Benchmark Calculations of Radiative Forcing by Greenhouse Gases
Benchmark Calculations of Radiative Forcing by Greenhouse Gases
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DOI：
10.1029/2020jd033483
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发表时间：
2020-12-16
影响因子：
4.4
通讯作者：
Tellier, Yoann
中科院分区：
文献类型：
--
作者：
Pincus, Robert;Buehler, Stefan A.;Tellier, Yoann
温室气体浓度的变化导致整个大气中辐射通量的变化。这种变化的值，即瞬时辐射强迫，在不同的气候模型中有所不同，部分原因是模型之间云、湿度和温度分布的差异，部分原因是辐射传输的近似处理引入的误差。本文介绍了辐射强迫模型比对项目中的一项实验，该实验使用逐行模型进行的基准计算来识别温室气体吸收和排放表示中的参数化误差。晴空温室气体瞬时强迫是使用一组 100 个剖面来计算的，这些剖面是从对当前条件的重新分析中选出的，代表了从工业化前时期到现在的全球年平均强迫，采样误差小于 0.01 W m(-2)。六个贡献的逐行模型一致认为这种强迫在 0.025 W m(-2) 以内，而即使是最近开发的参数化也具有 4 倍或更多倍的典型误差，这表明样本揭示了逐行模型之间的真正差异，并且参数化误差将很容易识别。逐行模型之间的一致性在长波中比在短波中更好，其中水蒸气连续体的不同处理会影响二氧化碳和甲烷强迫的估计。云对瞬时辐射强迫的影响是通过气候模型模拟来估计的，平流层温度变化引起的调整是通过假设固定的动态加热来估计的。仅对臭氧和二氧化碳的调整较大，平流层冷却会引入适度的非线性。
Changes in concentrations of greenhouse gases lead to changes in radiative fluxes throughout the atmosphere. The value of this change, the instantaneous radiative forcing, varies across climate models, due partly to differences in the distribution of clouds, humidity, and temperature across models and partly due to errors introduced by approximate treatments of radiative transfer. This paper describes an experiment within the Radiative Forcing Model Intercomparision Project that uses benchmark calculations made with line-by-line models to identify parameterization error in the representation of absorption and emission by greenhouse gases. Clear-sky instantaneous forcing by greenhouse gases is computed using a set of 100 profiles, selected from a reanalysis of present-day conditions, that represent the global annual mean forcing from preindustrial times to the present day with sampling errors of less than 0.01 W m(-2). Six contributing line-by-line models agree in their estimate of this forcing to within 0.025 W m(-2) while even recently developed parameterizations have typical errors 4 or more times larger, suggesting both that the samples reveal true differences among line-by-line models and that parameterization error will be readily identifiable. Agreement among line-by-line models is better in the longwave than in the shortwave where differing treatments of the water vapor continuum affect estimates of forcing by carbon dioxide and methane. The impacts of clouds on instantaneous radiative forcing are estimated from climate model simulations, and the adjustment due to stratospheric temperature changes estimated by assuming fixed dynamical heating. Adjustments are large only for ozone and for carbon dioxide, for which stratospheric cooling introduces modest nonlinearity.