100 Years of Progress in Boundary Layer Meteorology: A Condensed Version

100 years ago, our knowledge of the boundary layer was based on experience in agriculture, balloon and kite flights, and research on turbulence that was to accelerate in response to aviation. The diurnal cycle had been well-described near the surface and in the soil, it was known that low, protected areas got coldest on clear, calm nights, a well-mixed daytime boundary layer had been repeatedly documented, and the turning of wind with height in the atmospheric boundary layer (ABL) explained. Starting in the 1940s, near-surface flux-profile relationships based on semi-empirical relationships were developed. An increasingly sophisticated picture of the entire clear-air boundary layer emerged starting in the late 1960s, a result of the development of large eddy simulation, laboratory experiments, and aircraft with fast-response instruments to measure wind, temperature, and humidity. Important developments regarding the interaction of clouds with the subcloud layer began in the 1940s and 1950s, and with satellite remote sensing, lidars, and radar wind profilers, accelerated during and after the 1970s. During the subsequent decades, there was increased focus on evolving ABLs, ABLs over inhomogeneous surfaces, the nocturnal boundary layer, and ABLs in the Arctic and Antarctic. Much of this knowledge is incorporated in numerical schemes to describe the interaction of the ABL with the surface, low-level fluxes, and the ABL itself. Our focus here will be on a subset of this rich history, namely the development of flux-profile relationships in the lower boundary layer, the emergence of our understanding of the clear-air boundary layer, our emerging understanding of the boundary layer with clouds, and challenges and opportunities for the future.