Three decades of global trends in urban microwave backscatter, building volume and city GDP

Abstract

Most mapped urban information is essentially two-dimensional, e.g., areal extent by urban cover type. There is a gap in knowledge about patterns and changes of urban built-up volumes and development intensity globally. Here we use a new dataset of global microwave backscatter for 1993–2020 to explore this third dimension of urban growth across 477 large cities. Our results show that urban backscatter correlates with an independent estimate of building volume across 8000+ urban grid cells (0.05° lat/lon) in large cities in China, Europe, and the U.S.A. Regional rates of urban backscatter increase vary substantially across the three decades, with the highest rates in the 2010s across Asia, particularly in China and Southeast Asia. Microwave backscatter, a proxy for urban building volume, is correlated with Gross Domestic Product at the scale of urban grid cells across the globe, and at the city level across most regions. This time-series of scatterometer data provides an important tool for understanding both the spatial and temporal patterns of urban volumetric growth over the past several decades.