Planetary boundary layers

Another widely used concept is that of a planetary boundary layer (PBL) in contact with the surface of the Earth above which lies the "free atmosphere." This PBL is to some degree a physically mixed layer due to the effects of shear-induced turbulence and convective overturning near the Earth s surface. 

Figure 13-5 is the box model of the remote marine sulfur cycle that results from these assumptions. Many different data sets are displayed (and compared) as follows. Each box shows a measured concentration and an estimated residence time for a particular species. Fluxes adjoining a box are calculated from these two pieces of information using the simple formula, S-M/x. The flux of DMS out of the ocean surface and of nss-SOl back to the ocean surface are also quantities estimated from measurements. These are converted from surface to volume fluxes (i.e., from /ig S/(m h) to ng S/(m h)) by assuming the effective scale height of the atmosphere is 2.5 km (which corresponds to a reasonable thickness of the marine planetary boundary layer, within which most precipitation and sulfur cycling should take place). Finally, other data are used to estimate the factors for partitioning oxidized DMS between the MSA and SO2 boxes, for SO2 between dry deposition and oxidation to sulfate, and for nss-SO4 between wet and dry deposition. 

Typical concentrations of Hg species in the planetary boundary layer... 

The height of the atmospheric or planetary boundary layer under neutral conditions can be estimated from (Blackadar and Tennekes, 1%8)... 

Velocity and temperature gradients are confined to the surface layer defined by z < I-. Above L the wind velocity and potential temperature are virtually uniform with height. Venkatram (1978) has presented a method to estimate the value of the convective velocity scale w,. On the basis of this method, he showed that convective conditions in the planetary boundary layer are a common occurrence (Venkatram, 1980). In particular, the planetary boundary layer is convective during the daytime hours for a substantial fraction of each year ( 7 months). For example, for a wind speed of 5 m sec , a kinematic heat flux Qo as small as O.PC sec can drive the planetary boundary layer into a convective state. 

Vertical dispersion cannot be described in such simple terms (Kaimal et al., 1976). First, varies throughout the planetary boundary layer. In the region, L < z < O.lzi, o- , z, and a- scales with w, only above O.lzi. For Zi = 1500 m and an effective stack height of 400 m, the dispersing plume is controlled by an inhomogeneous region that is almost half the effective stack height. 

Blackadar, A. K., and Teimekes, H. (1968). Asymptotic similarity in neutral barotropic planetary boundary layers. J. Atmos. Sci. 25, 1015-1020. 

Businger, J. A., and Ayra, S. P. S. (1974). Height of the mixed layer in the stably stratified planetary boundary layer. Adv. Geophys. 18A, 73-92. 

Deardorff, J. W. (1970). A three-dimensional numerical investigation of the idealized planetary boundary layer. Geophys. Fluid Dyn. 1, 377-410. 

Lamb, R. G. (1978). A numerical simulation of dispersion from an elevated point source in the convective planetary boundary layer. Atmos. Environ. 12, 1297-1304. 

Lewellen, W. S., Teske, M., and Donaldson, C. duP. (1974). Turbulence model of diurnal variation in the planetary boundary layer. In Proceedings of the 1974 Heat Transfer and Fluid Mechanics Institute (L. R. Davis and E. R. Wilson, eds.), pp. 301-319. Stanford Univ. Press, Stanford, California. 

O Brien, J. (1970). On the vertical structure of the eddy exchange coefficient in the planetary boundary layer. J. Atmos. Sci. 27, 1213-1215. 

Wyngaard, J. C. (1975). Modeling the planetary boundary layer-extension to the stable case. Boundary Layer Meteorol. 9, 441-460. 

T. Smith, Jr., R. V. Arrieta, R. Rodriquez, and J. W. Birks, Vertical Profiling and Determination of Landscape Fluxes of Biogenic Nonmethane Hydrocarbons within the Planetary Boundary Layer in the Peruvian Amazon, J. Geophys. Res., 103, 25519-25532 (1998a). 

Altshuller, A. P and A. S. Lefohn, Background Ozone in the Planetary Boundary Layer over the United States, J. Air Waste Manage. Assoc., 46, 134-141 (1996). 

The structure of turbulence in the transition zone from a fully turbulent fluid to a nonfluid medium (often called the Prandtl layer) has been studied intensively (see, for instance, Williams and Elder, 1989). Well-known examples are the structure of the turbulent wind field above the land surface (known as the planetary boundary layer) or the mixing regime above the sediments of lakes and oceans (benthic boundary layer). The vertical variation of D(x) is schematically shown in Fig. 19.8b. Yet, in most cases it is sufficient to treat the boundary as if D(x) had the shape shown in Fig. 19.8a. 

In remote and unpolluted regions of the planetary boundary layer, natural sources of NOx (NO and N02) such as lightning, result in relatively small mixing ratios, typically being less than 20 pptv. In contrast, the amount of NOx in downtown city air is often above 100 ppbv. Thus N02 has a large tropospheric variability. Both the distribution of sources and the lifetime of N02 are very different in the troposphere compared to the stratosphere. 

Pa PACE PAGES PAHO PALE PAR PARCS PBL PCM PDV PhA PIK PIRA PIRATA POC POLDER Partial pressure in the atmosphere Permafrost And Climate in Europe Pilot Analysis of Global EcoSystems Pan American Health Organization Paleoclimates of Arctic Lakes and Estuaries Photosynthetic Active Radiation Paleoenvironmental ARCtic Science Planetary Boundary Layer Parallel Climate Model Pacific Decadal Variability Phytogenic Aerosol Potsdam-Institut fur Klimafolgenforschung Petroleum Industry Research Associates Pilot Research moored Array in the Tropical Atlantic Permanganate Oxidizable Carbon POLarization and Directionality of the Earth s Reflectances Princeton Ocean Model... 

Formation in the Planetary Boundary Layer, Atmos. Environ. 34 LVd d-lSTJ. 

Mellor GL, Yamada T (1974) A hierarchy of turbulence closure models for planetary boundary layers. J Atmos Sci 31 1791-1806... 

Zilitinkevich S, Esau I, Baklanov A (2007) Further comments on the equilibrium height of neutral and stable planetary boundary layers. Q J R Meteorol Soc 133 265-271... 

Semi-direct ejfect - affect planetary boundary layer (PBL) meteorology and photochemistry ... 

Idealized Planetary Boundary Layer, Geophys. Fluid Dynam. (1970) 1 (377), 377. 

Planetary Boundary Layer Using Characteristics of the Vertical Velocity Spectrum, J. Atmospheric Sci. (1968) 25 (6), 1026-1033. 

The oxidative capabihty of the atmosphere is not simply a function of chemistry. Convective storms can carry short-lived trace chemicals from the planetary boundary layer (the first few hundred to few thousand meters) to the middle and upper troposphere in only a few to several hours. This can influence the chemistry of these upper layers in significant ways by delivering, e.g., reactive hydrocarbons to high altitudes. Conversely, the occurrence of very stable conditions in the boundary layer can effectively trap chemicals near the surface for many days, leading to polluted air. Larger-scale circulations serve to carry gases around latitude circles on timescales of a few weeks, between the hemispheres on timescales of a year, and between the troposphere and stratosphere on timescales of a few years. 

Whole ecosystem and regional-scale discrimination is also assessed by evaluating the isotopic composition of CO2 in the atmospheric boundary layer (ABL also called planetary boundary layer (PBL), as well as convective boundary layer (CBL), when considered during times of convective enhancement by surface heating during the day). 

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