International atmospheric stations science drone aerial research measuring ozone O3, carbon methane CH4, carbon dioxide CO2, nitrogen oxides N2O, oxygen 02, water, mountain spruce Bily Kriz winter, sunshine pyranometer measurement incoming diffuse solar radiation, eddy covariance systems consist sonic anemometer scientific tower gas analyzer wind relevant gas fluctuations anemometer wind speed, air temperature humidity sensor, meteorological weather meteorology, monitoring technology