基于引力模型的海洋锋信息提取

海洋锋面是海洋水团特性明显不同的两种或几种水体之间的狭窄过渡带。本文旨在对遥感反演海洋温度场数据(SST),引入引力模型进行海洋锋面的检测。鉴于海洋锋受噪声干扰大,锋面强度小的特点,本文提出了基于引力算法的引力模型。其中,引力算法是将温度数据中的每一个像元点都作为一个独立的天体,其质量对应该像元的温度值,根据引力定律计算3×3区域中,邻域像元对中心点像元的引力和。模型首先对原始数据进行去0处理,为消除对原始数据明暗程度的依赖,对3×3区域数据进行归一化,然后利用函数对归一化后的数据进行增强处理,最后,以引力算法进行锋面检测。验证表明,该模型能有效强化不同区域或水体差异性,并能够有效针对海洋锋信息进行提取,受噪声影响小。     

Warmer-Get-Wetter or Wet-Get-Wetter? A Criterion to Classify Oceanic Precipitation

In this study, the temporal and spatial variations of observed global oceanic precipitation during 1979–2010 are investigated. It is found that the global trend in precipitation during this period varies at a rate of 1.5%/K of surface warming while the rate is 6.6%/K during 2006–2010. The precipitation is highly correlated with Sea Surface Temperature(SST) in both the temporal and the spatial patterns since the strong 1997–98 El Nino event. Considering the distributions of precipitation and SST, seven oceanic regions are classified and presented using the observed Global Precipitation Climatology Project(GPCP) data and Extended Reconstructed Sea Surface Temperatures, version 3(ERSST.v3) data. Further examining the mechanisms of the classified oceanic precipitation regions is conducted using the Tropical Rainfall Measuring Mission(TRMM) satellite, GFDL-ESM-2G model precipitation and SST data and Hadley Center sea ice and SST version 1(Had ISST1) data. More than 85% of global oceanic precipitations are controlled by either one or both of the warmer-get-wetter mechanism and wet-get-wetter mechanism. It is estimated that a 0.5 SST signal-to-noise ratio, representing the trend of SST time series to the standard deviation, is a criterion to distinguish the mechanism of a region. When the SST ratio is larger than 0.5, the precipitation of this region is controlled by the warmer-get-wetter mechanism. SST, rather than the humidity, is the pivotal factor. On the other hand, when the SST ratio is less than 0.5, the precipitation is controlled by the wet-get-wetter mechanism. The SST variability is a significant factor contributing to the precipitation variation.     

Mesoscale SST perturbation-induced impacts on climatological precipitation in the Kuroshio-Oyashio extension region,as revealed by the WRF simulations

Mesoscale coupling between perturbations of mesoscale sea surface temperature(SST) and lowlevel winds has been extensively studied using available high-resolution satellite observations. However, the climatological impacts of mesoscale SST perturbations(SST_(meso)) on the free atmosphere have not been fully understood. In this study, the rectified ef fect of SST_(meso) on local climatological precipitation in the KuroshioOyashio Extension(KOE) region is investigated using the Weather Research and Forecasting(WRF)Model; two runs are performed, one forced by low-resolution SST fields(almost no mesoscale signals) and another by additional high-resolution SST_(meso) fields extracted from satellite observations. Climatological precipitation response to SST_(meso) is characterized mainly by enhanced precipitation on the warmer flank of three oceanic SST fronts in this region. The results show that the positive correlation between the 10-m wind speed perturbations and SST_(meso) is well captured by the WRF model with a reasonable spatial pattern but relatively weak strength. The addition of SST_(meso) improves the climatological precipitation simulated by WRF with a better representation of fine-scale structures compared with satellite observations. A closer examination on the underlying mechanism suggests that while the pressure adjustment mechanism can explain the climatological precipitation enhancement along the fronts and the relatively high contribution of the convective precipitation, other factors such as synoptic events should also be taken into consideration to account for the seasonality of the precipitation response.     

Uncertainty representation of ocean fronts based on fuzzy-rough set theory

Analysis of ocean fronts' uncertainties indicates that they result from indiseemibility of their spatial position and fuzzi-ness of their intensity. In view of this, a flow hierarchy for uncertainty representation of ocean fronts is proposed on the basis of fuzzy-rough set theory. Firstly, raster scanning and blurring are carried out on an ocean front, and the upper and lower approximate sets, the indiscernible relation in fuzzy-rough theories and related operators in fuzzy set theories are adopted to represent its uncer-tainties, then they are classified into three sets: with members one hundred pereent belonging to the ocean front, belonging to the ocean front's edge and definitely not belonging to the ocean front. Finally, the approximate precision and roughness degree are util-ized to evaluate the ocean front's degree of uncertainties and the precision of the representation. It has been proven that the method is not only capable of representing ocean fronts' uncertainties, but also provides a new theory and method for uncertainty representation of other oceanic phenomena.     

The atmospheric wet pool： definition and comparison with the oceanic warm pool

The oceanic warm pool (OWP) defined by sea surface temperature (SST) is known as the "heat reservoir" in the ocean. The warmest portion in the ocean mirrors the fact that the wettest region with the largest accumulation of water vapor (WV) in the atmosphere, termed atmospheric wet pool (AWP), should be identified because of the well-known Clausius-Clapeyron relationship between SST and WV. In this study, we used 14-year simultaneous observations of WV and SST from January 1988 to December 2001 to define the AWP and investigate its coupling and co-variations with the OWP. The joint examination of the area variations, centroid locations, and zonal migrations of the AWP and OWP lead to a number of interesting findings. The results hopefully can contribute to our understanding of the air-sea interaction in general and characterization of El Nifio/La Nina events in particular.     

TIDAL FRONTS AND THEIR INFLUENCE ON PRAWN POSTLARVAE IMMIGRATION IN ALBATROSS BAY, THE GULF OF CARPENTARIA, AUSTRALIA

Studies of dynamics in Albatross Bay, the Gulf of Carpentaria, Australia, show strong tides of which M_2is the dominant constituent in the region. Tidal fronts are present and they can be modeled by a 2-Dtidal model. Density currents have also been observed with seasonal variations due to the influence ofwet or dry seasons. This paper reviews the effects of these dynamics on the migration of prawn postlarvae in AlbatrossBay and its estuaries. It is found that through its vertical movement triggered by change of salinity theprawn postlarvae can be transported from the coast to the estuary by tides within 2.8 weeks. Howeverthis horizontal displacement mechanism may be destroyed by the tidal front in Albatross Bay. Densitycurrents may alter prawn postlarvae positions in Albatross Bay on a seasonal scale.     

COAST SEA LEVEL AND ASIAN MONSOON SYSTEM A DOWNCALING EXERCISE FOR CHINESE COAST

CDntnbutionNo.3236fromtheInstituteofthenology,ChinaseAcadeInyofSdenas.KeyprojeCt396MandProjeCt4M76274supp0rtedbyNSFC,andabosupportedbypnsident'sboofCh1nereAedernyofSdenas.IwnODUruONThemonsoonisacirculationfeaturethatisplanetaryinscaleandhasanidentiliablesignalregardingitSsubsequentintensitysomeninemonthspriortotheaCtivestageofthesummrmonsoon(WbsterandYang,l992,Vemekar,l994).Furthertnre,thernagnitudeofthemons00n'svariabilityissubstantialandidentifiableoveralargearmindudingthePadficd…     

CHARACTERISTICS OF INTRASEASONAL VARIATIONS IN THE MIXED LAYER OF "WARM POOL" AREAS

Observational data obtained during the TOGA-COARE IOP in the "warm pool" area of the West-ern Tropical Pacific were used to analyze some characteristics of the intraseasonal variations in the mixedlayer. The influence of westerly burst and rainfall on SST, salinity. and mixed layer depth are discussed.There are two pairs of counteracting processes in the "warm pool" mixed layer: (1) The increase of mixedlayer depth caused by local westerly bursts and the decrease of mixed layer depth caused by larger scaleeasterly relaxation;(2) the vertical mixing by local wind and the strong stratification due to rainfall in themixed layer. Some possible mechanisms through the interactions between the intraseasonal time scale varia-tions of the oceanic mixed layer and atmospheric low frequency oscillations are revealed.     

Characteristics of intraseasonal variations in the mixed layer of “warm pool” areas

Observational data obtained during the TOGA-COARE IOP in the “warm pool” area of the Western Tropical Pacific were used to analyze some characteristics of the intraseasonal variations in the mixed layer. The influence of westerly burst and rainfall on SST, salinity and mixed layer depth are discussed. There are two pairs of counteracting processes in the “warm pool” mixed layer: (1) The increase of mixed layer depth caused by local westerly bursts and the decrease of mixed layer depth caused by larger scale easterly relaxation; (2) the vertical mixing by local wind and the strong stratification due to rainfall in the mixed layer. Some possible mechanisms through the interactions between the intraseasonal time scale variations of the oceanic mixed layer and atmospheric low frequency oscillations are revealed. Supported by National Natural Science Foundation of China (49276250) and LASG of Beijing.     

Identifying sky conditions in Iran from MODIS Terra and Aqua cloud products

Clouds can influence climate through many complex interactions within the hydrological cycle. Due to the important effects of cloud cover on climate, it is essential to study its variability over certain geographical areas. This study provides a spatial and temporal distribution of sky conditions, cloudy, partly cloudy, and clear days, in Iran. Cloud fraction parameters were calculated based on the cloud product(collection 6_L2) obtained from the Moderate Resolution Imaging Spectroradiometer(MODIS) sensors on board the Terra(MOD06) and Aqua(MYD06) satellites. The cloud products were collected daily from January 1, 2003 to December 31, 2014(12 years) with a spatial resolution of 5 km × 5 km. First, the cloud fraction data were converted into a regular geographic coordinate network over Iran. Then, the estimations from both sensors were analyzed. Results revealed that the maximum annual frequency of cloudy days occurs along the southern shores of the Caspian Sea, while the minimum annual frequency occurs in southeast Iran. On average, the annual number of cloudy and clear-sky days was 88 and 256 d from MODIS Terra, as compared to 96 and 244 d from MODIS Aqua. Generally, cloudy and partly cloudy days decrease from north to south, and MODIS Aqua overestimates the cloudy and partly cloudy days compared to MODIS Terra.     

A fast,edge-preserving,distance-regularized model with bilateral fi ltering for oil spill segmentation of SAR images

Marine oil spills are among the most signifi cant sources of marine pollution. Synthetic aperture radar(SAR) has been used to improve oil spill observations because of its advantages in oil spill detection and identifi cation. However, speckle noise, weak boundaries, and intensity inhomogeneity often exist in the oil spill regions of SAR imagery, which will seriously aff ect the accurate identifi cation of oil spills. To enhance marine oil spill segmentation of SAR images, a fast, edge-preserving framework based on the distance-regularized level set evolution(DRLSE) model was proposed. Specifi cally, a bilateral fi lter penalty term is designed and incorporated into the DRLSE energy function(BF-DRLSE) to preserve the edges of oil spills, and an adaptive initial box boundary was selected for the DRLSE model to reduce the operation time complexity. Two sets of RadarSat-2 SAR data were used to test the proposed method. The experimental results indicate that the bilateral filtering scheme incorporated into the energy function during level set evolution improved the stability of level set evolution. Compared with other methods, the proposed improved BF-DRLSE algorithm displayed a higher overall segmentation accuracy(97.83%). In addition, using an appropriate initial box boundary for the DRLSE method accelerated the global search process, improved the accuracy of oil spill segmentation, and reduced computational time. Therefore, the results suggest that the proposed framework is eff ective and applicable for marine oil spill segmentation.     

粒子群优化的半监督入侵检测算法

为解决无监督入侵检测算法检测率低,有监督的入侵检测不能有效的检测未知攻击的问题,提出了一种粒子群优化的半监督入侵检测算法,算法对少量的约束信息进行基于密度的扩展获得潜在约束得到聚类模型,以此指导未标记数据聚类,对仍没有确定类别的未标示数据使用粒子群优化的K均值算法进行聚类实现对异常的检测。改进的算法检测率达到83.7%,误报率减少至3.13%,总体效果优于无监督和有监督学习的入侵检测算法。     

Coast sea level and Asian monsoon system a downscaling exercise for Chinese coast

In this study, the authors examined the relationship between monthly sea level data and concurrent large-scale monthly mean sea level pressure and SST data for 1960 to 1990, which are reasonably well simulated by present day climate models; sea level variations due to variations of regional atmospheric forcing and oceanic circulation, are not adequately simulated by a global climate model because of insufficient spatial resolution. The authours applied a statistical “down scaling” strategy to sea level along the Chinese coast. Two interrelated processes were identified: one process is the local wind or wave set-up of water due to Asian monsoon wind anomalies; the other is the rainfall diluting effect in spring. At interdecadal time scale, the later becomes more important and most likely plays a major role in the planetary scale atmosphere-ocean interaction taking place in the eastern North Pacific. Contribution No. 3236 from the Institute of Oceanology, Chinese Academy of Sciences. Key project 39630060 and Project 49476274 supported by NSFC, and also supported by president's fund of Chinese Academy of Sciences.     

基于特征的海洋锋线过程时空数据模型分析与应用

客观世界存在时空场,大部分地理实体或现象在时空域具有动态变化特性,其空间、时间和属性是过程的统一体,传统的GIS时空数据模型在描述、表达、组织与分析这类数据时面临许多挑战。然而,基于特征的数据模型和以过程为对象的时空数据组织在动态数据的描述与表达的方面具有独特的优势。本文探讨了基于特征的线过程时空数据模型组织的六元组框架体系,实现空间、时间和属性的一体化存储和地理实体的动态分析。在分析线时空过程特性的基础上,归纳总结出3大类12个类别的线过程,进一步提出了基于特征的线过程时空数据模型(Feature-based Line Process Spatio-temporal Data Model)的概念;利用文件层次分块结构对时空线过程数据进行了组织与存储。最后以海洋锋为实例,探讨了该模型在时空数据组织、时空查询、时空过程提取和时空过程可视化等方面的应用。结果表明,该模型能够很好地应用于具有时空过程特性的线数据中,也为时空数据模型的总体设计提供借鉴。     

Impact of the Kuroshio Extension Oceanic Front on Autumn and Winter Surface Air Temperatures over North America

Mid-latitude air-sea interaction is an important topic that attracts a considerable amount of research interest. The Kuroshio Extension(KE) is one of the main western boundary currents and plays a critical role in the mid-latitude atmospheric circulation. This paper uses the NCEP/NCAR reanalysis and Hadley sea surface temperature datasets to investigate the influence of oceanic fronts in the KE region on surface air temperature in North America over the period 1949–2014. A significant correlation was found between the KE front intensity and the temperatures over North America in autumn and winter. A strong(weak) KE front anomaly in autumn is associated with an increasing(decreasing) surface temperature over western North America but a decreasing(increasing) surface temperature over eastern North America. In winter, central North America warms(cools) when the KE front is strong(weak). The response of the atmospheric circulation, including wind in the high and low troposphere, troughs, and ridges, to the strengthening(weakening) of the KE front is the main cause of these changes in surface temperature.     

Major mid-late Holocene cooling in the East China Sea revealed by an alkenone sea surface temperature record

Although the mid-late Holocene cold and dry event about 4000 years ago(the 4 ka event) has been observed almost globally, it was most prominent in terrestrial climate proxies from the lower latitudes. Here we evaluate the oceanic response to this event in terms of a Holocene sea surface temperature(SST) record reconstructed using the K'37U index for Core B3 on the continental shelf of the East China Sea. The record reveals a large temperature drop of about 5℃ from the mid-Holocene(24.7℃ at 5.6 ka) to the 4 ka event(19.2℃ at 3.8 ka). This mid-late Holocene cooling period in Core B3 correlated with(i) decreases in the East Asia summer monsoon intensity and(ii) the transition period with increased El Nino/Southern Oscillation activities in the Equatorial Pacific. Our SST record provides oceanic evidence for a more global nature of the mid-late Holocene climate change, which was most likely caused by a southward migration of the Intertropical Converge Zone in response to the decreasing summer solar insolation in the Northern Hemisphere. However, the large SST drop around Core B3 indicates that the mid-late Holocene cooling was regionally amplified by the initiation/strengthening of eddy circulation/cold front which caused upwelling and resulted in additional SST decrease. Upwelling during the mid-late Holocene also enhanced with surface productivity in the East China Sea as reflected by higher alkenone content around Core B3.     

基于滑动窗口的手机定位数据个体停留区域识别算法

手机的普及使手机定位数据成为分析个体时空行为特征的新兴重要数据源之一,并被逐渐应用到人口管理、城市规划、交通分析和流行病防控等众多领域的研究中。从手机定位数据中识别个体的停留区域是众多基于手机定位数据研究的重要基础环节。然而,当前常用的手机定位数据定位精度相对较低,且往往存在定位震荡和定位漂移导致的数据噪声,这些因素增加了从手机定位数据中识别停留区域的难度。为了提高从手机定位数据中识别个体停留区域的准确性,本研究结合个体行为的时空连续性,提出了一种基于滑动窗口的增长聚类算法。实验结果显示,相较常用的ST-DBSCAN算法和SMoT算法,对于采样时间间隔稀疏的手机定位数据,本研究提出的滑动窗口聚类算法在准确率方面的提升幅度最大可以达到35%。由于隐私问题,当前研究和应用中使用的大规模手机定位数据集中的时间分辨率往往较低,因此,本研究提出的滑动窗口聚类算法具有较为广泛的应用场景,可增强基于手机用户停留区域的众多研究结果的可靠性,为手机定位数据的广泛合理应用提供关键技术支撑。     

REGIONAL FEATURES OF LONG-TERM SST VARIATION IN THE WESTERN PACIFIC WARM POOL AREA

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Evolution of surface cold patches in the North Yellow Sea based on satellite SST data

Ten years(from 2005 to 2014) of satellite sea surface temperature(SST) data from the Advanced Very High Resolution Radiometer(AVHRR) are analyzed to reveal the monthly changes in surface cold patches(SCPs) in the main areas of the Northern Yellow Sea(NYS). The Canny edge detection algorithm is used to identify the edges of the patches. The monthly changes are described in terms of location, temperature and area. The inter-annual variations, including changes in the location and area of the SCPs from 2010 to 2014, are briefly discussed. The formation mechanisms of the SCPs in different periods are systematically analyzed using both in situ data and numerical simulation. The results show that from May to October, the location and area of the SCPs remain stable, with a north-south orientation. The SCPs altogether cover about 1? of longitude(124?E–125?E) in width and 2? of latitude(37.5?N–39.5?N) in length. In November, the SCP separates from the Jangsan Cape and forms a closed, isolated, and approximately circular cold patch in the central NYS. From May to October, the upwelling that leads to the formation of the SCP is mainly triggered by the headland residual current, wind field, climbing movement of the current and secondary circulation at the tide front. In November, cyclonic circulation in the NYS is primarily responsible for generating the upwelling that leads to the formation of the closed and isolated SCP.