An evaluation of the statistics of rainfall extremes in rain gauge observations, and satellite-based and reanalysis products using universal multifractals

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Confidence in the estimation of variations in the frequency of extreme events, and specifically extreme precipitation, in response to climate variability and change is key to the development of adaptation strategies. One challenge to establishing a statistical baseline of rainfall extremes is the disparity among the types of datasets (observations versus model simulations) and their specific spatial and temporal resolutions. In this context, a multifractal framework was applied to three distinct types of rainfall data to assess the statistical differences among time series corresponding to individual rain gauge measurements alone-National Climatic Data Center (NCDC), model-based reanalysis [North America Regional Reanalysis (NARR) grid points], and satellite-based precipitation products [Global Precipitation Climatology Project (GPCP) pixels]-for the western United States (west of 105°W). Multifractal analysis provides general objective metrics that are especially adept at describing the statistics of extremes of time series. This study shows that, as expected, multifractal parameters estimated from the NCDC rain gauge dataset map the geography of known hydrometeorological phenomena in the major climatic regions, including the strong orographic gradients from west to east; whereas the NARR parameters reproduce the spatial patterns of NCDC parameters, but the frequency of large rainfall events, the magnitude of maximum rainfall, and the mean intermittency are underestimated. That is, the statistics of the NARR climatology suggest milder extremes than those derived from rain gauge measurements. The spatial distributions of GPCP parameters closely match the NCDC parameters over arid and semiarid regions (i.e., the Southwest), but there are large discrepancies in all parameters in the midlatitudes above 40°N because of reduced sampling. This study provides an alternative independent backdrop to benchmark the use of reanalysis products and satellite datasets to assess the effect of climate change on extreme rainfall. © 2010 American Meteorological Society.






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Sun, X, and AP Barros (2010). An evaluation of the statistics of rainfall extremes in rain gauge observations, and satellite-based and reanalysis products using universal multifractals. Journal of Hydrometeorology, 11(2). pp. 388–404. 10.1175/2009JHM1142.1 Retrieved from

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Ana P. Barros

Edmund T. Pratt, Jr. School Distinguished Professor Emeritus of Civil and Environmental Engineering

Professor Ana Barros was born in Africa, grew up in Angola and Portugal, and has lived almost all of her adult life in the United States. She attended the Faculty of Engineering of the University of O’Porto where she obtained a summa cum laude Diploma in Civil Engineering with majors in Structures and Hydraulics in 1985, and a M.Sc. degree in Ocean Engineering in 1988 with a thesis focusing on numerical modeling of sediment transport in estuaries and coastal regions. In 1990, Dr. Barros completed and M.Sc. degree in Environmental Science Engineering at the OHSU/OGI School of Science and Engineering. She earned a Ph.D. in Civil and Environmental Engineering from the University of Washington, Seattle in 1993. Her graduate studies were supported in part by fellowships from the Portuguese Foundation for Science and Technology (FCT/JNICT), and NASA’s Graduate Fellowship program.  She is registered with the Portuguese Order of Professional Engineers since 1986. 

 Dr. Barros was in the engineering faculty at the University of Porto, Penn State University, and Harvard University before joining Duke University in 2004. Her primary research interests are in Hydrology, Hydrometeorology and Environmental Physics with a focus on water-cycle processes in the coupled land-atmosphere-biosphere system particularly in regions of complex terrain, the study of multi-scale interface phenomena in complex environments across the Earth Sciences, remote sensing of the environment (precipitation, clouds, soil moisture, and vegetation), climate predictability, extreme events and risk assessment of natural hazards. Prof. Barros is especially proud of having involved dozens of students in undergraduate research, a great majority of which continued their studies to earn graduate degrees in science and engineering.  Over recent years her work has focused on precipitation processes including microphysics and dynamics or orographic precipitation, and land-atmosphere interactions in mountainous regions from the Himalayas to the Andes and the Southern Appalachians including Land-Use Land-Cover Change impacts on regional climate. Her research relies on intensive field and laboratory experiments, large–scale computational modeling, nonlinear data analysis and environmental informatics.

Prof. Barros served in the Space Studies Board of the National Research Council, and in several committees of the Water Science and Technology Board and the Board of Atmospheric Sciences and Climate including the Climate Research Committee, and she was a member of the US National Committee for the International Hydrology Program (IHP) of the UNESCO.  She served as an elected member of the Council of the American Meteorological Society, and serves and served in several committees within the American Meteorological Society and the American Geophysical Union. Prof. Barros was a member of the NOAA’s Climate and Global Change Program and serves or has served in several working groups at NASA, NSF and DOE-ARM. She has been an active member of several professional organizations including the IEEE, ASCE, AGU, AMS, AAAS, EGS, ASEE, and AWRA, and she currently serves in the ASCE committee on Climate Change and Adaptation. Prof. Barros was the Chief Editor of the Journal of Hydrometeorology for five years, and she was an AE of the Journal of Hydrology until 2015 among other editor posts. She has been a Senior Fellow who the Energy and Climate Partnership of the Americas (ECPA) since 2011. 

Prof. Barros received Early Career Investigator awards from NSF and NASA in 1995 and 1996. She was a George W. Merck Faculty Fellow at Harvard University 1999-2003, and Packard Fellow nominee from Penn State University. She received the Prize Foundation A. Almeida in Engineering in 1985, and the Lorenz G. Straub Award for her Ph.D. thesis in 1993, and the NASA GSFC Robert H. Goddard Award (GPM GV Team), Category of Exceptional Achievement in Science in 2014 for contributions in support of the Global Precipitation Measurement Mission.  Dr. Barros is a Member of the ASCE, Senior Member of the IEEE, a Fellow of the American Meteorological Society, and a Fellow of the American Geophysical Union.  She was the AMS Sigma-Xi Distinguished Lecturer 2014-2015.

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