The impact of parameterising light penetration into snow on the photochemical production of NO x and OH radicals in snow
The impact of parameterising light penetration into snow on the photochemical production of NO x and OH radicals in snow
复制标题
参数化雪中光穿透对雪中 NO x 和 OH 自由基光化学产生的影响
DOI：
10.5194/acp-15-7913-2015
复制
发表时间：
2015
影响因子：
6.3
通讯作者：
M. Frey
中科院分区：
文献类型：
--
作者：
H. Chan;M. King;M. Frey
抽象的。雪的光化学过程驱动积雪中化学微量气体的产生，包括氮氧化物（NOx = NO + NO2）和氢氧化物自由基（HOx = OH + HO 2），然后将其释放到低层大气中。在全球尺度上，这些过程的耦合大气-雪模拟需要雪中光化通量的简单参数化，以减少计算成本。物理辐射传输（RT）方法和参数化的基础上的电子折叠的光化通量在雪中的深度之间的分歧进行了评估。特别是，硝酸根阴离子（NO3-），亚硝酸根阴离子（NO2-）和过氧化氢（H2 O2）在雪和二氧化氮（NO2）在积雪间隙空气的光解被认为是。从积雪的排放通量估计为产品的深度集成的光解速率系数，v，和在雪中的光解前体的浓度。深度积分光解速率系数（a）用RT模型（TUV）vTUV明确计算，和（B）用基于e折叠深度vze的简单参数化计算。用于评价的度量是基于由这两种方法确定的深度积分光解速率系数的比率vTUV/vze与1的偏差。该比率主要取决于峰的位置在光解作用光谱的化学物种，太阳天顶角和物理性质的积雪，即强烈依赖于光散射截面和光吸收杂质（即黑碳和HULIS）的质量比与密度的弱依赖性。对于NO_2、NO_2-、NO_3-和H_2O_2的光解，vTUV/vze的比值分别为0.82-1.35、0.88-1.28、0.93-1.27和0.91-1.28。与RT方法相比，e-折叠深度参数化低估了小太阳天顶角，高估了太阳天顶角约60°。提出了一种简单的算法来改进参数化，使NO_2、NO_2-、NO_3-和H_2O_2光解的vTUV/vze比值分别降低到0.97-1.02、0.99 -1.02、0.99-1.03和0.98-1.06。的e-折叠深度参数化可能会得到可接受的结果，在寒冷的极地雪与大太阳天顶角的NO3-阴离子和H2 O2的光解，但它可以通过基于太阳天顶角和多云的天空的校正得到改善。
Abstract. Snow photochemical processes drive production of chemical trace gases in snowpacks, including nitrogen oxides (NOx = NO + NO2) and hydrogen oxide radical (HOx = OH + HO2), which are then released to the lower atmosphere. Coupled atmosphere–snow modelling of theses processes on global scales requires simple parameterisations of actinic flux in snow to reduce computational cost. The disagreement between a physical radiative-transfer (RT) method and a parameterisation based upon the e-folding depth of actinic flux in snow is evaluated. In particular, the photolysis of the nitrate anion (NO3-), the nitrite anion (NO2-) and hydrogen peroxide (H2O2) in snow and nitrogen dioxide (NO2) in the snowpack interstitial air are considered. The emission flux from the snowpack is estimated as the product of the depth-integrated photolysis rate coefficient, v, and the concentration of photolysis precursors in the snow. The depth-integrated photolysis rate coefficient is calculated (a) explicitly with an RT model (TUV), vTUV, and (b) with a simple parameterisation based on e-folding depth, vze. The metric for the evaluation is based upon the deviation of the ratio of the depth-integrated photolysis rate coefficient determined by the two methods, vTUV/vze, from unity. The ratio depends primarily on the position of the peak in the photolysis action spectrum of chemical species, solar zenith angle and physical properties of the snowpack, i.e. strong dependence on the light-scattering cross section and the mass ratio of light-absorbing impurity (i.e. black carbon and HULIS) with a weak dependence on density. For the photolysis of NO2, the NO2- anion, the NO3- anion and H2O2 the ratio vTUV/vze varies within the range of 0.82–1.35, 0.88–1.28, 0.93–1.27 and 0.91–1.28 respectively. The e-folding depth parameterisation underestimates for small solar zenith angles and overestimates at solar zenith angles around 60° compared to the RT method. A simple algorithm has been developed to improve the parameterisation which reduces the ratio vTUV/vze to 0.97–1.02, 0.99–1.02, 0.99–1.03 and 0.98–1.06 for photolysis of NO2, the NO2- anion, the NO3- anion and H2O2 respectively. The e-folding depth parameterisation may give acceptable results for the photolysis of the NO3- anion and H2O2 in cold polar snow with large solar zenith angles, but it can be improved by a correction based on solar zenith angle and for cloudy skies.