Search results for "Meter"
showing 10 items of 16915 documents
In-line holography of cloud volumes applied to the measurement of raindrops and snowflakes
1998
Abstract The ground-based HODAR (HOlographic Droplet and Aerosol Recording) of the University of Mainz has been operational since 1989 on the Kleiner Feldberg Mountain Observatory near Frankfurt/Main, Germany, in a `small volume' configuration. With this setup an air volume of approximately 1 l can be in situ recorded, which allows it to image all aerosol particles and droplets with diameter larger than 6 μm contained in the sample volume in situ. Recently the beam diameter and optical path length of the inline system have been enlarged such that large cloud volumes (approximately 500 l) can be recorded on single holograms. During the holographic image reconstruction step in the laboratory,…
Radiative surface temperature and convective flux calculation over crop canopies
1988
The analysis presented in this paper aims at a better understanding of the potential role of radiative temperature, as measured by a radiometer over crops, in sensible heat flux calculation. Defining radiative temperature as the mean temperature of the surfaces viewed by the radiometer (leaves and soil surface) and assuming that an Ohm's law type formula can be used to express sensible heat flux as a function of the difference between air temperature and radiative temperature, the aerodynamic resistance which divides this temperature difference has been analytically defined. The parameters which appear in the resistance expression depend essentially on wind velocity and canopy structure but…
Particle surface area dependence of mineral dust in immersion freezing mode: investigations with freely suspended drops in an acoustic levitator and …
2014
Abstract. The heterogeneous freezing temperatures of supercooled drops were measured using an acoustic levitator. This technique allows one to freely suspend single drops in the air without any wall contact. Heterogeneous nucleation by two types of illite (illite IMt1 and illite NX) and a montmorillonite sample was investigated in the immersion mode. Drops of 1 mm in radius were monitored by a video camera while cooled down to −28 °C to simulate freezing within the tropospheric temperature range. The surface temperature of the drops was contact-free, determined with an infrared thermometer; the onset of freezing was indicated by a sudden increase of the drop surface temperature. For compari…
FIDO science payload simulating the Athena Payload
2002
[1] The Jet Propulsion Laboratory's Field Integrated Development and Operations rover (FIDO) emulates and tests operational rover capabilities for advanced Mars rover missions, such as those originally planned for the Mars Surveyor 2001 Rover and currently planned for the Athena Payload on the Mars Exploration Rovers scheduled for launch in 2003. This paper describes FIDO's science instrument payload, which is fully integrated with rover hardware and software. Remote science teams visualize instrument suite data and generate FIDO commands using the Web Interface for Telescience. FIDO's instrument suite has been used in terrestrial laboratory and field tests to simulate Mars operations, to t…
Investigation of the mixing layer height derived from ceilometer measurements in the Kathmandu Valley and implications for local air quality
2017
Abstract. In this study 1 year of ceilometer measurements taken in the Kathmandu Valley, Nepal, in the framework of the SusKat project (A Sustainable Atmosphere for the Kathmandu Valley) were analysed to investigate the diurnal variation of the mixing layer height (MLH) and its dependency on the meteorological conditions. In addition, the impact of the MLH on the temporal variation and the magnitude of the measured black carbon concentrations are analysed for each season. Based on the assumption that black carbon aerosols are vertically well mixed within the mixing layer and the finding that the mixing layer varies only little during night time and morning hours, black carbon emission fluxe…
Analysis of winter dust activity off the coast of West Africa using a new 24-year over-water advanced very high resolution radiometer satellite dust …
2006
A 24-year (1982-2005) winter daytime advanced very high resolution radiometer (AVHRR) data set has been processed utilizing a new over-water dust detection algorithm. The dust data are for the oceanic regions surrounding West Africa and provide a long-term remotely sensed continuous record of dustiness in the region. These AVHRR dust observations are comparable to dust records produced via the Total Ozone Mapping Spectrometer and Meteosat instruments. Strong positive correlations between the wintertime Jones North Atlantic Oscillation index and this dust record are observed across the entire oceanic region, corroborating earlier studies on the relationship between the two. Also consistent w…
AATSR land surface temperature product algorithm verification over a WATERMED site
2007
Abstract A new operational Land Surface Temperature (LST) product generated from data acquired by the Advanced Along-Track Scanning Radiometer (AATSR) provides the opportunity to measure LST on a global scale with a spatial resolution of 1 km 2 . The target accuracy of the product, which utilises nadir data from the AATSR thermal channels at 11 and 12 μm, is 2.5 K for daytime retrievals and 1.0 K at night. We present the results of an experiment where the performance of the algorithm has been assessed for one daytime and one night time overpass occurring over the WATERMED field site near Marrakech, Morocco, on 05 March 2003. Top of atmosphere (TOA) brightness temperatures (BTs) are simulate…
Nitric acid trihydrate nucleation and denitrification in the Arctic stratosphere
2014
Abstract. Nitric acid trihydrate (NAT) particles in the polar stratosphere have been shown to be responsible for vertical redistribution of reactive nitrogen (NOy). Recent observations by Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the CALIPSO satellite have been explained in terms of heterogeneous nucleation of NAT on foreign nuclei, revealing this to be an important formation pathway for the NAT particles. In state of the art global- or regional-scale models, heterogeneous NAT nucleation is currently simulated in a very coarse manner using a constant, saturation-independent nucleation rate. Here we present first simulations for the Arctic winter 2009/2010 applying a n…
In search of traceability: two decades of calibrated Brewer UV measurements in Sodankylä and Jokioinen
2016
Abstract. The two Brewer spectrophotometers of the Finnish Meteorological Institute at Jokioinen and Sodankylä have been operated according to the highest levels of the WMO∕GAW (World Meteorological Organization∕Global Atmosphere Watch) recommendations with rigorous quality control and quality assurance. The calibration of the instruments is based on annual recalibrations of primary standard lamps in the VTT MIKES Metrology National Standards Laboratory in Finland and an exhaustive measurement program with measurements of standard and working lamps in the on-site optical laboratories. Over the years, the maintenance of the calibration has produced data sets of approximately 2000 lamp scans …
EARLINET observations of the 14-22-may long-range dust transport event during SAMUM 2006: validation of results from dust transport modelling
2009
We observed a long-range transport event of mineral dust from North Africa to South Europe during the Saharan Mineral Dust Experiment (SAMUM) 2006. Geometrical and optical properties of that dust plume were determined with Sun photometer of the Aerosol Robotic Network (AERONET) and Raman lidar near the North African source region, and with Sun photometers of AERONET and lidars of the European Aerosol Research Lidar Network (EARLINET) in the far field in Europe. Extinction-to-backscatter ratios of the dust plume over Morocco and Southern Europe do not differ. Ångstr¨om exponents increase with distance from Morocco. We simulated the transport, and geometrical and optical properties of the dus…