An observational study of the structure of the nocturnal boundary layer

Abstract

In an effort to describe the basic vertical structure of the nocturnal boundary layer, observations from four experiments are analyzed. During the night, the depth of significant cooling appears to increase with time while the depth of the turbulence and height of the low level wind maximum tend to remain constant or decrease with time. Since the inversion layer extends above the low level wind maximum and shear is small in the region of the low level jet, the Richardson number reaches a maximum at the jet level and then decreases again with height. As a result, turbulence is observed to be a minimum at the height of the low level wind maximum and then increases again above this height.

The interaction of katabatic winds and mountain waves

“…25 and a maximum in Ri at the katabatic flow jet. Mahrt (1979) corroborates high values of Ri at the jet due to a minimum in 6d6z in that region.…”

Determining Boundary-Layer Height from Aircraft Measurements

“…The SBL height is sometimes estimated from the vertical wind profile, using e.g. the height of the low-level wind-speed maximum, often referred to as the low-level jet (LLJ) (Melgarejo and Deardorff 1974;Mahrt et al 1979). However, as pointed out by Balsley et al (2006) and Meillier et al (2008), using the jet maximum to define the SBL top sometimes gives conflicting results.…”

Analytical description of a nocturnal low‐level jet

“…4 of Gifford, 1952;Table VI of Bonner, 1968; Fig. 10 of Mahrt et al, 1979;Fig. 1a,b of Arya, 1981;Fig.…”