Introduction to the surface albedo climatology

The figures below show plots of surface albedo or more specifically blue sky surface albedo. Surface albedo describes the fraction of shortwave radiation (sunlight) that is reflected at the surface of the Earth, therefore it impacts the climate of the Earth as it regulates the energy balance. The surface albedo is generally decreasing in the current global warming mainly due to the decrease of sea ice and snow cover. The decreasing surface albedo causes an increase of sunlight absorption and thus a further warming. This process is known as the surface albedo feedback.

The albedo of a specific surface depends on the angular distribution and spectral composition of the illumination. Blue sky surface albedo may be understood as the "actual" surface albedo; it is a weighted mean of the surface albedo under direct and diffuse illumination conditions. The data is provided in the satellite product CLARA-A3, from which we used the global monthly mean product. The surface albedo is only retrieved under sunlit and cloud-free conditions. Therefore, there is no data at high latitude regions in winter and monhtly means may be missing in regions with high cloud coverage.

Climatogical averages

The two plots below shows the 1991-2020 monthly mean surface albedo. The only filter applied to the data was a requirement of having at least 15 valid monthly mean surface albedo fields behind the computation of a climatological mean. Choose between different months in the menu below.

Monthly anomalies

The next two plots shows monthly mean anomalies relative to the 1991-2020 monthly mean shown above. Choose between different months in the menu below and use the drawbar to see the anomalies of different years.

Average polar albedo timeseries

We now show the average sea and sea ice surface albedo above the polar circle both in the Arctic and the Southern Ocean. In the Arctic, the average is calculated from the May, June and July. In the Southern Ocean the selected onths are November, December and January in a way where the 2000 mean includes November and December 2000 and January 2001.

The months are selected as they are subject to most solar illumination and therefore has the most observations. However, observationsa are still missing in some grid cells. To minimize resulting bias in the area-average, the missing data is interpolated using the inverse-distance interpolation method. The red bars in the background of the graphs shows the percentage of missing data before interpolation.

The time series of average Arctic sea and sea ice albedo shows a strong decrease. This is not seen in Southern Ocean, which is characterized by large variability, but no significant trend.

Surface albedo of a high sea ice concentration region

The final plots shows the 1979-2024 time series of the May, June, July average surface albedo above 85°N, where the missing data has been interpolated as described above. This is a region of very high sea ice concentration, but the albedo of the sea ice can still change if the surface properties change, e.g., in the case of increased melt ponds or changes in the snow cover.