Disdrometer

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

Measurements of raindrop size distribution over Gadanki during southwest and north-east monsoon

Abstract: Simultaneous observations of disdrometer and optical rain gauge (at National MST Radar Facility, Gadanki) and their application in rainfall estimation are evaluated. Comparison of rain rate obtained from disdrometer and optical rain gauge in different precipitation events in different seasons show reasonably good agreement between the two instruments. Southern India has two distinct rainfall seasons, namely south-west (S-W) monsoon and north-east (N-E) monsoon periods. Disdrometer data analysis shows a clear seasonal dependence in radar reflectivity factor-rainfall rate (Z-R) relations (i.e. raindrop size distribution characteristics) in S-W monsoon and N-E monsoon periods over Gadanki. It is also found that during S-W monsoon precipitation generally has bigger drops than during N-E monsoon. During the S-W monsoon most of the precipitating cloud systems are associated with mesoscale convection activities. These precipitating systems are short­ lived (1-2 h) with high intensity of rainfall.

Rain observations with micro rain radar (MRR) over Thumba

Abstract: The Micro Rain Radar (MRR) a highly resolution radar operates at a frequency of 24 GHz installed at Thumba (8.5°N, 76.9°E) under Ka band propagation experiment is used extensively to characterize the tropical rain. This radar measurements of rain were obtained with fine spatial and temporal resolutions like One minute time resolution and 200 m height resolution. With this radar for the first time classification of precipitating systems are studied. With the presence or absence of bright band a radar signature of melting layer one can classify particular rain type as convective or stratiform. For present study MRR data from September 2005 onwards are collected. The main objective is to classify precipitation system into Stratiform and Convective with the presence or absence of Bright band. Another potential of this radar is ability to give information of vertical structure of fall velocity of hydrometeors. This also gives profiles of number concentration of various ranges of Drop sizes, liquid water content and rain rate for different heights. These results are compared with the collocated ground based Disdrometer. Attenuation at Microwave frequencies during the presence of rain is a serious concern to the communication. Once temporal and spatial information of DSD is known microwave attenuation can be studied. These results will be presented in this paper.

Statistical Analysis of the Raindrop Size Distribution Using Disdrometer Data

Abstract: The present study utilizes nine years of measurements taken from a Joss–Waldvogel disdrometer (JWD). From this dataset, thirty six rainfall events, were selected and categorized, respectively, in convective and stratiform types, according to specific criteria. Six statistical distributions namely the one- and two-parameter exponential, the two- and three-parameter lognormal and finally the two- and three-parameter gamma were fitted on the observed drop size distributions (DSDs). The goodness-of-fit between each statistical and the observed distribution was determined based on the Kolmogorov–Smirnov test. The results show that 72% of the stratiform events are best described by the three-parameter lognormal distribution while 28% are best described by the three-parameter gamma distribution. In the case of convective events, the results are more diversified; the two- and three-parameter gamma distribution fits best in 39% and 17% of the events, respectively, while the two- and three-parameter lognormal distribution fits best in 6% and 39% of the events. The one- and two-parameter exponential distribution was not the best fit in any case. Moreover, initial steps have already been taken in order for these findings to be used for calibration purposes of a recently employed X-band rainscanner in the Attica region in Greece.

Raindrop shapes and fall velocities in “turbulent times”

Abstract: . Raindrop shapes and fall velocities measured by 2-dimensional video disdrometer are presented for 2 high-wind/turbulent events. The shapes were reconstructed using a relatively new technique. 10 m height wind sensor data are used to derive proxy-indicators for turbulent intensities. Our results show strong gusts, directional wind shifts (i.e. shear) and/or inferred high turbulence intensity are correlated with reduced fall speeds, reaching values ∼25 %–30 % less than the expected values, i.e. sub-terminal fall speeds. Significant percentage (20 %–35 %) of asymmetric drops ( > 2 mm) deviating from the most probable axisymmetric shapes were also detected for some events with high turbulent intensities.

Comparison of radar derived slant path rain attenuations with the COMSTAR beacon fades at 28.56 GHz for summer and winter periods

Abstract: New results are described from an experiment for testing and improving the accuracy of radar derived slant path attenuations of the 28.56-GHz COMSTAR beacon signal using an electromechanical disdrometer located at Wallops Island, VA. Continued overall good agreement between measured and radar derived fades were noted on a case-by-case basis and statistically for the new data base.