Dust-induced modifications to the radiative fluxes/heating during a light-blocking haze episode over Delhi, India, 7–9th Nov 2017—triggered by long range transport from a severe Saudi Arabian dust storm—have been investigated with a regional NWP model, NCUM-R with prognostic dust-radiation feedbacks. The study employs ‘Double Radiation Calls’, wherein parallel runs of the radiation scheme ‘with’ (prognostic) and ‘without’ (diagnostic) dust radiative effects—while prognostic fields drive the forecast—isolate the dust-induced perturbations. The forecasted dust optical depth agreed spatially with the AOD from MODIS with Angstrom Exponent > 0.5, indicating that the dust was well mixed with the fine mode anthropogenic aerosols upwind. The ‘downward shortwave (SW) flux’ was diminished (upto − 12.9 Wm−2) in layers sampling (i) near-surface (L1Avg), (ii) well-mixed layer within the planetary boundary layer (PBL, L2Avg) and (iii) free-troposphere (FT, L3Avg). Dust-induced ‘Solar heating’ dominated in FT (upto 9.5 × 10–7 Ks−1) and the patches below (in L2Avg) exhibited a cooling, leading to thermal dipoles. The ‘upward longwave (LW) flux’ in FT was reduced and ‘LW heating’ prevailed in all levels—peak (2.5 × 10–6 Ks−1) in L2Avg—along with well-defined cooling zones in L1Avg. The dust–radiation interaction in turn influenced the boundary layer meteorology, manifested as (i) shallow PBLs that spatially correlate with dust-induced cooling of the boundary layer column, (ii) enhanced surface humidity and (iii) reduced visibility. The study is an instance of prognostic dust-radiation feedbacks improving the skill of NWP models in dust-laden regions.

中文翻译：

---

印度德里上空远距离尘埃输送过程中尘埃引起的辐射扰动：高分辨率区域 NWP 模型研究

2017 年 11 月 7 日至 9 日，印度德里上空的遮光雾霾事件期间由沙尘引起的辐射通量/加热变化（由严重的沙特阿拉伯沙尘暴的长距离传输触发）已使用区域 NWP 模型进行了调查，具有预测性尘埃辐射反馈的 NCUM-R。该研究采用了“双重辐射调用”，其中平行运行的辐射方案“有”（预测）和“没有”（诊断）尘埃辐射效应——而预测场驱动预测——隔离了尘埃引起的扰动。预测的尘埃光学深度在空间上与 MODIS 的 AOD 一致，埃指数 > 0.5，表明尘埃与逆风的细模式人为气溶胶很好地混合。在层采样 (i) 近地表 (L1Avg) 中，“向下短波 (SW) 通量”减少（高达 − 12.9 Wm−2），(ii) 行星边界层 (PBL, L2Avg) 和 (iii) 自由对流层 (FT, L3Avg) 内的良好混合层。灰尘引起的“太阳能加热”在 FT 中占主导地位（高达 9.5 × 10–7 Ks−1），下面的贴片（在 L2Avg 中）表现出冷却，导致热偶极子。FT 中的“向上长波 (LW) 通量”降低，并且“LW 加热”在所有水平（L2Avg 中的峰值（2.5 × 10–6 Ks-1））以及 L1Avg 中明确定义的冷却区中占主导地位。尘埃-辐射相互作用反过来影响边界层气象，表现为 (i) 浅层 PBL，与尘埃引起的边界层柱冷却在空间上相关，(ii) 增加表面湿度和 (iii) 能见度降低。该研究是预测性尘埃辐射反馈提高尘土地区 NWP 模型技能的一个实例。