Disdrometer

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

Dual-frequency radar Doppler spectral retrieval of rain drop size distributions and entangled dynamics variables

Abstract: A novel technique based on Ka-W band dual-wavelength Doppler spectra has been developed for the simultaneous retrieval of binned rain drop size distributions (DSD) and air state parameters like vertical wind and air broadening caused by turbulence and wind shear. The rationale underpinning the method consists in exploiting the peculiar features observed in Doppler spectra caused by the wavelength dependence of scattering and absorption properties. A notional study based on a large data set of DSDs measured by a two-dimensional video disdrometer demonstrates that the retrieval performs best for small/moderate air broadening spectral width and when mean volume diameters exceed at least 1 mm. The retrieval is also limited to ranges below cloud base and where the signal-to-noise ratio of both radars exceed 10 dB, which rules out regions affected by strong attenuation. Broadly speaking, it is applicable to rain rates comprised between roughly 1 and 30 mm h−1. Preliminary retrieval for observations at the Atmospheric Radiation Measurement Southern Great Plains site shows very good agreement with independent reflectivity measurements from a 0.915 GHz wind profiler. The proposed methodology shows great potential in linking microphysics to dynamics in rainfall studies.

Rain-induced attenuation effects on C-band dual-polarization meteorological radars

Abstract: An attenuation correction procedure is proposed and evaluated by simulations using raindrop size distribution obtained from ground-based disdrometer measurements. The results show that under certain conditions it is possible to retrieve C-band reflectivity factor (Z/sub H/) and differential reflectivity (Z/sub DR/) radar observables affected by attenuation along rain-filled propagation paths. Rainfall rates estimated from Z/sub H/ and Z/sub DR/ with and without attenuation correction are compared to determine the effects of attenuation and the capability of the correction procedure to account for it. >

C-Band Dual-Polarization Radar Observables in Rain

Abstract: C-band dual-linear polarization radar observables are simulated from disdrometer measurements in rainfall and from gamma-model raindrop-size distributions. It is shown that rainfall is clustered in certain sections of planes formed by selected pairs of radar observables, such as (ZH, ZDR), (ZH, ZDP), (ZH, KDP), and (ρ, ZDR). Measurements lying outside these rainfall cluster regions can be interpreted as being from ice- and mixed-phase hydrometeors. Relationships for estimating rainfall rate R from radar measurements of ZH, KDP, and (ZH, ZDR) are derived, and the latter is shown to produce the best results. An important problem for C-band measurements in the presence of rainfall is attenuation. For this purpose, relationships are derived for estimating specific attenuation and specific differential attenuation from the specific differential phase. The backscattering differential phase shift, which is a potential source of error in estimating KDP, is shown to be very sensitive to the drop-size dist...

Modeling the Variability of Drop Size Distributions in Space and Time

Abstract: The information on the time variability of drop size distributions (DSDs) as seen by a disdrometer is used to illustrate the structure of uncertainty in radar estimates of precipitation. Based on this, a method to generate the space–time variability of the distributions of the size of raindrops is developed. The model generates one moment of DSDs that is conditioned on another moment of DSDs; in particular, radar reflectivity Z is used to obtain rainfall rate R. Based on the fact that two moments of the DSDs are sufficient to capture most of the DSD variability, the model can be used to calculate DSDs and other moments of interest of the DSD. A deterministic component of the precipitation field is obtained from a fixed R–Z relationship. Two different components of DSD variability are added to the deterministic precipitation field. The first represents the systematic departures from the fixed R–Z relationship that are expected from different regimes of precipitation. This is generated using a simp...