Size‐resolved organic functional group (OFG) concentrations in aerosol particles were measured during January−February 2019 in Hefei, a major urban city in eastern China. Alkane, carboxylic acid, and hydroxyl groups were the main components of the organic aerosol (OA), contributing 35.0%, 22.5%, and 21.8%, respectively. The mass concentrations and size distributions of the OFGs strongly depended on ambient relative humidity (RH). Specifically, the OFG mass concentrations were 50% higher during the high‐RH periods than the low‐RH periods. The peak size of the OFGs size distribution was 0.56–1 μm during the high‐RH periods, while a peak size of 0.32–0.56 μm was observed during the low‐RH periods. In addition, the concentrations of the total OA, carboxylic acid, and hydroxyl groups were positively correlated with the photochemical age (PCA), with the high‐RH samples increasing faster (greater slope) with PCA and being associated with a higher oxygen‐to‐carbon ratio. These results suggest that aqueous‐phase processing likely enhanced the production of the OFGs, especially oxygenated functional groups. Further analysis of size distribution of the oxygenated OFGs and the viscosity of aerosols indicates that the secondary OFGs were formed via surface‐limited mechanisms under low‐RH conditions and volume‐limited mechanisms under high‐RH conditions. These findings reinforce the important role of multiphase chemistry in the formation and evolution of OAs.

In this paper, a water-based aerosol particle counter was used to measure aerosol number concentrations with high temporal resolution at a meteorological tower and on the ground, and the ultrasonic anemometer on the meteorological tower measured the data of the three-dimensional wind speed. The power spectrum of the aerosol particle number concentration fluctuation was obtained by using a Fourier transform, and the characteristics of the power spectrum were deeply analyzed. The results show that the aerosol concentration fluctuation power spectrum satisfies the Monin–Obukhov law in the low-frequency (0.02–0.25 Hz) part of the inertial subregion, which is consistent with the characteristics of atmospheric turbulent motion. Significant attenuation occurs in the high-frequency (0.3–5 Hz) range, which is mainly caused by the attenuation of the aerosol concentration by the intake pipe. Using the similarity of the power spectrum in the low-frequency part, using the “−5/3” line as a standard, the characteristic time of the measurement system is obtained by fitting the transfer function. The results show that in the flux measurement experiments in this paper, the characteristic time is usually less than 1 s. Finally, this paper uses the Fourier transform and wavelet transform to correct the high-frequency attenuation in the fluctuation of aerosol concentration and obtains the corrected aerosol flux. The results show that the effect of high-frequency attenuation on the flux is approximately 1–4% in this experiment.

Studying the Martian atmosphere is important in planetary science. The boundary layer turbulence is characterized at the Zhurong location using spectrum analysis, two-dimensional spectrum, and similarity theory. The results reveal that the atmospheric temperature and wind at the Zhurong location are consistent with Kolmogorov’s “-5/3” turbulence laws. The atmospheric movement at the Zhurong location has four usual weather scales: 50 m, 100 m, 150 m, and 200 m. The atmospheric refractive index structure parameters, and thus the effect of turbulence on the light propagation, at the Zhuong and Insight locations are 3 or 4 orders less than at the Perseverance location. The sensible heat flux values in the Zhurong location is mainly in the range of 0-10 W/m²and increases during measurement. The clear seasonal variability in heat flux flow with greater value in spring and summer than in autumn and winter is revealed at both the Zhuong and Insight locations.