Improving representation of convective transport for scale‐aware parameterization: 1. Convection and cloud properties simulated with spectral bin and bulk microphysics

Abstract

The ultimate goal of this study is to improve the representation of convective transport by cumulus parameterization for mesoscale and climate models. As Part 1 of the study, we perform extensive evaluations of cloud-resolving simulations of a squall line and mesoscale convective complexes in midlatitude continent and tropical regions using the Weather Research and Forecasting model with spectral bin microphysics (SBM) and with two double-moment bulk microphysics schemes: a modified Morrison (MOR) and Milbrandt and Yau (MY2). Compared to observations, in general, SBM gives better simulations of precipitation and vertical velocity of convective cores than MOR and MY2 and therefore will be used for analysis of scale dependence of eddy transport in Part 2. The common features of the simulations for all convective systems are (1) the model tends to overestimate convection intensity in the middle and upper troposphere, but SBM can alleviate much of the overestimation and reproduce the observed convection intensity well; (2) the model greatly overestimates Z e in convective cores, especially for the weak updraft velocity; and (3) the model performs better for midlatitude convective systems than the tropical system. The modeled mass fluxes of the midlatitude systems are not sensitive to microphysics schemes but are very sensitive for the tropical case indicating strong microphysics modification to convection. Cloud microphysical measurements of rain, snow, and graupel in convective cores will be critically important to further elucidate issues within cloud microphysics schemes.

Modeling the Impacts of Urbanization on Summer Thermal Comfort: The Role of Urban Land Use and Anthropogenic Heat

“…Finally, in this study, WRF is configured with a single high‐resolution (i.e., 3 km) domain forced by a reanalysis product with a much coarser resolution (i.e., 1°). Similar configurations have been applied by a few other researchers (e.g., Fan et al, ). However, we should admit that the too smooth driving meteorology might restrict the model performance in capturing the fine‐scale surface climate, particularly over areas close to the lateral boundaries, which may further influence the estimated magnitudes of the local effects induced by urbanization.…”

Cloud‐resolving model intercomparison of an MC3E squall line case: Part I—Convective updrafts

“…Even within the same dynamical model, results have shown a general sensitivity of CRM deep convection simulations to different cloud microphysics schemes, which often produce large differences in storm structure, dynamics, precipitation, and anvil characteristics [e.g., Li et al ., , ; Morrison et al ., ; Morrison and Milbrandt , ; Fan et al ., ; Khain et al ., ]. This spread of deep convective cloud properties leads to a large uncertainty in assessing aerosol impacts on these clouds as the magnitude and even the sign of changes in updraft strength and surface precipitation with aerosol loading often vary, depending upon the particular model and microphysics parameterization used [e.g., Van den Heever and Cotton , ; Fan et al ., , ; Khain et al ., ].…”

“…The squall‐line MCS case simulated in this study occurred on 20 May 2011, during the Midlatitude Continental Convective Clouds Experiment (MC3E) [ Petersen and Jensen , ; Jensen et al ., ], which was supported by both the U.S. Department of Energy Atmospheric Radiation Measurement Program (ARM) and NASA's Global Precipitation Measurement mission ground validation program in north‐central Oklahoma from 22 April to 6 June 2011. Detailed ground‐based and aircraft cloud dynamical and microphysical observations are available for this case [ Mather and Voyles , ; Jensen et al ., ], which has been a focus of several recent studies [e.g., Tao et al ., , ; Giangrande et al ., ; Fan et al ., ; Kumjian et al ., ; Marinescu et al ., ; Van Lier‐Walqui et al ., ; Saleeby et al ., ; Fridlind et al ., ]. Section 2 includes a more detailed description of the case and the relevant observations used in this study.…”

Sensitivity of Mountain Hydroclimate Simulations in Variable‐Resolution CESM to Microphysics and Horizontal Resolution

“…One proposal to alleviate this issue is to push climate models to the highest grid‐spacings possible, typically utilizing modern exascale computing systems (Reed & Dongarra, ). This has resulted in a recent surge in research and development addressing multi‐scale modeling (Iorio et al, ; O'Brien et al, ; Tao et al, ), scale‐aware physics (Fan et al, ; Gross et al, ; Herrington & Reed, ; Randall et al, ), and atmospheric models that span hydrostatic and nonhydrostatic scales (Ferguson et al, ; Heinzeller et al, ; Herrington & Reed, ; Park et al, ).…”