Comparison of different fittings of drop spectra for rainfall retrievals

Adirosi, Elisa; Baldini, Luca; Lombardo, Federico; Russo, Fabio; Napolitano, Francesco; Volpi, Elena; Tokay, Ali

doi:10.1016/j.advwatres.2015.05.009

Cited by 35 publications

(27 citation statements)

References 63 publications

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“…It is known that DSDs vary considerably in time and space during a rainfall event. In addition, an averaged DSD is closer to the exponential distribution than DSDs of smaller time intervals (1-5 min) [6]. Nevertheless, as the scope of this study is the operational calibration of the installed x-band rainscanner, it is practically impossible to change the implemented statistical distributions in such detailed time intervals.…”

Section: Statistical Distributionsmentioning

confidence: 93%

“…Then, they tested the adequacy of the gamma distribution through the Kolmogorov-Smirnov goodness-of-fit test, and finally they proposed a different parametrization of the DSD based on some statistical moments. Adirosi et al [6] found that the most of the measured DSD can be described by light-tailed distributions (such as the Weibull or the gamma distribution); however, there is a significant amount of spectra that appears to be better described by a heavy-tailed distribution (such as the lognormal distribution). Furthermore, comparing in pairs only the gamma and the lognormal distribution, they found that the gamma distribution performs better in about 70% of the times.…”

Section: Introductionmentioning

confidence: 99%

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Statistical Analysis of the Raindrop Size Distribution Using Disdrometer Data

2016

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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.

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Section: Statistical Distributionsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Statistical Analysis of the Raindrop Size Distribution Using Disdrometer Data

2016

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“…It would have been fortunate if the spurious drops could have easily been filtered out using a velocity filter similar to those employed in [3,8,14,15,[20][21][22]31,36,50,51], but Figure 12 suggests that no such simple technique will work to find these spurious drops. Furthermore, previous studies that used a drop velocity filter likely still included many of the spurious drops identified in this study.…”

Section: Vertical Fall Speeds Of Anomalous Dropsmentioning

confidence: 99%

Identification and Characterization of an Anomaly in Two-Dimensional Video Disdrometer Data

Larsen

Schönhuber

2018

Atmosphere

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The two-dimensional video distrometer (2DVD) is a well known ground based point-monitoring precipitation gauge, often used as a ground truth instrument to validate radar or satellite rainfall retrieval algorithms. This instrument records a number of variables for each detected hydrometeor, including the detected position within the sample area of the instrument. Careful analyses of real 2DVD data reveal an artifact-there are time periods where hydrometeor detections within parts of the sample area are artificially enhanced or diminished. Here, we (i) illustrate this anomaly with an exemplary 2DVD data set, (ii) describe the origin of this anomaly, (iii) develop and present an algorithm to help flag data potentially partially corrupted by this anomaly, and (iv) explore the prevalence and quantitative impact of this anomaly. Although the anomaly is seen in every major rain event studied and by every 2DVD the authors have examined, the anomaly artificially induces less than 3% of all detected drops and typically alters estimates of rain rates and accumulations by less than 2%.

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“…Walko et al, ; Milbrandt and Yau, ; ; Thompson et al, ; Morrison et al, ; Saleeby and van den Heever, ). Its frequent use is due in part to the fact that this particular PDF has been shown to be a good approximation of observed RSDs (Adirosi et al, ; ), although it appears that the goodness of fit of this PDF for hydrometeors other than rain has not been extensively examined. Furthermore, moment‐based characteristics are easily derived when using this size distribution function.…”

Section: Introductionmentioning

confidence: 99%

Relative sensitivities of simulated rainfall to fixed shape parameters and collection efficiencies

Freeman

Igel

Heever

2019

Quart J Royal Meteoro Soc

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Rainfall prediction by weather forecasting models is strongly dependent on the microphysical parametrization being utilized within the model. As forecasting models have become more advanced, they are more commonly using double‐moment bulk microphysical parametrizations. While these double‐moment schemes are more sophisticated and require fewer a priori parameters than single‐moment parametrizations, a number of parameter values must still be fixed for quantities that are not Prognosed or diagnosed. Two such parameters, the width of the rain drop size distribution and the choice of collection efficiencies between liquid hydrometeors, are examined here. Simulations of deep convective storms were performed in which the collection efficiency dataset and the a priori width of the rain drop size distribution (RSD) were individually and simultaneously modified. Analysis of the results show that the a priori width of the RSD was a larger control on the total accumulated precipitation (a change of up to 75% over the typical values tested in this article) than the choice of collection efficiency dataset used (a change of up to 10%). Changing the collection efficiency dataset produces most of the impacts on precipitation rates through changes in the warm rain process rates. On the other hand, the decrease in precipitation with narrowing RSDs occurs in association with the following processes: (a) decreased rain production due to increased evaporation, (b) decreased rain production due to decreased ice melting, and (c) slower raindrop fall speed which leads to longer residency times and changes in rain self‐collection. These results add to the growing body of work showing that the representation of hydrometeor size distributions is critically important, and suggests that more work should be done to better represent the width of the RSD in models, including further development of triple‐moment and bin schemes.

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Comparison of different fittings of drop spectra for rainfall retrievals

Cited by 35 publications

References 63 publications

Statistical Analysis of the Raindrop Size Distribution Using Disdrometer Data

Statistical Analysis of the Raindrop Size Distribution Using Disdrometer Data

Identification and Characterization of an Anomaly in Two-Dimensional Video Disdrometer Data

Relative sensitivities of simulated rainfall to fixed shape parameters and collection efficiencies

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