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Modeling impacts of dust mineralogy on fast climate response
Atmospheric Chemistry and Physics ( IF 5.2 ) Pub Date : 2024-06-28 , DOI: 10.5194/acp-24-7421-2024
Qianqian Song , Paul Ginoux , María Gonçalves Ageitos , Ron L. Miller , Vincenzo Obiso , Carlos Pérez García-Pando

Abstract. Mineralogical composition drives dust impacts on Earth's climate systems. However, most climate models still use homogeneous dust, without accounting for the temporal and spatial variation in mineralogy. To quantify the radiative impact of resolving dust mineralogy on Earth's climate, we implement and simulate the distribution of dust minerals (i.e., illite, kaolinite, smectite, hematite, calcite, feldspar, quartz, and gypsum) from Claquin et al. (1999) (C1999) and activate their interaction with radiation in the GFDL AM4.0 model. Resolving mineralogy reduces dust absorption compared to the homogeneous dust used in the standard GFDL AM4.0 model that assumes a globally uniform hematite volume content of 2.7 % (HD27). The reduction in dust absorption results in improved agreement with observation-based single-scattering albedo (SSA), radiative fluxes from CERES (the Clouds and the Earth's Radiant Energy System), and land surface temperature from the CRU (Climatic Research Unit) compared to the baseline HD27 model version. It also results in distinct radiative impacts on Earth's climate over North Africa. Over the 19-year (from 2001 to 2019) modeled period during JJA (June–July–August), the reduction in dust absorption in AM4.0 leads to a reduction of over 50 % in net downward radiation across the Sahara and approximately 20 % over the Sahel at the top of the atmosphere (TOA) compared to the baseline HD27 model version. The reduced dust absorption weakens the atmospheric warming effect of dust aerosols and leads to an alteration in land surface temperature, resulting in a decrease of 0.66 K over the Sahara and an increase of 0.7 K over the Sahel. The less warming in the atmosphere suppresses ascent and weakens the monsoon inflow from the Gulf of Guinea. This brings less moisture to the Sahel, which combined with decreased ascent induces a reduction of precipitation. To isolate the effect of reduced absorption compared to resolving spatial and temporal mineralogy, we carry out a simulation where the hematite volume content of homogeneous dust is reduced from 2.7 % to 0.9 % (HD09). The dust absorption (e.g., single-scattering albedo) of HD09 is comparable to that of the mineralogically speciated model on a global mean scale, albeit with a lower spatial variation that arises solely from particle size. Comparison of the two models indicates that the spatial inhomogeneity in dust absorption resulting from resolving mineralogy does not have significant impacts on Earth's radiation and climate, provided there is a similar level of dust absorption on a global mean scale before and after resolving dust mineralogy. However, uncertainties related to emission and distribution of minerals may blur the advantages of resolving minerals to study their impact on radiation, cloud properties, ocean biogeochemistry, air quality, and photochemistry. On the other hand, lumping together clay minerals (i.e., illite, kaolinite, and smectite), but excluding externally mixed hematite and gypsum, appears to provide both computational efficiency and relative accuracy. Nevertheless, for specific research, it may be necessary to fully resolve mineralogy to achieve accuracy.

中文翻译:


模拟灰尘矿物学对快速气候响应的影响



摘要。矿物成分导致灰尘对地球气候系统的影响。然而,大多数气候模型仍然使用均匀的尘埃,没有考虑矿物学的时间和空间变化。为了量化解决尘埃矿物学对地球气候的辐射影响,我们实施并模拟了 Claquin 等人提出的尘埃矿物(即伊利石、高岭石、蒙脱石、赤铁矿、方解石、长石、石英和石膏)的分布。 (1999) (C1999) 并在 GFDL AM4.0 模型中激活它们与辐射的相互作用。与标准 GFDL AM4.0 模型中使用的均质粉尘相比,解析矿物学减少了粉尘吸收,该模型假设全球统一的赤铁矿体积含量为 2.7 % (HD27)。与基于观测的单散射反照率 (SSA)、CERES(云和地球辐射能系统)的辐射通量以及 CRU(气候研究单位)的地表温度相比,灰尘吸收的减少提高了一致性基准 HD27 型号版本。它还对北非的地球气候产生明显的辐射影响。在 JJA 期间(6 月 - 7 月 - 8 月)的 19 年(从 2001 年到 2019 年)模拟期间,AM4.0 灰尘吸收的减少导致撒哈拉沙漠的净向下辐射减少了 50% 以上,并且减少了约 20%。与基线 HD27 模型版本相比,萨赫勒地区大气层顶部 (TOA) 的百分比。沙尘吸收的减少削弱了沙尘气溶胶的大气变暖效应,导致地表温度发生变化,导致撒哈拉地区温度降低0.66 K,萨赫勒地区温度升高0.7 K。大气变暖程度降低抑制了上升并削弱了来自几内亚湾的季风流入。 这给萨赫勒地区带来了更少的水分,再加上海拔下降,导致降水减少。为了隔离与解析时空矿物学相比吸收减少的影响,我们进行了模拟,其中均质灰尘的赤铁矿体积含量从 2.7% 减少到 0.9% (HD09)。 HD09 的灰尘吸收(例如,单散射反照率)与全球平均尺度上的矿物学物种模型的吸收相当,尽管仅由颗粒尺寸引起的空间变化较小。两个模型的比较表明,如果解决灰尘矿物学之前和之后全球平均尺度上的灰尘吸收水平相似,则解决矿物学导致的灰尘吸收的空间不均匀性不会对地球辐射和气候产生重大影响。然而,与矿物排放和分布相关的不确定性可能会模糊解析矿物以研究其对辐射、云特性、海洋生物地球化学、空气质量和光化学影响的优势。另一方面,将粘土矿物(即伊利石、高岭石和蒙皂石)集中在一起,但排除外部混合的赤铁矿和石膏,似乎可以提供计算效率和相对精度。尽管如此,对于具体的研究来说,可能需要充分解析矿物学才能达到准确性。
更新日期:2024-06-28
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