Abstract
A long-term dataset of 38 years (1982–2019) from the Advanced Very High Resolution Radiometer (AVHRR) satellite observations is applied to investigate the spatio-temporal seasonal trends in cloud fraction, surface downwelling longwave flux, and surface upwelling longwave flux over the Arctic seas (60~90° N) by the non-parametric methods. The results presented here provide a further contribution to understand the cloud cover and longwave surface radiation trends over the Arctic seas, and their correlations to the shrinking sea ice. Our results suggest that the cloud fraction shows a positive trend for all seasons since 2008. Both surface downwelling and upwelling longwave fluxes present significant positive trends since 1982 with higher magnitudes in autumn and winter. The spatial distribution of the trends is nearly consistent between the cloud fraction and the surface longwave radiation, except for spring over the Chukchi and Beaufort Seas. We further obtained a significant negative correlation between cloud fraction (surface downwelling/upwelling longwave fluxes) and sea-ice concentration during autumn, which is largest in magnitude for regions with substantial sea ice retreat. We found that the negative correlation between cloud fraction and sea-ice concentration is not as strong as that for the surface downwelling longwave flux. It indicates the increase in cloudiness may result in positive anomalies in surface downwelling longwave flux which is highly correlated with the sea-ice retreat in autumn.
Highlights
Sea ice has been accepted to be the most significant component of the Arctic climate system
This study aims at further investigating the seasonal trends and variations in clouds and surface longwave radiation over the Arctic seas by the APP-x dataset from 1982 to 2019
Our work is focused on investigating the long-term seasonal variations and trends in cloud fraction and surface longwave radiation over the Arctic seas north of 60◦ N and further analyzing the potential correlations with the sea ice concentration in autumn
Summary
Sea ice has been accepted to be the most significant component of the Arctic climate system. Arctic climate is influenced by different physical parameters through negative or positive feedback [8,9,10,11]. Among these parameters, clouds and radiation, contributing to the Arctic sea-ice stability by the cloud-radiative process, have become the focus of studies [12,13,14,15]. Clouds and radiation, contributing to the Arctic sea-ice stability by the cloud-radiative process, have become the focus of studies [12,13,14,15] It is well-known that clouds have an important influence on the net surface
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