干旱区生态环境知识资源中心

The regional dust morphology and spectral refractive indices (RIs; governed by hematite, Fe2O3 content at short wavelengths) are key elements for ascertaining direct radiative forcing of mineral dust aerosols. To provide morphological features of background mineral dust from a semi-arid zone in the vicinity of the Thar Desert, we carried out an expedition to the Jaipur city during late winter of 2012. Morphological analysis reveals the predominance of "Layered", "Angular" and "Flattened" particles, while the frequency distribution of a total of 235 dust particles shows the aspect ratio, AR and circularity parameter, CIR (measures of particle’s non-sphericity) typically similar to 1.4 and similar to 0.8, respectively. Sensitivity analysis at 550 nm wavelength reveals the equivalent sphere model may underestimate Single Scattering Albedo, SSA for the dust with low (similar to 1.1%) hematite by similar to 3.5%. Both underestimation (by similar to 5.6%) and overestimation (up to 9.1%) are probable in case of dust with high hematite content (similar to 5.68%). In addition, the effect of AR on the dust scattering is significant in case of dust with high hematite content. More such regionally representative dust morphological data are required for better estimation of regional radiative forcing of mineral dust aerosols.