Polarization aspects of the radar target scattering problem are reexamined. The optimization polarimetry is formulated and Kennaugh's method finding optimal polarizations modified extended to nonreciprocal bistatic cases. Our approach does not necessitate diagonalization operator therefore, a change-of-basis required. change-of-polarization-basis motivated by comparison experimental data taken with different antenna sets. Unitary matrix algebra used derive proper transformation formulas for...

Abstract. One of the major uncertainties in understanding Earth's climate system is interaction between solar radiation and aerosols atmosphere. Aerosols exposed to high humidity will change their chemical, physical, optical properties due increased water content. To model hydrated aerosols, atmospheric chemistry models often use volume weighted mixing rule predict complex refractive index (RI) when they interact with relative humidity, and, general, assume homogeneous mixing. This study...

The current understanding of fundamental processes in atmospheric clouds, such as nucleation, droplet growth, and the onset precipitation (collision–coalescence), is based on assumption that droplets undiluted clouds are distributed space a perfectly random manner, i.e. positions independently with uniform probability. We have analysed data from homogeneous cloud core to test this gain an nature transport. This done by examining one-dimensional cuts through using theory originally developed...

It is commonly understood that the number of drops one happens to measure as a function diameter in some sample represents drop size distribution. However, recent observations show rain "patchy" suggesting such seemingly "obvious" definition incomplete. That is, consists patches elementary distributions over range different scales. All measured distributions, then, are statistical mixtures these patches. Moreover, it shown interpretation distribution depends upon whether statistically...

Surface‐active organics such as humic‐like substances (HULIS) are abundant in aerosol particles and can lower the surface tension of cloud droplets forming on secondary organic biomass burning aerosols. How fast is diffusion these species, relative to time scale droplet growth? Here we report measurements solutions containing HULIS extracted from smoke pollution well those molecular weight‐fractionated aquatic fulvic acids. Diffusion coefficients estimated based Gibbs adsorption isotherms....

Although ground-level PM2.5 (particulate matter with aerodynamic diameter <2.5 μm) monitoring sites provide accurate measurements, their spatial coverage within a given region is limited and thus often insufficient for exposure epidemiological studies. Satellite data expand coverage, enhancing our ability to estimate location- and/or subject-specific exposures PM2.5. In this study, the authors apply mixed-effects model approach aerosol optical depth (AOD) retrievals from Geostationary...

It has been conjectured that roughness plays a role in surface nucleation, the tendency for freezing to begin preferentially at liquid-gas interface. Using high speed imaging, we sought evidence contact line on catalyst substrates with imposed characteristic length scales (texture). Length consistent critical nucleus size and δ∼τ/σ, where τ is relevant tension σ tension, range from nanometers micrometers. found nanoscale texture causes shift nucleation of ice supercooled water three-phase...

Abstract. The differences in North African dust emission regions and transport routes, between the boreal winter summer, are thoroughly documented. Here we re-examine spatial temporal characteristics of over tropical subtropical Atlantic Ocean, using 10 yr satellite data, order to better characterize different periods. We see a robust annual triplet: discernible rhythm "transatlantic weather". proposed partition is composed two heavy loading periods, associated here with northern-route...

Abstract Aircraft measurements of the ubiquitous marine stratocumulus cloud type, with over 3000 km in situ data from Pacific during Cloud System Evolution Trades experiment, show ability Holographic Detector for Clouds (HOLODEC) instrument to smoothly interpolate small and large droplet collected Droplet Probe 2DC instruments. The combined, comprehensive suite reveals a surprisingly contribution predrizzle size range 40–80 μm (transition droplets, or drizzlets), typically not measured...

Abstract Droplet positions in atmospheric clouds are random but possibly correlated on some scales. This ‘clustering’ must be quantified order to account for it theories of cloud evolution and radiative transfer. Tools as varied droplet concentration power spectrum, Fishing test, fractal correlation analysis have been used describe the small‐scale nature clouds, has difficult compare conclusions systematically. Here we show, by using correlation‐fluctuation theorem Wiener–Khinchin theorem,...

Abstract. A numerical cloud model is used to study the influence of aerosol on microphysics and dynamics moderate-sized, coastal, convective clouds that develop under same meteorological conditions. The results show polluted start their precipitation later precipitate less than clean but produce larger rain drops. evaporation process more significant at margins (compared cloud) due a higher drop surface area volume ratio it mostly from small It was found formation raindrops in efficient...

Abstract The spatial clustering of drops is a defining characteristic rain on all scales from centimeters to kilometers. It the physical basis for much observed variability in rain. authors report here temporal–spatial 1-min counts using network 21 optical disdrometers over small area near Charleston, South Carolina. These observations reveal significant differences between and temporal structures (i.e., clustering) different sizes drops, which suggest that cannot be used infer simply by an...

Abstract. The evaluation of aerosol radiative effect on broadband hemispherical solar flux is often performed using simplified spectral and directional scattering characteristics atmospheric underlying surface reflectance. In this study we present a rigorous yet fast computational tool that accurately accounts for detailed variability both angular properties reflectance in calculation direct effect. developed as part the GRASP (Generalized Retrieval Aerosol Surface Properties) project. We...

Abstract Clouds, crucial for understanding climate, begin with droplet formation from aerosols, but observations of this fleeting activation step are lacking in the atmosphere. Here we use a time-gated time-correlated single-photon counting lidar to observe cloud base structures at decimeter scales. Results show that air–cloud interface is not perfect boundary rather transition zone where transformation aerosol particles into droplets occurs. The observed distributions first-arriving photons...

The traditional statistical description of the spatial and temporal distributions cloud droplets raindrops is Poisson process, which tends to place drops as uniformly randomness allows. Yet, "clumpy" nature clouds precipitation apparent most casual observers well known physicists. Is such clumpiness consistent with statistics? authors explore possibility deviations from distribution using raindrop counting experiments. Disdrometer measurements during passage a squall line strongly indicate...

Recent studies have led to the statistical characterization of spatial (temporal) distributions cloud (precipitation) particles as a doubly stochastic Poisson process. This paper arrives at similar conclusion (larger-than-Poissonian variance) via more fundamental route physics and significantly extends previous findings in several ways. The focus is on structure distribution particles. A new approach for exploring clouds proposed using direct relation between number density variance pair...

The problem considered is one of finding the polarization state an antenna such that a power ratio due to two different objects optimized. It reduced optimization Hermitian forms which can be simultaneously diagonalized using well-known linear-algebraic construction. corresponding vectors are found. calculations performed directly on expression for energy density reflected wave as function transmitter and are, therefore, decoupled from receiving parameters. Such decoupling particularly...

Abstract. We use CALIOP nighttime measurements of lidar backscatter, color and depolarization ratios, as well particulate retrievals during the summer 2007 to study transatlantic dust properties downwind Saharan sources, examine influence nearby clouds on dust. Our analysis suggests that (1) under clear skies, while backscatter ratio do not change much with altitude longitude in Air Layer (SAL), increases decreases westward SAL; (2) vertical lapse rate ratio, introduced here, within SAL...

Abstract A network of optical disdrometers (including laser precipitation monitors and a two‐dimensional video disdrometer) was utilized to determine whether the recent reports “superterminal” raindrops were spurious results drop breakup occurring on instrumentation. Results unequivocally show that superterminal at small (less than 1 mm) sizes are ubiquitous, measurable over an extended area, appear in every rain event investigated. No evidence found suggest drops result due impact with...

On August 19, 1992, the Advanced Very High Resolution Radiometer (AVHRR) onboard NOAA‐12 and NASA's Total Ozone Mapping Spectrometer (TOMS) Nimbus‐7 satellite simultaneously detected mapped ash cloud from eruption of Mt. Spurr, Alaska. The spatial extent geometry derived two datasets are in good agreement both AVHRR split window IR (11–12µm brightness temperature difference) TOMS UV Aerosol Index (0.34–0.38µm ultraviolet backscattering absorption) methods give same range total mass....

The Bodélé depression of northern Chad is considered one the world's largest sources atmospheric mineral dust. Mineral composition such transported dust essential to our understanding climate forcing, mineralogy sources, aerosol optical properties, and deposition Amazon forests. In this study we examine hyperspectral information acquired over by EO‐1 Hyperion satellite during a storm event calm clean day. We show that, for suspended dust, absorption signature can be decoupled from...

Satellite imaging has emerged as a method for monitoring regional air pollution and detecting areas of high dust concentrations. Unlike ground observations, continuous data is available with global coverage terrestrial atmospheric components. In this study we test the utility different sources satellite to assess concentrations in Iraq. SeaWiFS MODIS Deep Blue (DB) aerosol optical depth (AOD) products were evaluated used characterize spatial temporal levels from late 1990s through 2010. The...