scholarly journals The impact of different nitrous acid sources in the air quality levels of the Iberian Peninsula

2010 ◽  
Vol 10 (11) ◽  
pp. 28183-28230 ◽  
Author(s):  
M. Gonçalves ◽  
D. Dabdub ◽  
W. L. Chang ◽  
F. Saiz ◽  
O. Jorba ◽  
...  
Keyword(s):  
Air Quality ◽  
Iberian Peninsula ◽  
Gas Phase ◽  
Urban Areas ◽  
Nitrous Acid ◽  
Quality Models ◽  
Chemical Mechanisms ◽  
Gas Phase Chemistry ◽  
Secondary Pollutants ◽  
Phase Chemistry

Abstract. Hydroxyl radical (OH) is a primary oxidant in the atmosphere and affects both gas-phase pollutants and particulate matter levels. Nitrous acid (HONO) acts as an important source of OH in the urban atmosphere. Therefore it is important to account accurately for HONO sources within air quality models in order to predict air pollution dynamics. HONO observations in urban areas are characterized by high concentrations at night and low concentrations around midday. Existing gas-phase chemical mechanisms do not reproduce the observed HONO levels, suggesting a lack of sources, such as direct emissions or heterogeneous reactions. Specific HONO emission rates, heterogeneous chemical mechanisms leading to its formation and related kinetics are still unclear. Therefore, most air quality models consider exclusively gas-phase chemistry related to HONO. This work applies the WRF-ARW/HERMES/CMAQ modeling system to quantify the effect of the addition of HONO sources in the predictability of HONO profiles, and its subsequent effect on secondary pollutants formation (mainly O3 and PM2.5). The modeling episode is based on a 2004 severe summertime pollution event in the Iberian Peninsula, using high resolution of 4 × 4 km2. Two different parameterizations for emissions and the hydrolysis of NO2 on wet surfaces are added as HONO sources in the atmosphere. Emissions have the largest impact on HONO levels, especially in urban areas, where they can contribute from 66% to 94% to the HONO peak concentration. Additionally, in urban environments, NO2 hydrolysis on building and vegetation surfaces contributes up to 30% to the HONO peak. Both, the available surface area and the relative humidity must be included as parameters affecting the NO2 hydrolysis kinetics. As a result, NO2 hydrolysis is negligible on aerosol surfaces, due to the small surface area available for reaction, and it is more effective in producing HONO below high relative humidity conditions. The addition of HONO sources affects the concentration of secondary pollutants. In particular, major changes are produced in the early morning, due to the higher OH release via HONO photolysis. Significant changes in PM2.5 concentrations are predicted, that can be 16% (2.6 μg m−3) higher in the new scenarios. When accounting for HONO sources, nitrate levels increase especially in urban areas and sulfates in areas downwind from conventional power plants in the Iberian Peninsula. Also, O3 peak concentrations are slightly affected (from 0.7 to 4 ppb, 1% to 4.5%). The improvement of the HONO sources representation within air quality models produces changes in O3 peak predictions and significantly affects the reaction pathways leading to aerosols formation. Therefore, HONO sources other than gas-phase chemistry should be accurately included within modeling frameworks.

Evaluation of aromatic oxidation reactions in seven chemical mechanisms with an outdoor chamber

2013 ◽  
Vol 10 (3) ◽  
pp. 245 ◽  
Author(s):  
Harshal M. Parikh ◽  
Harvey E. Jeffries ◽  
Ken G. Sexton ◽  
Deborah J. Luecken ◽  
Richard M. Kamens ◽  
...  
Keyword(s):  
Air Quality ◽  
Aromatic Ring ◽  
Aromatic Hydrocarbons ◽  
Urban Areas ◽  
Ring Opening ◽  
Chamber Wall ◽  
Oxidation Reactions ◽  
Quality Models ◽  
Chemical Mechanisms ◽  
Wide Range

Environmental context Regulatory air quality models used to develop strategies to reduce ozone and other pollutants must be able to accurately predict ozone produced from aromatic hydrocarbons. In urban areas, major sources of aromatic hydrocarbons are gasoline and diesel-powered vehicles. Our findings show that the representation of aromatic hydrocarbon chemistry in air quality models is an area of high uncertainty Abstract Simulations using seven chemical mechanisms are intercompared against O3, NOx and hydrocarbon data from photooxidation experiments conducted at the University of North Carolina outdoor smog chamber. The mechanisms include CB4–2002, CB05, CB05-TU, a CB05 variant with semi-explicit aromatic chemistry (CB05RMK), SAPRC07, CS07 and MCMv3.1. The experiments include aromatics, unsaturated dicarbonyls and volatile organic compound (VOC) mixtures representing a wide range of urban environments with relevant hydrocarbon species. In chamber simulations the sunlight is characterised using new solar radiation modelling software. A new heterogeneous chamber wall mechanism is also presented with revised chamber wall chemical processes. Simulations from all mechanisms, except MCMv3.1, show median peak O3 concentration relative errors of less than 25% for both aromatic and VOC mixture experiments. Although MCMv3.1 largely overpredicts peak O3 levels, it performs relatively better in predicting the peak NO2 concentration. For aromatic experiments, all mechanisms except CB4–2002, largely underpredict the NO–NO2 crossover time and over-predict both the absolute NO degradation slope and the slope of NO2 concentration rise. This suggests a major problem of a faster and earlier NO to NO2 oxidation rate across all the newer mechanisms. Results from individual aromatic and unsaturated dicarbonyl experiments illustrate the unique photooxidation chemistry and O3 production of several aromatic ring-opening products. The representation of these products as a single mechanism species in CB4–2002, CB05 and CB05-TU is not adequate to capture the O3 temporal profile. In summary, future updates to chemical mechanisms should focus on the chemistry of aromatic ring-opening products.

scholarly journals Elevated levels of OH observed in haze events during wintertime in central Beijing

2020 ◽  
Author(s):  
Eloise J. Slater ◽  
Lisa K. Whalley ◽  
Robert Woodward-Massey ◽  
Chunxiang Ye ◽  
James D. Lee ◽  
...  
Keyword(s):  
Gas Phase ◽  
Chemical Mechanism ◽  
Daily Maximum ◽  
Mixing Ratios ◽  
Gas Phase Chemistry ◽  
Photolysis Rates ◽  
Secondary Pollutants ◽  
High Pollution ◽  
Phase Chemistry

Abstract. Wintertime in situ measurements of OH, HO2 and RO2 radicals and OH reactivity were made in central Beijing during November and December 2016. Exceptionally elevated NO was observed on occasions, up to ~ 250 ppbv, believed to be the highest mole fraction for which there have then co-located radical observations. The daily maximum mixing ratios for radical species varied significantly day-to-day over the range 1–8 × 106 cm−3 (OH), 0.2–1.5 × 108 cm−3 (HO2) and 0.3–2.5 × 108 cm−3 (RO2). Averaged over the full observation period, the mean daytime peak in radicals was 2.7 × 106 cm−3, 0.39 × 108 cm−3 and 0.88 × 108 cm−3 for OH, HO2 and total RO2, respectively. The main daytime source of new radicals via initiation processes (primary production) was the photolysis of HONO (~ 83 %), and the dominant termination pathways were the reactions of OH with NO and NO2, particularly under polluted, haze conditions. The Master Chemical Mechanism (MCM) v3.3.1 operating within a box model was used to simulate the concentrations of OH, HO2 and RO2. The model underpredicted OH, HO2 and RO2, especially when NO mixing ratios were high (above 6 ppbv). The observation-to-model ratio of OH, HO2 and RO2 increased from ~ 1 (for all radicals) at 3 ppbv of NO to a factor of ~ 3, ~ 20 and ~ 91 for OH, HO2 and RO2, respectively, at ~ 200 ppbv of NO. The significant underprediction of radical concentrations by the MCM suggests a deficiency in the representation of gas-phase chemistry at high NOx. The OH concentrations were surprisingly similar (within 20 % during the day) inside and outside of haze events, despite j(O1D) decreasing by 50 % during haze periods. These observations provide strong evidence that gas-phase oxidation by OH can continue to generate secondary pollutants even under high pollution episodes, despite the reduction in photolysis rates within haze.

scholarly journals Improvement and further development in CESM/CAM5: gas-phase chemistry and inorganic aerosol treatments

2014 ◽  
Vol 14 (17) ◽  
pp. 9171-9200 ◽  
Author(s):  
J. He ◽  
Y. Zhang
Keyword(s):  
Air Quality ◽  
Gas Phase ◽  
Power Law ◽  
Global Scale ◽  
Particle Formation ◽  
New Particle Formation ◽  
Gas Phase Chemistry ◽  
Model Version ◽  
Inorganic Aerosol ◽  
Phase Chemistry

Abstract. Gas-phase chemistry and subsequent gas-to-particle conversion processes such as new particle formation, condensation, and thermodynamic partitioning have large impacts on air quality, climate, and public health through influencing the amounts and distributions of gaseous precursors and secondary aerosols. Their roles in global air quality and climate are examined in this work using the Community Earth System Model version 1.0.5 (CESM1.0.5) with the Community Atmosphere Model version 5.1 (CAM5.1) (referred to as CESM1.0.5/CAM5.1). CAM5.1 includes a simple chemistry that is coupled with a 7-mode prognostic Modal Aerosol Model (MAM7). MAM7 includes classical homogenous nucleation (binary and ternary) and activation nucleation (empirical first-order power law) parameterizations, and a highly simplified inorganic aerosol thermodynamics treatment that only simulates particulate-phase sulfate and ammonium. In this work, a new gas-phase chemistry mechanism based on the 2005 Carbon Bond Mechanism for Global Extension (CB05_GE) and several advanced inorganic aerosol treatments for condensation of volatile species, ion-mediated nucleation (IMN), and explicit inorganic aerosol thermodynamics for sulfate, ammonium, nitrate, sodium, and chloride have been incorporated into CESM/CAM5.1-MAM7. Compared to the simple gas-phase chemistry, CB05_GE can predict many more gaseous species, and thus could improve model performance for PM2.5, PM10, PM components, and some PM gaseous precursors such as SO2 and NH3 in several regions as well as aerosol optical depth (AOD) and cloud properties (e.g., cloud fraction (CF), cloud droplet number concentration (CDNC), and shortwave cloud forcing, SWCF) on the global scale. The modified condensation and aqueous-phase chemistry could further improve the prediction of additional variables such as HNO3, NO2, and O3 in some regions, and new particle formation rate (J) and AOD on the global scale. IMN can improve the prediction of secondary PM2.5 components, PM2.5, and PM10 over Europe as well as AOD and CDNC on the global scale. The explicit inorganic aerosol thermodynamics using the ISORROPIA II model improves the prediction of all major PM2.5 components and their gaseous precursors in some regions as well as downwelling shortwave radiation, SWCF, and cloud condensation nuclei at a supersaturation of 0.5% on the global scale. For simulations of 2001–2005 with all the modified and new treatments, the improved model predicts that on global average, SWCF increases by 2.7 W m−2, reducing the normalized mean bias (NMB) of SWCF from −5.4 to 1.2%. Uncertainties in emissions can largely explain the inaccurate prediction of precursor gases (e.g., SO2, NH3, and NO) and primary aerosols (e.g., black carbon and primary organic matter). Additional factors leading to the discrepancies between model predictions and observations include assumptions associated with equilibrium partitioning for fine particles assumed in ISORROPIA II, irreversible gas/particle mass transfer treatment for coarse particles, uncertainties in model treatments such as dust emissions, secondary organic aerosol formation, multi-phase chemistry, cloud microphysics, aerosol–cloud interaction, dry and wet deposition, and model parameters (e.g., accommodation coefficients and prefactors of the nucleation power law) as well as uncertainties in model configuration such as the use of a coarse-grid resolution.

scholarly journals Elevated levels of OH observed in haze events during wintertime in central Beijing

2020 ◽  
Vol 20 (23) ◽  
pp. 14847-14871
Author(s):  
Eloise J. Slater ◽  
Lisa K. Whalley ◽  
Robert Woodward-Massey ◽  
Chunxiang Ye ◽  
James D. Lee ◽  
...  
Keyword(s):  
Gas Phase ◽  
Chemical Mechanism ◽  
Daily Maximum ◽  
Mixing Ratios ◽  
Gas Phase Chemistry ◽  
Photolysis Rates ◽  
Secondary Pollutants ◽  
High Pollution ◽  
Phase Chemistry

Abstract. Wintertime in situ measurements of OH, HO2 and RO2 radicals and OH reactivity were made in central Beijing during November and December 2016. Exceptionally elevated NO was observed on occasions, up to ∼250 ppbv. The daily maximum mixing ratios for radical species varied significantly day-to-day over the ranges 1–8×106 cm−3 (OH), 0.2–1.5×108 cm−3 (HO2) and 0.3–2.5×108 cm−3 (RO2). Averaged over the full observation period, the mean daytime peak in radicals was 2.7×106, 0.39×108 and 0.88×108 cm−3 for OH, HO2 and total RO2, respectively. The main daytime source of new radicals via initiation processes (primary production) was the photolysis of HONO (∼83 %), and the dominant termination pathways were the reactions of OH with NO and NO2, particularly under polluted haze conditions. The Master Chemical Mechanism (MCM) v3.3.1 operating within a box model was used to simulate the concentrations of OH, HO2 and RO2. The model underpredicted OH, HO2 and RO2, especially when NO mixing ratios were high (above 6 ppbv). The observation-to-model ratio of OH, HO2 and RO2 increased from ∼1 (for all radicals) at 3 ppbv of NO to a factor of ∼3, ∼20 and ∼91 for OH, HO2 and RO2, respectively, at ∼200 ppbv of NO. The significant underprediction of radical concentrations by the MCM suggests a deficiency in the representation of gas-phase chemistry at high NOx. The OH concentrations were surprisingly similar (within 20 % during the day) in and outside of haze events, despite j(O1D) decreasing by 50 % during haze periods. These observations provide strong evidence that gas-phase oxidation by OH can continue to generate secondary pollutants even under high-pollution episodes, despite the reduction in photolysis rates within haze.

scholarly journals Improvement and further development in CESM/CAM5: gas-phase chemistry and inorganic aerosol treatments

2013 ◽  
Vol 13 (10) ◽  
pp. 27717-27777 ◽  
Author(s):  
J. He ◽  
Y. Zhang
Keyword(s):  
Air Quality ◽  
Gas Phase ◽  
Particle Formation ◽  
Cloud Microphysics ◽  
Specific Humidity ◽  
New Particle Formation ◽  
Gas Phase Chemistry ◽  
Model Version ◽  
Inorganic Aerosol ◽  
Phase Chemistry

Abstract. Gas-phase chemistry and subsequent gas-to-particle conversion processes such as new particle formation, condensation, and thermodynamic partitioning have large impacts on air quality, climate, and public health through influencing the amounts and distributions of gaseous precursors and secondary aerosols. Their roles in global air quality and climate are examined in this work using the Community Earth System Model version 1.0.5 (CESM1.0.5) with the Community Atmosphere Model version 5.1 (CAM5.1) (referred to as CESM1.0.5/CAM5.1). CAM5.1 includes a simple chemistry that is coupled with a 7-mode prognostic Modal Aerosol Model (MAM7). MAM7 includes classical homogenous nucleation (binary and ternary) and activation nucleation (empirical first-order power law) parameterizations, and a highly-simplified inorganic aerosol thermodynamics treatment that only simulates sulfate (SO42−) and ammonium (NH4+). In this work, a new gas-phase chemistry mechanism based on the 2005 Carbon Bond Mechanism for Global Extension (CB05_GE) and several advanced inorganic aerosol treatments for condensation of volatile species, ion-mediated nucleation (IMN), and explicit inorganic aerosol thermodynamics have been incorporated into CESM/CAM5.1-MAM7. Comparing to the simple gas-phase chemistry, CB05_GE can predict many more gaseous species, and improve model performance for PM2.5, PM10, PM2.5 components, and some PM gaseous precursors such as SO2 and NH3 in several regions, as well as aerosol optical depth (AOD) and cloud properties (e.g., cloud fraction (CF), cloud droplet number concentration (CDNC), and shortwave cloud forcing (SWCF)) on globe. The modified condensation and aqueous-phase chemistry further improves the predictions of additional variables such as HNO3, NO2, and O3 in some regions, and new particle formation rate (J) and AOD over globe. IMN can improve the predictions of secondary PM2.5 components, PM2.5, and PM10 over Europe, as well as AOD and CDNC over globe. The explicit inorganic aerosol thermodynamics using ISORROPIA II improves the predictions of all major PM2.5 components and their gaseous precursors in some regions, as well as near-surface temperature and specific humidity, precipitation, downwelling shortwave radiation, SWCF, and cloud condensation nuclei at a supersaturation of 0.5% over globe. With all the modified and new treatments, the improved model predicts that on a global average, SWCF decreases by 2.9 W m−2, reducing the overprediction of SWCF from 7.9% to 0.9%. Uncertainties in emissions can explain largely the inaccurate predictions of precursor gases (e.g., SO2, NH3, and NO) and primary aerosols (e.g., black carbon and primary organic matter). Additional factors leading to discrepancies between model predictions and observations include uncertainties in model treatments such as dust emissions, secondary organic aerosol formation, multiple-phase chemistry, cloud microphysics, aerosol-cloud interaction, and dry and wet deposition.

scholarly journals GNAQPMS v1.1: accelerating the Global Nested Air Quality Prediction Modeling System (GNAQPMS) on Intel Xeon Phi processors

2017 ◽  
Vol 10 (8) ◽  
pp. 2891-2904 ◽  
Author(s):  
Hui Wang ◽  
Huansheng Chen ◽  
Qizhong Wu ◽  
Junmin Lin ◽  
Xueshun Chen ◽  
...  
Keyword(s):  
Air Quality ◽  
Gas Phase ◽  
Quality Prediction ◽  
Xeon Phi ◽  
Prediction Modeling ◽  
Gas Phase Chemistry ◽  
Air Quality Prediction ◽  
Parallel Mode ◽  
Phase Chemistry ◽  
Intel Xeon

Abstract. The Global Nested Air Quality Prediction Modeling System (GNAQPMS) is the global version of the Nested Air Quality Prediction Modeling System (NAQPMS), which is a multi-scale chemical transport model used for air quality forecast and atmospheric environmental research. In this study, we present the porting and optimisation of GNAQPMS on a second-generation Intel Xeon Phi processor, codenamed Knights Landing (KNL). Compared with the first-generation Xeon Phi coprocessor (codenamed Knights Corner, KNC), KNL has many new hardware features such as a bootable processor, high-performance in-package memory and ISA compatibility with Intel Xeon processors. In particular, we describe the five optimisations we applied to the key modules of GNAQPMS, including the CBM-Z gas-phase chemistry, advection, convection and wet deposition modules. These optimisations work well on both the KNL 7250 processor and the Intel Xeon E5-2697 V4 processor. They include (1) updating the pure Message Passing Interface (MPI) parallel mode to the hybrid parallel mode with MPI and OpenMP in the emission, advection, convection and gas-phase chemistry modules; (2) fully employing the 512 bit wide vector processing units (VPUs) on the KNL platform; (3) reducing unnecessary memory access to improve cache efficiency; (4) reducing the thread local storage (TLS) in the CBM-Z gas-phase chemistry module to improve its OpenMP performance; and (5) changing the global communication from writing/reading interface files to MPI functions to improve the performance and the parallel scalability. These optimisations greatly improved the GNAQPMS performance. The same optimisations also work well for the Intel Xeon Broadwell processor, specifically E5-2697 v4. Compared with the baseline version of GNAQPMS, the optimised version was 3.51 × faster on KNL and 2.77 × faster on the CPU. Moreover, the optimised version ran at 26 % lower average power on KNL than on the CPU. With the combined performance and energy improvement, the KNL platform was 37.5 % more efficient on power consumption compared with the CPU platform. The optimisations also enabled much further parallel scalability on both the CPU cluster and the KNL cluster scaled to 40 CPU nodes and 30 KNL nodes, with a parallel efficiency of 70.4 and 42.2 %, respectively.

scholarly journals Description and evaluation of a detailed gas-phase chemistry scheme in the TM5-MP global chemistry transport model (r112)

2020 ◽  
Vol 13 (11) ◽  
pp. 5507-5548 ◽  
Author(s):  
Stelios Myriokefalitakis ◽  
Nikos Daskalakis ◽  
Angelos Gkouvousis ◽  
Andreas Hilboll ◽  
Twan van Noije ◽  
...  
Keyword(s):  
Gas Phase ◽  
Transport Model ◽  
Three Dimensional ◽  
Chemical Mechanism ◽  
Chemistry Transport Model ◽  
Chemical Mechanisms ◽  
Mixing Ratios ◽  
Gas Phase Chemistry ◽  
Time Requirements ◽  
Phase Chemistry

Abstract. This work documents and evaluates the tropospheric gas-phase chemical mechanism MOGUNTIA in the three-dimensional chemistry transport model TM5-MP. Compared to the modified CB05 (mCB05) chemical mechanism previously used in the model, MOGUNTIA includes a detailed representation of the light hydrocarbons (C1–C4) and isoprene, along with a simplified chemistry representation of terpenes and aromatics. Another feature implemented in TM5-MP for this work is the use of the Rosenbrock solver in the chemistry code, which can replace the classical Euler backward integration method of the model. Global budgets of ozone (O3), carbon monoxide (CO), hydroxyl radicals (OH), nitrogen oxides (NOx), and volatile organic compounds (VOCs) are analyzed, and their mixing ratios are compared with a series of surface, aircraft, and satellite observations for the year 2006. Both mechanisms appear to be able to satisfactorily represent observed mixing ratios of important trace gases, with the MOGUNTIA chemistry configuration yielding lower biases than mCB05 compared to measurements in most of the cases. However, the two chemical mechanisms fail to reproduce the observed mixing ratios of light VOCs, indicating insufficient primary emission source strengths, oxidation that is too fast, and/or a low bias in the secondary contribution to C2–C3 organics via VOC atmospheric oxidation. Relative computational memory and time requirements of the different model configurations are also compared and discussed. Overall, the MOGUNTIA scheme simulates a large suite of oxygenated VOCs that are observed in the atmosphere at significant levels. This significantly expands the possible applications of TM5-MP.

Spiers Memorial Lecture : Introductory lecture: chemistry in the urban atmosphere

2016 ◽  
Vol 189 ◽  
pp. 9-29 ◽  
Author(s):  
Urs Baltensperger
Keyword(s):  
Gas Phase ◽  
Urban Atmosphere ◽  
Multiple Time Scales ◽  
Memorial Lecture ◽  
Multiple Time ◽  
Gas Phase Chemistry ◽  
Complex Processes ◽  
Secondary Pollutants ◽  
Phase Chemistry ◽  
Aerosol Source

The urban atmosphere is characterised by a multitude of complex processes. Gaseous and particulate components are continuously emitted into the atmosphere from many different sources. These components are then dispersed in the urban atmosphereviaturbulent mixing. Numerous chemical reactions modify the gas phase chemistry on multiple time scales, producing secondary pollutants. Through partitioning, the chemical and physical properties of the aerosol particles are also constantly changing as a consequence of dispersion and gas phase chemistry. This review presents an overview of the involved processes, focusing on the contributions presented at this conference and putting them into a broader context. Advanced methods for aerosol source apportionment are presented as well, followed by some aspects of health effects related to air pollution.

scholarly journals A perspective on the development of gas-phase chemical mechanisms for Eulerian air quality models

2019 ◽  
Vol 70 (1) ◽  
pp. 44-70 ◽  
Author(s):  
William R. Stockwell ◽  
Emily Saunders ◽  
Wendy S. Goliff ◽  
Rosa M. Fitzgerald
Keyword(s):  
Air Quality ◽  
Gas Phase ◽  
Quality Models ◽  
Chemical Mechanisms ◽  
Phase Chemical

scholarly journals MP CBM-Z V1.0: design for a new Carbon Bond Mechanism Z (CBM-Z) gas-phase chemical mechanism architecture for next-generation processors

2019 ◽  
Vol 12 (2) ◽  
pp. 749-764
Author(s):  
Hui Wang ◽  
Junmin Lin ◽  
Qizhong Wu ◽  
Huansheng Chen ◽  
Xiao Tang ◽  
...  
Keyword(s):  
Air Quality ◽  
Gas Phase ◽  
Air Quality Model ◽  
Quality Model ◽  
Gas Phase Chemistry ◽  
Phase Chemistry ◽  
Bond Mechanism ◽  
Chemistry Module ◽  
Phase Chemical ◽  
Intel Xeon

Abstract. Precise and rapid air quality simulations and forecasting are limited by the computational performance of the air quality model used, and the gas-phase chemistry module is the most time-consuming function in the air quality model. In this study, we designed a new framework for the widely used the Carbon Bond Mechanism Z (CBM-Z) gas-phase chemical kinetics kernel to adapt the single-instruction, multiple-data (SIMD) technology in next-generation processors to improve its calculation performance. The optimization implements the fine-grain level parallelization of CBM-Z by improving its vectorization ability. Through constructing loops and integrating the main branches, e.g., diverse chemistry sub-schemes, multiple spatial points in the model can be operated simultaneously on vector processing units (VPUs). Two generation CPUs – Intel Xeon E5-2680 V4 CPU and Intel Xeon Gold 6132 – and Intel Xeon Phi 7250 Knights Landing (KNL) are used as the benchmark processors. The validation of the CBM-Z module outputs indicates that the relative bias reaches a maximum of 0.025 % after 10 h integration with -fp-model fast =1 compile flag. The results of the module test show that the Multiple-Points CBM-Z (MP CBM-Z) resulted in 5.16× and 8.97× speedup on a single core of Intel Xeon E5-2680 V4 and Intel Xeon Gold 6132 CPUs, respectively, and KNL had a speedup of 3.69× compared with the performance of CBM-Z on the Intel Xeon E5-2680 V4 platform. For the single-node tests, the speedup on the two generation CPUs can reach 104.63× and 198.50× using message passing interface (MPI) and 101.02× and 194.60× using OpenMP, and the speedup on the KNL node can reach 175.23× using MPI and 167.45× using OpenMP. The speedup of the optimized CBM-Z is approximately 40 % higher on a one-socket KNL platform than on a two-socket Broadwell platform and about 13 %–16 % lower than on a two-socket Skylake platform. We also tested a three-dimensional chemistry transport model (CTM) named Nested Air Quality Prediction Model System (NAQPMS) equipped with the MP CBM-Z. The tests illustrate an obvious improvement on the performance for the CTM after adopting the MP CBM-Z. The results show that the MP CBM-Z leads to a speedup of 3.32 and 1.96 for the gas-phase chemistry module and the CTM on the Intel Xeon E5-2680 platform. Moreover, on the new Intel Xeon Gold 6132 platform, the MP CBM-Z gains 4.90× and 2.22× speedups for the gas-phase chemistry module and the whole CTM. For the KNL, the MP CBM-Z enables a 3.52× speedup for the gas-phase chemistry module, but the whole model lost 24.10 % performance compared to the CPU platform due to the poor performance of other modules. In addition, since this optimization seeks to improve the utilization of the VPU, the model is more suitable for the new generation processors adopting the more advanced SIMD technology. The results of our tests already show that the benefit of updating CPU improved by about 47 % by using the MP CBM-Z since the optimized code has better adaptability for the new hardware. This work improves the performance of the CBM-Z chemical kinetics kernel as well as the calculation efficiency of the air quality model, which can directly improve the practical value of the air quality model in scientific simulations and routine forecasting.

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