Estimating Sea-Level Allowances for Atlantic Canada using the Fifth Assessment Report of the IPCC

Abstract

Sea-level allowances at 22 tide-gauge sites along the east coast of Canada are determined based on projections of regional sea-level rise for the Representative Concentration Pathway 8.5 (RCP8.5) from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5) and on the statistics of historical tides and storm surges (storm tides). The allowances, which may be used for coastal infrastructure planning, increase with time during the twenty-first century through a combination of mean sea-level rise and the increased uncertainty of future projections with time. The allowances show significant spatial variation, mainly a consequence of strong regionally varying relative sea-level change as a result of glacial isostatic adjustment (GIA). A methodology is described for replacement of the GIA component of the AR5 projection with global positioning system (GPS) measurements of vertical crustal motion; this significantly decreases allowances in regions where the uncertainty of the GIA models is large. For RCP8.5 with GPS data incorporated and for the 1995–2100 period, the sea-level allowances range from about 0.5?m along the north shore of the Gulf of St. Lawrence to more than 1?m along the coast of Nova Scotia and southern Newfoundland.     

An ozone depletion event in the sub-arctic surface layer over Hudson Bay,Canada

During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) program, aircraft flights during April 7–11, 2000 revealed a large area air mass capped below ∼500 m altitude over Hudson Bay, Canada in which ozone was reduced from normal levels of 30–40 ppbv to as low as 0.5 ppbv. From some of the in-situ aircraft measurements, back-trajectory calculations, the tropospheric column of BrO derived from GOME satellite measurements, and results from a regional model, we conclude that the event did not originate from triggering of reactive halogen release in the sub-Arctic region of Hudson Bay but resulted from such an event occurring at higher latitudes over the islands of the northern Canada Archipelago and nearby Arctic Ocean with subsequent transport over a distance of 1,000–1,500 km to Hudson Bay. BrO _x remained active during this transport despite considerable changes in the conditions of the underlying surface suggesting that chemical recycling during transport dominated any local halogen input from the surface. If all of the tropospheric column density of BrO is distributed uniformly within the surface layer, then the mixing ratio of BrO derived from the satellite measurements is at least a factor of 2–3 larger than derived indirectly from in situ aircraft measurements of the NO/NO₂ ratio.     

Secular Trends in Tidal Parameters along the Coast of Japan

The secular trends for local tidal datums, tide ranges, and tidal harmonic constituents at 13 tidal gauge stations located along the coast of Japan were analyzed in this study. The general trends for mean higher high water (MHHW), mean high water (MHW), diurnal tide range (DTR), mean tide range (MTR), and relative mean sea level (RMSL) were positive, and for mean lower low water (MLLW) and mean low water (MLW) the trends were negative. The variation patterns were largest at Kushiro and Ofunato stations, both located in the open waters of the North Pacific Ocean. The tidal datums and tide ranges remained fairly stable at the Hakodate station, and an opposite trend was observed at the Maisaka station. The analysis of tidal harmonic constituents revealed a less pronounced pattern. The most distinct trend was observed for the M₂ amplitude, which appears to be negative at a majority of the stations. The largest decrease in the M₂ amplitude was observed at Kushimoto and Mera stations, also located in the open waters of the North Pacific Ocean. The negative trend is attributed to decreasing water depths at these stations, owing to small-scale local processes.     

Variations in momentum,mass and heat fluxes due to changes in the sea surface temperature of Hudson Bay

Abstract

The atmospheric model of Danard et al. (1983) is used to investigate the changes in heat, mass and momentum fluxes at the air‐sea interface in Hudson Bay when the seasonal sea surface temperature is varied. Comparisons of model predictions with data from a meteorological buoy located 400 km offshore showed that the model predicted the variations in wind speed and air temperature fairly well but underestimated their magnitudes. In addition it provided offshore heat and mass fluxes for which no direct observations were available.

The most important parameter determining air‐sea fluxes is the temperature difference between air and water. This determines the stability and the degree of vertical convection of the air. In the spring the colder water stabilizes the air, which depresses vertical convection. This reduces wind stress and evaporation while increasing the heat flux into the water. During the fall, the opposite occurs. The sea surface temperature is thus buffered against man‐made changes. When the temperature is decreased, for example, as the result of hydroelectric development in surrounding watersheds, the heat flux into the water increases while the wind stress decreases. Both effects increase the sea surface temperature, opposing the initial decrease. A one‐degree depression of sea surface temperature in summer is slowly offset by increased heating and no noticeable change in temperature remains at the end of the fall.     

Measurements of Atmospheric Concentrations of Reduced Sulphur Compounds in the All Saints Bay Area in Bahia,Brazil

Atmospheric concentrations of several reduced sulphur compounds (H₂S, COS, CH₃SH, CH₃SCH₃, CS₂) originating from both natural and anthropogenic sources were measured at a number of locations in the All Saints Bay area and Reconcavo Baiano, Brazil.The volatile reduced sulphur compounds were collected by pre-concentration using cryo-tubes. Analysis of these compounds was carried out at a later date using gas chromatography with a flame photometric detector. In areas dominated by biogenic sources, the COS concentration varied between 0.5 and 1.0 ppbv, consistent with its normal global distribution in the atmosphere.Areas without direct industrial influence showed low atmospheric concentrations for all volatile sulphur compounds ( 0.25 ppb_v).The anthropogenic influence of the Petrochemical Complex in Camaçari resulted in relatively high levels of some reduced sulphur compounds, such as COS (8 ppb_v), CH₃SH (1.50 ppb_v), H₂S (1.35 ppb_v) and CS₂ (0.3 ppb_v). In mangrove areas, the H₂S concentrations (0.2 ppb_v) were almost twice as high as those in the air masses arriving from the Atlantic Ocean. The maximum H₂S concentrations were found in the industrial area of the Petrochemical Complex in Camaçari, but did not reach the limit of human perception (0.14 ppb_v) and rarely reached the typical recognizable smelling level (0.40 ppb_v). Industrial emissions from the Landulfo Alves Refinery increased the COS, DMS and CS₂ concentrations to 2.0, 0.55 and 0.2 ppb_v, respectively.     

2009年秋季珠江口咸潮与风场变化的关系

利用珠江口大万山站潮位资料,横栏岛风资料和磨刀门、横门水道咸潮观测资料,采用对比和相关分析等方法,分析2009年秋季珠江口咸潮与潮位、风场变化的关系,1984～2009年秋、冬月份海平面长期变化趋势。结果表明:咸潮的发生均对应着高海面期且风向偏东,而低潮位时期且偏北风有利于补水。月平均海平面变化方面,珠江口与南海呈准同步变化。大万山站1984～2009年9、11和12月的海平面上升率高达5～6mm/月。2009年9、10月的海平面为近30年来的最高值年,11月为第3高值年。     

Measurements and Parametrizations of the Atmospheric Boundary-Layer Height at Dome C,Antarctica

An experimental campaign, Study of the Atmospheric Boundary Layer Environmental at Dome C, was held during 2005 at the French-Italian station of Concordia at Dome C. Ground-based remote sensors, as well as in situ instrumentation, were used during the experimental campaign. The measurements allowed the direct estimation of the polar atmospheric boundary-layer height and the test of several parametrizations for the unstable and stable boundary layers. During the months of January and February, weak convection was observed while, during the polar night, a long-lived stable boundary layer occurred continuously. Under unstable stratification the mixing-layer height was determined using the sodar backscattered echoes and potential temperature profiles. The two estimations are highly correlated, with the mixing height ranging between 30 and 350 m. A simple prognostic one-dimensional model was used to estimate the convective mixing-layer height, with the correlation coefficient between observations and model results being 0.66. The boundary-layer height under stable conditions was estimated from radiosounding profiles as the height where the critical Richardson number is reached; values between 10 and 150 m were found. A visual inspection of potential temperature profiles was also used as further confirmation of the experimental height; the results of the two methods are in good agreement. Six parametrizations from the literature for the stable boundary-layer height were tested. Only the parametrization that considers the long-lived stable boundary layer and takes into account the interaction of the stable layer with the free atmosphere is in agreement with the observations.     

对流单体在杭州湾入海时的强度变化分析

为了研究对流单体在杭州湾入海时的强度变化情况,更好地预报对流单体的变化趋势,统计了2007年1月到2010年6月舟山雷达观测到的148个对流单体,以组合反射率因子、顶高、垂直液态含水量、径向速度、冰雹指数等条件来判断对流单体是加强还是维持或减弱。发现对流单体在海岸线附近加强或维持的几率比较大,在北岸入海后加强以及在南岸入海后减弱的几率较大,在傍晚到凌晨加强或维持的几率较大。对三个加强的典型个例,分别分析了海岸线附近的温湿特性、地面风的辐合、大气的层结稳定性等情况。对148个单体所处时刻的气温和相对湿度资料用GRADS进行插值,绘出等值线,然后统计整个杭州湾海域的最大气温差和相对湿度差以及水平风切变情况。统计结果：加强的单体,其环境温度、湿度梯度、风切变明显比减弱的大。最后得出结论,判断一个对流单体在杭州湾入海时是加强还是减弱,应从海岸线附近的温湿特性、地面风的辐合情况、大气的层结稳定性三方面的条件综合考虑。     

南极中山站太阳紫外辐射测值比较

比较分析了2017年南极中山站3种仪器测量地面太阳紫外B（UVB）波段和紫外A（UVA）波段的辐照度。以Brewer光谱仪测值为参考,国产宽波段FSUVB日射表在UVB（波段280~315 nm）的辐照度相对误差为（55±75）%,误差随大气臭氧总量的增加呈上升趋势,但在南极“臭氧洞”期间偏低。Yankee UVB宽波段日射表在UVB（波段280~320 nm）的辐照度相对误差为（-31±22）%;国产宽波段FSUVA日射表在UVA（波段315~400 nm）的辐照度相对误差为（23±5.9）%。太阳天顶角低于80°的晴天以Tropospheric Ultraviolet Visible（TUV）辐射模式计算结果为参考时,FSUVB,Yankee UVB和FSUVA辐照度的平均相对误差分别为（30±37）%,（-22±19）%和（27±6.4）%,而Brewer相对误差未超过3.5%。国产宽波段UV日射表测值偏高,反映出波长较长的杂散光对太阳辐照度测值影响明显。     

Modelling Sea Surface Temperature (SST) in the Hudson Bay Complex Using Bulk Heat Flux Parameterization: Sensitivity to Atmospheric Forcing,and Model Resolution

ABSTRACT

Sea surface temperature (SST) from four Nucleus for European Modelling of the Ocean (NEMO) model simulations is analyzed to study the bulk flux parameterization to compute SST over the Hudson Bay Complex (HBC) for the summer months (August and September) from 2002 to 2009. The NEMO simulation was forced with two atmospheric forcing sets with different resolutions: the Coordinated Ocean-ice Reference Experiment, version 2 (COREv2), as the lower resolution and the Canadian Meteorological Centre’s Global Deterministic Prediction System Reforecasts (CGRF) as the higher resolution. The CGRF forcing is also implemented in the third and fourth runs using different runoff data and different NEMO resolutions (1/12° versus 1/4°). Results show that all four modelled SSTs followed observed SST patterns, with regional differences in SST bias between simulations with different atmospheric forcing. The SST differences are small between simulations forced with the same atmospheric forcing but with different model resolution or runoff. This implies that the model resolution and runoff have a small effect on the simulated SST in the HBC. Moreover, to better capture the effect of near-surface temperature (T_air) on simulated SST, we conducted three analyses using the Haney flux linearization formula. Results from these assessments did not indicate any direct influence on the model-simulated SSTs by T_air. Looking at the heat flux as a signature for SST showed that both averaged spatial distribution and time series of net heat flux produced by the three CGRF forcing simulations were higher than the net heat flux generated by the CORE 2 simulation. This was generally true for all four components of the total heat flux (sensible, latent, shortwave, and longwave) individually as well. Total heat flux in summer is governed by the shortwave heat flux, with values up to 120?W?m^?2 in August, and the longwave heat flux is the main contributor to the total heat flux differences. These heat flux differences lead to corresponding colder model SSTs for the CGRF runs and warmer SSTs for the CORE 2 simulations.     

2001年7月27日临汾区域性暴雨天气过程分析

本文应用数值预报产品，常规天气图，卫星云图及大气探测等资料，对2001年7月27日临汾区域性暴雨天气过程产生的环流形势，水汽和热力条件及动力机制进行了分析和研究，进一步揭示临汾市暴雨发生的环境流场和物理量场的特征。     

陆地上爆发性温带气旋的暖锋后弯结构分析

尽管关于温带气旋发展和演变的观点不尽相同,但目前普遍被接受的两种模型是：挪威气旋模型、Shapiro和Keyser模型。以FY-2E卫星云图为基础,先给出8个温带气旋过程实例,然后结合常规高空、地面观测及NCEP的1°×1°再分析场等资料,通过个例分析,对暖锋后弯气旋发生发展的环流背景、结构及成因进行分析。结果表明：(1)卫星云图显示东亚陆地上温带气旋存在T-bone结构和暖锋后弯的事实。(2)温带气旋发生在500 hPa东亚大陆中高纬两脊一槽的背景下,槽加深及下游脊的发展有利于气旋的发展,与经典温带气旋发生发展的环流背景类似。(3) 2012年5月11—13日个例分析表明蒙古气旋中存在锋面波动、锋面断裂、T-bone结构和暖锋后弯、暖核被隔离现象;暖核可从地面向上伸展到600 hPa。(4)在地面气旋初生和发展阶段,地面气旋中心西侧高低层正相对涡度区呈后倾结构;当高低层正涡度区几乎垂直重合时,地面气旋停止发展;气旋中心西侧对流层中低层的锋区一直存在。(5)当高低层涡度平流差值为正、300 hPa正涡度平流引起的辐散叠加到对流层中低层锋区之上,地面气旋才会生成和发展。逐渐增强的暖平流从气旋中心的东部和北部向气旋的西部和西南部输送,从而形成了卫星云图上的T-bone结构和暖锋后弯现象。

     

CHAMP卫星观测的热层大气密度变化特征

采用2001-2010年CHAMP（CHAllenging Minisatellite Payload）卫星高精度加速度计反演的热层大气总质量密度观测数据,对400 km高度大气密度的变化特征进行了分析与研究。结果表明,太阳辐射高低整体上控制着热层大气密度数值大小变化,在太阳宁静期热层大气密度受地磁活动控制,其最大值区域在地磁12-18时（地方时）内移动,重复周期为4~5个月,与地磁活动的Ap指数变化相似。对比经验模式与CHAMP卫星观测值,两者偏差纬向分布较均匀,经向变化明显;当太阳活动处于中低水平即F_10.7小于120时,模式值偏高5%~10%;当F_10.7大于130时,模式值偏低10%以上。为经验模式的改进提供相应的参考。     

Reconstruction of the Surface-Layer Vertical Structure from Measurements of Wind,Temperature and Humidity at Two Levels

A comparison of sensible heat flux derived from ultrasonic-anemometer measurements and profile-derived values shows strong systematic bias in the stable branch. One of the two effects, large sonic-based values combined with small profile-based values, can be explained as due to katabatic flows down the terrain slope. The other effect, large profile-based values combined with small sonic-based values, can only partially be explained as due to intermittent turbulence. The remainder occurs at small stability and indicates a possible systematic kink in ultrasonic-anemometer eddy-correlation values. Evaluation of the temperature-profile parameter θ _* contributes to further clarification by reducing the systematic bias and confirming the katabatic-flow explanation. Also, the intermittent-turbulence influence is confirmed by the θ _* evaluation, but the combination of large profile-based values with small sonic-based values does not vanish outside the more clearly defined intermittent-turbulence region. This is associated with a strongly increased occurrence of opposite-sign sonic values. Neutral profile values are frequently associated with considerably unstable sonic values of θ _*.     

临震前地球放气与大气顶射出光谱辐射

通过不同分辨率的辐射传输计算，分析了大气中CH4浓度增加对大气顶射出光谱辐射率的影响。在某些波段，射出光谱辐射率在CH4浓度显著增加时会有明显的减少，而气溶胶和水汽等的变化造成的影响又较小。这种通道的射出辐射可反映出大气中CH4浓度的增加，从而有可能通过卫星辐射测量对地震前孕震区大气中CH4浓度增加这一地震前兆进行监测。