EGU2020-2632
https://doi.org/10.5194/egusphere-egu2020-2632
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The distribution of positive and negative turbulent heat diffusivity under urban pollution conditions

Zhe Zhang1,2, Yu Shi1, Haijion Sun1,2, Lei Liu1, and Fei Hu1,2
Zhe Zhang et al.
  • 1State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
  • 2University of Chinese Academy of Sciences, Beijing 100049, China

Turbulent diffusion efficiently transports momentum, heat, and matter and affects their transfers between the surface and the atmosphere. As an important parameter in describing turbulent diffusion, turbulent heat diffusivity KH has scarcely been studied in the context of frequent urban pollution in recent years. In this study, KH under urban pollution conditions was directly calculated based on the K-theory. We found an obvious diurnal variation in KH and its varying vertical distributions for each case and with time. Interestingly, the height of negative KH rises gradually after sunrise, peaks at noon, and falls near sunset. Negative KH is unusually significant at sunrise and sunset and approximately 140 m during most of the night. The magnitude and fluctuation in KH are smaller in the pollutant accumulation stage (CS) at all levels than in the pollutant transport stage (TS) and pollutant removal stage (RS). Turbulent diffusion may greatly affect PM2.5 concentration at the CS because of the negative correlation between PM2.5 concentration and the absolute value of KH at the CS accompanied by weak wind speed. The applicability of the K-theory is not very good during either day or at night. Note that these problems are inherent in K-theory when characterizing complex systems, such as turbulent diffusion, and require new frameworks or parameterization schemes. These findings may provide valuable insights for improving or establishing a new parameterization scheme for KH and promote the study of turbulent diffusion, air quality forecasting, and weather and climate modeling.

How to cite: Zhang, Z., Shi, Y., Sun, H., Liu, L., and Hu, F.: The distribution of positive and negative turbulent heat diffusivity under urban pollution conditions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2632, https://doi.org/10.5194/egusphere-egu2020-2632, 2020