Characterizing global urban change 1993-2018 with space-borne microwave scatterometry

Abstract:

Human population is rapidly urbanizing, with consequences for resource consumption, energy use and greenhouse gas emissions, and ecosystem and public health. Predicting global urbanization's impact on various facets of the earth system requires spatio-temporal quantification of urban rates of change with globally consistent, well-calibrated data. Microwave scatterometer backscatter data provide a distinct perspective on the earth's surface, complementing other remote sensing data to create a more comprehensive picture of the Earth System. Recent work has shown that Ku-band microwave backscatter data provides unique information on global urbanization. Here we analyze global urban and suburban trends in microwave backscatter from 1993 – 2018, using Ku-band scatterometer data from QuikScat, 1999-2009, and C-band scatterometer data from ERS-1, 1993-1996, ERS-2, 1996-2000, and ASCAT-A/B, 2007-2018. We evaluate ASCAT C-band backscatter strength against new, regional building height, footprint, and volume products. We compare mean summer backscatter trends across the different eras and instruments for 400+ large cities (>1M) around the world, combining microwave backscatter trends with trends in urban built fraction mapped by the Global Human Settlement Layers to cluster these cities into several categories of 25-year change trajectories.