Question

During the First World War, an acute disruption of international telegraphic communications deprived Scandinavian meteorologists of vital weather reports from the Atlantic Ocean and western Europe. In response to this data deficit, the Norwegian physicist Vilhelm Bjerknes, alongside his son Jacob Bjerknes and collaborator Halvor Solberg, established the Bergen School of Meteorology in 1918. Rather than relying on traditional statistical climatology or sparse upper-air balloon soundings—which were prohibitively expensive and logistically impractical during wartime shortages—the Bergen group compensated by establishing an extraordinarily dense regional network of surface observation stations across southern Norway.

By systematically analyzing synchronous surface observations of barometric pressure, wind direction, and temperature variations from these closely spaced stations, Jacob Bjerknes identified that mid-latitude storms do not develop uniformly across homogeneous air masses. Instead, he observed that weather systems coalesce along sharp, narrow transition zones separating distinct air masses of polar and tropical origin. Drawing a conscious metaphor from the contemporary military terminology of the Western Front, the Bergen researchers coined the term 'fronts' to designate these boundaries. In their foundational 1919 and 1921 publications, they demonstrated that extratropical cyclones originate as small wave-like disturbances along a quasi-stationary polar front. As warm, moisture-laden air ascends over a wedge of denser, colder air, atmospheric pressure drops, amplifying the wave into a mature, rotating cyclonic vortex until the cold front eventually overtakes the warm front in a process they termed occlusion.

Although the Bergen School's conceptual framework eventually revolutionized global weather forecasting, it encountered substantial resistance from established meteorological institutions outside Scandinavia. Traditional meteorologists in Britain and Germany argued that purely two-dimensional surface observations could not capture the fundamentally three-dimensional thermodynamic processes governing atmospheric circulation. Critics specifically maintained that the appearance of distinct surface discontinuities was an artifact of local topography and surface friction rather than an intrinsic feature of large-scale tropospheric dynamics. It was not until the late 1930s, when regular aviation-based radiosonde soundings provided direct empirical verification of upper-tropospheric frontal structures, that the Bergen model gained universal international consensus.

According to the passage, the Bergen meteorologists established a dense regional network of surface observation stations primarily because