Separating radiative forcing by aerosol–cloud interactions and rapid cloud adjustments in the ECHAM–HAMMOZ aerosol–climate model using the method of partial radiative perturbations
Separating radiative forcing by aerosol–cloud interactions and rapid cloud adjustments in the ECHAM–HAMMOZ aerosol–climate model using the method of partial radiative perturbations
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DOI：
10.5194/acp-19-15415-2019
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发表时间：
2019-12
影响因子：
6.3
通讯作者：
J. Mülmenstädt;E. Gryspeerdt;M. Salzmann;P. Ma;S. Dipu;J. Quaas
中科院分区：
文献类型：
--
作者：
J. Mülmenstädt;E. Gryspeerdt;M. Salzmann;P. Ma;S. Dipu;J. Quaas
抽象的。利用部分辐射摄动(PRP)方法中的离线辐射传输模拟方法，将ECHAM-HAMMOZ气溶胶气候模式中的气溶胶-云相互作用(ERFaci)的有效辐射强迫分解为人为的云滴数目变化和调整液水路径和云组分的辐射强迫。在−0.5 2和−0.5 3W m−2上，人为云滴数目变化和液态水路径调整所模拟的辐射强迫强度大致相等，而−0.31W m−2上的云量调整较弱(分别占ERFaci总量的38%、39%和2 3%)；在地理上，中国、副热带东部海洋边界、北大西洋和太平洋、欧洲和北美东部地区的3个ERFaci分量在地理上都较弱。空间相关分析表明，时间平均液态水路径调整与时间平均辐射强迫成正比，而云量调整与辐射强迫的关系不是很直接。虽然暖云ERFaci的估计对冰和暖云上的混合相云的处理相对不敏感，但有迹象表明，柱中对冰的更多限制处理导致液体水路径调整的估计幅度的低偏差和液滴数量强迫的估计幅度的高偏差。由于本工作是首次将气溶胶有效辐射强迫分解为辐射强迫和云的快速调整，因此进行了理想化的实验以证明PRP结果是准确的。实验表明，使用低频(日或月)时间平均模式输出的云性场低估了ERF，但3小时平均输出是足够频繁的。
Abstract. Using the method of offline radiative transfer modeling within the partial radiative perturbation (PRP) approach, the effective radiative forcing by aerosol–cloud interactions ( ERFaci ) in the ECHAM–HAMMOZ aerosol climate model is decomposed into a radiative forcing by anthropogenic cloud droplet number change and adjustments of the liquid water path and cloud fraction. The simulated radiative forcing by anthropogenic cloud droplet number change and liquid water path adjustment are of approximately equal magnitude at −0.52 and −0.53 W m−2 , respectively, while the cloud-fraction adjustment is somewhat weaker at −0.31 W m−2 (constituting 38 %, 39 %, and 23 % of the total ERFaci , respectively); geographically, all three ERFaci components in the simulation peak over China, the subtropical eastern ocean boundaries, the northern Atlantic and Pacific oceans, Europe, and eastern North America (in order of prominence). Spatial correlations indicate that the temporal-mean liquid water path adjustment is proportional to the temporal-mean radiative forcing, while the relationship between cloud-fraction adjustment and radiative forcing is less direct. While the estimate of warm-cloud ERFaci is relatively insensitive to the treatment of ice and mixed-phase cloud overlying warm cloud, there are indications that more restrictive treatments of ice in the column result in a low bias in the estimated magnitude of the liquid water path adjustment and a high bias in the estimated magnitude of the droplet number forcing. Since the present work is the first PRP decomposition of the aerosol effective radiative forcing into radiative forcing and rapid cloud adjustments, idealized experiments are conducted to provide evidence that the PRP results are accurate. The experiments show that using low-frequency (daily or monthly) time-averaged model output of the cloud property fields underestimates the ERF, but 3-hourly mean output is sufficiently frequent.