Tan et al. (2026) Observational characteristics of cloud-radiation-precipitation during 2019 drought period in Yunnan of Southwest China

Identification

• Journal: Climate Dynamics
• Year: 2026
• Date: 2026-04-01
• Authors: Y. X. Tan, Xinqiang Zhou, Bing Chen, Jiandong Li, Guo Lin, Xiaohong Liu, Tao Luo
• DOI: 10.1007/s00382-026-08152-w

Research Groups

• Key Laboratory of Atmospheric Environment and Processes in Boundary Layer in the Low-Latitude Plateau region, Department of Atmospheric Science, School of Earth Science, Yunnan University, Kunming, China
• Meteorological Bureau of Yiliang County, Kunming, Yunnan Province, China
• Key Laboratory of Earth System Numerical Modeling and Application, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
• Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, CO, USA
• Department of Atmospheric Sciences, Texas A&M University, College Station, TX, USA
• Key Laboratory of Atmospheric Optics, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, China

Short Summary

This study analyzes cloud-radiation-precipitation changes during the extreme drought period from April to June 2019 in Yunnan, Southwest China, revealing that anomalous subsidence and reduced water vapor transport led to decreased cloud cover and a weakened cloud radiative cooling effect, intensifying and sustaining the drought through a "hot-dry" feedback cycle.

Objective

• To investigate the characteristics and potential feedback mechanisms of cloud-radiation processes during the extreme drought in Yunnan, Southwest China, from April to June 2019, and their relationship with regional precipitation and surface energy balance.

Study Configuration

• Spatial Scale: Yunnan region of Southwest China (21°N–30°N and 97°E–106.5°E).
• Temporal Scale: Extreme drought period: April to June 2019. Climatological average/comparison period: 2001–2022. Daily time series from March to June for 2019 and the 2001–2022 average.

Methodology and Data

• Models used: Not applicable (observational/reanalysis study).
• Data sources:
  • Global Precipitation Measurement (GPM) IMERG Final-Run dataset (daily average precipitation; 0.1° × 0.1° spatial resolution).
  • ERA5 reanalysis dataset (meteorological variables including 2-meter air temperature, relative humidity, vertical velocity, total column water vapor, volumetric soil water content in 0–7 cm layer; 0.25° × 0.25° spatial resolution).
  • Cloud and the Earth’s Radiant Energy System (CERES) EBAF Edition 4.1 dataset (surface shortwave and longwave radiative fluxes under clear-sky and all-sky conditions; 1.0° × 1.0° spatial resolution).
  • CERES SYN (Synoptic TOA and Surface Fluxes and Clouds) SYN1deg dataset and CldTypHist dataset (cloud physical properties including total cloud cover, high clouds, mid-high clouds, effective radius of liquid water particles, liquid water path, total cloud optical thickness; 1.0° × 1.0° spatial resolution).
  • CN05.1 dataset (interpolated product from Chinese surface stations, 0.25° × 0.25° spatial resolution, used for GPM validation).

Main Results

• Yunnan experienced a severe high-temperature drought from April to June 2019, with a cumulative precipitation decrease of 149.11 mm and a surface 2-meter air temperature increase of 1.33 °C compared to historical averages.
• Dominant anomalous subsidence and reduced water vapor transport were identified as primary causes of the drought.
• During the drought, total cloud cover decreased by 8.54%, cloud optical thickness decreased by 0.9, liquid water path was reduced by 0.01269 kg m⁻², and the effective radius of liquid water particles declined by 0.89 × 10⁻⁶ m.
• Surface shortwave cloud radiative forcing decreased by 17.78 W m⁻², and net surface cloud radiative forcing dropped by 14.82 W m⁻², indicating a significant weakening of the cloud's cooling effect.
• The diminished cloud cooling effect led to more solar radiation reaching the surface, causing an anomalous rise in surface temperature, which in turn decreased soil moisture and reduced local water vapor evaporation, thereby intensifying and sustaining the drought through a "hot-dry" feedback cycle.

Contributions

• Provides a systematic analysis of cloud-radiation effects during droughts in Yunnan, clarifying how clouds influence the regional surface energy balance and precipitation.
• Elucidates the roles and mechanisms of cloud processes in the extreme drought event of April-June 2019 in Yunnan.
• Offers scientific insights into extreme droughts in southwestern China, including the repeatability and general applicability of the identified cloud–radiation feedback mechanism.

Funding

• National Natural Science Foundation of China (No. 42175046)
• Key Fund Project of Basic Research of Yunnan Province (No. 202501AS070065)
• National Natural Science Foundation of China (No. 42065009)
• National Scientific and Technological Infrastructure “Earth System Numerical Simulation Facility” (https://cstr.cn/31134.02.EL)

Citation

@article{Tan2026Observational,
  author = {Tan, Y. X. and Zhou, Xinqiang and Chen, Bing and Li, Jiandong and Lin, Guo and Liu, Xiaohong and Luo, Tao},
  title = {Observational characteristics of cloud-radiation-precipitation during 2019 drought period in Yunnan of Southwest China},
  journal = {Climate Dynamics},
  year = {2026},
  doi = {10.1007/s00382-026-08152-w},
  url = {https://doi.org/10.1007/s00382-026-08152-w}
}