Xie et al. (2025) Untangling the inhibitory effect of polluted dust on weak precipitation based on raindrop size distribution observation

Identification

• Journal: Environmental Earth Sciences
• Year: 2025
• Date: 2025-12-16
• Authors: Xiangshan Xie, Baolong Shi, Lili Xu, Neng Ruan, Quan Yuan, Jinyan Wang
• DOI: 10.1007/s12665-025-12717-z

Research Groups

• Dongting Lake National Climate Observatory, Yueyang, China
• Hunan Key Laboratory of Meteorological Disaster Prevention and Reduction, Changsha, China
• Yueyang Meteorological Bureau of Hunan Province, Yueyang, China
• Key Laboratory of Climate Resource Development and Disaster Prevention in Gansu Province, College of Atmospheric Sciences, Lanzhou University, Lanzhou, China

Short Summary

This study investigates the distinct impacts of polluted dust and anthropogenic aerosols on precipitation microphysical processes in Shanghai, China, using raindrop size distribution observations. It reveals that polluted dust inhibits weak precipitation by suppressing large raindrop formation, while anthropogenic aerosols promote convective precipitation, increasing large raindrop concentration and delaying rainfall peaks.

Objective

• To clarify the mechanism of the inhibition of polluted dust on weak precipitation based on raindrop size distribution (DSD) observations.
• To analyze the influence of anthropogenic aerosols on precipitation microphysical characteristics under different air quality conditions.

Study Configuration

• Spatial Scale: Pudong Monitoring Station, Shanghai, China (31.23°N, 121.53°E). Regional scale for reanalysis data covering East Asia/China.
• Temporal Scale: January 1st, 2021 to December 31st, 2022 (2 years of DSD data). Specific dust events in March 2021 were analyzed.

Methodology and Data

• Models used: HYSPLIT (for 72-hour back-trajectory analysis).
• Data sources:
  • Raindrop Size Distribution (DSD) data: Observed by OTT Parsivel2 disdrometer at Pudong Monitoring Station, Shanghai (1-minute resolution, 75,602 valid samples). Quality control included excluding drops with diameter < 0.3 mm, samples with < 10 raindrops, and rain intensity below 2.78 x 10⁻⁷ mm s⁻¹.
  • Air pollutant data: Hourly PM10, PM2.5, and Air Quality Index (AQI) from the National Meteorological Information Center in China.
  • Hourly meteorological data (rainfall): National Meteorological Information Center in China.
  • ERA5 reanalysis data: Hourly wind fields (0.25° × 0.25°) at 8.5 x 10⁴ Pa and 1.0 x 10⁵ Pa from the European Centre for Medium-Range Weather Forecasts (ECMWF).
  • MERRA-2 reanalysis data: Dust mixing ratio (0.500° × 0.625° horizontal, 3-hour temporal resolution, specifically bin 5 for 6–10 µm dust) from NASA.
  • Rainfall type classification: Based on 10-minute DSD samples; stratiform precipitation (rain intensity R > 1.39 x 10⁻⁴ mm s⁻¹ with standard deviation σR < 4.17 x 10⁻⁴ mm s⁻¹); convective precipitation (R > 1.39 x 10⁻³ mm s⁻¹ with σR > 4.17 x 10⁻⁴ mm s⁻¹).
  • Polluted dust event definition: MERRA-2 dust concentration (bin 5) above seasonal threshold, concurrent surface PM10 levels > 150 µg m⁻³, and HYSPLIT 72-hour back-trajectories confirming origin from major Asian dust source regions.
  • Weak precipitation definition: Daily precipitation less than 9.9 mm (average rain rate R < 1.14 x 10⁻⁴ mm s⁻¹).

Main Results

• Inhibitory Effect of Polluted Dust on Weak Precipitation:
  • Compared to dust-free precipitation, polluted dust precipitation showed an average increase of 13.8% in small raindrop concentration (diameter < 1 mm) and a decrease of 19.2% in large raindrop concentration (diameter > 3 mm).
  • Polluted dust precipitation exhibited a smaller mass-weighted average diameter (Dm) and a larger normalized concentration intercept parameter (Log10 N_w).
  • This inhibition is attributed to the chemical aging of dust aerosols (sulfate and nitrate coatings) enhancing their hygroscopicity, leading to a higher concentration of smaller cloud droplets and suppressed collision-coalescence efficiency.
• Promotional Effect of Anthropogenic Aerosols on Convective Precipitation:
  • Under high pollution conditions (PM10: 45–229 µg m⁻³), the average concentration of small raindrops in stratiform precipitation decreased by 63.5% compared to clean conditions.
  • In convective precipitation under high pollution, the average concentration of large raindrops increased by 8.04 times compared to clean conditions, while small raindrop concentration decreased by 19.2%.
  • Convective precipitation under high pollution conditions exhibited increased total rainfall and a delayed diurnal rainfall peak (peak at 15:00 compared to 13:00/19:00 in clean conditions).
  • This suggests anthropogenic aerosols initially suppress warm-rain processes by creating more numerous but smaller cloud droplets, but subsequently invigorate convective systems through enhanced latent heat release via ice-phase processes, leading to delayed but intensified rainfall with larger raindrops.

Contributions

• Provides the first quantitative observational evidence from DSD data in the Yangtze River Delta region demonstrating the significant suppressive effect of polluted dust on weak precipitation.
• Distinguishes the different impact mechanisms of polluted dust and anthropogenic aerosols on precipitation microphysical processes.
• Offers new observational insights and mechanistic understanding for aerosol-precipitation interactions.
• Provides valuable constraints for improving aerosol parameterization schemes in numerical models.

Funding

• Innovative Development Project of Hunan Meteorological Bureau (No.CXFZ2025-MSXM43)
• Joint Funds of the National Natural Science Foundation of China (No.U2342205)
• Key Natural Science Foundation of Gansu Province (No. 23JRRA1030)

Citation

@article{Xie2025Untangling,
  author = {Xie, Xiangshan and Shi, Baolong and Xu, Lili and Ruan, Neng and Yuan, Quan and Wang, Jinyan},
  title = {Untangling the inhibitory effect of polluted dust on weak precipitation based on raindrop size distribution observation},
  journal = {Environmental Earth Sciences},
  year = {2025},
  doi = {10.1007/s12665-025-12717-z},
  url = {https://doi.org/10.1007/s12665-025-12717-z}
}