A comprehensive raindrop collision outcome regime diagram that delineates the physical conditions associated with the outcome regimes (i.e., bounce, coalescence, and different breakup types) of ...binary raindrop collisions is proposed. The proposed diagram builds on a theoretical regime diagram defined in the phase space of collision Weber numbers We and the drop diameter ratio p by including critical angle of impact considerations. In this study, the theoretical regime diagram is first evaluated against a comprehensive dataset for drop collision experiments representative of raindrop collisions in nature. Subsequently, the theoretical regime diagram is modified to explicitly describe the dominant regimes of raindrop interactions in (We, p) by delineating the physical conditions necessary for the occurrence of distinct types of collision-induced breakup (neck/filament, sheet, disk, and crown breakups) based on critical angle of impact consideration. Crown breakup is a subtype of disk breakup for lower collision kinetic energy that presents distinctive morphology. Finally, the experimental results are analyzed in the context of the comprehensive collision regime diagram, and conditional probabilities that can be used in the parameterization of breakup kernels in stochastic models of raindrop dynamics are provided.
The application of the 2D-video disdrometer to measure fall speed and snow size distribution and to derive liquid equivalent snow rate, mean density–size and reflectivity–snow rate power law is ...described. Inversion of the methodology proposed by Böhm provides the pathway to use measured fall speed, area ratio and ‘3D’ size measurement to estimate the mass of each particle. Four snow cases from the Light Precipitation Validation Experiment are analyzed with supporting data from other instruments such as the Precipitation Occurrence Sensor System (POSS), Snow Video Imager (SVI), a network of seven snow gauges and three scanning C-band radars. The radar-based snow accumulations using the 2DVD-derived Ze–SR relation are in good agreement with a network of seven snow gauges and outperform the accumulations derived from a climatological Ze–SR relation used by the Finnish Meteorological Institute (FMI). The normalized bias between radar-derived and gauge accumulation is reduced from 96% when using the fixed FMI relation to 28% when using the Ze–SR relations based on 2DVD data. The normalized standard error is also reduced significantly from 66% to 31%. For two of the days with widely different coefficients of the Ze–SR power law, the reflectivity structure showed significant differences in spatial variability. Liquid water path estimates from radiometric data also showed significant differences between the two cases. Examination of SVI particle images at the measurement site corroborated these differences in terms of unrimed versus rimed snow particles. The findings reported herein support the application of Böhm's methodology for deriving the mean density–size and Ze–SR power laws using data from 2D-video disdrometer.
•Use 2DVD to measure the fall speed, area ratio and ‘3D’ size of snowflake and compute the snow size distribution (SSD).•Inverted Böhm’s equation to estimate the density-size relations. Use SSD and density-size relation to compute Ze and liquid equivalent snow rate (SR) and fit to a daily Z-SR power-law relation.•4 winter events from LPVEx are analyzed.•Apply Z-SR relation along with 3 FMI C-band radars to compute daily accumulated SR and compare them with 7 FMI snow gauges.
Estimates of snow microphysical properties obtained by analyzing collections of individual particles are often limited to short timescales and coarse time resolution. Retrievals using disdrometer ...observations coincident with bulk measurements such as radar reflectivity and snowfall amounts may overcome these limitations; however, retrieval techniques using such observations require uncertainty estimates not only for the bulk measurements themselves, but also for the simulated measurements modeled from the disdrometer observations. Disdrometer uncertainties arise due to sampling and analytic errors and to the discrete, potentially truncated form of the reported size distributions. Imaging disdrometers such as the Snowflake Video Imager and 2-D Video Disdrometer provide remarkably detailed representations of snow particles, but view limited projections of their three-dimensional shapes. Particle sizes determined by such instruments underestimate the true dimensions of the particles in a way that depends, in the mean, on particle shape, also contributing to uncertainties. An uncertainty model that accounts for these uncertainties is developed and used to establish their contributions to simulated radar reflectivity and snowfall rate. Viewing geometry effects are characterized by a parameter, , that relates disdrometer-observed particle size to the true maximum dimension of the particle. Values and uncertainties for are estimated using idealized ellipsoidal snow particles. The model is applied to observations from seven snow events from the Canadian CloudSat/CALIPSO Validation Project (C3VP), a mid-latitude cold-season cloud and precipitation field experiment. Typical total uncertainties are 4 dB for reflectivity and 40–60% for snowfall rate, are highly correlated, and are substantial compared to expected uncertainties for radar and precipitation gauge observations. The dominant sources of errors are viewing geometry effects and the discrete, truncated form of the size distributions. While modeled Ze–S relationships are strongly affected by assumptions about snow particle mass properties, such relationships are only modestly sensitive to owing to partially compensating effects on both the reflectivity and snowfall rate.
Periodic oscillations of raindrops falling at terminal velocity in natural rain are visualized for the first time by high-speed imaging. These images show the existence of an oscillation mode with ...the same frequency as the fundamental harmonic, but with shape different than that predicted by linear theory. These oscillations cause a lateral drift with a speed of approximately 20%-30% of the drop terminal velocity and without a preferred direction. These experimental observations serve as an insightful illustration of the potential benefit of applying high-speed imaging technology to investigate the dynamical microstructure of rainfall at the raindrop scale. PUBLICATION ABSTRACT
Raindrops impacting the rough sea modify its surface and its backscattering coefficient. This roughness change essentially depends on the rain content in very large drops, which is highly variable ...from one drop size distribution model to another. However, it has been observed that the radar reflectivity of raindrops has a drop size dependence very similar to that of the ringwaves induced by rain on the surface. From a numerical analysis on various drop size distributions, rain rates, and frequencies from 3 to 35 GHz, a relationship between the sea surface elevation variance of ringwaves resulting from drop impact and the rain radar reflectivity Z is established. It is found to be weakly dependent on the raindrop size distribution model. This link is expected to lead to better estimates of the surface roughness, and in turn, via electromagnetic scattering models, it could improve algorithms for near nadir rain radar retrieval.
This paper presents an analysis of drop size effects on ring-wave spectra and radar scatterometer returns from a water surface agitated by artificial rain. For this purpose, monodisperse and ...polydisperse rain events were generated in the laboratory for a wide range of rain rates and various drop sizes. The water droplets reached the surface at terminal velocity. In all cases, the radar average power is well modelled by a linear function of the power spectral density at the Bragg resonant wavelength. The drop size is found to have a strong impact on the spectral shape of the ring-waves and on their total energy. A log-Gaussian model characterizes well the ring-wave spectra and empirical expressions of the spectrum parameters are given. Ring-wave energy increases with rain rate and drop size, and is found to be proportional to the kinetic energy of a single drop, indicating that one may use a model in which all drops contribute to the ring-wave energy in proportion to their squared momentum. The results from the monodisperse rain experiments are used to construct a model for natural rain. Data from the polydisperse rain experiments show that a nonlinear model which relates dissipation to the total rainfall rate provides excellent agreement with the measurements. This analysis also shows the important impact of a few large drops on the ring-wave spectrum. The model proposed can be extended to natural rains either by using measurements of the drop size distribution or by assuming a drop size distribution model that is appropriate to the study region. It is concluded that it is important to characterize ring-wave spectra as a function of rain rate and drop size distribution to develop robust radar scattering models for rain-roughened seas.
We present an analysis of ring-wave and scatterometer data from a water surface that was agitated by simulated rain. Water droplets of 2.8mm diameter impacted the water surface at almost terminal ...velocity, and the rain rates cover a wide range of conditions (5 to 200mm hr
−1
). Both the ring-wave energy and backscattered power from the GHz scatterometer increase as R increases, but the growth rates slacken at higher rain intensities. Ring-wave frequency spectra and wavenumber spectra are well represented by log-Gaussian spectral models. The results can be used to guide development of microwave scattering models.
Correspondence: 1 Corresponding Author: José A. Ramos-Vara, Animal Disease Diagnostic Laboratory, Purdue University, 406 South University, West Lafayette, IN 47907. ramosja{at}purdue.edu ...Correspondence: 2 Dr. Kiupel is Chair of the AAVLD Subcommittee on Standardization of IHC.
This document is the consensus of the American Association of Veterinary Laboratory Diagnosticians (AAVLD) Subcommittee on Standardization of Immunohistochemistry on a set of guidelines for immunohistochemistry (IHC) testing in veterinary laboratories. Immunohistochemistry is a powerful ancillary methodology frequently used in many veterinary laboratories for both diagnostic and research purposes. However, neither standardization nor validation of IHC tests has been completely achieved in veterinary medicine. This document addresses both issues. Topics covered include antibody selection, fixation, antigen retrieval, antibody incubation, antibody dilutions, tissue and reagent controls, buffers, and detection systems. The validation of an IHC test is addressed for both infectious diseases and neoplastic processes. In addition, storage and handling of IHC reagents, interpretation, quality control and assurance, and troubleshooting are also discussed. Proper standardization and validation of IHC will improve the quality of diagnostics in veterinary laboratories.
Key Words: Animal diseases diagnostic immunohistochemistry standardization validation
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The SAR of a series of sterically hindered sulfonamide hydroxamic acids with relatively large P
1′ groups is described. The compounds typically spare MMP-1 while being potent inhibitors of ...MMP-13. The metabolically more stable compounds in the series contain either a monocyclic or bicyclic pyran ring adjacent to the hydroxamate group. Despite the sparing of MMP-1, pre-clinical and clinical studies revealed that fibrosis in rats and MSS in humans is still produced.
Rain affects wind retrievals from scatterometric measurements of the sea surface. To depict the additional roughness caused by rain on a wind driven surface, we use a ring-wave spectral model. This ...enables us to analyse the rain effect on Ku band scatterometric observations from two laboratory experiments. Calculations based on the small perturbation method provide good simulation of scattering measurements for the rain-only case, whereas for combined wind and rain cases, the boundary perturbation method is appropriate.
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