Abstract
Snow-induced radiative forcing (SnRF), defined as the instantaneous perturbation of the Earth’s shortwave radiation at the top of the atmosphere (TOA), results from variations in the terrestrial snow cover extent (SCE), and is critical for the regulation of the Earth’s energy budget. However, with the growing seasonal divergence of SCE over the Northern Hemisphere (NH) in the past two decades, novel insights pertaining to SnRF are lacking. Consequently, the contribution of SnRF to TOA shortwave radiation anomalies still remains unclear. Utilizing the latest datasets of snow cover, surface albedo, and albedo radiative kernels, this study investigated the distribution of SnRF over the NH and explored its changes from 2000 to 2019. The 20-year averaged annual mean SnRF in the NH was −1.13 ± 0.05 W m−2, with a weakening trend of 0.0047 Wm−2 yr−1 (p < 0.01) during 2000–2019, indicating that an extra 0.094 W m−2 of shortwave radiation was absorbed by the Earth climate system. Moreover, changes in SnRF were highly correlated with satellite-observed TOA shortwave flux anomalies (r = 0.79, p < 0.05) during 2000–2019. Additionally, a detailed contribution analysis revealed that the SnRF in snow accumulation months, from March to May, accounted for 58.10% of the annual mean SnRF variability across the NH. These results can assist in providing a better understanding of the role of snow cover in Earth’s climate system in the context of climate change. Although the rapid SCE decline over the NH has a hiatus for the period during 2000–2019, SnRF continues to follow a weakening trend. Therefore, this should be taken into consideration in current climate change models and future climate projections.
Highlights
Snow cover is an integral component of the cryosphere and represents one of the three essential climate variables (ECVs) for snow in the Global Climate Observing System (GCOS) [1], which plays a crucial role in the Earth’s climate system by regulating the surface energy budget [2,3,4]
We verified the performance of the C3S surface albedo through a cross-comparison with the snow cover dataset
We calculated the variabilities of the annual mean snow-induced radiative forcing (Sn RF) and identified the dominant month that controlled the annual mean Sn RF
Summary
Snow cover is an integral component of the cryosphere and represents one of the three essential climate variables (ECVs) for snow in the Global Climate Observing System (GCOS) [1], which plays a crucial role in the Earth’s climate system by regulating the surface energy budget [2,3,4]. As a result of the high reflectivity of snow cover, the presence or absence of snow cover plays a key role in the regulation of the heating and cooling patterns of the Earth’s surface, more than any other land surface category. The reduced reflected shortwave radiation at the top of the atmosphere (TOA) is known as snow-induced radiative forcing (Sn RF) [2,5,6], which is critical for regulating Earth’s energy budget. The reduced reflected shortwave radiation at the top of the atmosphere (TOA) is known as snow-induced radiative forcing (Sn RF) [2,5,6], which is critical for regulating Earth’s energy budget. 4.0/).
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