A performance comparison between nonlinear similarity functions in bulk parameterization for very stable conditions

Three sets of nonlinear similarity functions for strong stability are selected to compare their performance in bulk parameterization. To uncover their advantages and disadvantages, theoretical and measurement analyses are made with four profile metrics and the Deacon number technique. Main disadvantages include the negligence of the different transfer efficiency between momentum and heat, the flux cutoff due to the upper limit in gradient Richardson number (Ri) and the ignorance of limited stability range where the dimensionless gradient functions ( and ) approach constants. Accordingly, three suggestions are made for future improvement. First, the functions for wind velocity and potential temperature should have the same function form, but with different coefficients. Second, and should approach constants only within a certain stability range. Third, the limit value in Ri should be avoided to widen their applicability in flux modeling. Furthermore, quantitative comparisons in transfer coefficients for moment and sensible heat (C _D and C _H) are made among the similarity functions in the bulk Richardson number (Ri _B) range 0 < Ri _B < 1. Generally, significant discrepancy is found, which may approach a factor of two and three at large Ri _B in C _D and C _H, respectively. Finally, a new recommendation is made to one of the three sets, mainly because of its ability to predict C _D and C _H that decrease rather slowly in very stable conditions.     

Comparisons of Measured and Modelled Ozone Deposition to Forests in Northern Europe

The performance of a new dry deposition module, developedfor the European-scale mapping and modelling of ozone flux to vegetation, was tested against micrometeorological ozone and water vapour flux measurements. The measurement data are for twoconiferous (Scots pine in Finland, Norway spruce in Denmark) and one deciduous forest (mountain birch in Finland). On average, themodel performs well for the Scots pine forest, if local inputdata are used. The daytime deposition rates are somewhat over-predicted at the Danish site, especially in the afternoon. The mountain birch data indicate that the generic parameterisationof stomatal responses is not very representative of this northernspecies. The module was also tested by using modelled meteorological data that constitute the input for a photochemical transport model.     

甲基汞的大气-水-土壤界面交换通量

通过模拟实验和野外实测,对甲基汞在大气－水和大气－土壤的界面交换进行了初步研究．结果表明,甲基汞释放通量与水中的甲基汞浓度有关,水－气体系中甲基汞释放通量大于水－土－气体系中甲基汞释放通量;甲基汞在大气－土壤界面的释放通量为０．２１～３．０９ｎｇ·ｍ^-2·ｈ^-1;在大气－水界面的释放通量为０．１４～０．７９ｎｇ·ｍ^-2·ｈ^-1．     

青岛近岸海域二甲基硫排放和大气中二甲基硫浓度变化

为研究我国受人为干扰严重的近岸海域DMS排放规律,利用固体吸附-解吸的富集采样方法和冷却预浓缩的分析方法,分别在2001年夏秋季和2002年春秋季,对青岛近岸海域海水和大气中的二甲基硫进行了采样和分析.结果表明,海水中DMS浓度和海气排放通量呈现明显的空间分布和季节变化.夏季,青岛近岸的海水DMS平均浓度最高,达1169.47 ng·L^-1;春季最低,只有226.99 ng·L^-1.河口区、风景旅游区和奥运赛场区在夏季有显著的从高到低的浓度梯度变化,而春秋季不明显.DMS海气排放通量主要由海水浓度决定,因此两者呈现一致的变化规律.海洋大气中的DMS也呈现夏季较高(256.44 ng·m^-3),秋季较低(195.64 ng·m^-3)的季节变化.文中还初步探讨了大气DMS的日变化情况.     

贵州红枫湖地区冷暖两季土壤/大气界面间汞交换通量的对比

采用动力学通量箱(Dynamic Flux Chamber,DFC)与高时间分辨率自动大气测汞仪联用技术,于2002年7月和2003年3月对红枫湖地区土壤/大气界面上汞交换通量进行了测定.夏冬2季土壤-大气汞的交换通量分别为(27.4±40.1)ng·(m²·h)^-1(n=255)和(5.6±19.4)ng·(m²·h)^-1(n=192).夏季汞交换通量和光照、气温及土壤温度的相关系数分别为0.74、0.83和0.80,而冬季分别为0.88、0.56和0.59.对比研究表明:暖季土壤向大气的释汞通量远高于冷季;2个季节光照、温度等气象因素对土壤/大气界面间汞交换均有重要的影响.     

秋季羰基硫在植物与大气间的交换

利用静态箱法研究了秋季羰基硫(COS)在六种北京常见树种与大气间的交换．结果表明：法国梧桐、槐树、龙爪槐、玉兰、柳树对COS有吸收,油松没有吸收,树木与大气间COS的交换通量受树种、环境温度、光照、COS初始浓度等因素的影响．一般来说．温度高、光照强时,以上树种与大气间COS的交换强;空气中COS初始浓度高时,植物对COS的吸收通量高,植物对COS的吸收达到饱和较植物对CO2的吸收以及异戊二烯的排放持续时间长．     

秋季COS和DMS在草坪与大气间的交换

利用静态箱法研究了羰基硫 (COS)和二甲基硫 (DMS)在绿化草坪与大气之间的交换 .在秋季 ,草坪对COS的吸收通量为 0 75— 1 4 5 μg·m- 2 ·h- 1 ,对DMS的排放通量为0 0 5— 0 35 μg·m- 2 ·h- 1 .COS和DMS的交换通量与环境温度、光照及初始浓度等因素有关 ,其中 ,周围大气COS的浓度对草坪吸收COS的影响最为明显 .草坪对COS的吸收通量与DMS的排放通量呈正相关 ,相关系数 (R2 )大于 0 7.此外 ,COS的垂直分布也表明草坪对COS具有明显的吸收作用     

巢湖二氧化碳排放特征及其潜在影响因素

为探讨浅水湖泊CO2排放的时空格局及与CDOM来源组成潜在关联机制,于1月(枯水期)、4月(平水期)、7月(丰水期)不同水文情景下富营养浅水巢湖进行野外观测,采用扩散系数—顶空瓶法观测表层水体CO2浓度(cCO2)和通量(FCO2),并探讨CO2排放的潜在驱动因素,尤其是对CDOM来源组成的响应机制.结果表明,巢湖全湖...     

MBR的工艺优势及应用发展

MBR被认为是21世纪最有发展前景的高新技术之一,被研究用于各种污水的治理。但MBR存在缺点,那就是膜污染问题,膜污染问题是阻碍MBR发展和更广泛使用的最大障碍。     

中国八大湖泊冬季水-气界面CO2通量

采用静态箱-气相色谱法对中国不同地区八个湖泊(洞庭湖、鄱阳湖、巢湖、南四湖、洪泽湖、抚仙湖、洱海、滇池)冬季水体的水-气界面CO2通量进行了24h连续观测。结果表明:冬季洞庭湖、巢湖、洱海和滇池24h均为大气CO2的汇,其通量分别为-23.78、-16.08、-24.38、-17.94mg·m-2·h-1;鄱阳湖、南四湖水体则为大气CO2的源,其通量分别为35.76、27.64mg·m-2·h-1;洪泽湖和抚仙湖在晴天时为大气CO2的汇,夜间或阴天为大气CO2的源,但从24h的平均通量来看,洪泽湖为大气CO2的汇,通量为-26.56mg·m-2·h-1;抚仙湖为大气CO2的源,通量16.01mg·m-2·h-1。