Kinetics of Spinodal Phase Separation in Unstable Thin Liquid Films

We study universality in the kinetics of spinodal phase separation in unstable thin liquid films, via simulations of the thin film equation. It is shown that in addition to morphology and free energy,the number density of local maxima in the film profile can also be used to identify the early, intermediate and late stages of spinodal phase separation. A universal curve between the number density of local maxima and rescaled time describes the kinetics of early stage in d = 2, 3. The Lifshitz-Slyozov exponent of -1/3 describes the kinetics of the late stage in d = 2 even in the absence of coexisting equilibrium phases.Comment: 5 figure

Bulk Level to Individual Particle Level Chemical Composition of Atmospheric Dust Aerosols (PM5) over a Semi-Arid Urban Zone of Western India (Rajasthan)

Mineral dust particles in the lower atmosphere may significantly influence radiative and optical budgets, along with the net chemical balance, through their interactions with ambient chemicals. Their ability to absotb/scatter incoming radiation strongly depends on their chemical composition (i.e., distribution of major crustal elements), but as yet there is no adequate regional database with regard to this for the Indian region. To create a regional database of background mineral dust from a semi-arid zone of western India, we measured the chemical composition of ambient particles (with aerodynamic diameter <= 5 mu m; PM5), collected from seven locations of Jaipur city (in the vicinity of Thar Desert; Rajasthan) at varying altitudes, during late-winter of 2012. The chemical compositions of the sampled particles at both bulk and individual levels were measured using X-ray fluorescence (XRF) and Scanning Electron Microscope equipped with Energy Dispersive X-ray (SEM-EDX) techniques, respectively. Significant differences in chemical compositions were observed among the seven sites, yet the bulk chemical compositions of the particles were broadly consistent with those of individual particles. Average elemental ratios of Mg/Al, Si/Al, K/Al, Ca/Al, Mn/Al, Fe/Al were found to be 0.44 +/- 0.22, 1.96 +/- 0.90, 0.65 +/- 0.22, 1.52 +/- 0.40, 0.84 and 1.54 +/- 1.67, respectively. We also estimated the complex refractive index (RIs at 550 nm wavelength) for the studied sites, yielding an average n and k (the real and imaginary parts of RI, respectively) of (1.56 +/- 0.03) + (6.5 +/- 4.6) x 10(-3)i, with the aerosols collected from Kukas Hill area (27.02 degrees N, 75.85 degrees E) having the highest iron (Fe) mass fraction (similar to 43%). Non-crustal elements e.g., Cu, S, C, Ag and Pb were found only in aerosols over the main city Birla Temple (Jaipur) at ground level (26.89 degrees N, 75.81 degrees E)

Morphology of Atmospheric Particles over Semi-Arid Region (Jaipur, Rajasthan) of India: Implications for Optical Properties

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

Temporal derivative of Total Solar Irradiance and anomalous Indian summer monsoon: An empirical evidence for a Sun–climate connection

Identifying the pattern of natural climate variability is of immense importance to delineate the effects of anthropogenic climate changes. Global and regional climates are suspected to vary, in unison or with delays, with the Total Solar Irradiance (TSI) at decadal to centennial timescales. Here we show that the Indian summer monsoon rainfall correlates well with the temporal derivative of TSI on multi-decadal timescales. This linkage between the temporal derivative of TSI and the Indian summer monsoon is tested and corroborated both for the instrumental period (1871–2006) and for the last $ 300 years using a speleothem d18O record representing rainfall in southwestern India. Our analyses indicate that anomalous dry periods of the Indian monsoon are mostly coincident with negative TSI derivative. This study thus demonstrates the potential of ‘TSI derivative’ as an important indicator of natural monsoon variability on an interdecadal timescale