Topic
Disdrometer
About: Disdrometer is a research topic. Over the lifetime, 930 publications have been published within this topic receiving 23092 citations.
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TL;DR: In this article, the authors report on fall speed measurements of raindrops in light-to-heavy rain events from two climatically different regimes (Greeley,Colorado, and Huntsville, Alabama) using the high-resolution Meteorological Particle Spectrometer (MPS) and a third-generation (170 µm resolution) 2-D video divergence device (2DVD).
Abstract: . We report on fall speed measurements of raindrops in light-to-heavy
rain events from two climatically different regimes (Greeley,
Colorado, and Huntsville, Alabama) using the high-resolution
(50 µm ) Meteorological Particle Spectrometer (MPS) and
a third-generation (170 µm resolution) 2-D video
disdrometer (2DVD). To mitigate wind effects, especially for the
small drops, both instruments were installed within a 2∕3 -scale
Double Fence Intercomparison Reference (DFIR) enclosure. Two cases
involved light-to-moderate wind speeds/gusts while the third case
was a tornadic supercell and several squall lines that passed over
the site with high wind speeds/gusts. As a proxy for turbulent
intensity, maximum wind speeds from 10 m height at the
instrumented site recorded every 3 s were differenced with
the 5 min average wind speeds and then squared. The fall speeds
vs. size from 0.1 to 2 and >0.7 mm were derived from the
MPS and the 2DVD, respectively. Consistency of fall speeds from the
two instruments in the overlap region (0.7–2 mm ) gave
confidence in the data quality and processing methodologies. Our
results indicate that under low turbulence, the mean fall speeds
agree well with fits to the terminal velocity measured in the
laboratory by Gunn and Kinzer from 100 µm up to
precipitation sizes. The histograms of fall speeds for 0.5, 0.7, 1
and 1.5 mm sizes were examined in detail under the same
conditions. The histogram shapes for the 1 and 1.5 mm sizes
were symmetric and in good agreement between the two instruments
with no evidence of skewness or of sub- or super-terminal fall
speeds. The histograms of the smaller 0.5 and 0.7 mm drops
from MPS, while generally symmetric, showed that occasional
occurrences of sub- and super-terminal fall speeds could not be
ruled out. In the supercell case, the very strong gusts and
inferred high turbulence intensity caused a significant broadening
of the fall speed distributions with negative skewness (for drops of
1.3, 2 and 3 mm ). The mean fall speeds were also found to
decrease nearly linearly with increasing turbulent intensity
attaining values about 25–30 % less than the terminal
velocity of Gunn–Kinzer, i.e., sub-terminal fall speeds.
38 citations
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TL;DR: In this article, the authors describe two-di-two-dimensional rain cell size statistics employing radar and disdrometer data bases spanning more than 5 years and all seasons.
Abstract: Results of an investigation are given describing two-di-two-dimensional rain cell size statistics employing radar and disdrometer data bases spanning more than 5 years and all seasons. Radar data were obtained employing the SPANDAR radar located at the NASA Wallops Flight Facility, Wallops Island, Virginia. These data corresponded to approximately 100 low-elevation azimuthal antenna scans encompassing 17 rain days. For each of these rain days, disdrometer data were also obtained. Analysis of the regression relations relating the rain rates to the disdrometer data enabled the determination of least square fit radar reflectivity factors. The individual disdrometer results along with the radar data were employed with a contouring program. More than 22 000 contours were generated, where each isopleth belonged to predefined rain rate intervals. Computing the areas of each of these contours, statistics were generated relating the equi-circle contour diameters and rain rate categories. Two types of contour have been analyzed. One pertained to the above-described isopleth regardless of the rain rate levels interior to it. Another type corresponded to those isopleths in which the rain rates interior to it were equal or greater than the isopleth values. These isopleths were referred to as "total" and "cell" contours, respectively. An abundance of total and cell contours were observed belonging to all rain rate categories. In particular, a dominant number of smallarea contours were observed belonging to the lower rain rate levels. The results showed that the average and median "equi-circle" cell contour diameters were 2.4 and 1.9 km, respectively.
38 citations
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TL;DR: In this article, the authors present a measurement campaign to address several error sources associated with rainfall estimates from microwave links in cellular communication networks, including rainfall, solid precipitation, temperature, fog, antenna wetting due to rain or dew, and clutter.
Abstract: . We present a measurement campaign to address several error sources associated
with rainfall estimates from microwave links in cellular communication
networks. The core of the experiment is provided by three co-located
microwave links installed between two major buildings on opposite sides of
the small town of Wageningen, approximately 2 km apart: a 38 GHz formerly
commercial microwave link, as well as 26 and 38 GHz (dual-polarization)
research microwave links. Transmitting and receiving antennas have been
attached to masts installed on the roofs of the two buildings, about 30 m
above the ground. This setup was complemented with an infrared large-aperture
scintillometer, installed over the same path, as well as five laser
disdrometers positioned at several locations along the path and an automated
rain gauge. Temporal sampling of the received signals was performed at a rate
of 20 Hz. The setup was monitored by time-lapse cameras to assess the state
of the antennas as well as the atmosphere. The experiment was active between
August 2014 and December 2015. Data from an existing automated weather
station situated just outside Wageningen was further used to compare and to
interpret the findings. In addition to presenting the experiment, we also
conduct a preliminary global analysis and show several cases highlighting the
different phenomena affecting received signal levels: rainfall, solid
precipitation, temperature, fog, antenna wetting due to rain or dew, and
clutter. We also briefly explore cases where several phenomena play a role. A
rainfall intensity ( R ) – specific attenuation ( k ) relationship was
derived from the disdrometer data. We find that a basic rainfall retrieval
algorithm without corrections already provides a reasonable correlation to
rainfall as measured by the disdrometers. However, there are strong
systematic overestimations (factors of 1.2–2.1) which cannot be attributed
to the R – k relationship. We observe attenuations in the order of 3 dB
due to antenna wetting under fog or dew conditions. We also observe
fluctuations of a similar magnitude related to changes in temperature. The
response of different makes of microwave antennas to many of these phenomena
is significantly different even under the exact same operating conditions and
configurations.
37 citations
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TL;DR: In this paper, the performances of two couples of disdrometers based on different measuring principles are compared: a classical Joss-Waldvogel dis-rometer and a recently developed device, called the Pludix tested in Ferrara, Italy, and the two-dimensional video dis-remeter (2DVD) tested in Cabauw, The Netherlands.
37 citations
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TL;DR: In this article, the physical characteristics of raindrop size distribution (DSD) in an equatorial heavy rain region based on three years of disdrometer observations carried out at Universiti Teknologi Malaysia's (UTM) campus in Kuala Lumpur, Malaysia.
Abstract: This work investigates the physical characteristics of raindrop size distribution (DSD) in an equatorial heavy rain region based on three years of disdrometer observations carried out at Universiti Teknologi Malaysia’s (UTM’s) campus in Kuala Lumpur, Malaysia. The natural characteristics of DSD are deduced, and the statistical results are found to be in accordance with the findings obtained from others disdrometer measurements. Moreover, the parameters of the Gamma distribution and the normalized Gamma model are also derived by means of method of moment (MoM) and maximum likelihood estimation (MLE). Their performances are subsequently validated using the rain rate estimation accuracy: the normalized Gamma model with the MLE-generated shape parameter µ was found to provide better accuracy in terms of long-term rainfall rate statistics, which reflects the peculiarities of the local climatology in this heavy rain region. These results not only offer a better understanding of the microphysical nature of precipitation in this heavy rain region but also provide essential information that may be useful for the scientific community regarding remote sensing and radio propagation.
37 citations