Improving the Simulation of Diurnal and Sub-Diurnal Precipitation over Different Climate Regimes
Contacts: Shaocheng XieDavid NeelinPeter BechtoldHsi-Yen Ma

As understanding and improving the modeling of diurnal and sub-diurnal precipitation processes can have a broad impact on the fidelity of climate simulations, this proposed GASS project focuses on advancing the model capability through multimodel intercomparison studies against observations using a hierarchical modeling framework.

The overall goals are to:

  • understand what processes control the diurnal and sub-diurnal variation of precipitation over different climate regimes in observations and models and,
  • identify the deficiencies and missing physics in current Global Climate Models (GCMs) to gain insights for further improving the parameterization of convection in GCMs.

Potential research themes are:

  • Interaction between convection and water vapor
  • Nocturnal convection over land
  • Diurnal cycle of convection over ocean
  • Convection transition


  • A hierarchical model approach including Single-Column Model (SCM), Cloud-Resolving Model (CRM), Large-Eddy Simulations (LES), Regional model, and GCM.
  • Case studies vs. statistical studies
  • Short-range hindcasts vs. climate simulations

Current Status:

  • Participating Models:
    – 11 SCMs (E3SM, E3SM-Trigger, E3SM-SILHS, SCAM5/6, SAM0-UNICON, SKIM, CMC, SMCPCP, ICON, TaiESM) from 8 model groups
    – 2 CRMs (MONC and DWD)
    – 9 GCMs and 2 RGCMs (CAM6-CTL, CAM6-Trig, CMCGEM, ECMWF-IFS, E3SMv2, E3SMv2-CAPETrig, MPAS, TaiESM1, UMGA7, UMGA8, NUIST-WRF) from 8 model groups.
  • The multi-year long-term SCM intercomparison study over the ARM SGP and Amazon (MAO) sites completed. A summary paper is published in QJRMS.
  • The GCM intercomparison results are being actively analyzed. A manuscript will be ready for co-author internal review soon.
  • Need project leads for the CRM and LES intercomparison study.


Tang, S., Xie, S., Guo, Z., Hong, S.-Y. et al. (2022). Long-term single-column model intercomparison on diurnal cycle of precipitation over mid-latitude and tropical land, Quart J Roy Meteor Soc 1–29.

Tao, C., Xie, S., Ma, H.-Y. et al. (2023): Diurnal Cycle of Precipitation Over Tropical and Midlatitude Lands: GCM Inter-Comparison. In Preparation.

More information on the modeling approach, participation, timelines, coordination with other projects, and publication can be found here.