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In the tropics, habitat fragmentation alters forest-climate interactions in diverse ways. On a local scale (<1 km), elevated desiccation and wind disturbance near fragment margins lead to sharply increased tree mortality, altering canopy-gap dynamics, plant-community composition, biomass dynamics, and carbon storage. Fragmented forests are also highly vulnerable to edge-related fires, especially in regions which have periodic droughts or strong dry seasons. At landscape to regional scales (10-1,000 km), habitat fragmentation may have complex effects on forest-climate interactions, with important consequences for atmospheric circulation, water cycling, and precipitation. Positive feedbacks among deforestation, regional climate change, and fire could pose a serious threat for some tropical forests, but the details of such interactions are poorly understood.

The chapter begins with a phenomenological treatment of the observed atmospheric circulation. It then goes on to discuss how the barotropic model arises as a so-calledbalanced model of the slow, vorticity-driven dynamics, from the more general shallowwater model which also admits inertia-gravity waves. This is important because large-scale atmospheric turbulence exhibits aspects of both balanced and unbalanced dynamics. Because of the first-order importance of zonal flows in the atmospheric general circulation, the large-scale turbulence is highly inhomogeneous, and is shaped by the nature of the interaction between zonal flows and Rossby waves described eloquently by Michael McIntyre as a wave-turbulence jigsaw puzzle. This motivates a review of the barotropic theory of wave, mean-flow interaction, which is underpinned by the Hamiltonian structure of geophysical fluid dynamics.

This chapter starts by exploring some basic principles of weather. It then describes California’s Mediterranean climate from the standpoint of atmospheric circulation. This is followed by short-term weather conditions associated with fire spread, and climate variability and its possible role in fire regimes. The Mediterranean climate results from seasonal changes in global circulation, including California’s marginal position to the jet stream and the presence of cold, upwelling ocean waters offshore. The weather influences fire outcomes by altering vegetation fuel moisture and the efficiency of heat transfer in combustion. The El Niño/Southern Oscillation and the Pacific Decadal Oscillation influence the amount and distribution of water vapor that is evaporated into the air, condensed into clouds, and rained back to earth. The effect of precipitation variability is modulated by patch structure in which changes in regional fire hazard result in only finite portions of stands achieving flammability thresholds.

The climate is changing from human activities. This has major implications for the future and for human society and ecosystems, including birds. However, it is often masked by natural variability and there is great weather-related variability. This chapter reviews observed changes in climate, with a focus on changes in surface climate including variations in major patterns (modes) of climate variability and teleconnections. Of particular importance are changes in extremes. It describes how natural and anthropogenic drivers of climate change are assessed using climate models and concludes with a brief summary of future projected changes in climate and their impacts.

This chapter discusses mercury cycling and contamination in the Alaskan arctic. It provides a framework for investigating the behavior and fate of many contaminants in polar regions. It looks into the role atmospheric circulation and chemistry in affecting the transport and deposition of both inorganic and organic substrates on local and global scales. It analyzes a series of reports by the Arctic Monitoring and Assessment Program in determining mechanisms that transport contaminants, including mercury, to the arctic and identifies their effects on the arctic ecosystem.

Wherever the wind blows, some of its energy is dissipated — converted to entropy — by the shearing of air against air; this happens at all elevations. However, the losses are far greater in the lower-most layer because of friction with the surface — the drag of moving air as it passes across land or water. Drag also affects the direction of the wind, making atmospheric circulation far more complicated than it is aloft. This chapter discusses the following: surface winds; vertical movements of the air; water vapor and energy transfers; storms; how atmospheric energy is dissipated; and the energy in a rainstorm.