Summertime Diurnal Variability of Formaldehyde Over the Contiguous United States: Constraints From Pandonia Global Network
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Zhao, Tianlang, Jingqiu Mao, Xiaoyi Zhao, et al. “Summertime Diurnal Variability of Formaldehyde Over the Contiguous United States: Constraints From Pandonia Global Network.” Geophysical Research Letters 52, no. 20 (2025): e2025GL116033. https://doi.org/10.1029/2025GL116033.
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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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The diurnal cycle of Formaldehyde (HCHO) provide critical insights into tropospheric photochemistry. Here we use tropospheric HCHO retrievals from the Pandonia Global Network (PGN), combined with NASA's GEOS Composition Forecast (GEOS-CF) model to understand the diurnal variation of summertime HCHO across the contiguous US. While PGN HCHO tropospheric column (HCHOₜᵣₒₚ) shows a weak diurnal cycle in most regions, a distinct midday peak is found at the urban sites of Southern US (mainly in Houston), likely driven by highly reactive VOC emissions. For the vertical profile of HCHO mixing ratio within the Planetary Boundary Layer (PBL), PGN shows a significant decrease from 0.5 to 2 km while GEOS-CF exhibits an excessively well-mixed vertical shape. This discrepancy in HCHO profile leads to an overestimated HCHOₜᵣₒₚ in GEOS-CF in Northeast Coastal US and Southeast US. These findings offer valuable insights for interpreting geostationary satellite observations and understanding model biases in surface ozone (O₃).