A linear CO chemistry parameterization in a chemistry-transport model: evaluation and application to data assimilation
A linear CO chemistry parameterization in a chemistry-transport model: evaluation and application to data assimilation
复制标题
DOI：
10.5194/acp-10-6097-2010
复制
发表时间：
2010-01-01
影响因子：
6.3
通讯作者：
Edwards, D. P.
中科院分区：
文献类型：
--
作者：
Claeyman, M.;Attie, J. -L.;Edwards, D. P.
本文基于一氧化碳（CO）连续性方程的一阶近似，对对流层和平流层的一种新的线性参数化方法进行了评价。该线性方案（以下简称LINCO）已在三维化学输运模型（CTM） MOCAGE （MOdele de Chimie Atmospherique Grande Echelle）中实现。首先，将一年半的LINCO模拟结果与详细的化学方案输出结果进行了比较。两种方案之间的平均差异在对流层约为+/- 25 ppbv（十亿分之一体积）或15%，在平流层为+/- 10 ppbv或100%。其次，LINCO已与覆盖对流层（对流层污染测量：MOPITT）和平流层（微波边缘测深仪：MLS）的卫星仪器以及主要在对流层上层和平流层下层飞行的飞机（空中客车在用飞机测量臭氧和水蒸气：MOZAIC计划）的各种观测结果进行了比较。在对流层，LINCO的季节变化以及垂直和水平分布与MOPITT CO观测值非常接近。然而，在700 hPa时，在LINCO和MOPITT之间观察到类似于-40 ppbv的偏置。在平流层中，MLS和LINCO呈现出类似的大尺度模式，但在模式低估了CO浓度的两极上空除外。在UTLS中，与独立的MOZAIC文件相比，LINCO呈现出小于2%的小偏差。第三，我们使用变分3D-FGAT（适当时间的首次猜测）方法与MOCAGE结合，对MOPITT CO进行了长达一年半的吸收。与独立的MOZAIC剖面相比，数据同化极大地改善了700 ~ 350 hPa对流层CO垂直分布。在146 hPa处，与MLS观测相比，同化CO的分布也得到改善，在热带地区的偏差减少了2倍。研究证实，线性格式能较好地模拟对流层和平流层下层CO的分布。因此，线性方案的低计算成本为在高分辨率和数年期间进行自由运行和CO数据同化运行开辟了新的前景。
This paper presents an evaluation of a new linear parameterization valid for the troposphere and the stratosphere, based on a first order approximation of the carbon monoxide (CO) continuity equation. This linear scheme (hereinafter noted LINCO) has been implemented in the 3-D Chemical Transport Model (CTM) MOCAGE (MOdele de Chimie Atmospherique Grande Echelle). First, a one and a half years of LINCO simulation has been compared to output obtained from a detailed chemical scheme output. The mean differences between both schemes are about +/- 25 ppbv (part per billion by volume) or 15% in the troposphere and +/- 10 ppbv or 100% in the stratosphere. Second, LINCO has been compared to diverse observations from satellite instruments covering the troposphere (Measurements Of Pollution In The Troposphere: MOPITT) and the stratosphere (Microwave Limb Sounder: MLS) and also from aircraft (Measurements of ozone and water vapour by Airbus in-service aircraft: MOZAIC programme) mostly flying in the upper troposphere and lower stratosphere (UTLS). In the troposphere, the LINCO seasonal variations as well as the vertical and horizontal distributions are quite close to MOPITT CO observations. However, a bias of similar to -40 ppbv is observed at 700 hPa between LINCO and MOPITT. In the stratosphere, MLS and LINCO present similar large-scale patterns, except over the poles where the CO concentration is underestimated by the model. In the UTLS, LINCO presents small biases less than 2% compared to independent MOZAIC profiles. Third, we assimilated MOPITT CO using a variational 3D-FGAT (First Guess at Appropriate Time) method in conjunction with MOCAGE for a long run of one and a half years. The data assimilation greatly improves the vertical CO distribution in the troposphere from 700 to 350 hPa compared to independent MOZAIC profiles. At 146 hPa, the assimilated CO distribution is also improved compared to MLS observations by reducing the bias up to a factor of 2 in the tropics. This study confirms that the linear scheme is able to simulate reasonably well the CO distribution in the troposphere and in the lower stratosphere. Therefore, the low computing cost of the linear scheme opens new perspectives to make free runs and CO data assimilation runs at high resolution and over periods of several years.