver-aged. The results indicate that, for low SSS and SST distributions, the SSS retrieval by procedure a) has less biases compared with that by procedure b), while the two procedures give almost the same retrieval results for high SSS and SST sea regions. 相似文献
3.
Permittivity of a sea foam layer is very important in investigating ocean brightness temperature model. At microwave frequency, the Rayleigh method is developed to estimate the effective permittivity of the sea foam layer. To simplify the tedious calculation of sea foam effective permittivity at L band(1.4 GHz), Pade’ approximation is adopted to fit the sea foam effective permittivity computed by the Rayleigh method. With this fitting formula, a new brightness temperature model of sea foam layer defined by certain geophysical parameters, such as air volume fraction(AVF), sea surface temperature(SST), sea surface salinity(SSS) and thickness of foam layer d, is given. Furthermore, the sensitivities of the brightness temperature model to SST, SSS, d and AVF of a sea foam layer at L band are discussed. The sensitivities are ranked from most to least in the order:(1) d;(2) AVF;(3) SSS;(4) SST. This result indicates that the measurement errors of d and AVF have significant impacts on the retrievals of SSS and SST. With the experimental brightness temperature data, the SSS and AFV are retrieved by cost function. 相似文献
4.
In this study, we present a comprehensive comparison of the sea surface wind ?eld measured by scatterometer(Ku-band scatterometer) aboard the Chinese HY-2 A satellite and the full-polarimetric radiometer WindSat aboard the Coriolis satellite. The two datasets cover a four-year period from October2011 to September 2015 in the global oceans. For the sea surface wind speed, the statistical comparison indicates good agreement between the HY-2 A scatterometer and WindSat with a bias of nearly 0 m/s and a root mean square error(RMSE) of 1.13 m/s. For the sea surface wind direction, a bias of 1.41° and an RMSE of 20.39° were achieved after excluding the data collocated with opposing directions. Furthermore,discrepancies in sea surface wind speed measured by the two sensors in the global oceans were investigated.It is found that the larger dif ferences mainly appear in the westerlies in the both hemispheres. Both the bias and RMSE show latitude dependence, i.e., they have signi?cant latitudinal ?uctuations. 相似文献
5.
Improvement of mono-window algorithm for retrieving land surface temperature from HJ-1B satellite data 总被引：2，自引：0，他引：2
The thermal infrared channel (IRS4) of HJ-1B satellite obtains view zenith angles (VZA) up to ±33°. The view angle should be taken into account when retrieving land surface temperature (LST) from IRS4 data. This study aims at improving the mono-window algorithm for retrieving LST from IRS4 data. Based on atmospheric radiative transfer simulations,a model for correcting the VZA effects on atmospheric transmittance is proposed. In addition,a generalized model for calculating the effective mean atmospheric temperature is developed. Validation with the simulated dataset based on standard atmospheric profiles reveals that the improved mono-window algorithm for IRS4 obtains high accuracy for LST retrieval,with the mean absolute error (MAE) and root mean square error (RMSE) being 1.0 K and 1.1 K,respectively. Numerical experiment with the radiosonde profile acquired in Beijing in winter demonstrates that the improved mono-window algorithm exhibits excellent ability for LST retrieval,with MAE and RMSE being 0.6 K and 0.6 K,respectively. Further application in Qinghai Lake and comparison with the Moderate-Resolution Imaging Spectroradiometer (MODIS) LST product suggest that the improved mono-window algorithm is applicable and feasible in actual conditions. 相似文献
6.
1 INTRODUCTIONThe South China Sea (SCS) is a semi-enclosedmarginal sea in western North Pacific Ocean withvery complex topography and is the important pas-sage connecting the Pacific and Indian Oceans. Ithas great impact to the global climate and a greatinterest of many oceanography researchers. Twodominant surface hydrographic and circulation fea-tures in the northern SCS are a strong fresh waterexpansion and a warm and high-salinity seawaterintrusion such as the SCS Diluted Water… 相似文献
7.
Effect of compressive strength on the performance of the NEMO-LIM model in Arctic Sea ice simulation
Satellite records show that the extent and thickness of sea ice in the Arctic Ocean have significantly decreased since the early 1970s. The prediction of sea ice is highly important, but accurate simulation of sea ice variations remains highly challenging. For improving model performance, sensitivity experiments were conducted using the coupled ocean and sea ice model (NEMO-LIM), and the simulation results were compared against satellite observations. Moreover, the contribution ratios of dynamic and thermodynamic processes to sea ice variations were analyzed. The results show that the performance of the model in reconstructing the spatial distribution of Arctic sea ice is highly sensitive to ice strength decay constant (Crhg). By reducing the Crhg constant, the sea ice compressive strength increases, leading to improved simulated sea ice states. The contribution of thermodynamic processes to sea ice melting was reduced due to less deformation and fracture of sea ice with increased compressive strength. Meanwhile, dynamic processes constrained more sea ice to the central Arctic Ocean and contributed to the increases in ice concentration, reducing the simulation bias in the central Arctic Ocean in summer. The root mean square error (RMSE) between modeled and the CryoSat-2/SMOS satellite observed ice thickness was reduced in the compressive strength-enhanced model solution. The ice thickness, especially of multiyear thick ice, was also reduced and matched with the satellite observation better in the freezing season. These provide an essential foundation on exploring the response of the marine ecosystem and biogeochemical cycling to sea ice changes.
相似文献8.
The rate of regional sea level rise(SLR) provides important information about the impact of human activities on climate change.However,accurate estimation of regional SLR can be severely affected by sea surface height(SSH) change caused by the Pacific Decadal Oscillation(PDO-SSH).Here,the PDOSSH signal is extracted from satellite altimeter data by multi-variable linear regression,and regional SLR in the altimeter era is calculated,before and after removing that signal.The results show that PDO-SSH trends are rising in the western Pacific and falling in the eastern Pacific,with the strongest signal confined to the tropical and North Pacific.Over the past 20 years,the PDO-SSH accounts for about 30%-40%of altimeter-observed SLR in the regions 8°-15°N,130°-160°E and 30°-40°N,170°-220°E.Along the coast of North America,the PDO-SSH signal dramatically offsets the coastal SLR,as the sea level trends change sign from falling to rising. 相似文献
9.
Diatom data of 192 surface sediment samples from the marginal seas in the western Pacific together with modern summer and winter sea surface temperature and salinity data were analyzed.The results of canonical correspondence analysis show that summer sea-surface salinity(SSS) is highly positively correlated with winter SSS and so is summer sea-surface temperature(SST) with winter SST.The correlations between SSSs and SSTs are less positively correlated,which may be due to interactions of regional current pa... 相似文献
10.
Generalized linear models (GLM) and generalized additive models (GAM) were used to standardize catch per unit fishing effort
(CPUE) of Ommastrephes bartramii for Chinese squid-jigging fishery in Northwest Pacific Ocean. Three groups of variables were considered in the standardization:
spatial variables (longitude and latitude), temporal variables (year and month) and environmental variables, including sea
surface temperature (SST), sea surface salinity (SSS) and sea level height (SLH). CPUE was treated as the dependent variable
and its error distribution was assumed to be log-normal in each model. The model selections of GLM and GAM were based on the
finite sample-corrected Akaike information criterion (AICC) and pseudo-coefficient (Pcf) combined P-value, respectively. Both GAM and GLM analysis showed that the month was the most important variable affecting CPUE and could
explain 21.3% of variability in CPUE while other variables only explained 8.66%. The interaction of spatial and temporal variables
weakly influenced the CPUE. Moreover, spatio-temporal factors may be more important in influencing the CPUE of this squid
than environmental variables. The standardized and nominal CPUEs were similar and had the same trends in spatio-temporal distribution,
but the standardized CPUE values tended to be smaller than the nominal CPUE. The CPUE tended to have much higher monthly variation
than annual variations and their values increased with month. The CPUE became higher with increasing latitude-high CPUE usually
occurred in 145°E–148°E and 149°E–162°E. The CPUE was higher when SST was 14–21°C and the SLH from −22 cm to −18 cm. In this
study, GAM tended to be more suitable than GLM in analysis of CPUE. 相似文献
11.
In this paper, we use the optimum interpolation sea surface temperature (OISST) provided by the National Center for Environmental Prediction (NCEP) to replace the temperature in the top three layers in the ISHII data, and make use of the modified ISHII temperature data to calculate the thermosteric sea level (called modified steric sea level (SSL) hereafter). We subtract the modified SSL and the steric sea level (called ordinary SSL hereafter) derived from the ISHII temperature and salinity from the steric sea level (SSL) provided by the Gravity Recovery and Climate Experiment (GRACE), respectively, and find that the rms error of the difference of the former is obviously smaller than that of the latter. Therefore we reach the conclusion that under the assumption that the GRACE SSL is accurate, the modified SSL can reflect the true steric sea level more accurately. Making use of the modified SSL, we can find that the modified SSL in sea areas of different spatial scales shows an obvious rising trend in the upper 0-700 m layer for the period 1982-2006. The global mean SSL rises with a rate of 0.6 mm year-1 .The modified SSLs in sea areas of different spatial scales all show obvious oscillations with period of one year. There are oscillations with periods of 4-8 years in global oceans and with periods of 2-7 years in the Pacific. The Empirical Orthogonal Function method is applied to the sea areas of different spatial scales and we find that the first modes all have obvious 1-year period oscillations, the first mode of the global ocean has 4-8 year period oscillations, and that of the Pacific has 2-6 year period oscillations. The spatial distribution of the linear rising trend of the global modified SSL in the upper 0-700 m layer is inhomogeneous with intense regional characteristics. The modified SSL linear trend indicates a zonal dipole in the tropical Pacific, rising in the west and descending in the east. In the North Atlantic, the modified SSL indicates a meridional dipole, rising in the latitude band of 20°N-40°N and 45°N-65.5°N and descending obviously in the latitude band of 40°N-45°N. 相似文献
12.
A new ocean wave and sea surface current monitoring system with horizontally-(HH) and vertically-(VV) polarized X-band radar
was developed. Two experiments into the use of the radar system were carried out at two sites, respectively, for calibration
process in Zhangzi Island of the Yellow Sea, and for validation in the Yellow Sea and South China Sea. Ocean wave parameters
and sea surface current velocities were retrieved from the dual polarized radar image sequences based on an inverse method.
The results obtained from dual-polarized radar data sets acquired in Zhangzi Island are compared with those from an ocean
directional buoy. The results show that ocean wave parameters and sea surface current velocities retrieved from radar image
sets are in a good agreement with those observed by the buoy. In particular, it has been found that the vertically-polarized
radar is better than the horizontally-polarized radar in retrieving ocean wave parameters, especially in detecting the significant
wave height below 1.0 m. 相似文献
13.
APPLICATION OF NONLINEAR MULTI-CHANNEL ALGORITHMS FOR ESTIMATING SEA SURFACE TEMPERATURE WITH NOAA 14 AVHRR DATA 总被引：1，自引：0，他引：1
李晓峰 《中国海洋湖沼学报》2000,18(3):199-207
ＩＮＴＲＯＤＵＣＴＩＯＮＳｉｎｃｅｔｈｅｅａｒｌｙ 1 970ｓ,ｔｈｅＡｄｖａｎｃｅｄＶｅｒｙＨｉｇｈＲｅｓｏｌｕｔｉｏｎＲａｄｉｏｍｅｔｅｒ(ＡＶＨＲＲ)ｏｎｂｏａｒｄｔｈｅＮａｔｉｏｎａｌＯｃｅａｎｉｃａｎｄＡｔｍｏｓｐｈｅｒｉｃＡｄｍｉｎｉｓｔｒａｔｉｏｎ (ＮＯＡＡ)ｓｅｒｉｅｓｏｆＰｏｌａｒ ｏｒｂｉｔｉｎｇＯｐｅｒａｔｉｏｎａｌＥｎ ｖｉｒｏｎｍｅｎｔａｌＳａｔｅｌｌｉｔｅｓ (ＰＯＥＳ)ｈａｓｂｅｅｎｕｓｅｄｆｏｒｓｅａｓｕｒｆａｃｅｔｅｍｐｅｒａｔｕｒｅ (ＳＳＴ)ｒｅｔｒｉｅｖａｌａｎｄｃｌｏｕ… 相似文献
14.
Using the wave model WAVEWATCH III(WW3), we simulated the generation and propagation of typhoon waves in the South China Sea and adjacent areas during the passage of typhoon Nesat(2011). In the domain 100°–145°E and 0°–35°N, the model was forced by the cross-calibrated multi-platform(CCMP) wind fi elds of September 15 to October 5, 2011. We then validated the simulation results against wave radar data observed from an oil platform and altimeter data from the Jason-2 satellite. The simulated waves were characterized by fi ve points along track using the Spectrum Integration Method(SIM) and the Spectrum Partitioning Method(SPM), by which wind sea and swell components of the 1D and 2D wave spectra are separated. There was reasonable agreement between the model results and observations, although the WW3 wave model may underestimate swell wave height. Signifi cant wave heights are large along the typhoon track and are noticeably greater on the right of the track than on the left. Swells from the east are largely unable to enter the South China Sea because of the obstruction due to the Philippine Islands. During the initial stage and later period of the typhoon, swells at the fi ve points were generated by the propagation of waves that were created by typhoons Haitang and Nalgae. Of the two methods, the 2D SPM method is more accurate than the 1D SIM which overestimates the separation frequency under low winds, but the SIM method is more convenient because it does not require wind speed and wave direction. When the typhoon left the area, the wind sea fractions decreased rapidly. Under similar wind conditions, the points located in the South China Sea are affected less than those points situated in the open sea because of the infl uence of the complex internal topography of the South China Sea. The results reveal the characteristic wind sea and swell features of the South China Sea and adjacent areas in response to typhoon Nesat, and provide a reference for swell forecasting and offshore structural designs. 相似文献
15.
Using genetic algorithms to calibrate a dimethylsulfide production model in the Arctic ocean 总被引：1，自引：0，他引：1
瞿波 《中国海洋湖沼学报》2010,28(3):573-582
The global climate is intimately connected to changes in the polar oceans. The variability of sea ice coverage affects deep-water formations and large-scale thermohaline circulation patterns. The polar radiative budget is sensitive to sea-ice loss and consequent surface albedo changes. Aerosols and polar cloud microphysics are crucial players in the radiative energy balance of the Arctic Ocean. The main biogenic source of sulfate aerosols to the atmosphere above remote seas is dimethylsulfide (DMS). Recent research suggests the flux of DMS to the Arctic atmosphere may change markedly under global warming. This paper describes climate data and DMS production (based on the five years from 1998 to 2002) in the region of the Barents Sea (30–35°E and 70–80°N). A DMS model is introduced together with an updated calibration method. A genetic algorithm is used to calibrate the chlorophyll-a (CHL) measurements (based on satellite SeaWiFS data) and DMS content (determined from cruise data collected in the Arctic). Significant interannual variation of the CHL amount leads to significant interannual variability in the observed and modeled production of DMS in the study region. Strong DMS production in 1998 could have been caused by a large amount of ice algae being released in the southern region. Forcings from a general circulation model (CSIRO Mk3) were applied to the calibrated DMS model to predict the zonal mean sea-to-air flux of DMS for contemporary and enhanced greenhouse conditions at 70–80°N. It was found that significantly decreasing ice coverage, increasing sea surface temperature and decreasing mixed-layer depth could lead to annual DMS flux increases of more than 100% by the time of equivalent CO2 tripling (the year 2080). This significant perturbation in the aerosol climate could have a large impact on the regional Arctic heat budget and consequences for global warming. 相似文献
16.
气溶胶光学厚度作为描述气溶胶光学特性的重要参数之一, 被广泛应用于空气质量监测及辐射传输模型的大气订正等研究中。卫星遥感可快速反演获取大范围气溶胶信息, 但其产品通常因云覆盖或暗目标算法等原因而存在空间覆盖率较低的问题, 且产品时相受限于卫星过境时间。水平能见度作为描述气溶胶光学特性的另一重要参数, 由分布广泛的气象台站一日8 次固定时间多次发布。建立水平能见度与气溶胶光学厚度的转换关系, 可实现对卫星反演气溶胶光学厚度的有益补充。本文利用2001-2009 年的MODIS气溶胶光学厚度产品与中国华东地区71 个气象台站的水平能见度数据, 对描述两者转换关系的Peterson 模型进行区域优化。采用分区域高斯曲线拟合的方法, 对影响转换精度的主要参数气溶胶标高随时间变化规律开展研究和模拟。利用2010 年数据对优化模型进行精度及区域适用性验证。结果表明, 优化后模型的气溶胶光学厚度估算均方根误差为0.31, 低于原模型误差;精度基本上与单站点优化模型一致, 但在实用性方面优于单站点优化模型。 相似文献
17.
Subtropical sea surface salinity(SSS) maximum is formed in the subtropical South Indian Ocean(SIO) by excessive evaporation over precipitation and serves as the primary salt source of the SIO. Spaceborne SSS measurements by Aquarius satellite during September 2011–May 2015 detect three disconnected SSS maximum regions(35.6) in the eastern(105°E–115°E, 38°S–28°S), central(60°E–100°E, 35°S–25°S), and western(25°E–40°E, 38°S–20°S) parts of the subtropical SIO, respectively. Such structure is however not seen in gridded Argo data. Analysis of Argo pro?le data con?rms the existence of the eastern maximum patch and also reveals SSS overestimations of Aquarius near the western and eastern boundaries. Although subjected to large uncertainties, a mixed-layer budget analysis is employed to explain the seasonal cycle of SSS. The eastern and central regions reach the highest salinity in February–March and lowest salinity in August–September, which can be well explained by surface freshwater forcing(SFF) term. SFF is however not controlled by evaporation( E) or precipitation( P). Instead, the large seasonal undulations of mixed layer depth(MLD) is the key factor. The shallow(deep) MLD in austral summer(winter) ampli?es(attenuates) the forcing ef fect of local positive E-P and causes SSS rising(decreasing). Ocean dynamics also play a role. Particularly, activity of mesoscale eddies is a critical factor regulating SSS variability in the eastern and western regions. 相似文献
18.
Seasonality and causes of the Yellow Sea Warm Current 总被引：1，自引：0，他引：1
To study the seasonality and causes of the Yellow Sea Warm Current (YSWC) in detail, rotated empirical orthogonal function (REOF) and extended associate pattern analysis are adopted with daily sea surface salinity (SSS), sea surface temperature (SST) and sea surface height (SSH) datasets covering 1126 days from American Navy Experimental Real-Time East Asian Seas Ocean Nowcast System in the present paper. Results show that in the Yellow and East China Seas, the YSWC is a mean barotropic flow as compensation of winter-monsoon-driven surface currents, which has been directly observed. When East Asia winter monsoon weakens, so do the meridional pressure gradient of the surface seawater and the YSWC, while the transversal pressure gradient changes rather slowly that results in the YSWC left turning. In addition, there is southward mean flow compensation of summer-monsoon-driven surface currents, which actually was also directly ob-served. 相似文献
19.
HUANG Fei WANG Hong QIAN Junping WANG Guofu 《中国海洋大学学报(英文版)》2006,5(3):207-212
Based on the atmospheric horizontal visibility data from forty-seven observational stations along the eastern coast of China near the Taiwan Strait and simultaneous NOAA/AVHRR multichannel satellite data during January 2001 to December 2002, the spectral characters associated with visibility were investigated. Successful retrieval of visibility from multichannel NOAA/AVHRR data was performed using the principal component regression （PCR） method. A sample of retrieved visibility distribution was discussed with a sea fog process. The correlation coefficient between the observed and retrieved visibility was about 0.82, which is far higher than the 99.9% confidence level by statistical test. The rate of successful retrieval is 94.98% of the 458 cases during 2001 2002. The error distribution showed that high visibilities were usually under-estimated and low visibilities were over-estimated and the relative error between the observed and retrieved visibilities was about 21.4%. 相似文献
20.
The Greenland Sea,Iceland Sea,and Norwegian Sea (GIN seas) form the main channel connecting the Arctic Ocean with other Oceans,where significant water and energy exchange take place,and play an important role in global climate change.In this study steric sea level,associated with temperature and salinity,in the GIN seas is examined based on analysis of the monthly temperature and salinity fields from Polar science center Hydrographic Climatology (PHC3.0).A method proposed by Tabata et al.is used to calculate steric sea level,in which,steric sea level change due to thermal expansion and haline contraction is termed as the thermosteric component (TC) and the halosteric component (SC),recpectively.Total steric sea level (TSSL) change is the sum of TC and SC.The study shows that SC is making more contributions than TC to the seasonal change of TSSL in the Greenland Sea,whereas TC contributes more in the Norwegian and the Iceland Seas.Annual variation of TSSL is larger than 50 mm over most regions of the GIN Seas,and can be larger than 200 mm at some locations such as 308 mm at 76.5 N,12.5 E and 246 mm at 77.5 N,17.5 W. 相似文献