Abstract
The paper presents a comparison of sea ice concentration (SIC) derived from satellite microwave radiometry data and dedicated ship observations. For the purpose, the NASA Team (NT), Arctic Radiation and Turbulence Interaction Study (ARTIST) Sea Ice (ASI), and Variation Arctic/Antarctic Sea Ice Algorithm 2 (VASIA2) algorithms were used as well as the database of visual ice observations accumulated in the course of 15 Arctic expeditions. The comparison was performed in line with the SIC gradation (in tenths) into very open (1–3), open (4–6), close (7–8), very close and compact (9–10,10) ice, separately for summer and winter seasons. On average, in summer NT underestimates SIC by 0.4 tenth as compared to ship observations, while ASI and VASIA2 by 0.3 tenth. All three algorithms overestimate total SIC in regions of very open ice and underestimate it in regions of close, very close, and compact ice. The maximum average errors are typical of open ice regions that are most common in marginal ice zones. In winter, NT and ASI also underestimate SIC on average by 0.4 and 0.8 tenths, respectively, while VASIA2, on the contrary, overestimates by 0.2 tenth against the ship data, however, for open and close ice the average errors are significantly higher than in summer. In the paper, we also estimate the impact of ice melt stage and presence of new ice and nilas on SIC derived from NT, ASI, and VASIA2.
Highlights
Every year, persistent ice cover forms on the surface of the Arctic seas due to harsh climate conditions typical of the polar regions
The NASA Team (NT), Arctic Radiation and Turbulence Interaction Study (ARTIST) Sea Ice (ASI), and Variation Arctic/Antarctic Sea Ice Algorithm 2 (VASIA2) algorithms were used as well as the database of visual ice observations accumulated in the course of 15 Arctic expeditions
We estimate the impact of ice melt stage and presence of new ice and nilas on sea ice concentration (SIC) derived from NT, ASI, and VASIA2
Summary
Persistent ice cover forms on the surface of the Arctic seas due to harsh climate conditions typical of the polar regions. Many algorithms have been developed to retrieve sea ice concentration (SIC) from passive microwave remote sensing data [7]. Shipboard visual observations are conducted once per hour (or per three hours) According to this method, ice condition is determined at one point every 10–20 km, depending on the speed of the ship in ice [20,24]. We evaluate NASA Team (NT), Arctic Radiation and Turbulence Interaction Study (ARTIST) Sea Ice (ASI), and Variation Arctic/Antarctic Sea Ice Algorithm 2 (VASIA2) against ship data obtained in various seasons, and demonstrate the effects of ice melt and presence of new ice and nilas on the difference in SIC estimation
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