After the approximate mean, the mean backscatter value of the profile between 200 and 400 m above the surface (S300) is compared to a predefined threshold value (T300). For T300, we used a value of 1.0 × 10?6 m?1sr?1 for ICESat-2 and 1.0 × 10?7 m?1sr?1 for CATS (since CATS uses 1,064 nm and molecular scattering at this wavelength is an order of magnitude lower). If S300 is less than T300, no attempt is made to determine the PBLH for this average profile (PBLH is set to zero). This condition occurs when there are enough opaque clouds above it due to the approximate average distance to significantly attenuate the signal. If the average value of 200 to 400 m is greater than T300, the profile 300 m above the surface shall be examined and continued upwards until two successive containers fall below a second threshold (Ttop) defined at 0,70xS300. If this condition occurs less than 7 (4) km above the surface above land (water), the first container (lower height) of the 2 consecutive containers determines the PBLH. If this state is not reached within 7 (or 4) km of the surface, PBLH is set to zero. If the resulting PBLH is nonzero at coarse resolution, it is used to define a 1 km wide vertical window around which fine medium profiles are sought for PBLH. The fine search starts at the bottom of the 1 km wide window and continues upwards, always looking for 2 consecutive containers that fall under Ttop.
If it is under the window plate, the thin PBLH is set to the first (bottom) of the 2 containers. If not found before reaching the top of the window, the fine PBLH is set to the approximate average PBLH. If the coarse PBLH is zero, all corresponding fine PBLHs are zero. CATS data are well suited for detecting PBLH and have the potential to determine the daily variability of PBLH at seasonal and regional scales (since its orbit is not sun-synchronous). CATS provides robust attenuated backscatter data of 1,064 nm with a high signal-to-noise ratio (SNR) of 1,064 nm, especially at night (Pauly et al., 2019). This special effects ratio results in a minimum backscatter (BMD), the lowest backscatter value that PBL clouds, and the mixing height of aerosols can detect (Yorks et al., 2016). In addition, the total backscatter signal at 1,064 nm has a lower molecular contribution, particularly near the surface, compared to longer wavelengths (Yorks et al., 2021). CATS also observed different local times at each transfer, with the entire daily cycle covered approximately every 60 days due to the 51.8° angle of inclination of the ISS orbit. These samples have enabled multiple studies of seasonal, regional, and daily cloud and aerosol variability (Noel et al., 2018; Chepfer et al., 2019; Lee et al., 2019; Yu et al., 2021). The gradient rate in the PBL is unstable and vertical motion results in the transport of significant amounts of energy upwards due to the buoyancy of air that has come into contact with the surface. A mixed layer forms at a height where the static stability of the air forms a barrier against thermally induced upward movements.
This extreme occurs almost daily in the arid areas of the world and the barrier to upward mixing is often the tropopause itself. On average, at mid-latitudes, the unstable or mixed PBL is generally 1 to 2 km deep. Thus, the structure of the boundary layer and in particular its depth and the assumptions concerning the drive have a direct influence on the diffusivity of the vortex used in the parameterization. An equation for h is usually contained in a non-local diagram, compared to diagnosing the height of the boundary layer from turbulent kinetic energy performed in a local closure scheme. Equations (A.53) and (A.54) show that the deviation of the variable altitude of the local wind from its geostrophic value is due to the turbulence stress. Physically, the load reduces the wind speed, which reduces the Coriolis force. However, the compressive gradient force remains unchanged, creating an imbalance between the forces. Since the strength of the pressure gradient is greater than the Coriolis force, the wind assumes a component directed towards the pressure gradient. Now suppose that at z=, u=0 and v=0 and at an upper bound, u?ug and v?vg. For simplicity, suppose vg=0. We can then write Another IBL is developing near the coast.
For example, during the day in mid-season and in the warm season, the relatively unstable mass of sea air carried by the sea breeze becomes unstable as it moves inland, so that a mixed layer develops.