Recently, Dr. Wang Yong published a paper online as the first author called “Simulation of Precipitation Extremes Using a Stochastic Convective Parameterization in the NCAR CAM5 under Different Resolutions” on Journal of Geophysical Research – Atmospheres, with Professor Zhang Guangjun. The paper founds improvements to extreme precipitation are achieved across three different resolutions (2°, 1°, and 0.5°) with the incorporation of the Plant-Craig stochastic deep convection scheme into the Zhang-McFarlane deterministic parameterization in the Community Atmospheric Model version 5 (CAM5). This research will have a profound impact on the future projection of extreme precipitation in climate models. The corresponding author of this paper is Professor Zhang Guangjun from the Department of Earth System Science.

CAM5 with the stochastic deep convection scheme (experiment (EXP)) simulates the precipitation extreme indices better than the standard version (control). At 2° and 1° resolutions, EXP increases high percentile ( > 99th) daily precipitation over the United States, Europe, and China, resulting in a better agreement with observations. However, at 0.5° resolution, due to enhanced grid-scale precipitation with increasing resolution, EXP overestimates extreme precipitation over southeastern U.S. and eastern Europe. The reduced biases in EXP at each resolution bene？t from a broader probability distribution function of convective precipitation intensity simulated.

Figure1. Biases in different CTL simulations over ( ？rst row) contiguous U.S., (second row) Europe, (third row) China, and (fourth row) land between 50°S and 50°N, measured against EOBS, NOAA CPC, CMA, and TRMM observational data sets, respectively, for the 99th percentile extreme precipitation (daily aggregated values), period 1991 – 1992. Top left title indicates the grid original resolution of CAM5. For comparison, 1° and 0.5° simulations along with observations are regridded to 2° model resolution grids. RMSE is the root-mean-square value of the bias across all grid boxes.

Figure 2. Same as Figure 1 but for different EXP simulations.

Figure 3. Fraction of grid-scale precipitation in different CTL and EXP simulations with their native grids over China over all days exceeding the 99th percentile extreme precipitation (daily aggregated values) for the period of 1991 – 1992.

Journal of Geophysical Research – Atmospheres is the authoritative magazine in the field of the atmospheric science, according to Thomson Reuters's 2017 reference report, its impact factor is 3.454.