Abstract
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%.
Highlights
The two-dimensional video disdrometer (Joanneum Research, Graz, Austria) is an optical system designed to identify and measure individual rain drops falling through a sensing area of approximately 100 cm2
The fraction of the field of view that is affected by this anomaly is typically small, and the anomaly most commonly induces spurious detections of very small drops that do not substantially affect the measured rain accumulations
Typical errors in rain accumulation due to this effect appear to be on the order of no more than 1–2% of total rain accumulations
Summary
The two-dimensional video disdrometer (hereafter 2DVD) (Joanneum Research, Graz, Austria) is an optical system designed to identify and measure individual rain drops falling through a sensing area of approximately 100 cm2 This instrument, initially developed in the early 1990s, has been continuously improved and serves as an important tool in a wide variety of studies related to rain characterization and ground validation [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29]. We find the total effect of this anomaly to induce a slight overestimation of no more than about 1–2% above the detected accumulations in an absence of the anomaly
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