Spring and summertime diurnal surface ozone fluxes over the polar snow at Summit, Greenland

Continuous surface-layer ozone flux measurements over the polar, year-round snowpack at Summit, Greenland, resulted in deposition velocities (v(d)) that were smaller than most previous assumptions and model inputs. Substantial seasonal differences were seen in the ozone v(d) behavior. Spring, daytime ozone v(d) values showed low variability and were consistently <= 0.01 cm s(-1). During summer, ozone fluxes displayed distinct diurnal cycles, and evidence for regular occurrences of bi-directional behavior. Summer, daytime v(d) ranged between similar to 0.01 to 0.07 cm s(-1). Maximum summertime downward fluxes (ozone deposition) coincided with the hours of maximum solar radiation, i.e., noon afternoon. During summer nighttime hours upward ozone fluxes were observed. These upward fluxes were interpreted as ozone production in a shallow layer near and above the snow surface with resulting upward ozone fluxes out of the shallow surface layer. Comparisons with published observations from temperate, midlatitude sites suggest different controls and behavior of ozone fluxes, and that ozone fluxes over snow depend on a myriad of parameters, including solar irradiance, snow chemical and physical properties, snowpack depth, and the type of substrate underneath the snow. Citation: Helmig, D., L. D. Cohen, F. Bocquet, S. Oltmans, A. Grachev, and W. Neff (2009), Spring and summertime diurnal surface ozone fluxes over the polar snow at Summit, Greenland, Geophys. Res. Lett., 36, L08809, doi:10.1029/2008GL036549.