Impact of Convection‐Permitting and Model Resolution on the Simulation of Mesoscale Convective System Properties Over East Asia

Abstract

In this study, two limited‐area convection‐permitting models (ICON‐CPMs) and convection‐parameterized models (ICON‐CParMs) covering the Asia monsoon region from ICOsahedral Nonhydrostatic model are conducted to investigate the sensitivities of Mesoscale Convective Systems (MCSs) to convection configurations and horizontal resolutions. We find that ICON‐CPMs outperform ICON‐CParMs and ERA5 in number, lifetime, size, shape, orientation, effective speed, and MCS‐mean precipitation. Compared to the satellite observation, MCSs in ICON‐CParMs and ERA5 are oversized (30%–66%) and have longer (21%–29%) lifetimes but occur less (37%–46%) frequently. When turning off the convection scheme, performances are improved to a large extent. The underestimation of MCS‐mean precipitation rates in ICON‐CParMs and ERA5 are improved in ICON‐CPMs. Moisture budgets show that low‐level winds rather than moisture determine the strength of MCS‐mean precipitation rate. The strong low‐level convergence produces strong updrafts in ICON‐CPMs and eventually results in strong MCS precipitation. The overly intense convective precipitation of MCSs in CPMs is an inherent problem since the scale of convection triggered at the gray zone grid spacing is larger than that in the real world. Although the MCS‐mean precipitation rate is closer to the satellite observation in ICON‐CPMs, it is actually a compensation for overly strong convective precipitation and overly weak stratiform precipitation. Upgrading resolution from 8 to 4 km in ICON‐CPMs has benefits in simulating MCS lifetime, size, shape, orientation, and precipitation but not in MCS number.

Contribution of Mesoscale Convective Systems to Floods in the East Asian Summer Monsoon Region

“…We further filter out cold cloud systems that fail to meet that cold core (Tb < 220 K) over 5,000 km 2 that lasts for at least 3 hr and convective core (precipitation intensity >5 mm hr 1 ) over 2500 km 2 that lasts for at least 2 hr. These thresholds are in line with Ding et al (2023) which are proved to be more applicable to MCS tracking in East Asia. MCSs over Asia from 2000 to 2021 are tracked.…”

“…We apply the MCS tracking method used in Ding et al (2023), which mainly contains three steps: (a) detecting cloud features based on Tb, (b) linking cloud features over time, and then (c) filtering out the cold cloud systems without cold core characteristics and convective characteristics. A cold cloud system is defined as a contiguous area over 10,000 km 2 with Tb < 241 K that persists for at least 4 hr.…”