publications

2024

1. Seasonal Characteristics of Forecasting Uncertainties in Surface PM2.5 Concentration Associated with Forecast Lead Time over the Beijing-Tianjin-Hebei Region

   Qiuyan Du ,  Chun Zhao ,  Jiawang Feng ,  Zining Yang ,  Jiamin Xu ,  Jun Gu , and 3 more authors

   Advances in Atmospheric Sciences, Mar 2024

   天气要素的预报误差对污染预报的影响

   Abs

   Forecasting uncertainties among meteorological fields have long been recognized as the main limitation on the accuracy and predictability of air quality forecasts. However, the particular impact of meteorological forecasting uncertainties on air quality forecasts specific to different seasons is still not well known. In this study, a series of forecasts with different forecast lead times for January, April, July, and October of 2018 are conducted over the Beijing-Tianjin-Hebei (BTH) region and the impacts of meteorological forecasting uncertainties on surface PM2.5 concentration forecasts with each lead time are investigated. With increased lead time, the forecasted PM2.5 concentrations significantly change and demonstrate obvious seasonal variations. In general, the forecasting uncertainties in monthly mean surface PM2.5 concentrations in the BTH region due to lead time are the largest (80%) in spring, followed by autumn (~50%), summer (~40%), and winter (20%). In winter, the forecasting uncertainties in total surface PM2.5 mass due to lead time are mainly due to the uncertainties in PBL heights and hence the PBL mixing of anthropogenic primary particles. In spring, the forecasting uncertainties are mainly from the impacts of lead time on lower-tropospheric northwesterly winds, thereby further enhancing the condensation production of anthropogenic secondary particles by the long-range transport of natural dust. In summer, the forecasting uncertainties result mainly from the decrease in dry and wet deposition rates, which are associated with the reduction of near-surface wind speed and precipitation rate. In autumn, the forecasting uncertainties arise mainly from the change in the transport of remote natural dust and anthropogenic particles, which is associated with changes in the large-scale circulation.

2. Global convection-permitting model improves subseasonal forecast of plum rain around Japan

   Jun Gu ,  Chun Zhao ,  Mingyue Xu ,  Jiawang Feng ,  Gudongze Li ,  Yongxuan Zhao , and 3 more authors

   Environmental Research Letters, Aug 2024

   2nd_paper

   Abs

   In 2020 early summer, a historically severe rainy season struck East Asia, causing extensive damage to life and property. Subseasonal forecast of this event challenges the limits of rainy season predictability. Employing the integrated atmospheric model across scales and the Sunway supercomputer, we conducted ensemble one-month forecasts at global 3 km, variable 4–60 km, and global 60 km resolutions. The global convection-permitting forecast accurately captures the rainband, while other forecasts exhibited northward and weaker shifts due to the northward shifts of the atmospheric rivers over Japan, attributed to intensified Western North Pacific Subtropical High (WNPSH). Further, the double-ITCZ-like tropical rainfall pattern in Western Pacific in global convection-permitting forecast contributes to a more accurate WNPSH and rainband. In contrast, other forecasts show a single-ITCZ-like pattern in Western Pacific, leading to a northward-shifted WNPSH and rainband, advocating the importance of accurately representing tropical convections, as they can significantly affect mid-/high-latitude weather and climate.

2023

1. Establishing a Modeling System in 3-km Horizontal Resolution for Global Atmospheric Circulation triggered by Submarine Volcanic Eruptions with 400 Billion Smoothed Particle Hydrodynamics

   Shenghong Huang ,  Junshi Chen ,  Ziyu Zhang ,  Xiaoyu Hao ,  Jun Gu ,  Hong An , and 15 more authors

   In Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis , Aug 2023

   火山模式

   Abs

   People are increasingly concerned about how tectonic processes affect climate and vice versa. We establish a cross-sphere modeling system for volcanic eruptions and atmosphere circulation on a new Sunway supercomputer with a spatial resolution from 10m locally to 3km globally, using an improved multimedium and multiphase smoothed particle hydrodynamics (SPH) combined with a fully coupled meteorology-chemistry global atmospheric modeling scheme. We achieve 400 billion particles and 80% parallel efficiency using 39,000,000 processor cores. The simulation captures the whole dynamic process of the Tonga eruption from shock waves, earthquakes, tsunamis, mushroom clouds to the following 6–7 days of transport and diffusion of ash and water vapor, and preliminarily obtains the influence effect of full coupling of volcano, earthquake, ocean and atmosphere. This work is of great significance for deeply understanding the interaction between tectonic processes and climate change, and establishing an early warning simulation system for similar global hazard events.

2. Toward Earth System Modeling with Resolved Clouds and Ocean Submesoscales on Heterogeneous Many-Core HPCs

   Shaoqing Zhang ,  Shiming Xu ,  Haohuan Fu ,  Lixin Wu ,  Zhao Liu ,  Yang Gao , and 31 more authors

   National Science Review, Mar 2023

   Abs

   With the aid of the newly-developed ‘Sunway’ heterogeneous architecture supercomputer which has a world-leading HPC capability, a series of high-resolution coupled Earth system models (HR-ESMs) up to 5 km atmosphere and 3 km ocean have been developed. These models can meet the needs of multiscale interaction studies with different computational costs. Here we describe the progress of HR-ESM development, with an overview of the major advancement of international Earth science community in HR-ESMs. We also show the preliminary results of HR-ESMs in capturing the major weather-climate extremes in the atmosphere and ocean, stressing the importance of permitted clouds and ocean submesoscale eddies in modeling tropical cyclones and eddy-mean flow interactions, paving for further model development to resolve finer-scales with even higher resolution and more realistic physics. Finally, in addition to increasing model resolution, the development procedure for a nonhydrostatic cloud and ocean submesoscale resolved ESM was discussed, laying out the major scientific directions of such a huge modeling advancement.

3. Appropriately representing convective heating is critical for predicting catastrophic heavy rainfall in 2021 in Henan Province of China

   Mingyue Xu ,  Chun Zhao ,  Jun Gu ,  Jiawang Feng ,  Gudongze Li ,  and  Jianping Guo

   Environmental Research Communications, May 2023

   对流潜热释放

   Abs

   An unprecedented heavy rainfall event occurred in Henan Province of central China during 19–20 July 2021 with the maximum hourly rainfall rate of 201.9 mm, which broke the historical record in mainland China. To investigate the impacts of predicted atmospheric circulation on the regional convection-permitting prediction of this event, two sets of nested experiments with different convective parameterizations (GF and MSKF) in the outer domain and at convection-permitting resolution in the inner domain are performed with the Weather Research and Forecasting (WRF) model. The analysis found the prediction of ‘21.7’ rainstorm at convection-permitting resolution in the inner domain is largely affected by convective scheme in the outer domain. The atmospheric circulation forcing from the outer domain with different convective schemes is significantly different, which ultimately affects the regional synoptic pattern and precipitation in the refined region through lateral boundary forcing. The difference in regional prediction at convection-permitting resolution can be mitigated by adjusting convective latent heat parameterization in the outer domain. This work highlights that appropriately parameterizing convective latent heat is the key to provide reasonable large-scale forcing for regionally predicting this catastrophic heavy rainfall event at convection-permitting resolution, which may also be applicable to other events and other regions.

4. Southern Himalayas rainfall as a key driver of interannual variation of pre-monsoon aerosols over the Tibetan Plateau

   Weichen Liu ,  Chun Zhao ,  Mingyue Xu ,  Jiawang Feng ,  Qiuyan Du ,  Jun Gu , and 2 more authors

   npj Climate and Atmospheric Science, Jun 2023

   Abs

   The Tibetan Plateau (TP) is one of the most climate-sensitive regions around the world. Aerosols imported from adjacent regions reach their peak during the pre-monsoon season and play a vital role in the TP environment. However, the strong interannual variation in aerosols transported to the TP has not been fully understood. Here, we show that the interannual variability of pre-monsoon aerosols transported to the TP is influenced more by rainfall over the southern Himalayas than near-surface wind. Rainfall modulates fire events and biomass burning emissions and reduces aerosols over the TP by wet scavenging. Contrary to the role of wind in increasing aerosol transport, the positive correlation between wind and aerosols in the TP reported in previous studies is contributed by the negative interannual correlations between wind and rainfall and between rainfall and fire events over the southern Himalayas. This study highlights the co-variability of wind and rainfall and their confounding impacts on aerosols in the southern Himalayas and over the TP. With pre-monsoon rainfall projected to increase in adjacent regions of southern TP, aerosol transport to the TP may be mitigated in the future.

5. swMPAS-A: Scaling MPAS-A to 39 Million Heterogeneous Cores on the New Generation Sunway Supercomputer

   Xiaoyu Hao ,  Tao Fang ,  Junshi Chen ,  Jun Gu ,  Jiawang Feng ,  Hong An , and 1 more author

   IEEE Transactions on Parallel and Distributed Systems, Jan 2023

   Conference Name: IEEE Transactions on Parallel and Distributed Systems

   Abs

   With the computing power of High-Performance Computing (HPC) systems having stepped into the exascale era, more complex problems can be solved with scientific applications on a large scale. However, due to the significant performance gap between computing nodes and storage subsystems, suboptimal design for the Input/Output (I/O) module will significantly impede the efficiency of scientific applications, especially for the ubiquitous atmosphere applications. Two-phase I/O implemented in N-to-1 mode creates a serious bottleneck that hinders the scalability for the Model for Prediction Across Scales-Atmosphere (MPAS-A) on the new generation Sunway supercomputer. To address the I/O problem, we apply a custom data reorganization method to enable N-to-M I/O mode to exploit the parallel file system’s performance and limit the data transfer among MPI ranks to a restricted scope to alleviate communication overhead. Moreover, we have conducted several methods to accelerate the computations, including the redesign for tracer transport, a hybrid buffering scheme, and a three-level parallelization scheme, which allows MPAS-A to use all heterogeneous computing resources efficiently. Experimental results show admirable scalability and efficiency of our I/O method, which achieves speedups of 41× and 58.9× for input and output compared with the raw I/O method on 30,000 MPI ranks. By scaling MPAS-A to 39 million heterogeneous cores, we demonstrate the necessity of a well-constructed I/O module for a real-world atmosphere application. Speed tests show that our optimization methods obtain good results for computations, and MPAS-A achieves a speed of 0.82 Simulated Day per Hour (SDPH) and 0.76 parallel efficiency of strong scaling with 600,000 MPI ranks.

6. Simulating Atmospheric Dust With a Global Variable-Resolution Model: Model Description and Impacts of Mesh Refinement

   Jiawang Feng ,  Chun Zhao ,  Qiuyan Du ,  Mingyue Xu ,  Jun Gu ,  Zhiyuan Hu , and 1 more author

   Journal of Advances in Modeling Earth Systems, Jan 2023

   Abs

   In this study, a global variable-resolution modeling framework of atmospheric dust and its radiative feedback is established and evaluated. In this model, atmospheric dust is simulated simultaneously with meteorological fields, and dust-radiation interactions are included. Five configurations of global mesh with refinement at different resolutions and over different regions are used to explore the impacts of regional refinement on modeling dust lifecycle at regional and global scales. The model reasonably produces the overall magnitudes and spatial variabilities of global dust metrics such as surface mass concentration, deposition, aerosol optical depth, and radiative forcing compared to observations and previous modeling results. Two global variable-resolution simulations with mesh refinement over major deserts of North Africa (V16 km-NA) and East Asia (V16 km-EA) simulate less dust emissions and smaller dry deposition rates inside the refined regions due to the weakened near-surface wind speed caused by better resolved topographic complexity at higher resolution. The dust mass loadings over North Africa are close to each other between V16 km-NA and the quasi-uniform resolution (∼120 km) (U120 km), while over East Asia, V16 km-EA simulates higher dust mass loading. Over the non-refined areas with the same resolution, the difference between global variable-resolution and uniform-resolution experiments also exists, which is partly related to their difference in dynamic time-step and the coefficient for horizontal diffusion. Refinement at convection-permitting resolution around the Tibetan Plateau (TP) simulates less dust due to its more efficient wet scavenging from resolved convective precipitation around the TP against coarse resolution.

2022

1. Establishing a non-hydrostatic global atmospheric modeling system at 3-km horizontal resolution with aerosol feedbacks on the Sunway supercomputer of China

   Jun Gu ,  Jiawang Feng ,  Xiaoyu Hao ,  Tao Fang ,  Chun Zhao ,  Hong An , and 7 more authors

   Science Bulletin, Mar 2022

   Abs

   During the era of global warming and highly urbanized development, extreme and high impact weather as well as air pollution incidents influence everyday life and might even cause the incalculable loss of life and property. Although, with the vast development of atmospheric model, there still exists substantial numerical forecast biases objectively. To predict accurately extreme weather, severe air pollution, and abrupt climate change, the numerical atmospheric model requires not only to simulate meteorology and atmospheric compositions simultaneously involving many sophisticated physical and chemical processes but also at high spatiotemporal resolution. Global integrated atmospheric simulation at spatial resolutions of a few kilometers remains challenging due to its intensive computational and input/output (I/O) requirement. Through multi-dimension-parallelism structuring, aggressive and finer-grained optimizing, manual vectorizing, and parallelized I/O fragmenting, an integrated Atmospheric Model Across Scales (iAMAS) was established on the new Sunway supercomputer platform to significantly increase the computational efficiency and reduce the I/O cost. The global 3-km atmospheric simulation for meteorology with online integrated aerosol feedbacks with iAMAS was scaled to 39,000,000 processor cores and achieved the speed of 0.82 simulation day per hour (SDPH) with routine I/O, which enabled us to perform 5-day global weather forecast at 3-km horizontal resolution with online natural aerosol impacts. The results demonstrate the promising future that the increasing of spatial resolution to a few kilometers with online integrated aerosol feedbacks may significantly improve the global weather forecast.

2021

1. Convection‐Permitting Hindcasting of Diurnal Variation of Mei‐yu Rainfall Over East China With a Global Variable‐Resolution Model

   Mingyue Xu ,  Chun Zhao ,  Jun Gu ,  Jiawang Feng ,  Samson Hagos ,  L. Ruby Leung , and 4 more authors

   Journal of Geophysical Research: Atmospheres, Jul 2021

   Meiyu

   Abs

   Two sets of 48-h hindcast experiments for Mei-yu season using non-hydrostatic global variable-resolution model (MPAS-Atmosphere) with regional refinement at 4 km resolution (V4km) and uniform 60 km resolution (U60km) are first-time conducted to attempt at simulating the Mei-yu rainfall in 2015 over East China. The analysis focuses on the seasonal average of diurnal variation of precipitation amount (PA), intensity (PI), and frequency (PF). Both simulations reasonably reproduce the spatial distribution of PA. V4km is more skillful in simulating the spatial distributions and magnitudes of PF and PI. The diurnal cycle of Mei-yu rainfall shows a major early morning peak and a minor afternoon peak, contributed by precipitation during two sub-periods with distinct synoptic circulations. With strong Mei-yu in the first sub-period, the diurnal variation of PA is controlled by nocturnal southwesterly jet. V4km overestimates the morning peak mainly due to its bias in simulating boundary layer inertial oscillation. Although differences in PA between the simulations are small, U60km overestimates PF and underestimates PI. With weak Mei-yu in the second sub-period, the diurnal variation of PA is controlled by both synoptic circulation and local convection. At both resolutions, deviations in the large-scale circulation modulated by a few typhoons lead to positive biases in the morning peak of PA. After removing the typhoon impacts, V4km captures the observed diurnal cycle of PA well, while U60km significantly underestimates PA and PI particularly in the afternoon. Future studies focusing on advancing modeling of southwesterly jet and typhoons may further improve convection permitting simulation of Mei-yu rainfall.