Abstract
Abstract. Spectral albedo of the snow surface in the visible/near-infrared range has been measured for 3 years by an automatic spectral radiometer installed at Dome C (75° S, 123° E) in Antarctica in order to retrieve the specific surface area (SSA) of superficial snow. This study focuses on the uncertainties of the SSA retrieval due to instrumental and data processing limitations. We find that when the solar zenith angle is high, the main source of uncertainties is the imperfect angular response of the light collectors. This imperfection introduces a small spurious wavelength-dependent trend in the albedo spectra which greatly affects the SSA retrieval. By modeling this effect, we show that for typical snow and illumination conditions encountered at Dome C, retrieving SSA with an accuracy better than 15 % (our target) requires the difference of response between 400 and 1100 nm to not exceed 2 %. Such a small difference can be achieved only by (i) a careful design of the collectors, (ii) an ad hoc correction of the spectra using the actual measured angular response of the collectors, and (iii) for solar zenith angles less than 75°. The 3-year time series of retrieved SSA features a 3-fold decrease every summer which is significantly larger than the estimated uncertainties. This highlights the high dynamics of near-surface SSA at Dome C.
Highlights
The summer surface energy budget on the ice sheets is largely controlled by the absorption of solar energy by snow (Van As et al, 2005; Ettema et al, 2010)
The objective of the present study is to describe the automatic spectral radiometer that we developed and installed at Dome C (75◦ S, 123◦ E) and the data processing developed to estimate time series of spectral albedo and specific surface area (SSA) from the raw irradiance measurements
We focus on the uncertainties of the estimated albedo and SSA
Summary
The summer surface energy budget on the ice sheets is largely controlled by the absorption of solar energy by snow (Van As et al, 2005; Ettema et al, 2010). G. Picard et al.: Spectral albedometer to estimate snow SSA face Radiation Network (BSRN) stations and some automatic weather stations deployed by the Institute of Marine and Atmospheric research (Utrecht University) provide time series of broadband albedo measured using upward- and downward-looking pyranometers. Picard et al.: Spectral albedometer to estimate snow SSA face Radiation Network (BSRN) stations and some automatic weather stations deployed by the Institute of Marine and Atmospheric research (Utrecht University) provide time series of broadband albedo measured using upward- and downward-looking pyranometers These sensors are subject to many artifacts such as imperfect response at high solar zenith angle, leveling and frost, which are difficult to correct (van den Broeke et al, 2004; Bogren et al, 2016).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
