Purpose

General Circulation Models (GCMs) for weather forecasts and climate simulations continue having difficulties in modeling the diurnal and sub-diurnal precipitation particularly over land. The issue is related to inappropriate representation of the processes that control sub-diurnal phenomenon like convection, and phenomena with timescales around the order of diurnal, like mesoscale systems. Problems in simulating the diurnal cycle of precipitation are primarily due to shortcomings and deficiencies in representing convection initiation, evolution, and propagation, as well as the interaction between convection and its large-scale atmospheric environment and the underlying land surface.
 
This project focuses on improving the model capability to simulate diurnal and sub-diurnal precipitation phenomena through multimodel intercomparison studies against observations. The overall goal is to understand what processes control the diurnal and sub-diurnal variation of precipitation over different climate regimes in observations and in models and identify the deficiencies and missing physics in current GCMs to gain insights for further improving the parameterization of convection in GCMs.

 

Research Themes

  • Interaction between convection and water vapor:
    • Identify the processes that primarily control the diurnal and sub-diurnal variability in precipitation over different climate regimes and evaluate how well current GCMs represent these processes, and in particular the statistical relationships that describe the interaction between convection and moisture fields under various synoptic conditions against observations (e.g., GoAmazon).
    •  
  • Nocturnal convection over land:
    • Identify the processes that primarily control nocturnal elevated convection at SGP and evaluate how well current GCMs represent these processes. The MC3E, PECAN field campaigns, as well as ARM long-term observations will provide observational insights into this issue, and support for modeling investigations.
    •  
  • Convection transition:
    • Identify the processes that primarily control the transition from shallow to deep convection over land and evaluate how well current GCMs represent these processes.
    •  
  • Diurnal cycle of convection over ocean:
    • Identify the processes that primarily control diurnal cycle of convection over ocean and evaluate how well current GCMs represent these processes.

 

A hierarchy modeling approach

A hierarchy of models including single column models (SCMs)/Cloud-Resolving Models (CRMs), Cloud Permitting Models (CPMs), and GCMs is proposed to be used in the multimodel intercomparison study to diagnose and investigate the associated processes and model biases in depth.