The article by Alfred K. Blackadar explores the phenomenon of boundary layer wind maxima and their significance for the growth of nocturnal inversions. The author notes that a sharp maximum in wind speed is frequently observed below 3000 feet at night, often associated with extremely large wind shear at low levels. This maximum is typically supergeostrophic and occurs at the top of the nocturnal inversion. The characteristic velocity profile promotes an orderly growth of the nocturnal inversion, with the supergeostrophic wind speeds suggesting the induction of inertia oscillations when the daytime mixing constraint is released around sunset. The article discusses the horizontal distribution of wind in these layers, which has led to the term "low-level jet" being used to describe the maximum in the vertical profile of wind speed. The occurrence of such maxima is widespread in the United States and is associated with various meteorological phenomena, including squall lines and severe weather. The low-level wind shear, while often a nuisance for aircraft, can be hazardous due to rapid loss of lift during descent. The author also examines the relationship between the geostrophic wind and the nocturnal inversion, finding that the wind speed at the level of the jet maximum is significantly supergeostrophic. This excess wind speed cannot be explained by the anticyclonic curvature of the contour field or changes in the horizontal temperature distribution. The article further discusses the stability of nocturnal inversions, suggesting that a jet-like profile with the wind maximum at the top of the inversion promotes orderly and controlled growth. The diurnal wind variations are attributed to the superposition of three wind systems: a circulation between the southwestern United States and its surroundings, a circulation between the plains and the mountains, and a circulation between the sea and the continent. The author proposes that after the nocturnal inversion begins to form, turbulent mixing rapidly dies away above the inversion, allowing heat and momentum to be transferred to the surface, leading to the continuous upward growth of the inversion. The article concludes with a detailed analysis of the deviations from the geostrophic wind, using data from O'Neill, Nebraska, to illustrate the periodic variations in wind speed and direction. The author suggests that refining the simplified explanation provided could improve predictions of wind profiles and that further studies are needed to understand the periodic variations in eddy viscosity.The article by Alfred K. Blackadar explores the phenomenon of boundary layer wind maxima and their significance for the growth of nocturnal inversions. The author notes that a sharp maximum in wind speed is frequently observed below 3000 feet at night, often associated with extremely large wind shear at low levels. This maximum is typically supergeostrophic and occurs at the top of the nocturnal inversion. The characteristic velocity profile promotes an orderly growth of the nocturnal inversion, with the supergeostrophic wind speeds suggesting the induction of inertia oscillations when the daytime mixing constraint is released around sunset. The article discusses the horizontal distribution of wind in these layers, which has led to the term "low-level jet" being used to describe the maximum in the vertical profile of wind speed. The occurrence of such maxima is widespread in the United States and is associated with various meteorological phenomena, including squall lines and severe weather. The low-level wind shear, while often a nuisance for aircraft, can be hazardous due to rapid loss of lift during descent. The author also examines the relationship between the geostrophic wind and the nocturnal inversion, finding that the wind speed at the level of the jet maximum is significantly supergeostrophic. This excess wind speed cannot be explained by the anticyclonic curvature of the contour field or changes in the horizontal temperature distribution. The article further discusses the stability of nocturnal inversions, suggesting that a jet-like profile with the wind maximum at the top of the inversion promotes orderly and controlled growth. The diurnal wind variations are attributed to the superposition of three wind systems: a circulation between the southwestern United States and its surroundings, a circulation between the plains and the mountains, and a circulation between the sea and the continent. The author proposes that after the nocturnal inversion begins to form, turbulent mixing rapidly dies away above the inversion, allowing heat and momentum to be transferred to the surface, leading to the continuous upward growth of the inversion. The article concludes with a detailed analysis of the deviations from the geostrophic wind, using data from O'Neill, Nebraska, to illustrate the periodic variations in wind speed and direction. The author suggests that refining the simplified explanation provided could improve predictions of wind profiles and that further studies are needed to understand the periodic variations in eddy viscosity.