Temperature Inversion and Clouds Over the Arctic Ocean Observed by the 5th Chinese National Arctic Research Expedition

The Arctic is of great significance to global weather and climate systems. However, its atmospheric conditions have yet to be fully understood, partly because of the lack of intensive observations. Here we reported on the characteristics of lower troposphere over the Arctic Ocean using high-resolution radiosonde data collected during the 5th Chinese National Arctic Research Expedition from July to September 2014. Statistical analyses showed that temperature inversion (TI) occurred most frequently below 700 m, without apparent temporal variability between morning and noon. In contrast, the occurrence frequency of morning surface-based inversion (SBI) was always higher than at noon in the whole boundary layer, whereas the elevated inversion (EI) frequency seemed much lower in the morning compared with at noon. More frequent deeper clouds tended to occur in the morning than at noon, which led to more frequent EI than SBI. SBI was found to dominate the clear-sky condition, whereas EI was generally observed under cloudy conditions. Regarding the seasonal variation, deep TI and clouds dominated during the first intensive observational period (IOP-1; July 21-31) because of warm advection in combination with heating effects induced by long-range transported black carbon (BC). During IOP-2 (August 1-18), synoptic scale subsidence prevailed, with frequent EI and SBI partly caused by BC accumulation over the Arctic Ocean. In comparison, more clouds and less TI occurred during IOP-3 (August 27-September 11) largely due to the outbreaking polar vortex. These observations contribute to a better understanding of vertical temperature and cloud structures under global warming.