Search results for "Humidity"
showing 10 items of 291 documents
Critical analysis of empirical ground heat flux equations on a cereal field using micrometeorological data
2009
The rate at which the net radiation is transferred to the soil as ground heat flux varies with surface characteristics. Surface energy balance algorithms use empirical relationships taking into account the effects of the canopy cover to insulate the soil through vegetation indexes, the soil capacity to absorb incoming net radiation via the albedo, and the surface temperature promoting the energy transfer. However empirical relationships are often dependent on local conditions, such as the soil humidity and vegetation type. Ground heat flux assumes a minimum value in case of full canopy cover and a maximum value for dry bare soil. Aim of the present research is the critical analysis of some …
Sensitivity of scope modelled GPP and fluorescence for different plant functional types
2014
This study addresses the question which factors are responsible for reported positive correlations between solar induced fluorescence (SIF) and gross primary production (GPP). A sensitivity analysis of the model SCOPE, which simulates photosynthesis, fluorescence emission and radiative transfer in canopies, has been carried out for four different plant functional types (PFT): tropical rainforest, C4 crops, C3 crops, and tundra, located in distinct climate zones: tropical everwet (Af), tropical with seasonal drought (savannah, Aw), temperate (Cf), and continental tundra (Dfd). Literature values for structural and physiological parameters and climate reanalysis data were used as input. The ef…
Evaluation of Local Scale PM Pollution Levels in Typical Street Canyon in Riga
2013
The present study describes long term PM10 and PM2.5 changes in typical street canyon with particular emphasis on seasonal, diurnal variations in context with meteorological data. In order to understand PM10 pollution sources during 28 April 2007-31 December 2007, chemical composition measurements were done with particular emphasis on heavy metals (As, Cd, Ni, and Pb), crustal material (Ca, Mg, Na, and K) and anions (sulphates, nitrates, chlorides). Meteorological data used for this evolutional analysis were measured close to traffic related stations and several meteorological parameters were analyzed in relation to particulate measurements. Keep in mind that atmospheric aerosols are genera…
Isotope disequilibrium effects: The influence of evaporation and ventilation effects on the carbon and oxygen isotope composition of speleothems – A …
2012
Abstract In order to improve the understanding of variations of speleothem δ18O and δ13C values in the context of palaeoclimate research, it is important to quantify the isotope fractionation processes influencing the δ18O and δ13C values of stalagmites. Here we present an extended version of speleothem stable isotope model that accounts for evaporation and condensation effects during precipitation of calcite. The ISOLUTION-model allows to calculate the effect of evaporation on δ18Ocalcite and δ13Ccalcite values in dependence on relative humidity and wind velocity. Our results reveal that evaporation may have a significant effect on δ18Ocalcite and δ13Ccalcite due to the loss of H2O from th…
Impact analysis of MPL and PEM thickness on temperature distribution within PEFC operating at relatively higher temperature
2020
Abstract In Japan, it is recommended to operate Polymer Electrolyte Fuel Cell (PEFC) at temperature around 90 °C for stationary applications during the period from 2020 to 2025. However, the present PEFC is using Nafion polymer electrolyte membrane (PEM) and operated within the temperature range from 60 °C to 80 °C. It is important to understand the temperature distribution in a cell of PEFC for improving the performance and to realize the long life span. This study focuses on use of micro porous layer (MPL), which can promote the moisture transfer in order to control the temperature distribution. The aim of this study is to analyze the impact of MPL on temperature distribution at reaction …
Upper tropospheric water vapour and its interaction with cirrus clouds as seen from IAGOS long-term routine in-situ observations
2017
IAGOS (In-service Aircraft for a Global Observing System) performs long-term routinein situobservations of atmospheric chemical composition (O3, CO, NOx, NOy, CO2, CH4), water vapour, aerosols, clouds, and temperature on a global scale by operating compact instruments on board of passenger aircraft. The unique characteristics of the IAGOS data set originate from the global scale sampling on air traffic routes with similar instrumentation such that the observations are truly comparable and well suited for atmospheric research on a statistical basis. Here, we present the analysis of 15 months of simultaneous observations of relative humidity with respect to ice (RHice) and ice crystal number …
Affinity scale between a carrier and a drug in DPI studied by atomic force microscopy.
2002
The dry powder inhalers (DPIs) consist, in the most cases, of ordered mixture where the particles adhesion results of interactions between the drug and the carrier. Generally, one step of production process is the micronization of the drug particles in order to reduce the size for ordered mixing optimization. But this operation is known to partially create an amorphous surface. In this case, surrounding storage conditions, like relative humidity (RH), are able to modify the percentage of amorphous drug surface. The aim of this study was to investigate surface reactivity, surface energy and direct force measurements by atomic force microscopy (AFM) between lactose (carrier) and zanamivir (dr…
In situ measurements of ice saturation in young contrails
2014
Relative humidity with respect to ice (RHi) is a major factor controlling the evolution of aircraft contrails. High-resolution airborne H2O measurements in and near contrails were made at a rate of 4.2 Hz using the novel water vapor mass spectrometer AIMS-H2O with in-flight calibration during the CONtrail, volcano, and Cirrus ExpeRimenT (CONCERT) 2011. Three 2 min old contrails were sampled near 11 km altitude. Independent of the ambient supersaturation or subsaturation over ice, the mean of the RHi frequency distribution within each contrail is shifted toward ice saturation. This shift can be explained by the high ice surface area densities with corresponding RHi relaxation times on the or…
Influence of greenhouse different coverings on chemical and physical risk factors
2005
Crop production in greenhouses needs the use of chemicals and requires high levels of temperature and relative humidity to assure the increasing of crop production. This can cause risks for the health of the operators, especially if they are not equipped with protection devices. The risks may also vary with the type and/or size and/or shape of the protected structures. In order to determine the influence of different coverings on type and amount of risks, chemical and physical risk factors were measured inside greenhouses with different cladding materials (glass panels and plastic films) after crop management. In these two different greenhouses typologies, that were similar for location and…
Sensor response time evaluations of trace hydrogen gaseous species with platinum using Kelvin Probe
2012
Kelvin Probe (KP), a non-contact, non-destructive vibrating capacitor device, was used to measure the work function (WF) difference of thin Pt films, deposited on oxidized silicon substrates, with highly diluted H 2 gas, in ppm levels, in the presence of with and without relative humidity (RH). Response times were extracted from the behavior of WF shift as a function of H 2 concentration values. Measurements were compared for zero and non-zero RH conditions at a fixed temperature of 30°C. Changes in WF were evaluated by using HP VEE program, suitably modified for the present measurements. The events were executed step by step for every second time interval through an input formatted file. T…