▲ 作者：Bin Ma, Zhaohui Shang, Yi Hu, Keliang Hu, Yongjiang Wang, Xu Yang, Michael C. B. Ashley, Paul Hickson & Peng Jiang
▲ 連結：https://www.nature.com/articles/s41586-020-2489-0
▲ 摘要
南極高原上站點的特徵是在一個強而薄的邊界層之上的自由大氣中，湍流相對較弱。在此，我們報告夜晚使用差分圖像運動監視器在冰穹A得到的觀測結果。在海拔僅8米的地方，它記錄下的觀測數據低至0.13弧秒，提供的觀測數據可與冰穹C的20米高度的觀測數據相媲美。這表明邊界層在8米以下的時間佔31%，平均觀測時間為0.31弧秒，與自由大氣觀測一致。觀測和邊界層厚度與近地表溫度梯度有較強的相關性。這種相關性證實了從聲波雷達上發現的冰穹A邊界層的中值厚度約為14米。邊界層較薄，使得望遠鏡在其上方定位不那麼困難，因此可以更容易地進入自由大氣層。▲ Abstract
Sites on the Antarctic plateau are characterized by comparatively weak turbulence in the free atmosphere above a strong but thin boundary layer. Here we report measurements of night-time seeing at Dome A, using a differential image motion monitor. Located at a height of just 8 metres, it recorded seeing as low as 0.13 arcseconds, and provided seeing statistics that are comparable to those at a height of 20 metres at Dome C. This indicates that the boundary layer was below 8 metres for 31 per cent of the time, with median seeing of 0.31 arcseconds, consistent with free-atmosphere seeing. The seeing and boundary-layer thickness are found to be strongly correlated with the near-surface temperature gradient. The correlation confirms a median thickness of approximately 14 metres for the boundary layer at Dome A, as found from a sonic radar. The thinner boundary layer makes it less challenging to locate a telescope above it, thereby giving greater access to the free atmosphere.