Module 6 Review and Exam

1. PBL structure: the PBL has four basic layers, including the:
   • surface layer: layer closest to the Earth, where the turbulent forces are relatively constant. Roughly 20-200 meters above the surface, this layer is also known as the constant flux layer
   • the mixed layer: also called the convective layer, this is a layer that forms during the day, and is an area of considerable mixing and convective motion
   • the stable layer: also called the nocturnal boundary layer, this layer forms at night, and is characterized by light winds and weaker turbulence than in the mixed layer
   • residual layer: a transition layer between the mixed layer and the stable layer, one that has some "residual" characteristics of the mixed layer, but becoming more like the stable layer
2. mixing height of the PBL: the reading described how the mixing height is determined and its effects on air quality. The mixing height is that height to which the air is considered to be well-mixed
3. Monin-Obukhov length: a measure of the PBL, this parameter is a rough measure of the height at which turbulence is generated more by buoyancy than by wind shear. Daytime values over land are typically between 1 and 50 meters for the Monin-Obukhov length (L)
4. influencing factors in PBL science
   • energy budget: a measure of inflow and outflow of energy, with higher energy values being tied directly to turbulence and mixing
   • moisture: this reading describes the effect of moisture on the PBL, the more moisture representing more heat retained in the PBL
   • diurnal variations: these variations refer to the daily cycle, with a specific focus on changes in temperature as a significant influencing factor in PBL science
   • buoyancy: buoyancy affects the turbulence and the mixing of the air, with more turbulence and mixing during the day, significantly due to buoyancy
   • shear: wind shear and its effect on turbulence is directly tied to the roughness of the surface
   • aerodynamic roughness length: a measure of the roughness of the Earth's surface, used in determining wind shear and turbulent kinetic energy (TKE)
5. fundamental PBL processes: in Unit 3, we discussed some of the basic processes in the PBL, including:
   • weather processes: looking again at turbulence, this time exploring the mathematics of the gradient Richardson number
   • pollutant removal processes: a general discussion on removal mechanisms, such as wet and dry deposition, and chemical reactions
   • evapotranspiration: discussion on how the amount of moisture, especially as a result of evapotranspiration, influences the stability of the PBL

Module Post-Test Test