Rong Fu, Ph.D. - US grants

9507987 Fu This project involves the application of state-of-the-art climate observations, especially satellite data, and simple numerical models to clarify the processes that control the amount and distribution of water vapor in the upper troposphere in the middle latitudes. Understanding these processes is critical to understanding the earth's radiation budget and the potential for global warming. The objectives of the project are to: (1) identify the main sources of and mechanisms controlling upper tropospheric water vapor in the middle latitudes, especially the relative importance of large-scale horizontal advection and vertical transport by local convection and (2) examine whether these processes are adequately represented in general circulation models. The research will contribute directly to the goals of NSF's Water and Energy - Atmospheric, Vegetative, and Earth Interactions (WEAVE) effort. The educational component of this CAREER award consists of a variety of activities involving both graduate and undergraduate students and an effort to encourage underrepresented groups, particularly women, to pursue careers in the physical sciences.***

Abstract ATM-9419715 Dickinson, Robert E. University of Arizona Title: Land-Atmosphere Interactions - A Core Program in Support of Community Climate Modeling This project focuses on understanding and parameterizing the interactions between land and the atmosphere in the context of global change models. Its objectives are: to establish, through data analyses, numerical process studies and model stimulations, the function of the most important atmospheric processes, from the viewpoint of coupling to land-surface processes; and on the basis of these studies, to develop new or improved parameterizations for GCMs, implement and test these parameterizations in NCAR community climate system models, and provide successful parameterizations to the NCAR climate modeling community. This proposal brings together and supports a strong research team with a wide variety of background and experience, each with important individual skills. The proposed work will: expand the basic understanding of the processes responsible for land-atmosphere coupling; determine how these operate in NCAR community models; determine how these processes differ, if they do, from those in other climate models of comparable merit; determine how these observations, sensitivity studies, and model intercomparisons are necessary to clarify the relative correctness of differing parameterizations; and develop indicated new treatments that are suitable, in the context of GCM's, for future improvements and upgrades by the scientific community. Individual subprojects designed to pursue these objectives include: studies of interactions between the land surface and clouds in the planetary boundary (PBL); characterization of cloud radiative fluxes and their coupling to the land surface; parameterization of the effects of mesoscale circulations in a GCM, including moist processes, clouds and precipitation; observation characterization of relationships between cloud properties, atmospheric thermodynamics propert ies, and land cover; observational search for effects of Amazon deforestation on cloud processes; further exploration of climate effects of Amazon deforestation to better understand land-surface interactions; and paleoclimatic linkages. These studies will use satellite, radiosonde, and surface data for their observational analyses. Satellite data analyses will emphasize the use of a local archive of high-resolution (30 km) ISCCP data. They will also use integrations of mesoscale and global climate models, with an emphasis for the latter on NCAR community models. Theoretical and parameterizations analyses will use mesoscale model integration and various 1-D convection parameterizations. The proposed work will contribute substantially to great understanding of and confidence in the use of NCAR climate system models for projections of future climate. This will be done by promoting major advances in what is arguably now one of the weakest aspects of model performance from the viewpoint of scientific understanding and practical aspects of climate simulation. The performance of the proposed research will provide training and education on these questions for a generation of graduate students and post-doctoral trainees. This award is under the USGCRP, Climate Modeling, Analysis and Prediction (CMAP) project.

ABSTRACT ATM -9727140 Dickinson, Robert A. University of Arizona TITLE: Land-Ocean-Atmosphere Interactions: Mechanisms for the Seasonal Variations in Precipitation Over Tropical Land This study will combine observations and modeling to examine the mechanisms responsible for seasonal variations of precipitation over tropical land and to determine how these variations are affected by land-atmosphere interactions. The problems involved in the difficulties with the simulation of North American monsoon and the wet season over the eastern equatorial Amazon by the NCAR CCM3 climate model will be investigated. Diagnostic analyses and numerical simulation will address the relative roles of land versus ocean SST in determining the onset of the wet season and the observed spatial patterns. This work will further advance climate modeling effort which will assist in attempting more accurate prediction of tropical climate.

This project is an investigation of factors that influence the start and end of the rainy season in tropical South America and hence influence agricultural productivity and the availability of water resources. The objectives are: (i) to determine the influence of large-scale circulation anomalies, especially those forced by interannual variations of sea-surface temperatures in the adjacent oceans, on the key thermal and dynamic factors that control the onset and demise of the rainy season over the northern part of South America, (ii) to explore how land-surface processes and bio-mass burning modify the atmospheric boundary layer conditions needed for the onset of the rainy season by influencing pre-seasonal climate conditions, (iii) to characterize the link between regional climates in tropical South America, Central and North America via cross-equatorial flow and to identify the underlying dynamic processes. The approach to be taken consists of a diagnostic study of a number of data sets relevant to the climatology of the region. The data include: ECMWF reanalyses, South American rain gauge data, in situ surface fluxes and soil moisture from the Large Scale Biosphere-Atmosphere Experiment in Amazonia, instantaneous cloud data from the International Satellite Cloud Climatology Project, aerosol optical depth from the Total Ozone Mapping Spectrometer, and the NASA-Ames 8-km Amazon Ecology Mapping data.

The rain forest of the Amazon accounts for roughly 15 percent of the Earth's terrestrial photosynthesis, and there is concern that anthropogenic global warming could lead to reduced rainfall and a "die-back" of what is arguably the world's greatest forest. Such a die-back could have serious implications for the biodiversity of the Amazon, and it could also lead to a substantial increase in global airborne carbon dioxide. But whether or not such die-back will occur is highly uncertain, and climate models show a wide range of projections for global warming-induced rainfall change over the Amazon. This project will address the question of future rainfall change by examing Amazon rainfall variability and associated dynamical mechanisms over the period of available observations, and determining the extent to which these mechanisms are correctly represented in climate models. The work has three main objectives: 1) to determine observationally whether or not rainfall seasonality and drought severity have changed significantly over the Amazon during the past few decades and, if so, what mechanisms have caused these changes; 2) to determine whether the observed rainfall changes are mainly attributable to natural climate variability or to forcing by anthropogenic emissions; 3) to validate the physical processes that control rainfall seasonality and drought severity in climate models, in order to reduce uncertainty in projections of future climate change in the Amazon. The work is based on the hypothesis that drought severity has increased over the past few decades due to more late onsets and early endings of the rainy season. A further hypothesis is that wet season onsets have been occurring later and wet season terminations earlier in recent decades over the southern Amazon due to warming of the tropical esastern Pacific and northern tropical Atlantic. Delays of the wet season onset are also hypothesized to occur as the result of a polward shift of the Southern Hemisphere subtropical jets, and because of agricultural burning.

Aside from the benefits of the research for understanding and anticipating drought in the Amazon, the project will support education and the advancement of science education in the United States and in countries of the Amazon region. The present work will 1) support climate research and education programs in Amazonian countries by training PhD students, especially women from Amazonian countries, and collaborating with newly formed climate programs in that region; 2) support outstanding minority high school students from rural Texas and undergraduate students in climate science; 3) communicate research results and general climate science to the public.

Extreme weather, such as persistent dry spells, heatwaves, fire weather, is a major cause of natural disasters. Its impacts on lives, public health, economy, and environment have been escalating rapidly in recent decades. For example, the wildfires in 2018 over California, induced by intensive fire weather, have caused over $126.1-192.9 billion economic loss. Yet, we do not fully understand its underlying causes. For example, the following questions are still perplexing the scientific community. Why do extreme events occur sometimes, but not at other times under similar atmospheric flow patterns? Why do warm season extreme dry spells and hot days occur together sometimes, but not at other times? Why do some extreme weather types, such as fire weather during the largest wildfires in western United State, appear to become less explainable by the synoptic circulation since 2000 compared to those from the time in the 1980s’ and 90s’? <br/><br/>This project will apply state-of-the-art statistical analyses to capture the variety and complexity of the synoptic wind patterns responsible for the extreme events. More importantly, the roles of clouds, precipitation, and aerosols relative to atmospheric dynamic process in intensifying extreme weather will be investigated. Furthermore, an integrated approach will be applied to systematically characterize the atmospheric physical and dynamic processes and land surface feedbacks behind extreme dry and wet spells, hot days, fire weather and floods. The multifaceted and integrated approach will clarify the relative roles of the atmospheric dynamics and physical processes in determining extreme weather and concurrence of multiple extreme weather types. Such an approach could lead to a paradigm shift from event-based and synoptic-circulation-focused approaches that have dominated the literature in this research area, and significantly advance our understanding of extreme weather, especially for that which cannot be sufficiently explained by synoptic circulation anomalies. <br/><br/>The project will train a woman PhD student, undergraduate summer research interns, and a postdoctoral researcher, and incorporate its research results into a large upper-division undergraduate science course. These activities will contribute to the NSF educational mission and future workforce of physical and dynamic meteorology. The proposed public outreach through media will enable the PI to translate the latest research result about extreme weather from this project to meaningful or even actionable information for society. <br/><br/>The project was co-funded by NSF Physical and Dynamic Meteorology and Climate and Large-scale Dynamics programs.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.