VARIABILITY OF NO AND NO2 ABOVE THE SNOWPACK AT SUMMIT, GREENLAND

• Main Author: Wang, Zhixin
• Format: Text
• Language: unknown
• Published: Digital Commons @ Michigan Tech 2015
• Subjects: diurnal cycle; nitrogen oxides; seasonal cycle; snowpack; summit; variability; Atmospheric Sciences; Arctic; Greenland; polar night
• Online Access: https://digitalcommons.mtu.edu/etds/1006; https://digitalcommons.mtu.edu/cgi/viewcontent.cgi?article=2007&context=etds

Nitric oxide (NO) and nitrogen dioxide (NO2) were measured at levels of approximately 7.5 m, 3 m, and 0.5 m above the surface snowpack at Summit, Greenland from July 2008 to July 2010, respectively, with two sets of instrument systems. Instrument I measured NO and NO2 at levels of 3 m and 0.5 m with two inlets, and instrument II measured NO and NO2 at a level of 7.5 m plus total reactive nitrogen oxides (NOy) at the same level with one inlet. Compared to previous measurements, the data provided the first year-round simultaneous record of NO and NO2 at different levels above the snowpack at a high latitude Arctic site. Apparent seasonal and diurnal cycles were observed for both NO and NO2 at different levels. NO reached high levels when solar radiation was high from late spring to summer in a seasonal scale and at around noon in a diurnal scale, while NO2 reached high levels from early spring to early fall in a seasonal scale and from afternoon to night in a diurnal scale. The vertical gradients of NO and NO2 between 3 m and 0.5 m above the snowpack suggested the emission of NO from the surface snowpack. An improved mechanism for snowpack photochemistry at Summit is proposed to explain the seasonal variability of NO and NO2. Furthermore, a pollution event study showed that FLEXPART retroplume simulations were in agreement with the measurements. During polar night season, NO2 exactly followed FLEXPART simulation. Nitrate accumulation through snowpack deposition was proposed to attribute NO2 increase in early spring. In sunlight season, nitrate deposition was proposed to occur during the pollution events and was re-emitted from the snowpack via photolysis after the event, resulting in subsequent NO2 increase.