The correct answer is that it is the nation's primary weather-observing network.
The ASOS (Automated Surface Observing System) units are the automated sensor suites, which are created to serve aviation and meteorological requirements. There are presently more than 900 ASOS locations in the United States.
These systems usually report at hourly intervals, however, it also reports unique observations if weather conditions modify briskly and cross aviation operation thresholds. The ASOS functions as a main climatological observing network in the United States.
