Impact of vertical resolution on the transport of passive tracers in the ECHAM4 model
Impact of vertical resolution on the transport of passive tracers in the ECHAM4 model
复制标题
垂直分辨率对 ECHAM4 模型中被动示踪剂传输的影响
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
R. Sausen
中科院分区：
文献类型：
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作者：
C. Land;J. Feichter;R. Sausen
采用两种不同垂直分辨率的环流模式ECHAM4模拟了被动示踪剂14CO2和SF6的输移过程：19层模式的标准模式（L19）和39层模式的高分辨率模式（L39）。我们研究了垂直分辨率对模拟输运特性的影响。两种模式都能捕获对流层中观测到的SF6浓度，但在平流层中SF6混合比被高估了。L39通常比L19计算出更高的平流层SF6混合比。这种偏差随着高度的增加而增加。模拟剖面之间的差异部分归因于L39比L19强的剩余平均经向环流，部分归因于初始全球恒定SF6浓度。模拟的14CO2表面浓度和垂直剖面与观测值的比较表明，气候模式ECHAM4中垂直分辨率的增加降低了平流层-对流层交换的强度。L39比L19更能反映对流层顶的急剧梯度。这导致通过对流层顶的向下输送减弱。然而，与观测结果相比，即使在L39模拟中，下行输运仍然太强。
Abstract The transport of the passive tracers 14CO2 and SF6 has been modelled with two versions of the general circulation model ECHAM4 with different vertical resolutions: the standard model with 19 model layers (L19) and a higher-resolution version with 39 layers (L39). We study the impact of vertical resolution on the modelled transport characteristics. Both models are able to capture the observed SF6concentrations in the troposphere, but in the stratosphere the SF6 mixing ratios are overestimated. L39 generally calculates higher stratospheric SF6 mixing ratios than L19. This deviation increases with altitude. The difference between the modelled profiles is partly attributed to the residual mean meridional circulation, which is stronger in L39 than in L19, and partly to the initial globally constant SF6 concentration. The comparison of modelled 14CO2 surface concentrations and vertical profiles with observations has shown that an increased vertical resolution in the climate model ECHAM4 reduces the strength of stratosphere–troposphere exchange. L39 allows a better representation of sharp gradients at the tropopause than L19. This results in a weaker downward transport across the tropopause. However, compared to observations the downward transport is still too strong even in the L39 simulation.