On the Interactions Between Clouds, Radiation, Turbulence and Vegetation in the Atmospheric Boundary Layer


Book Description

This thesis explores and quantifies how the surface and vegetation, through photosynthesis, and clouds through light and dynamics, impact each other. These interactions are very relevant for the amount of temperature, humidity and other properties of the lower atmosphere and, as a consequence, of the weather we experience. A very detailed model simulating the air flow in the atmosphere is used. We investigate the interactions and responses in matters of seconds and within meters through idealized studies. We do so at three different locations in the world with differing climates, clouds and vegetation: Netherlands in the mid-latitudes, Benin in Southern West Africa and the Amazonas rainforest in Brazil. We find that when these interactions are taken into account new features arise in the spatial structure and properties of the surface and lower atmosphere.




The Atmospheric Boundary Layer


Book Description

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.







Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE) Science Plan


Book Description

Cumulus convection is an important component in the atmospheric radiation budget and hydrologic cycle over the Southern Great Plains and over many regions of the world, particularly during the summertime growing season when intense turbulence induced by surface radiation couples the land surface to clouds. Current convective cloud parameterizations contain uncertainties resulting in part from insufficient coincident data that couples cloud macrophysical and microphysical properties to inhomogeneities in boundary layer and aerosol properties. The Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE) campaign is designed to provide a detailed set of measurements that are needed to obtain a more complete understanding of the life cycle of shallow clouds by coupling cloud macrophysical and microphysical properties to land surface properties, ecosystems, and aerosols. HI-SCALE consists of 2, 4-week intensive observational periods, one in the spring and the other in the late summer, to take advantage of different stages and distribution of "greenness" for various types of vegetation in the vicinity of the Atmospheric Radiation and Measurement (ARM) Climate Research Facility's Southern Great Plains (SGP) site as well as aerosol properties that vary during the growing season. Most of the proposed instrumentation will be deployed on the ARM Aerial Facility (AAF) Gulfstream 1 (G-1) aircraft, including those that measure atmospheric turbulence, cloud water content and drop size distributions, aerosol precursor gases, aerosol chemical composition and size distributions, and cloud condensation nuclei concentrations. Routine ARM aerosol measurements made at the surface will be supplemented with aerosol microphysical properties measurements. The G-1 aircraft will complete transects over the SGP Central Facility at multiple altitudes within the boundary layer, within clouds, and above clouds.




Coastal Meteorology


Book Description

Almost half the U.S. population lives along the coast. In another 20 years this population is expected to more than double in size. The unique weather and climate of the coastal zone, circulating pollutants, altering storms, changing temperature, and moving coastal currents affect air pollution and disaster preparedness, ocean pollution, and safeguarding near-shore ecosystems. Activities in commerce, industry, transportation, freshwater supply, safety, recreation, and national defense also are affected. The research community engaged in studies of coastal meteorology in recent years has made significant advancements in describing and predicting atmospheric properties along coasts. Coastal Meteorology reviews this progress and recommends research that would increase the value and application of what is known today.




An Introduction to Boundary Layer Meteorology


Book Description

Part of the excitement in boundary-layer meteorology is the challenge associated with turbulent flow - one of the unsolved problems in classical physics. An additional attraction of the filed is the rich diversity of topics and research methods that are collected under the umbrella-term of boundary-layer meteorology. The flavor of the challenges and the excitement associated with the study of the atmospheric boundary layer are captured in this textbook. Fundamental concepts and mathematics are presented prior to their use, physical interpretations of the terms in equations are given, sample data are shown, examples are solved, and exercises are included. The work should also be considered as a major reference and as a review of the literature, since it includes tables of parameterizatlons, procedures, filed experiments, useful constants, and graphs of various phenomena under a variety of conditions. It is assumed that the work will be used at the beginning graduate level for students with an undergraduate background in meteorology, but the author envisions, and has catered for, a heterogeneity in the background and experience of his readers.







Conceptual Boundary Layer Meteorology


Book Description

Conceptual Boundary Layer Meteorology: The Air Near Here explains essential boundary layer concepts in a way that is accessible to a wide number of people studying and working in the environmental sciences. It begins with chapters designed to present the language of the boundary layer and the key concepts of mass, momentum exchanges, and the role of turbulence. The book then moves to focusing on specific environments, uses, and problems facing science with respect to the boundary layer. - Uses authentic examples to give readers the ability to utilize real world data - Covers boundary layer meteorology without requiring knowledge of advanced mathematics - Provides a set of tools that can be used by the reader to better understand land-air interactions - Provides specific applications for a wide spectrum of environmental systems




Exploring the Interface of Land-atmosphere Interactions and Boundary Layer Cloud Physics


Book Description

Boundary layer clouds are fundamental components of the climate system because of their first order impacts on the global energy balance. While marine boundary layer clouds have received most of the attention in this field because of their connection to global climate sensitivity and radiative forcing, continental boundary layer clouds also play a crucial role in controlling the amount of radiation reaching the land surface. Sitting at the top of the atmospheric boundary layer, these clouds are fundamentally linked to underlying land surface processes. We present three studies that explore the connection between land-atmosphere interactions and shallow clouds with eye toward improving process-based understanding of this system. The first shows that marine boundary layer clouds are an important sink for aerosol particles over the southeast Atlantic Ocean, helping mitigate the impact of continental African biomass burning aerosols transported to the vicinity of these low clouds. Then, we look to ground our mechanistic understanding of the response of continental shallow cumulus clouds to two different land cover changes, boreal forest expansion and tropical deforestation, using an idealized modeling framework. This analysis reveals the importance of environmental context, especially soil moisture availability and background atmospheric humidity, in determining the response of the convective boundary layer and cloud cover to these land surface perturbations. The co-evolution of boundary layer and lifting condensation level heights also emerges as key and should motivate examination of results from models that cannot faithfully represent these parameters. Finally, using a combination of the same idealized modeling system and observations from two ARM sites, we explore the effects of variations in the surface energy budget, in response to both land cover change and natural variability, on boundary layer convective velocities, initial shallow cumulus updraft speeds and the number of aerosol particles activated into cloud droplets. While the simulations and observations show that surface heat fluxes are not likely the dominant driver of changes in shallow cumulus droplet number in most settings, environments with lower evaporative fractions do favor a stronger coupling. We connect each of these studies to larger questions in cloud physics and land-atmosphere interactions, and hope to motivate further work on the detailed properties of this system.