28 research outputs found
Combined vertical-velocity observations with Doppler lidar, cloud radar and wind profiler
Case studies of combined vertical-velocity measurements of Doppler lidar, cloud radar and wind profiler are presented. The measurements were taken at the Meteorological Observatory, Lindenberg, Germany. Synergistic products are presented that are derived from the vertical-velocity measurements of the three instruments: a comprehensive classification mask of vertically moving atmospheric targets and the terminal fall velocity of water droplets and ice crystals corrected for vertical air motion. It is shown that this combination of instruments can up-value the measurement values of each single instrument and may allow the simultaneous sensing of atmospheric targets and the motion of clear air
Combining cloud radar and radar wind profiler for a value added estimate of vertical air motion and particle terminal velocity within clouds
Vertical-stare observations from a 482âMHz radar wind profiler and a
35âGHz cloud radar are combined on the level of individual Doppler
spectra to measure vertical air motions in clear air, clouds and
precipitation. For this purpose, a separation algorithm is proposed to remove
the influence of falling particles from the wind profiler Doppler spectra and
to calculate the terminal fall velocity of hydrometeors. The remaining error
of both vertical air motion and terminal fall velocity is estimated to be
better than 0.1âmâsâ1 using numerical simulations. This
combination of instruments allows direct measurements of in-cloud vertical
air velocity and particle terminal fall velocity by means of ground-based
remote sensing. The possibility of providing a profile every 10âs
with a height resolution of â<â100âm allows further insight into the
process scale of in-cloud dynamics. The results of the separation algorithm
are illustrated by two case studies, the first covering a deep frontal cloud
and the second featuring a shallow mixed-phase cloud.</p
Aerosol backscatter profiles from ceilometers: validation of water vapor correction in the framework of CeiLinEx2015
With the rapidly growing number of automated single-wavelength backscatter
lidars (ceilometers), their potential benefit for aerosol remote sensing
received considerable scientific attention. When studying the accuracy of
retrieved particle backscatter coefficients, it must be considered that most
of the ceilometers are influenced by water vapor absorption in the spectral
range around 910 nm. In the literature methodologies have been proposed to correct for this
effect; however, a validation was not yet performed. In
the framework of the ceilometer intercomparison campaign CeiLinEx2015 in
Lindenberg, Germany, hosted by the German Weather Service, it was possible to
tackle this open issue. Ceilometers from Lufft (CHM15k and CHM15kx, operating
at 1064 nm), from Vaisala (CL51 and CL31) and from Campbell Scientific
(CS135), all operating at a wavelength of approximately 910 nm, were
deployed together with a multi-wavelength research lidar (RALPH) that served
as a reference. In this paper the validation of the water vapor correction is
performed by comparing ceilometer backscatter signals with measurements of
the reference system extrapolated to the water vapor regime. One inherent
problem of the validation is the spectral extrapolation of particle optical
properties. For this purpose AERONET measurements and inversions of RALPH
signals were used. Another issue is that the vertical range where validation
is possible is limited to the upper part of the mixing layer due to incomplete
overlap and the generally low signal-to-noise ratio and signal artifacts
above that layer. Our intercomparisons show that the water vapor correction
leads to quite a good agreement between the extrapolated reference signal and
the measurements in the case of CL51 ceilometers at one or more wavelengths
in the specified range of the laser diode's emission. This ambiguity is due
to the similar effective water vapor transmission at several wavelengths. In
the case of CL31 and CS135 ceilometers the validation was not always
successful. That suggests that error sources beyond the water vapor
absorption might be dominant. For future applications we recommend monitoring
the emitted wavelength and providing âdarkâ measurements on a regular
basis.</p
Kakucs-Balla-domb. A case study in the absolute and relative chronology of the Vatya culture
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Combining cloud radar and radar wind profiler for a value added estimate of vertical air motion and particle terminal velocity within clouds
Vertical-stare observations from a 482MHz radar wind profiler and a 35GHz cloud radar are combined on the level of individual Doppler spectra to measure vertical air motions in clear air, clouds and precipitation. For this purpose, a separation algorithm is proposed to remove the influence of falling particles from the wind profiler Doppler spectra and to calculate the terminal fall velocity of hydrometeors. The remaining error of both vertical air motion and terminal fall velocity is estimated to be better than 0.1ms-1 using numerical simulations. This combination of instruments allows direct measurements of in-cloud vertical air velocity and particle terminal fall velocity by means of ground-based remote sensing. The possibility of providing a profile every 10s with a height resolution of < 100m allows further insight into the process scale of in-cloud dynamics. The results of the separation algorithm are illustrated by two case studies, the first covering a deep frontal cloud and the second featuring a shallow mixed-phase cloud
Combined vertical-velocity observations with Doppler lidar, cloud radar and wind profiler
Case studies of combined vertical-velocity measurements of Doppler lidar,
cloud radar and wind profiler are presented. The measurements were taken at
the Meteorological Observatory, Lindenberg, Germany. Synergistic products are
presented that are derived from the vertical-velocity measurements of the
three instruments: a comprehensive classification mask of vertically moving
atmospheric targets and the terminal fall velocity of water droplets and ice
crystals corrected for vertical air motion. It is shown that this combination
of instruments can up-value the measurement values of each single instrument
and may allow the simultaneous sensing of atmospheric targets and the motion
of clear air
Field campaign LINEX 96/1 -- Possibilities of water vapor observation in the free atmosphere
Field campaign for the comparison of SOUSY radar wind measurements with rawinsonde and model data
A field campaign was carried out from 26
October to 7 November 1992, using the SOUSY-VHF radar and a mobile rawinsonde
system installed and operated nearby to produce vertical wind profiles. The
purpose of this campaign was to compare the two types of wind measurements with
one another and with results from forecast models. Numerical algorithms were
developed and applied to the radar data in order to eliminate random errors,
correct for velocity aliasing, and calculate the effective zenith angle of the
off-vertical beams. Differences between wind profiler data and rawinsonde or
model results depend not only upon the errors of the different systems, but also
on temporal and spatial variations of the wind field. Therefore, methods for the
comparison of radar and rawinsonde data were developed which take into
consideration these variations. The practical potential of these methods is
demonstrated by comparisons of rawinsonde and radar wind profiles. The
comparison of radar data and model output shows excellent agreement in the
direction and in the speed of the wind at virtually all altitudes. An evaluation
of the quality of wind profiler measurements is possible using the estimation of
variance and variability of wind components
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Chronology of the Burial Finds from Scythian Monuments in Southern Siberia and Central Asia
From the 16th International Radiocarbon Conference held in Gronigen, Netherlands, June 16-20, 1997.We present here new radiocarbon dates for the different barrows (burial mounds) of the nomadic tribes of the Scythian period in the Khakassia and Tuva regions (Central Asia). The time scale of these barrows is compared with the elite barrows of the Sayan-Altai. In agreement with archaeological evidence, some barrows in Khakassia are chronologically close in time to the Arzhan barrow. The first 14C dates produced for the barrows from the Tuva region belong to a later Scythian period, compared with the elite Arzhan barrow. We determined the final stage of the barrow construction, but to establish the starting time, more dates are necessary (both by dendrochronology and 14C).This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202
Field campaign for the comparison of SOUSY radar wind measurements with rawinsonde and model data
A field campaign was carried out from 26 October to 7 November 1992, using the SOUSY-VHF radar and a mobile rawinsonde system installed and operated nearby to produce vertical wind profiles. The purpose of this campaign was to compare the two types of wind measurements with one another and with results from forecast models. Numerical algorithms were developed and applied to the radar data in order to eliminate random errors, correct for velocity aliasing, and calculate the effective zenith angle of the off-vertical beams. Differences between wind profiler data and rawinsonde or model results depend not only upon the errors of the different systems, but also on temporal and spatial variations of the wind field. Therefore, methods for the comparison of radar and rawinsonde data were developed which take into consideration these variations. The practical potential of these methods is demonstrated by comparisons of rawinsonde and radar wind profiles. The comparison of radar data and model output shows excellent agreement in the direction and in the speed of the wind at virtually all altitudes. An evaluation of the quality of wind profiler measurements is possible using the estimation of variance and variability of wind components