Effects of low-carbon energy adoption on airborne particulate matter concentrations with feedbacks to future climate over California

California plans to reduce emissions of long-lived greenhouse gases (GHGs) through adoption of new energy systems that will also lower concentrations of short-lived absorbing soot contained in airborne particulate matter (PM). Here we examine the direct and indirect effects of reduced PM concentrations under a low-carbon energy (GHG-Step) scenario on radiative forcing in California. Simulations were carried out using the source-oriented WRF/Chem (SOWC) model over California with 12 km spatial resolution for the year 2054. The avoided aerosol emissions due to technology advances in the GHG-step scenario reduce ground level PM concentrations by ~8.85% over land compared to the Business as Usual (BAU) scenario, but changes to meteorological parameters are more modest. Top of atmospheric forcing predicted by the SOWC model increased by 0.15 W m^-2, surface temperature warmed by 0.001 K, and planetary boundary layer height (PBLH) increased by 2.20 cm in the GHG-Step scenario compared to the BAU scenario. PM climate feedbacks are small because the significant changes in ground level PM concentrations associated with the GHG-Step scenario are limited to the first few hundred meters of the atmosphere, with little change for the majority of the vertical column above that level. As an order-of-magnitude comparison, the long-term effects of global reductions in GHG emissions (RCP8.5 – RCP4.5) lowered average surface temperature over the California study domain by approximately 0.76 K. The effects of long-lived climate pollutants such as CO₂ are much stronger than the effects of short-lived climate pollutants such as PM soot over California in the year 2054.加利福尼亚州计划通过采用新型能源系统，减少长寿命温室气体（GHGs）的排放，同时降低大气颗粒物（PM）中所含的短寿命吸光性烟尘的浓度。本研究针对低碳能源（GHG-Step）情景下PM浓度降低对加利福尼亚州辐射强迫的直接与间接影响展开分析。研究采用源导向型WRF/Chem（SOWC）模型，以12千米的空间分辨率对2054年的加利福尼亚州进行数值模拟。相较于常规情景（BAU），GHG-Step情景下因技术进步所避免的气溶胶排放，使陆地区域近地面PM浓度降低约8.85%，但气象参数的变化相对平缓。与BAU情景相比，SOWC模型预测的大气顶辐射强迫升高0.15 W·m⁻²，地表温度上升0.001 K，行星边界层高度（PBLH）升高2.20厘米。由于GHG-Step情景下近地面PM浓度的显著变化仅局限于大气层前数百米范围内，该高度以上大部分垂直柱体的浓度几乎无变化，因此PM气候反馈效应微弱。作为量级对比，全球温室气体减排的长期效应（RCP8.5 – RCP4.5）使加利福尼亚研究区域的平均地表温度降低约0.76 K。2054年，加利福尼亚州境内长寿命气候污染物（如二氧化碳）的影响远强于PM烟尘等短寿命气候污染物的影响。