Distributions and Relationships of CO<Subscript>2</Subscript>, O<Subscript>2</Subscript>, and Dimethylsulfide in the Changjiang (Yangtze) Estuary and Its Adjacent Waters in Summer

The distributions and relationships of O₂, CO₂, and dimethylsulfide (DMS) in the Changjiang (Yangtze) Estuary and its adjacent waters were investigated in June 2014. In surface water, mean O₂ saturation level, partial pressure of CO₂ (pCO₂), and DMS concentrations (and ranges) were 110% (89%–167%), 374 μatm (91–640 μatm), and 8.53 nmol L^?1 (1.10–27.50 nmol L^?1), respectively. The sea-to-air fluxes (and ranges) of DMS and CO₂ were 8.24 μmol m^?2 d^?1 (0.26–62.77 μmol m^?2 d^?1), and ?4.7 mmol m^?2 d^?1 (?110.8-31.7 mmol m^?2 d^?1), respectively. Dissolved O₂ was oversaturated, DMS concentrations were relatively high, and this region served as a sink of atmospheric CO₂. The pCO₂ was significantly and negatively correlated with the O₂ saturation level, while the DMS concentration showed different positive relationships with the O₂ saturation level in different water masses. In vertical profiles, a hypoxic zone existed below 20 m at a longitude of 123°E. The stratification of temperature and salinity caused by the Taiwan Warm Current suppressed seawater exchange between upper and lower layers, resulting in the formation of a hypoxic zone. Oxidative decomposition of organic detritus carried by the Changjiang River Diluted Water (CRDW) consumed abundant O₂ and produced additional CO₂. The DMS concentrations decreased because of low phytoplankton biomass in the hypoxic zone. Strong correlations appeared between the O₂ saturation level, pCO₂ and DMS concentrations in vertical profiles. Our results strongly suggested that CRDW played an important role in the distributions and relationships of O₂, CO₂, and DMS.     

Using genetic algorithms to calibrate a dimethylsulfide production model in the Arctic ocean

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.     

Comparison Between Early and Late 21~(st)C Phytoplankton Biomass and Dimethylsulfide Flux in the Subantarctic Southern Ocean

Time-series of chlorophyll-a(CHL),a proxy for phytoplankton biomass,and various satellite-derived climate indicators are compared in a region of the Subantarctic Southern Ocean(40°-60°S,110°-140°E)for years 2012-2014.CHL reached a minimum in winter(June)and a maximum in late summer(early February).Zonal mean CHL decreased towards the south.Mean sea surface temperature(SST)ranged between 8℃and 15℃and peaked in late February.CHL and SST were positively correlated from March to June,negatively correlated from July to September.CHL and wind speed(WIND)were negatively correlated with peak WIND occurred in winter.Wind direction(WIRD)was mostly in the southwest to westerly direction.The Antarctic Oscillation index(AAO)and CHL were negatively correlated(R=−0.58),indicating that as synoptic wind systems move southwards,CHL increases,and conversely when wind systems move northwards,CHL decreases.A genetic algorithm is used to calibrate the biogeochemical DMS model’s key parameters.Under 4×CO2(after year 2100)Regional mean SST increases 12%-17%,WIND increases 1.2ms−1,Cloud Cover increases 4.8%and mixed layer depth(MLD)decreases 48m.The annual CHL increases 6.3%.The annual mean DMS flux increase 25.2%,increases 37%from day 1 to day 280 and decrease 3%from day 288 to day 360.The general increase of DMS flux under 4×CO2 conditions indicates the Subantarctic regional climate would be affected by changes in the DMS flux,with the potential for a cooling effect in the austral summer and autumn.     

Spike in phytoplankton biomass in Greenland Sea during 2009 and the correlations among chlorophyll-a,aerosol optical depth and ice cover

The distributions and correlations of chlorophyll-a(Chl-a),aerosol optical depth(AOD)and ice cover in the southeast Arctic Ocean-Greenland Sea(10°W–10°E,70°–80°N)between 2003 and 2009 were studied using satellite data and statistical analyses.Regression analysis showed correlations between Chl-a and AOD,Chl-a and ice cover,and AOD and ice cover with different time lags.The time lag of Chl-a and AOD indicated their long-term equilibrium relationship.Peaks in AOD and Chl-a and generally occurred in May and July,respectively.Despite the time lag,the correlation between Chl-a and AOD in the study region was as high as 0.7.The peak gap between Chl-a and AOD shifted for about 6 weeks during 2003–2009.In the summer and autumn of 2009,Chl-a and AOD levels were much higher than during the other years,especially in the northern band of the study region(75°–80°N).The driving forces for this localized increase in phytoplankton biomass could be mainly attributed to the very high rate of ice melting in spring and early summer and the high wind speed in autumn,together with the increased deposition of aerosol throughout the year.The unusually high AOD in the spring of 2003 was mainly due to a massive fi re in Russia,which occurred in the fi rst half of the year.Over the 7 years of the study,the sea surface temperature generally decreased.This may have been due to the release of dimethylsulfi de into the air,excreted in large amounts from abundant phytoplankton biomass,and its subsequent reaction,form large amounts of aerosol,and resulting in regional cooling.     

厦门市林地与建设用地对大气气溶胶空间分布的影响分析

分析大气气溶胶空间分布的影响因素有助于理解其变化机制与规律,从而为大气环境质量的调控提供科学依据。本文以厦门市为例,利用MODIS-Aqua卫星遥感影像,反演了大气气溶胶光学厚度。同时,选取Landsat8 OLI卫星数据,进行土地覆被分类。在此基础上,利用相关分析、一元线性回归模型和方差分解,对比研究了城市林地和建设用地对大气气溶胶空间分布的影响作用,得出以下结论：① 暗像元与插值法的结合适合厦门地区春季气溶胶光学厚度的反演;② 建设用地上空气溶胶光学厚度值明显高于林地;③ 林地对气溶胶空间分布的影响作用强于建设用地。本研究对缓解城市大气污染和改善城市生态环境具有重要参考价值和意义。     

华东地区MODIS与OMI气溶胶光学厚度数据融合

气溶胶光学厚度（AOD）表征气溶胶对光的衰减作用,体现大气混浊度或大气中气溶胶总含量,其卫星产品是研究近年来不断恶化的大气环境与空气质量的良好数据源。AOD卫星产品种类较多,但数据存在较大的不确定性;气溶胶全球监测网（AERONET）的地基数据精度高,但空间覆盖度较差。泛克里金法（UK）能在数据融合过程中更多地考虑描述对象的空间相关性,并且简单易行、结果可靠。因此,本文采用该方法,结合二次多项式波段插值法和回归分析方法,在AERONET AOD数据的基础上,对2008年11月华东地区臭氧监测仪（OMI）和中分辨率成像光谱仪（MODIS）的AOD产品进行了融合。结果表明：二次多项式的AOD波段插值方法,能提供比Angstrom波长指数法更为精准的AOD插值结果;AOD融合产品的空间分辨率高于OMI AOD,覆盖率大于OMIAOD和MODIS AOD,且其精度优于这2种AOD卫星产品;融合产品图显示,2008年11月,华东地区的AOD总体呈现南低北高的趋势,高值区主要分布在长江三角洲部分地区、安徽东北部、苏鲁交界处,以及山东西部;低值区主要为江苏以南大部。相比于前人研究,本文证实了AERONET AOD站点数据少、融合的数据源（卫星AOD产品）过境时间不一致的情况下,UK方法仍然有效。本文提出的融合系统,可为相关研究提供空间覆盖更全、精度更高的AOD数据。     

城市气溶胶光学厚度空间格局特征多指标综合分析

本文以厦门市为例,基于MODIS影像反演的大气气溶胶光学厚度（AOD）,利用空间自相关和景观格局指数从数量、形态和结构方面综合分析了2014年各月份（5月和9月除外）AOD时空格局变化。结果表明,研究区AOD具有明显的时空分布差异,林地上空的AOD处于较低等级,建设用地上空AOD大部分处于中高等级;AOD在春夏季较大,在秋冬季较小。AOD分布存在显著正空间自相关性,而且主要存在高高（HH）、低低（LL）、高低（HL）3种聚集模式。低低聚集模式主要分布在厦门市的北部山区;高高（HH）和高低（HL）模式主要分布在本岛东北部新城和本岛外各新城的城区。在景观格局指数方面,从秋冬季节到春夏季节期间,研究区气溶胶光学厚度高等级斑块增加,景观结构趋于复杂,景观异质性增加。对AOD时空格局变化进行多指标综合分析可以更加深入、细致、全面地刻画气溶胶的变化规律,有助于精确评估气溶胶对环境、气候等的影响,为城市可持续发展提供决策支持。     

基于太阳光度计的成都双流地区夏季气溶胶光学特性研究

选取成都信息工程学院航空港校区为研究区,利用CE318太阳光度计于2013年6月期间连续观测的数据反演气溶胶光学厚度,Angstrom指数和粒子谱分布,然后进行气溶胶光学特性分析,结果表明:气溶胶光学厚度随波长增加而减少;气溶胶光学厚度随人为活动和天气等诸多因素变化而变化;平均波长指数显示该地区气溶胶中小粒子占主控地位,平均直径在1.2μm左右;平均浑浊度系数为0.44,大气处于浑浊状态;粒子谱分布呈双峰型,证明该地区为城市气溶胶类型,也详细表明气溶胶粒径的变化。     

STUDY ON THE ANALYSIS AND DISTRIBUTION OF DIMETHYL SULFIDE IN THE EAST CHINA SEA

A method is described for determining dimethylI sulfide (DMS) in seawater. DMS was first extractedfrom the seawater using organic reagent, then reverse-extracted by 5% HgCl2. In the laboratory DMS wasreleased by concentrated HCI and finally measured by GC-FPD. The limit of detection me O.05 ng ofS. Measurements of DMS along surface transects and on wtital profibe across the EaSt China Sca (Ers)continental sheif showed tha itS conodIations of S in the surface seawater ranged from 64-180 ng/L andthat itS vertical djstribuion was divided into 3 trpes. Model talculations of a stagnant film show a DMSflux of 10.6 umol/m_2d the air-sea inteIha.     

利用Sentinel-3A OLCI可见光通道反演台湾岛气溶胶光学厚度

OLCI（Ocean Land Colour Instrument）作为MERIS（Medium Resolution Imaging Spectrometer）的后继升级版传感器,在气溶胶反演中存在潜在优势,但是目前利用OLCI数据进行气溶胶监测的研究较少。因此,本文针对OLCI多通道反射特征开发了OLCI云检测算法,并对传统查找表构建方法进行改进,根据观测几何特征提出动态查找表法,并通过光谱卷积方式等效转换MODIS和OLCI红蓝通道地表反射率并获取OLCI红蓝通道地表反射率固定关系,进而实现台湾岛550 nm处的AOD反演。与550 nm处AERONET level 2.0 AOD验证结果首先表明不同季节、不同站点的精度表现存在一定差异,其次相对于同期MOD04_3K AOD产品,本文反演结果与全球气溶胶自动观测网（AERONET）站点实测值之间表现出更显著 的相关性（R²=0.8199）,均方根误差（RMSE）从0.175下降到0.113,相对平均误差（RME）从33.6%下降到26.7%,且67.5%的OLCI AOD落在预测误差（EE）区间内,明显大于MOD04_3K AOD落在预测误差区间的百分比（55.7%）。此外,误差分析表明,当实际AOD值较低时,红蓝通道地表反射率之间关系的误判会导致较为明显的AOD反演相对误差。     

Dissolved and Particulate Dimethylsulfoxide in the South China Sea During Winter

The distributions of particulate and dissolved dimethylsulfoxide(DMSOp, DMSOd) were studied for the first time in the surface water of the South China Sea(SCS) in January 2010. The concentrations of DMSOp ranged from 2.6 to 56.8 nmol L~(-1) with an average of 11.1 ± 2.2 nmol L~(-1), and those of DMSOd ranged from 11.8 to 335.1 nmol L~(-1) with an average of 50.0 ± 16.5 nmol L~(-1). DMSOd dominated over both dimethylsulfide(DMS) and dissolved dimethylsulfoniopropionate(DMSPd) by 1–3 orders of magnitude and represented the major dissolved dimethyl sulfur pool. In addition, DMSOp/chlorophyll-a ratios varied from 2.7 to 180.7 mmol g~(-1) with an average of 30.5 ± 9.6 mmol g~(-1). DMSOd concentrations displayed a significant negative relationship with sea surface temperature(SST) and sea surfaces salinity(SSS) in the whole study area. The distribution of DMSOd in the coastal waters was obviously influenced by the Pearl River discharge, with high concentrations appearing around the river mouth. In the offshore waters, a significant correlation was observed between the DMSOp and DMSOd concentrations, suggesting that DMSOd was mainly from the diffusion of intracellular DMSO rather than from the photochemical and biological oxidation of DMS.     

Quantification of the impact of environmental factors on chlorophyll in the open ocean

Many previous studies of the impact of oceanic environmental factors on chlorophyll(CHL)in a specific region focused on sea surface temperature(SST),mixed-layer depth(MLD),or wind stress(WS) alone.In this study,relationship between CHL and all those environmental factors(SST,MLD,and WS) in the open ocean was quantified for five regions within the subtropical gyres and the variation trend of 13-year(2003-2015) was analyzed using satellite observations and Argo measurements.The correlation analysis results show that MLD was correlated positively with CHL,SST was correlated negatively with CHL,and the correlation between CHL and WS was either positive or negative.Based on the significance of the correlations,models representing the relationships were established using the multiple linear regression and analyzed,showing that the environmental factors were the major determinants of CHL change.The regression coefficients show that both SST and MLD have remarkable effect on CHL.Our derived models could be used to diagnose the past changes,understand present variability,and predict the future state of CHL changes based on environmental factors,and help us understand the dynamics of CHL variation in the open ocean.     

一种基于FY3D/MERSI2的AOD遥感反演方法

针对目前国产卫星对气溶胶遥感监测应用较少的情况,本研究综合暗象元和SARA算法优势,基于FY-3D MERSI2数据构建了一套气溶胶光学厚度(Aerial Optical Depth, AOD)快速遥感反演方法。首先,引入了传统暗象元算法中的地表反射率经验关系,然后利用AERONET长时间序列的地基观测数据,构建了红波段和蓝波段气溶胶光学厚度、不对称因子和单次散射率之间的关系,最后利用MOD04和AERONET的AOD产品对研究反演结果进行了验证和评估分析。结果发现：① 本研究反演的AOD不仅保持了与MODIS的气溶胶产品空间分布的一致性,而且合理地呈现了AOD的高值分布,改进了MOD04气溶胶产品在云和亮目标方面反演缺失问题;② 利用AERONET地基观测结果对本研究获取的MERSI2的AOD反演结果进行了对比分析,发现二者具有较高的线性相关性,蓝波段AOD线性相关系数超过0.85;③ 利用MERSI2数据完整地捕捉到了2018年3月9—14日京津冀及周边区域的一次重污染过程中气溶胶时空分布变化情况,这也说明了FY3D卫星具备良好的气溶胶遥感监测能力,为我国灰霾监测和预警提供参考依据。本研究对大力发展国产卫星在大气环境遥感的应用有重要参考意义。     

Influence of dimethylsulfide produced by marine algae on the global climate

DMS (dimethylsulfide), a breakdown product of cellular solutes of many species of macroalgae andphytoplankton plays an important role in regulating global climate and counteracting partly the "greenhouse" effect.In this paper, the advance and prospects of DMS study are reviewed and discussed with respectto DMS sample storage, measurement and importance in regulating global climate and the acidity ofrain and aerosol.     

集成多源遥感数据的PM2.5浓度空间分布制图

针对传统地面稀疏站点监测PM_2.5浓度以点带面的缺陷,本研究拟借助多源遥感数据开展了地面大气细颗粒物PM_2.5浓度空间分布模拟研究。以京津冀地区2013年的年均、季均PM_2.5浓度模拟图为例,用简化的气溶胶反演算法（SARA）反演了 1 km高分辨率AOD,并结合高分辨率遥感提取污染相关地理要素,对研究区PM_2.5浓度空间分布进行地理统计模拟及优选。结果表明：① SARA算法反演的AOD与地基AERONET相关性达0.99,能准确地反映研究区AOD的时空分布特征;② 集成多源遥感数据的地理加权回归模型拟合度高（平均R²-0.66）,其空间模拟显示研究区平均PM_2.5污染南部城镇最重,中东部城区次之,西北山区较轻;③ 研究区PM_2.5污染程度高,全年平均模拟浓度高达75 μg/m³,在气候环境及主要污染源季节性差异驱动下,浓度分布季节性特征显著,冬季污染最严重,而夏、秋季相对较轻。该成果对于精细把握PM_2.5污染特征,指导污染防控具有重要意义。     

Geographical Variation and Influencing Factors of Spartina alterniflora Expansion Rate in Coastal China

Biological invasion poses a huge threat to ecological security.Spartina alterniflora was introduced into China in 1979,and its arrival corresponded with negative effects on native ecosystems.To explore geographical variation of its expansion rate in coastal China,we selected 43 S.alterniflora sites from Tianjin Coastal New Area to Beihai.The area expansion rate,expansion rate paralleling and vertical to the shoreline were analysed based on Landsat images and field survey in 2015.Simple Ocean Data Assimilation(SODA)and climate data were collected to statistically analyse the influential factors of expansion rate.Results showed that significant difference of S.alterniflora area expansion rate among different latitude zones(P<0.01),increasing from 6.08%at southern(21°N–23°N)to 19.87% in Bohai Bay(37°N–39°N)along latitude gradient.There was a significant difference in expansion rate vertical to shoreline in different latitude zones(P<0.01)with the largest occurring in Bohai Bay(256m/yr,37°N–39°N),and showed an decreasing tendency gradually from north to south.No significant difference and latitudinal clines in expansion rate paralleling to shoreline were observed.Expansion rate had significant negative correlation with mean seawater temperature,the lowest seawater temperature,current zonal velocity and meridional velocity and presented a reducing trend as these biotic factors increased;however,they were not significantly correlated with the highest seawater temperature and mean seawater salinity.We identified significant correlations between expansion rate and annual mean temperature,the lowest temperature in January and annual precipitation,but there was little correlation with annual diurnal difference in temperature and the highest temperature in July.The rapid expansion rate in high-latitude China demonstrated a higher risk of potential invasion in the north;dynamic monitoring and control management should be established as soon as possible.     

Dimethylsulfide in the South China Sea

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1011号台风“凡亚比”粤西暴雨二次加强过程的分析

为了能够深入了解1011号台风"凡亚比"粤西暴雨过程发生发展机制,采用天气学诊断方法、Ncep1°×1°再分析资料和观测降水资料对凡亚比登陆后在广东西部地区造成的两次暴雨过程进行了研究。通过初步诊断分析得到以下结论:粤西暴雨二次增强的主要原因是强冷空气侵入和水汽输送增加,二次增强过程偏南风主导的水汽条件造成了暴雨增强。假相当位温的垂直剖面显示暴雨主要发生在等值线密集陡峭的区域,等值线的斜率增加对暴雨二次增强有指示作用。湿位涡在暴雨区为上正下负的垂直分布形式,对流层上层高值位涡向下传递,高层干冷空气与低层暖湿气流交汇促使降水增加。     

Simulated perturbation in the sea-to-air flux of dimethylsulfide and the impact on polar climate

Marine biogenic emission of dimethylsulfide(DMS) has been well recognized as the main natural source of reduced sulfur to the remote marine atmosphere and has the potential to affect climate,especially in the polar regions.We used a global climate model(GCM) to investigate the impact on atmospheric chemistry from a change to the contemporary DMS flux to that which has been projected for the late 21~(st) century.The perturbed simulation corresponded to conditions that pertained to a tripling of equivalent CO_2, which was estimated to occur by year 2090 based on current worst-case greenhouse gas emission scenarios.The changes in zonal mean DMS flux were applied to 50°S-70°′S Antarctic(ANT) and65°N-80°N Arctic(ARC) regions.The re sults indic ate that the re are clearly diffe rent impacts after perturb ation in the southern and northern polar regions.Most quantities related to the sulfur cycle show a higher increase in ANT.However,mo st sulfur compounds have higher peaks in ARC.The perturbation in DMS flux leads to an increase of atmo spheric DMS of about 45% m ANT and 33.6% in ARC.The sulfur dioxide(S02) vertical integral increases around 4 3 % in ANT and 7.5% in ARC.Sulfate(S04) vertical integral increases by 17% in ANT and increases around 6% in ARC.Sulfur emissions increases by 21% in ANT and increases by 9.7%in ARC.However,oxidation of DMS by OH increases by 38.2% in ARC and by 15.17% in ANT.Aerosol optical depth(AOD) increases by 4% in the ARC and by 17.5% in the ANT,and increases by 22.8% in austral summer.The importance of the perturbation of the biogenic source to future aerosol burden in polar regions leads to a cooling in surface temperature of 1 K in the ANT and 0.8 K in the ARC.Generally,polar regions in the Antarctic Ocean will have a higher offsetting effect on warming after DMS flux perturbation.     

Effect of the Zagros Mountains on the spatial distribution of precipitation

In order to examine the effect of the Zagros Mountains on precipitation, first, the annual and Seasonal rainfall indices （rain days frequency, rain amount, daily rainfall intensity, and heavy rains） from 43 stations in 1995 - 2004 between the 30° N to 35° N parallels over the mountain range were analyzed. Second, the effect of the Zagros Mountains was studied through the computation of the spatial correlations between the precipitation parameters and the topographic indices （station site elevation, station mean elevation within a radius of 2.5 km, mean elevation of 9 blocks along each of the eight Cartesian directions, and the elevation differences of these 9 blocks from the station mean elevation）. The results showed that in the cold season the maximal rainfall occurs on the upper range of west slope, while in warm season it spreads over the study area. The correlations between precipitation and elevation indices were positive on the north of the stations and negative on the south of the stations, that is, the higher elevations of the stations to the north force the uplifting of the moist air masses and increase rainfall at the stations, while the lower elevations to their south lead the movement of the moist air masses to the stations. This is due to the fact that these stations or slopes are exposed to the moist air masses coming from the Mediterranean Sea and the Persian Gulf. The heavy rain days and the summer sporadic rain events do not show significant correlations with the topographic indices. The findings indicate that the Zagros Mountains intensify the cold period frontal rains especially over the west slope and block the moist air masses from entering the interior parts of the country. Moreover, these mountains play a secondary role in creating rain days. But they are very important in the production of precipitation in the area. Therefore, their absence will decrease the amount of rainfall to their west and, in return, expand the dry climates of their west and east.