Search results for "water content"

Effect of environmental humidity and coating on aroma transfer through treated papers

2012

Abstract Coupled transfers of aroma compounds and water vapour were investigated by varying the relative humidity gradient of storage (50% or 90%) of two paper packaging at 25 °C. These papers differed in their coating surface: both were identically impregnated then supercalendered, and only one was twice coated on both sides with a synthetic barrier substance. Permeability and solubility coefficients were determined. The coating treatment was more effective to decrease the permeabilities of water vapour and ethyl ester than the effect of RH. On the contrary, the RH modified the water content of the treated papers and affected more strongly their permeability and solubility to cis-3-hexenol…

Sensitivities of Amazonian clouds to aerosols and updraft speed

2017

Abstract. The effects of aerosol particles and updraft speed on warm-phase cloud microphysical properties are studied in the Amazon region as part of the ACRIDICON-CHUVA experiment. Here we expand the sensitivity analysis usually found in the literature by concomitantly considering cloud evolution, putting the sensitivity quantifications into perspective in relation to in-cloud processing, and by considering the effects on droplet size distribution (DSD) shape. Our in situ aircraft measurements over the Amazon Basin cover a wide range of particle concentration and thermodynamic conditions, from the pristine regions over coastal and forested areas to the southern Amazon, which is highly poll…

Observed and Simulated Variability of Droplet Spectral Dispersion in Convective Clouds Over the Amazon

2021

In this study, the variability of the spectral dispersion of droplet size distributions (DSDs) in convective clouds is investigated. Analyses are based on aircraft measurements of growing cumuli near the Amazon basin, and on numerical simulations of an idealized ice‐free cumulus. In cleaner clouds, the relative dispersion ϵ, defined as the ratio of the standard deviation to the mean value of the droplet diameter, is negatively correlated with the ratio of the cloud water content (qc) to the adiabatic liquid water content (qa), while no strong correlation between ϵ and qc/qa is seen in polluted clouds. Bin microphysics numerical simulations suggest that these contrasting behaviors are associ…

2017

Abstract. During free fall in clouds, ice hydrometeors such as snowflakes and ice particles grow effectively by riming, i.e., the accretion of supercooled droplets. Volatile atmospheric trace constituents dissolved in the supercooled droplets may remain in ice during freezing or may be released back to the gas phase. This process is quantified by retention coefficients. Once in the ice phase the trace constituents may be vertically redistributed by scavenging and subsequent precipitation or by evaporation of these ice hydrometeors at high altitudes. Retention coefficients of the most dominant carboxylic acids and aldehydes found in cloud water were investigated in the Mainz vertical wind tu…

A Theoretical Study of the Wet Removal of Atmospheric Pollutants. Part III: The Uptake, Redistribution, and Deposition of (NH4)2SO4Particles by a Con…

1988

Abstract Our model for the scavenging of aerosol particles has been coupled with the two-dimensional form of the convective cloud model of Clark and Collaborators. The combined model was then used to simulate a convective warm cloud for the meteorological situation which existed at 1100 LST 12 July 1985 over Hawaii; assuming an aerosol size distribution of maritime number concentration and of mixed composition with (NH4)2SO4 as the soluble compound. A shallow model cloud developed 26 min after the onset of convection leading to moderate rain which began after 45 min and ended after 60 min. Various parameters which characterize the dynamics and micophysics of the cloud, as well as the scaven…

The Effect of Intense Air Drying on Material Distribution and Quality in Coated Papers

2003

Abstract The aim of this study was to find out what will happen to paper coating quality and material gradients if coating is dried in one air dryer at a high convection rate (150 kg/m2h). Different printing papers were coated, calendered and printed with pilot machines. The binder and pigment gradients of the coated, and also printed, samples were analyzed with LIPS (Laser Induced Plasma Spectrometry). It was found that drying affects the migration of starch, but not latex. Total air drying can be used to dry printing papers, if air temperature, velocity and moisture content can be separately controlled. The control of web temperature is more important for paper quality formation in a coat…

Thermally Induced Structural Modification of Silica Nanoparticles Investigated by Raman and Infrared Absorption Spectroscopies

2010

We report an experimental investigation by Raman and infrared (IR) absorption spectroscopies on the structural modifications induced by isochronal thermal treatments on amorphous SiO2 nanoparticles (fumed silica). In particular, three different commercial types of this material, characterized by particle mean diameters of 7, 14, and 40 nm, were subjected to thermal treatments from 100 up to 1000 °C. We found that some properties of fumed silica, such as the SiOSi mean bond angle, ring size distribution, and surface adsorbed water content, are drastically different from those of common bulk silica materials and intimately related to the particles' dimension. The SiOSi mean bond angle, probed…

L-Band vegetation optical depth for crop phenology monitoring and crop yield assessment

2018

Vegetation Optical Depth (VOD) at L-band is highly sensitive to the water content and above-ground biomass of vegetation. Hence, it has great potential for monitoring crop phenology and for providing crop yield forecasts. Recently, the Multi-Temporal Dual Channel Algorithm (MT -DCA) has been proposed to retrieve L-band VOD from Soil Moisture Active Passive (SMAP) measurements. In previous research, SMAP VOD has been compared to crop phenology and has been used to derive crop yield estimates. Here, we review and expand these initial research studies. In particular, we quantify the capability of VOD to detect different crop stages, and test different VOD metrics (i.e., maximum, range and inte…

Analysis of the linkages between rainfall and land surface conditions in the West African monsoon through CMAP, ERS-WSC, and NOAA-AVHRR data

2005

International audience; The European Remote Sensing Wind Scatterometer (ERS-WSC) backscattering coefficient, NOAA Advanced Very High Resolution Radiometer (NOAA-AVHRR) Normalized Difference Vegetation Index (NDVI), and Climate Prediction Center Merged Analysis Precipitation ( CMAP) precipitation data sets are studied over the period August 1991 to December 2000 to document ( 1) the interannual and intra-annual evolutions of vegetation photosynthetic activity and soil-vegetation water content over West Africa and ( 2) their two-way links with precipitation. Over the Sahel, at interannual timescales the strongest relationships between vegetation, soil moisture, and precipitation are observed …

Ecohydrology in Mediterranean areas: a numerical model to describe growing seasons out of phase with precipitations

2008

The probabilistic description of soil moisture dynamics is a relatively new topic in hydrology. The most common ecohydrological models start from a stochastic differential equation describing the soil water balance, where the unknown quantity, the soil moisture, depends both on spaces and time. Most of the solutions existing in literature are obtained in a probabilistic framework and under steady-state condition; even if this last condition allows the analytical handling of the problem, it has considerably simplified the same problem by subtracting generalities from it. <br><br> The steady-state hypothesis, appears perfectly applicable in arid and semiarid climatic areas like th…