Land, atmosphere, and oceans interact with each other through energy, mass, and momentum exchanges. These interactions regulate climate variability and influence climate changes at the regional scale. One notable example of highly influential land-atmosphere-ocean interactions on regional climates is monsoonal systems that influence a substantial portion of the world’s population. In this dissertation, the present and future climates of West Africa (WA) and South America (SA), two important monsoon regions, were studied utilizing Regional and Global Climate Models (RCMs and GCMs), mathematical techniques and data mining tools, and observational data (in-situ, remote-sensing, and reanalysis). The objective is to advance our understanding on the role of land-atmosphere-ocean feedbacks, especially vegetation-climate interactions, in the climate variability, change, and extremes over these regions. Special attention was given to the improvement of climate simulations and reliability of future climate projections by quantifying and/or reducing uncertainties from multiple sources. As part of this dissertation, two new approaches concerning regional climate modeling and projection were developed, each pertaining to one of the geographic domains. One is the Ensemble-based Reconstructed Forcings (ERF) method that faithfully reproduces the Multi-Model Ensemble (MME) mean but requires only a fraction of the computational cost of the conventional MME approach, which is critical for reducing the high uncertainties in the outlook of future precipitation change over WA. The other newly developed approach tackle the nesting practice, a major source of RCM bias that causes (large-scale) circulation in SA to drift away from that of the driving GCMs. To this end, a new paradigm of regional climate modeling was proposed that includes the influential oceans within the RCM domain to better resolve the large-scale circulation of the SA climate. Results from a fully coupled regional climate model, with and without dynamic vegetation, revealed significant influence of vegetation-climate interactions on the mean and variability of the surface hydroclimate of the two regions of focus. Precipitation, surface temperature, evapotranspiration, and soil moisture were all strongly influenced. In particular, results from both numerical experiments and observational data analysis indicated that tropical oceanic variability plays a dominant role in precipitation variability over SA, including the unprecedented extreme drought of 2016; in addition, greenhouse gas warming was found to significantly contribute to the amplification of the 2016 drought, especially during the pre-monsoon season. Natural vegetation dynamics improves the model performance in capturing the anomalies of surface water storage but has a negligible impact on precipitation anomalies of this extreme drought. Results of this research help advance our understanding and improve our capability to quantify and predict climate variability, change, and extremes over WA and SA.

Originally published in 1987, this book brings together information previously buried in specialist sources and makes it available to the student in a non-technical and well-illustrated synthesis. It builds a clear and detailed picture of the climates of West Africa, describing and explaining them and showing how crucial this understanding is to everyday life. The climate’s relevance to water resources, agriculture, health and industry is systematically considered.

Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 186. Amazonia and Global Change synthesizes results of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) for scientists and students of Earth system science and global environmental change. LBA, led by Brazil, asks how Amazonia currently functions in the global climate and biogeochemical systems and how the functioning of Amazonia will respond to the combined pressures of climate and land use change, such as Wet season and dry season aerosol concentrations and their effects on diffuse radiation and photosynthesis Increasing greenhouse gas concentration, deforestation, widespread biomass burning and changes in the Amazonian water cycle Drought effects and simulated drought through rainfall exclusion experiments The net flux of carbon between Amazonia and the atmosphere Floodplains as an important regulator of the basin carbon balance including serving as a major source of methane to the troposphere The impact of the likely increased profitability of cattle ranching. The book will serve a broad community of scientists and policy makers interested in global change and environmental issues with high-quality scientific syntheses accessible to nonspecialists in a wide community of social scientists, ecologists, atmospheric chemists, climatologists, and hydrologists.

As societies transition to evidence-based adaptation and management there is increasing recognition of the need for understanding climate change and variability dynamics and impacts at regional levels and for various activities. This book is a contribution toward that goal. Readers interested in climate change management will find detailed discussions of climatic variability dynamics in selected regions as well as new innovative ways of monitoring climate change, assessing climate risks, and predicting impacts. Those interested in refreshing the fundamentals of climate change and climate variability will find a very accessible review of the status of knowledge on the subject, including a balanced interrogation of available evidence. In an attempt to keep the book accessible, every effort was made to minimize technical jargon without compromising scientific accuracy. The result should be useful to researchers, practitioners, and policy makers.