An Efficient Numerical Model Of The Planetary Atmospheric Boundary Layer

This paper presents an efficient two-dimensional time-dependent one-layer boundary layer model designed specifically for use in general circulation models. Two fundamental problems associated with the boundary layer parameterization are examined using the one-dimensional version of the model. These are the effects of different PBL parameterization schemes and different flux profiles on the model wind and temperatures. This paper concludes that the effect of different PBL parameterization is very significant on temperature calculation but less important on the wind speed. In general, the use of linear flux profiles for the vertical divergence of momentum, heat and moisture is found to be satisfactory. We conclude this study by testing the validity of our two-dimensional model by comparing it with multi-level boundary layer model results. For this purpose, a numerical integration was done to simulate a stably stratified air flow passing from smooth to rough surfaces. (Author).

The book gives a comprehensive and lucid account of the science of the atmospheric boundary layer (ABL). There is an emphasis on the application of the ABL to numerical modelling of the climate. The book comprises nine chapters, several appendices (data tables, information sources, physical constants) and an extensive reference list. Chapter 1 serves as an introduction, with chapters 2 and 3 dealing with the development of mean and turbulence equations, and the many scaling laws and theories that are the cornerstone of any serious ABL treatment. Modelling of the ABL is crucially dependent for its realism on the surface boundary conditions, and chapters 4 and 5 deal with aerodynamic and energy considerations, with attention to both dry and wet land surfaces and sea. The structure of the clear-sky, thermally stratified ABL is treated in chapter 6, including the convective and stable cases over homogeneous land, the marine ABL and the internal boundary layer at the coastline. Chapter 7 then extends the discussion to the cloudy ABL. This is seen as particularly relevant, since the extensive stratocumulus regions over the subtropical oceans and stratus regions over the Arctic are now identified as key players in the climate system. Finally, chapters 8 and 9 bring much of the book's material together in a discussion of appropriate ABL and surface parameterization schemes in general circulation models of the atmosphere that are being used for climate simulation.

Although the technology of observation and prediction of atmospheric systems draws upon many common fields, until now the interrelatedness and interdisciplinary nature of these research fields have scarcely been discussed in one volume containing fundamental theories, numerical methods, and operational application results. This is a book to provide in-depth explorations of the numerical methods developed to better understand atmospheric systems, which are introduced in eight chapters. Chapter 1 presents an efficient algorithm for tropical cyclone center determination by using satellite imagery. Chapter 2 aims to identify atmospheric systems with a new polarization remote sensing method. Chapters 3-8 place emphasis on enhancing the performance of numerical models in the prediction of atmospheric systems that should be valuable for researchers and forecasters.

This volume is a collection of lectures given at the two colloquia on atmospheric flows over complex terrain with applications to wind energy and air pollution, organized and sponsored by ICTP in Trieste, Italy. The colloquia were the result of the recognition of the importance of renewable energy sources, an important aspect which grows yearly as the environmental problems become more pronounced and their effects more direct and intense, while at the same time, the wise management of the Earth's evidently limited resources becomes imperative.It is divided into two main parts. The first, which comprises Chaps. 1 to 4, presents the structure of the atmospheric boundary layer with emphasis in the region adjacent to the ground. The second, Chaps. 5 to 10, discusses methods for the numerical computation of the wind field on an arbitrary terrain. The unique feature of this book is that it does not stop at the theoretical exposition of the analytical and numerical techniques but includes a number of codes, in a diskette, where the mechanisms and techniques presented in the main part are implemented and can be run by the reader. Some of the codes are of instructional value while others can be utilized for simple operational work.Some of the lecturers are: D N Asimakopoulos, C I Aspliden, V R Barros, A K Blackadar, G A Dalu, A de Baas, D Etling, G Furlan, D P Lalas, P J Mason, C F Ratto and F B Smith.

Much of the work has concentrated on interactions between the soil model and the model of the atmospheric boundary layer and the behavior of the boundary-layer package within the Air Force Global Spectral Model. Such studies have underscored the importance of the formulation of surface properties and transport within the underlying soil. Work during the contract period also focussed on elimination of several inadequacies of boundary-layer modelling. The inclusion of the statistical impact of subgrid variations of surface properties leads to a surface exchange coefficient which varies more smoothly with stability and does not decrease as rapidly with very stable conditions. Such modifications reduce the nocturnal cooling which is usually overestimated in boundary-layer models. Other improvements of the boundary-layer model in stable conditions have resulted from increasing the critical Richardson number in the boundary-layer depth formulation and adopting the Kondo formulation for the eddy diffusivity. The development of a formulation for boundary-layer cumulus has allowed inclusion of cloud-induced drying. Although this formulation leads to significant improvement of the boundary-layer predictions in cloudy situations, the general problem is far from solved. Keywords: Atmospheric boundary layer; Surface energy balance; Soil model; Stable layer parameterization; Surface fluxes. (jhd).