Disdrometer

About: Disdrometer is a research topic. Over the lifetime, 930 publications have been published within this topic receiving 23092 citations.

Estimation of drop size distribution from the low frequency components in the rain generated underwater acoustic noise

Abstract: Drop size distribution (DSD) is an important parameter that completely characterizes the rain and rain generated acoustic energy. This paper presents a simple and efficient method for measuring the DSD of rain by analyzing the low‐frequency components in the spectrum of rain generated acoustic noise underwater. A specially designed sensor assembly captures the acoustic noise produced due to the raindrop impacts on the water surface. Every individual drop produces acoustic noise comprising the low frequency components which has distinct characteristics in the time domain. It has been found that these distinct features vary with the size of the droplets and its velocity. Experimental evidences show that the acoustic energy of the low frequency signal is related to the size of the drops that caused the acoustic noise and, hence, the energy of the drops generated acoustic signal is a measure of the drop size. An algorithm for detecting and computing the energy of these low frequency components leading to the estimation of DSD of rain is presented in this paper. This approach has been employed in developing a Disdrometer based automatic rain gauge, which is simple, reliable, and cost effective.

Characteristic of Raindrop Size Distribution Using Two-dimensional Video Disdrometer Data in Daegu, Korea

Abstract: Abstact: This study analyzes Two-dimensional video disdrometer (2DVD) data while summer 2011-2012 in Daegu region and compares with Marshall and Palmer (MP) distribution to find out statistical characteristics and characteristics variability about drop size distribution (DSD) of Daegu region. As the characterize DSD of Daegu region, this study uses single moment parameters such as rainfall intensity (R), reflectivity factor (Z) and double moment parameters such as generalized characteristics number concentration (N0') and generalized characteristics diameter (Dm'). Also, this study makes an assumption that DSD function can be expressed as general gamma distribution. The results of analysis show that DSD of Daegu region has log10N0' =2.37, Dm' =1.04 mm, and c =2.37, μ =0.39 on average. When the assumption of MP distribution is used, these figures then end up with the different characteristics; log10N0' =2.27, Dm' =0.9 mm, c =1, μ =1 on average. The differences indicate liquid water content (LWC) of Daegu distribution is generally larger than MP distribution at equal Z. Second, DSD shape of Daegu distribution is concave upward. Other important facts are the characteristics of Daegu distribution change when Z changes. DSD shape of Daegu region changes concave downward (c =2.05~2.55, μ =0.33~0.77) to cubic function-like shape (c =3.0, μ = −0.13~ −0.33) at Z > 45 dBZ. 35 dBZ ≤ Z > 45 dBZ group of Daegu distribution has characteristics similar to maritime cluster of diverse climate DSD study. However, Z > 45 dBZ group of Daegu distribution has a difference from the cluster.

Drop-by-Drop Radar Cross Section Calculations for Sand C-band Weather Radar Frequencies

Abstract: Recent studies revealed that scattering calculations at weather radar frequencies using individual drop shapes result in better agreement between simulated and measured polarimetric weather radar parameters, than if established rotational symmetric shape models are used. In the present work, thousands of individual rain drops that were detected with a 2D Video Disdrometer during a tropical storm, were reconstructed and their individual radar cross sections (RCS) were calculated by automatizing a commercial EM solver software. The calculations were carried out at the common weather radar frequencies at 2.8 GHz and 5.625 GHz, both for horizontal and vertical polarization. It is evaluated to what extend the RCS can differ for drops with an equal volume, it is discussed how the scattering parameters of individual drops scale within S- and C-band frequencies, and it is shown for one sample drop what effect the modelling granularity has on determined radar cross section values.

Characteristics of Raindrop Size Distribution Over a Tropical Location, Kolkata

Abstract: Raindrop size distribution (DSD) characteristics of monsoon and pre-monsoon seasons over Kolkata are analyzed by using three years raindrop size data from Joss–Waldvogel disdrometer located at Kolkata. The probability of occurrence DSD for different rain rate cluster has been observed for monsoon and pre-monsoon season. The mean raindrop concentration at a particular drop diameter and rain rate has been observed for both the seasons. The variations of number concentration with drop diameter and time have also been shown for monsoon and pre-monsoon season. The diurnal variations of DSD have also been investigated.

Impact of Scattering Model on Disdrometer Derived Attenuation Scaling

Abstract: NASA Glenn Research Center (GRC), the Air Force Research Laboratory (AFRL), and the Politecnico di Milano (POLIMI) are currently entering the third year of a joint propagation study in Milan, Italy utilizing the 20 and 40 GHz beacons of the Alphasat TDP#5 Aldo Paraboni scientific payload. The Ka- and Q-band beacon receivers were installed at the POLIMI campus in June of 2014 and provide direct measurements of signal attenuation at each frequency. Collocated weather instrumentation provides concurrent measurement of atmospheric conditions at the receiver; included among these weather instruments is a Thies Clima Laser Precipitation Monitor (optical disdrometer) which records droplet size distributions (DSD) and droplet velocity distributions (DVD) during precipitation events. This information can be used to derive the specific attenuation at frequencies of interest and thereby scale measured attenuation data from one frequency to another. Given the ability to both predict the 40 gigahertz attenuation from the disdrometer and the 20 gigahertz time-series as well as to directly measure the 40 gigahertz attenuation with the beacon receiver, the Milan terminal is uniquely able to assess these scaling techniques and refine the methods used to infer attenuation from disdrometer data. In order to derive specific attenuation from the DSD, the forward scattering coefficient must be computed. In previous work, this has been done using the Mie scattering model, however, this assumes a spherical droplet shape. The primary goal of this analysis is to assess the impact of the scattering model and droplet shape on disdrometer-derived attenuation predictions by comparing the use of the Mie scattering model to the use of the T-matrix method, which does not assume a spherical droplet. In particular, this paper will investigate the impact of these two scattering approaches on the error of the resulting predictions as well as on the relationship between prediction error and rain rate.