Release of mercury from intertidal sediment to atmosphere in summer and winter

The release of mercury from intertidal sediment to atmosphere was studied based on the simulated experiment. The experiment samples were collected from the Haibo Estuary (S1) and the Licun Estuary (S2) of the Jiaozhou Bay in China,which are seriously polluted with mercury. The results show that the mercury in sediment releases rapidly to atmosphere under solar radiation. After 8 hours of solar radiation,mercury concentrations decrease from 5.62 μg/g and 2.92 μg/g to 2.34 μg/g and 1.39 μg/g in S1 and S2 sediments respectively in summer,and decrease from 5.62 μg/g and 2.92 μg/g to 4.58 μg/g and 2.13 μg/g respectively in winter. The mercury species in the sediment change markedly under solar radiation. The concentrations of mercury bound to organic matter decrease significantly from 2.73 μg/g to 0.31 μg/g in S1 and from 2.07 μg/g to 0.31 μg/g in S2,and the released mercury mainly comes from mercury bound to organic matter. Mercury flux shows distinguishing characteristic of diurnal change,and it increases rapidly in the morning with the rising of solar radiation intensity,but decreases in the afternoon. The mercury flux increases with sediment temperature and solar radiation intensity. The rapid release of mercury in intertidal sediment plays an important role in the regional mercury cycle.     

大气对AVHRR通道反射太阳辐射各向异性的影响

在不同太阳天顶角及不同地表条件下,通过辐射传输计算,考察了大气对NOAA/AVHRR可见和近红外通道辐射强度各向异性转换系数的影响。结果表明,在地表为朗伯面的情况下,大气气溶胶有增强辐射强度的各向异性和改变辐射强度角分布型式的作用。     

一种海面微波散射模式的迭代解

采用随机粗糙面上部分覆盖球形气泡的海面微波散射模式,将非均质大气中的光散射的辐射传输理论推广到此模式中去,得到了辐射强度满足的积分方程关系式。     

2002年南宁不同下垫面温度及紫外线辐射强度评价

对南宁2002年沥青、水泥等不同下垫面温度观测资料和紫外线辐射强度观测资料进行分析，结果表明：沥青、水泥日最高温度均比同期气温明显偏高；南宁属紫外线高辐射地区。     

筑物年预计雷击次数的计算及避雷针电磁辐射强度的危害分析

介绍了计算现代智能建筑物在 1a内可能遭到雷击损伤的次数 ,包括来自临近区域的雷电通过输入线路而引进过压损害 ;利用电磁辐射理论计算了避雷针接闪辐射强度。     

西北戈壁区夏季一次降水前后土壤温度变化规律分析

利用简单的土壤热传导方程建立模型,并结合小波变换方法,分析了2004年6月22日～8月18日金塔绿洲附近观测的戈壁土壤温度序列,重点关注地下10 cm的土壤温度变化.结果表明,在观测时段土壤温度除了有明显的日变化外,还存在周期为准4天和准两周的波动.利用滑动相关分析后发现,太阳向下短波辐射强度与土壤温度日变化能量存在显著的正相关,这与利用土壤热传导模型分析土壤日变化振幅年变化的相关研究的结论一致.太阳向下短波辐射强度与准4天周期波动实部分量在降水前后存在负相关关系.比较观测时段土壤温度准4天波动能量与同时期的天空温度,发现准4天波动可能与持续增强的云逆辐射有关.通过分析降水前后土壤温度、土壤含水量的变化,发现二者的日变化在降水后与降水前相比,振幅增大,位相前移.这一结果可以用土壤热扩散率在一定范围内随土壤含水量增大而增大得到解释.最后利用回归分析发现T10的准两周波动可能与更大范围的大气环流场异常有关.     

Simulation of snow processes beneath a boreal scots pine canopy

A physically-based multi-layer snow model Snow-Atmosphere-Soil-Transfer scheme(SAST)and a land surface model Biosphere-Atmosphere Transfer Scheme(BATS)were employed to investigate how boreal forests influence snow accumulation and ablation under the canopy.Mass balance and energetics of snow beneath a Scots pine canopy in Finland at different stages of the 2003-2004 and 2004 2005 snow seasons are analyzed.For the fairly dense Scots pine forest,drop-off of the canopy-intercepted snow contributes,in some cases,twice as much to the underlying snowpack as the direct throughfall of snow.During early winter snow melting,downward turbulent sensible and condensation heat fluxes play a dominant role together with downward net longwave radiation.In the final stage of snow ablation in middle spring,downward net all- wave radiation dominates the snow melting.Although the downward sensible heat flux is comparable to the net solar radiation during this period,evaporative cooling of the melting snow surface makes the turbulent heat flux weaker than net radiation.Sensitivities of snow processes to leaf area index(LAI)indicate that a denser canopy speeds up early winter snowmelt,but also suppresses melting later in the snow season. Higher LAI increases the interception of snowfall,therefore reduces snow accumulation under the canopy during the snow season;this effect and the enhancement of downward longwave radiation by denser foliage outweighs the increased attenuation of solar radiation,resulting in earlier snow ablation under a denser canopy.The difference in sensitivities to LAI in two snow seasons implies that the impact of canopy density on the underlying snowpack is modulated by interannual variations of climate regimes.     

恒星包层中平均辐射强度的计算

本讨论了中央激发源在其周围包层中产生的平均辐射强度的计算问题。计算表明,通常星云理论中计算平均辐射强度的公式仅适用于光学薄的情况，且光学浓度必须用从源表面开始计量的距离计算。在有物质抛射的恒星包层中，中央星产生的平均辐射强度必须严格计算，特别是在减速星风情况下，本提出了严格计算的公式。     

1991年5月10日太阳射电爆发中Spike辐射的准周期振荡特征

本文叙述了由北京天文台的射电高时间分辨率偏振计在2545MHz和 2645MHz频率上同时观测到的一个与日面光学耀斑共生的47GB型射电大爆发，并对它的辐射强度的准周期进行了研究。     

到达地面的太阳紫外辐射强度的观测

紫外辐射强度的公众服务一般用紫外线指数来表示，是衡量某地正午前后到达地面的太阳紫外辐射对人体皮肤（或眼睛）可能损害的程度指标,沱主要依赖于纬度，季节，平流层臭氧，云况，海拔，地面反照率和大气污染状态等条件，紫外线辐射强度的观测主要使用紫外光谱辐射计与滤光片式的紫外辐射表。