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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

Journal ArticleDOI
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

Journal ArticleDOI
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

Journal ArticleDOI
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

Journal ArticleDOI
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


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202378
2022114
202151
202059
201972
201840