Constraining cloud lifetime effects of aerosols using A‐Train satellite observations
Constraining cloud lifetime effects of aerosols using A‐Train satellite observations
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DOI：
10.1029/2012gl052204
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发表时间：
2012-08
影响因子：
5.2
通讯作者：
Minghuai Wang;S. Ghan;Xiaohong Liu;T. L’Ecuyer;Kai Zhang;H. Morrison;M. Ovchinnikov;R. Easter;R. Marchand;D. Chand;Y. Qian;J. Penner
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文献类型：
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作者：
Minghuai Wang;S. Ghan;Xiaohong Liu;T. L’Ecuyer;Kai Zhang;H. Morrison;M. Ovchinnikov;R. Easter;R. Marchand;D. Chand;Y. Qian;J. Penner
在估算过去和未来气候变化的辐射强迫时，气溶胶的间接效应仍然是最大的不确定性。对云寿命效应的观测限制尤其具有挑战性，因为很难将气溶胶效应与气象影响分开。在这里，我们使用了三个全球气候模型，包括一个多尺度气溶胶-气候模型PNNL - MMF，来表明降水概率对气溶胶负荷的依赖，称为降水频率敏感性（Spop），是对气溶胶扰动（λ）的液态水路径响应的一个很好的测量，因为Spop和λ都强烈依赖于自转换的大小，这是一种通过云滴之间的碰撞形成降水的模型。这提供了一种利用卫星观测来约束全球气候模式中的云寿命效应的方法。根据CloudSat、MODIS和AMSR - E观测估计的海洋云的Spopin比全球气候模式估计的要低得多，这表明云凝结核浓度加倍会使液态水路径增加不到5%。这意味着气溶胶间接效应对海洋上空短波云辐射强迫的影响比目前全球气候模式模拟的要小得多（传统气溶胶气候模式的影响减少了三分之一）。需要进一步的工作来量化卫星衍生的spop估计中的不确定性，并检验Spopin高分辨率模型。
Aerosol indirect effects have remained the largest uncertainty in estimates of the radiative forcing of past and future climate change. Observational constraints on cloud lifetime effects are particularly challenging since it is difficult to separate aerosol effects from meteorological influences. Here we use three global climate models, including a multi‐scale aerosol‐climate model PNNL‐MMF, to show that the dependence of the probability of precipitation on aerosol loading, termed the precipitation frequency susceptibility (Spop), is a good measure of the liquid water path response to aerosol perturbation (λ), as both Spop and λ strongly depend on the magnitude of autoconversion, a model representation of precipitation formation via collisions among cloud droplets. This provides a method to use satellite observations to constrain cloud lifetime effects in global climate models. Spopin marine clouds estimated from CloudSat, MODIS and AMSR‐E observations is substantially lower than that from global climate models and suggests a liquid water path increase of less than 5% from doubled cloud condensation nuclei concentrations. This implies a substantially smaller impact on shortwave cloud radiative forcing over ocean due to aerosol indirect effects than simulated by current global climate models (a reduction by one‐third for one of the conventional aerosol‐climate models). Further work is needed to quantify the uncertainties in satellite‐derived estimates ofSpop and to examine Spopin high‐resolution models.