Observing Earth critical zone processes in the Bayelva basin (CZO@Bayelva). Data represents the average values and the corresponding standard deviation of Net Ecosystem Exchange (NEE), Ecosystem Respiration (ER) and Gross Primary Productivity (GPP) obtained from two different sites in the tundra of the Bayelva river basin: One site (named CZ) is located in the vicinity of the Climate Change Tower. The other one (named "Airport") is in the vicinity of the Ny Alesund Airport. Each average value is obtained as a mean over a set of around 20 point measures for each plot and each sampling date. Flux data are complemented by measurements of soil temperature, soil volumetric water content, air temperature and relative humidity, and solar irradiance. CO2 fluxes are measured using a flux chamber and a LI-COR IRGA by means of the Dynamic Flux Chamber method.

The column water vapor or Precipitable Water Vapor (PWV) is measured at Thule Air Base (76.5°N, 68.8°W), Greenland, by means of a ground-based millimeter-wave spectrometer (GBMS) installed at 220 m a.s.l. The GBMS observes rotational lines of atmospheric molecules emitting between 230 and 280 GHz, with a spectral pass band of 600 MHz. The PWV is calculated from direct measurements of atmospheric opacity (tau) at the indicated frequencies by using the linear relation PWV = a+tau*b, where a and b depend only on frequency. Measurements have a temporal resolution of 15 minutes and are carried out continuously when the GBMS is operated.

Aerosol particles that can aid the formation of ice crystals in clouds are known as ice nucleating particles (INPs). These particles play a critical role in Arctic cloud formation and regional climate. However, it remains challenging for global climate models (GCMs) to well represent Arctic INPs. To understand the biases in the GCMs, we compare simulated results from a GCM with long-term meteorological, aerosol, and INP measurements at one surface station in Ny-Ålesund, Svalbard. We find that the simulated aerosol properties are biased from the observations within one order of magnitude, due to uncertainties in modeling physical and chemical aerosol processes. Using soil samples collected from Ny-Ålesund, we derived a new fit that relates local HLD with INP concentrations. This fit shows strong ice nucleating ability at warm temperatures, indicating the presence of organic matter in local HLD. Incorporating the new fit for local HLD INPs along with parameterizations representing INPs from other terrestrial and marine sources, our model reproduces measured INP concentrations reasonably well. Our comparison highlights the importance of local HLD to the Arctic INP population. Our findings emphasize the need for long-term Arctic measurements and better representation of HLD in GCMs to improve the understanding in Arctic INP properties and their role in Arctic cloud formation.