Total surface shortwave flux distributions 1901-2017 in support of carbon cycle modelling.

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 and stratospheric 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. 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 stratospheric aerosol optical depth is taken from the climatology by Sato et al. (doi:10.1029/93JD02553, 1993), which has been updated to 2012. Years 2013-2017 are assumed to be background years so replicate background year 2010. That assumption is supported by the Global Space-based Stratospheric Aerosol Climatology time series (1979-2016; Thomason et al., doi:10.5194/essd-10-469-2018, 2018). 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年时段内逐6小时的总向下短波辐射通量分布。辐射传输计算基于对流层与平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。研究方法参考了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。
对流层气溶胶光学厚度的分品类时间序列取自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。为修正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比例缩放，使其与2003—2017年期间通过大气成分CAMS再分析（Inness等人，doi:10.5194/acp-19-3515-2019, 2019）得到的全球月平均数据一致——该再分析数据同化了气溶胶光学厚度的卫星反演结果。
平流层气溶胶光学厚度的时间序列取自Sato等人1993年的气候学数据集（doi:10.1029/93JD02553, 1993），该数据集已更新至2012年。2013—2017年被设为背景年份，采用2010年作为背景年的复制数据。这一假设得到了全球天基平流层气溶胶气候学时间序列（1979—2016年；Thomason等人，doi:10.5194/essd-10-469-2018, 2018）的支持。
云量的时间序列通过对日本再分析（JRA；Kobayashi等人，doi:10.2151/jmsj.2015-001, 2015）模拟得到的逐6小时云量分布进行比例缩放得到，使其与CRU TS v4.03数据集（Harris等人，doi:10.1038/s41597-020-0453-3, 2020）中的月平均云量相匹配。
地表辐射通量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与云存在相互作用，且这些气溶胶-云相互作用的辐射效应与对流层气溶胶的气溶胶-辐射相互作用的辐射效应成比例，比例因子取自HadGEM2-ES的模拟结果。除气溶胶和云之外的大气成分被设置为恒定的标准中纬度夏季大气状态。