Snow Albedo Seasonality and Trend from MODIS Sensor and Ground Data at Johnsons Glacier, Livingston Island, Maritime Antarctica

Abstract

The aim of this work is to investigate whether snow albedo seasonality and trend under all sky conditions at Johnsons Glacier (Livingston Island, Antarctica) can be tracked using the Moderate Resolution Imaging Spectroradiometer (MODIS) snow albedo daily product MOD10A1. The time span is from December 2006 to February 2015. As the MOD10A1 snow albedo product has never been used in Antarctica before, we also assess the performance for the MOD10A1 cloud mask. The motivation for this work is the need for a description of snow albedo under all sky conditions (including overcast days) using satellite data with mid-spatial resolution. In-situ albedo was filtered with a 5-day windowed moving average, while the MOD10A1 data were filtered using a maximum filter. Both in-situ and MOD10A1 data follow an exponential decay during the melting season, with a maximum decay of 0.049/0.094 day−1 (in-situ/MOD10A1) for the 2006–2007 season and a minimum of 0.016/0.016 day−1 for the 2009–2010 season. The duration of the decay varies from 85 days (2007–2008) to 167 days (2013–2014). Regarding the albedo trend, both data sets exhibit a slight increase of albedo, which may be explained by an increase of snowfall along with a decrease of snowmelt in the study area. Annual albedo increases of 0.2% and 0.7% are obtained for in-situ and MOD10A1 data, respectively, which amount to respective increases of 2% and 6% in the period 2006–2015. We conclude that MOD10A1 can be used to characterize snow albedo seasonality and trend on Livingston Island when filtered with a maximum filter.

Evaluation of the MODIS (C6) Daily Albedo Products for Livingston Island, Antarctic

“…Only these months were selected to avoid biases caused by seasonal variations and also because data availability is highly variable in the remaining months. Although MODIS describes the temporal evolution of the in situ data, a greater dispersion in the satellite data was observed, as already referred to by, among other authors, Stroeve et al [25] for Greenland and Calleja et al [12] for our study area. It has been shown that the best results with MODIS are obtained after the application of filters that correct for the increase in temporal variability with respect to in situ data, described among others by Calleja et al [12], Stroeve et al [25], and Box et al [20].…”

“…Figure 2 shows in situ albedo values, MOD10A1, MYD10A1, and MCD43 (BSA and WSA) for J-F-M. As can be seen, the distribution of the in situ data values is much more homogeneous than in the MODIS products, where extremely low values are observed. An increasing trend in albedo has been documented for the study area in the study period (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015) based on data from MOD10A1 C5 and in situ data [12]. With C6 data, in all cases, there is an increasing trend.…”

“…Albedo was measured at JG using two Kipp-Zonen CNR-1 pyranometers, one for incident radiation (global and direct) and another for reflected radiation. The pyranometers are placed 3 m above the snow and they are replaced each two years with calibrated ones [12]. Direct and diffuse radiation were obtained from the JCI station, which provides values of diffuse radiation (measured with KIPP-ZONEN CM11 pyranometers) and direct radiation (measured with KIPP-ZONEN CH1 pyranometers) each ten minutes…”

“…The RGB: 1-6-7 composition was used for the visualization, for which the central wavelength of these bands was 645, 1640, and 2130 nm, respectively. This composition is useful because it distinguishes the cloud pixels (in white) from the snow pixels (in red) [12,47].…”

“…Both studies were conducted with Advanced Very High Resolution Radiometer (AVHRR) data of 5 km spatial resolution. In addition, Calleja et al [12] studied the albedo evolution on Livingston Island, South Shetland Islands (SSI) archipelago, using data from Moderate Resolution Imaging Spectroradiometer (MODIS) snow albedo daily product (MOD10A1) (C5; 500 m of spatial resolution) and in situ data. These authors described an increasing albedo trend during the study period (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015) of 2% and 6%, in the in situ and MOD10A1 data, respectively.…”