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New Paper: Meteorological controls on daily variations of nighttime surface urban heat islands

Tuesday, 08 December 2020 10:09

Daily dynamics of nighttime SUHIs in Beijing. Subplots a1 – a4 illustrate the daily dynamics (dots) and mid-term variations (solid lines) of the four SUHI features (I, A, e, and φ) from 2012 to 2016, with the grey lines denoting the start (end) of each year. Subplots b1 – b6 illustrate examples of the fitted nighttime Gaussian-derived SUHIs for six days (within the orange bars in subplots a1 – a4), and subplot c compares these six Gaussian ellipses (Lai et al. 2020)

A new research paper by Benjamin Bechtel from the Urban Climate Group was published at the end of November. You can find the article here.

Abstract

Most previous studies of surface urban heat islands (SUHIs) have focused solely on their controlling factors on a seasonal/annual timescale, while the controls on daily variations are largely unknown. By extracting the daily variations of nighttime SUHI features using the Gaussian model and investigating their correlations with various explanatory factors, we have attempted to determine the controls on SUHIs on a daily-basis over Chinese cities. Specific controls of weather conditions on the intensity, extent, shape, and centroid of the SUHIs were identified. Our results show that: (1) SUHI intensity (SUHII) was considerably more sensitive to weather conditions than the SUHI footprint (i.e., extent, shape, and centroid). (2) Meteorological variables including relative humidity, accumulated precipitation, and aerosol optical depth, had the greatest impact on SUHI intensity; whereas factors related to temperature fluctuations (day-to-day fluctuations of surface and air temperature) were the main factors influencing SUHI extent, shape, and the direction in which SUHI centroid varies. (3) Antecedent precipitation substantially impacted the subsequent SUHIs under clear-skies, changing both the SUHI itself and its sensitivity to other factors. Typically, the clear-sky SUHIs directly following rainfall showed a higher dependence on the relative humidity, soil moisture and aerosol, but were less affected by wind. (4) The meteorological contributions to the daily nighttime SUHIIs varied among Chinese cities with different bioclimatic conditions. In general, they were stronger in temperate zones than in subtropical zones. Our results provide an improved understanding of the controls on SUHIs on a daily timescale, as well as a foundation for predicting daily SUHIs based on the influencing meteorological variables.