Total surface shortwave flux distributions 1901-2017 in support of carbon cycle modelling: No stratospheric aerosols

This dataset offers 6-hourly distributions of the total downward shortwave flux over the period 1901-2017. Radiative transfer calculations are based on monthly-averaged distributions of tropospheric aerosol optical depth, and 6-hourly distributions of cloud fraction. Methods follow those described in the Methods section of Mercado et al. (doi:10.1038/nature07949, 2009), but with updated input datasets. This version of the dataset excludes the radiative effects of stratospheric aerosols. The time series of speciated tropospheric aerosol optical depth is taken from the historical and RCP8.5 simulations by the HadGEM2-ES climate model (Bellouin et al., doi:10.1029/2011JD016074, 2011). To correct for biases in HadGEM2-ES, tropospheric aerosol optical depths are scaled over the whole period to match the global and monthly averages obtained over the period 2003-2017 by the CAMS Reanalysis of atmospheric composition (Inness et al., doi:10.5194/acp-19-3515-2019, 2019), which assimilates satellite retrievals of aerosol optical depth. The time series of cloud fraction is obtained by scaling the 6-hourly distributions simulated in the Japanese Reanalysis (JRA; Kobayashi et al., doi:10.2151/jmsj.2015-001, 2015) to match the monthly-averaged cloud cover in the CRU TS v4.03 dataset (Harris et al. doi:10.1038/s41597-020-0453-3, 2020). Surface radiative fluxes account for aerosol-radiation interactions from both tropospheric and stratospheric aerosols, and for aerosol-cloud interactions from tropospheric aerosols, except mineral dust. Tropospheric aerosols are also assumed to exert interactions with cloud. The radiative effects of those aerosol-cloud interactions are assumed to scale with the radiative effects of aerosol-radiation interactions of tropospheric aerosols, using regional scaling factors derived from HadGEM2-ES. Atmospheric constituent other than aerosols and clouds are set to a constant standard mid-latitude summer atmosphere.

本数据集提供了1901-2017年间逐6小时的总向下短波通量分布。辐射传输计算基于对流层气溶胶光学厚度的月平均分布，以及云量的逐6小时分布。计算方法参照Mercado等人2009年发表于《自然》（doi:10.1038/nature07949, 2009）的方法章节，但采用了更新后的输入数据集。本版本数据集未纳入平流层气溶胶的辐射效应。对流层气溶胶光学厚度的分物种时间序列取自HadGEM2-ES气候模型（Bellouin等人，doi:10.1029/2011JD016074, 2011）的历史情景与RCP8.5情景模拟结果。为校正HadGEM2-ES的模拟偏差，研究人员对整个研究时段的对流层气溶胶光学厚度进行了缩放，以匹配2003-2017年间通过大气成分CAMS再分析（Inness等人，doi:10.5194/acp-19-3515-2019, 2019）得到的全球逐月平均结果——该再分析数据同化了气溶胶光学厚度的卫星反演产品。云量的时间序列则通过对日本再分析（Japanese Reanalysis，JRA；Kobayashi等人，doi:10.2151/jmsj.2015-001, 2015）的逐6小时模拟结果进行缩放得到，以匹配CRU TS v4.03数据集（Harris等人，doi:10.1038/s41597-020-0453-3, 2020）中的月平均云量。地表辐射通量同时考虑了对流层与平流层气溶胶的气溶胶-辐射相互作用，以及对流层气溶胶（矿物粉尘除外）的气溶胶-云相互作用。研究同时假设对流层气溶胶会与云发生相互作用，且这类气溶胶-云相互作用的辐射效应可通过基于HadGEM2-ES推导得到的区域缩放因子，与对流层气溶胶的气溶胶-辐射相互作用的辐射效应建立缩放关系。除气溶胶与云之外的大气成分均设置为恒定的标准中纬度夏季大气状态。