Robust Nocturnal and Early Morning Summer Rainfall Peaks over Continental East Asia in a Global Multiscale Modeling Framework

Abstract

The diurnal cycle of convection and precipitation is an important atmospheric feature. It also poses a great challenge to global numerical atmospheric modeling. Over continental East Asia, most global models cannot well capture the nocturnal and early morning peaks of summer rainfall. This problem may lead to dry biases and limit the modeling skills. This study investigates this problem using a global multiscale modeling framework (Super-Parameterized CAM5; SPCAM5). The nocturnal and early morning peaks, which are almost absent in CAM5 and a coarser-resolution SPCAM5, can be successfully captured by SPCAM5 with a moderate increase in the horizontal resolution. On the lee side of the Tibetan Plateau, SPCAM5 generates robust eastward propagating rainfall signals, which correspond to the moving convective systems, as revealed by the heating and drying profiles. Over the eastern plain of China, the early morning peaks become more evident, corresponding to a stratiform-type heating structure in the midlevel. A sensitivity experiment with altered grid-scale forcing also suggests the important preconditioning role of the vertical moisture advection in regulating the early morning peaks. These results highlight the added value of representing multiscale processes to the successful simulation of the diurnal cycle over continental East Asia.

AMIP Simulations of a Global Model for Unified Weather‐Climate Forecast: Understanding Precipitation Characteristics and Sensitivity Over East Asia

“…This resolution sensitivity is similar to SPCAM5 when its resolution is increased from 2° to 1° (cf., ZC16; Zhang, Chen, & Wang, 2019), but more evident. At 1°, SPCAM5 better supports some moving signals than CAM5 and produces similar stratiform heating patterns for this region, but it's overly strong rainfall rates at the higher topography (Figure 11b) seem to be a systematic problem.…”

“…The most distinctive diurnal mode over East Asia, nocturnal‐to‐early‐morning versus late‐afternoon peaks, can be reproduced by both SPCAM5 and GRIST. ZC16 and Zhang, Chen, and Wang 2019 compared CAM5 and SPCAM5 simulations of the diurnal cycles over East Asia. In summary, their studies indicated that, while improved parameterizations contribute to a better performance at a given resolution, a certain degree of resolution is still necessary to provide favorable dynamical conditions, leading to beneficial resolution sensitivity.…”

“…CAM5 does not show early morning rainfall peaks. Its convective rainfall mostly occurs in the afternoon (cf., ZC16; Zhang, Chen, & Wang, 2019). CAM5 shows weaker midlevel heating magnitudes and weaker vertical moisture advection between 500–850 hPa than SPCAM5 in the early morning (Figure 14f).…”

“…In particular, state‐of‐the‐art climate models are struggling to distinguish a fundamental continental diurnal mode: nocturnal‐to‐early‐morning peak versus late‐afternoon peak, and lacking some beneficial resolution sensitivity. In contrast, super‐parameterized GCMs (e.g., Randall et al., 2019) that can explicitly resolve dynamics at various scales, demonstrate relatively better performance than equivalent‐resolution conventional GCMs (e.g., ZC16; Zhang, Chen, & Wang, 2019—See references and descriptions therein). It is worthwhile knowing that, although super‐parameterized GCMs have a high‐resolution process model to resolve cloud‐scale dynamics, they do not possess superior ability to resolve GCM's grid‐scale motions than equivalent‐resolution conventional models.…”

Precipitation Diurnal Cycle in Germany Linked to Large-Scale Weather Circulations

“…Furthermore, it aids in the development of numerical weather models, which struggle to improve their representation of the PDC [10][11][12]. Such a challenge has been studied recently [13][14][15][16], particularly because the accuracy of a climate model on a daily scale reflects its quality in properly representing the physical processes or in parameterizing them.…”