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<p>The microprocessor without interlocked piped stages (MIPS) and LoongArch are reduced instruction set computing (RISC) processor architectures, which have advantages in terms of energy consumption and efficiency. There are few studies on the application of MIPS and LoongArch central processing units (CPUs) in geoscientific numerical models. In this study, the Loongson 3A4000 CPU platform with the MIPS64 architecture and the Loongson 3A6000 CPU platform with the LoongArch architecture were used to establish the runtime environment for the air quality modelling system Weather Research and Forecasting–Comprehensive Air Quality Model with extensions (WRF-CAMx) in the Beijing–Tianjin–Hebei region. The results show that the relative errors for the major species (NO<span class="inline-formula">₂</span>, SO<span class="inline-formula">₂</span>, O<span class="inline-formula">₃</span>, CO, PNO<span class="inline-formula">₃</span>, and PSO<span class="inline-formula">₄</span>) between the MIPS and X86 benchmark platforms are within <span class="inline-formula">±</span>0.1 %. The maximum mean absolute error (MAE) of major species ranged up to 10<span class="inline-formula">⁻²</span> ppbV or <span class="inline-formula">µ</span>g m<span class="inline-formula">⁻³</span>, the maximum root mean square error (RMSE) ranged up to 10<span class="inline-formula">⁻¹</span> ppbV or <span class="inline-formula">µ</span>g m<span class="inline-formula">⁻³</span>, and the mean absolute percentage error (MAPE) remained within 0.5 %. The CAMx takes about 195 min on the Loongson 3A4000 CPU, 71 min on the Loongson 3A6000 CPU, and 66 min on the Intel Xeon E5-2697 v4 CPU, when simulating a 24 h case with four parallel processes using MPICH. As a result, the single-core computing capability of the Loongson 3A4000 CPU for the WRF-CAMx modelling system is about one-third of the Intel Xeon E5-2697 v4 CPU, and the one of Loongson 3A6000 CPU is slightly lower than that of Intel Xeon E5-2697 v4 CPU; but, the thermal design power (TDP) of Loongson 3A4000 is 40 W, while the TDP of Loongson 3A6000 is 38 W, only about one-fourth of that of Intel Xeon E5-2697 v4, whose TDP is 145 W. The results also verify the feasibility of cross-platform porting and the scientific usability of the ported model. This study provides a technical foundation for the porting and optimization of numerical models based on MIPS, LoongArch, or other RISC platforms.</p>