Impact of horizontal resolution on the regional climate simulations of the summer 1998 extreme rainfall along the Yangtze River Basin

Abstract

[1] In this study, the effects of varying horizontal grid resolutions on the regional climate model (RCM) simulation of the summer 1998 extreme rainfall events along the middle to lower reaches of the Yangtze-River Basin (YRB-ML) are examined using the Pennsylvania State University-National Center for Atmospheric Research mesoscale model (i.e., MM5). Results show that the MM5 simulation with the finest grid size of 4 km reproduces reasonably well the rainfall intensity and rainbelt distribution over the YRB-ML during all the Meiyu phases, whereas lower-resolution simulations tend to shift the east-west-oriented major rainbelt southwestward as a result of the generated local storms and excessive rainfall during the second Meiyu rainy phase in which vertical (horizontal) wind shears are weak (strong). The excessive rainfall occurs during the evening hours when the low-level jet is relatively strong and in the Meiyu frontal zone where convergence of warm and moist air is pronounced. Results reveal the importance of incorporating convective parameterizations in removing potential instability in heavy rain-producing storms even for RCMs with 3-5 km horizontal resolutions. It is highly desirable to use higher-resolution models with realistic parameterized and grid-scale cloud physics schemes to study the regional climate of heavy rainfall events.

Numerical Simulation of the Heavy Rainfall in the Yangtze-Huai River Basin during Summer 2003 Using the WRF Model

“…The core speed is nearly 4 to 6 m s 1 greater than the value obtained from the FNL analysis. This result is similar to that obtained from the low-level wind simulation for the summer of 1998 using the Pennsylvania State University-National Center for Atmospheric Research mesoscale model (i.e., MM5) (Liu et al, 2008(Liu et al, , 2010. The relative humidity distributions shown by the FNL data and the WRF simulation are similar, but the region north of the Huai River Basin in the simulation is relatively dry.…”

“…The atmosphere and soil initial conditions are both taken from the six-hourly global analysis data provided by the 1.0×1.0-degree grids of the National Centers for Environmental Prediction (NCEP) Final (FNL) operational model. As in Liu et al (2008Liu et al ( , 2010, we adopt a buffer zone of approximately 1000 km (30 grid intervals) along each lateral boundary to keep the incoming large-scale flows reasonably well defined. The FNL data are also used as the atmospheric lateral boundary conditions for the model.…”

“…Compared to the coarse-resolution general circulation models, the primary advantage of the RCM approach is that it furnishes a better description of orographic forcing, based on smaller grid sizes (Yu et al, 2010). Although many uncertainties and problems still exist on the choices of the RCM domain range (Xue et al, 2007), the horizontal grid size (Liu et al, 2010), and the underlying physical models Corresponding author: LIU Hong-Bo, hongboliu@mail.iap.ac.cn (Cha et al, 2008;Yhang and Hong, 2008;Liu and Wang, 2011), the performance of RCMs is still preferable for the purpose of regional climate simulation.…”

Performance of convective parameterization schemes in Asia using RegCM: Simulations in three typical regions for the period 1998–2002

“…Efforts have been made in recent decades to develop and improve regional climate models (RCMs), but many problems remain; for example, the lateral boundary conditions (Liang et al, 2001;Wu et al, 2005), horizontal resolution, size match of a region (Vannitsem and Chomé, 2005;Xue et al, 2007;Liu et al, 2010), and the parameterization schemes of unique physical processes (Cha et al, 2008;Yhang and Hong, 2008). Moreover, the selection of an appropriate convective parameterization scheme (CPS) in RCMs is a major source of error and has significant impact on regional climate model predictions (Pal et al, 2007).…”

Subkilometer Simulation of a Torrential-Rain-Producing Mesoscale Convective System in East China. Part I: Model Verification and Convective Organization

“…13d and 14a,b suggests that the absence of an intense meso-high or cold dome accounts for the less realistically organized convection and rainfall fields in both sensitivity simulations. Similar results were also shown by Liu et al (2010) in the regional climate simulations of the summer 1998 extreme rainfall in east China using even the finest grid size of 4 km. Similarly, with the use of convective parameterizations, Liao and Tan (2005) and Wang and Ni (2006) also produced excessive rainfall and a low-level mesolow or mesovortex associated with the torrential-rain-producing storm in their 12and 9-km grid-spacing simulations, respectively.…”