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Error in the sampling area of an optical disdrometer: consequences in computing rain variables.
R Fraile1, A Castro, M Fernández-Raga
1Department of Physics, IMARENAB, University of León, 24071 León, Spain. roberto.fraile@unileon.es
Thescientificworldjournal
|July 12, 2013
Summary
Optic disdrometers overestimate sampling area for large raindrops, leading to significant underestimations in rain intensity and reflectivity calculations. Correcting this sampling area is crucial for accurate measurements.
Area of Science:
- Meteorology
- Hydrology
- Instrument Science
Background:
- Optic disdrometers are crucial for measuring raindrop size distributions.
- The nominal sampling area of disdrometers often differs from the effective area, especially for larger drops.
- This discrepancy can introduce errors in derived rainfall parameters.
Purpose of the Study:
- To improve the estimation of characteristic uncertainties in optic disdrometers.
- To calculate the effective sampling area based on raindrop size.
- To assess the influence of sampling area errors on rainfall intensity and reflectivity factor computations.
Main Methods:
- Analysis of optic disdrometer data, focusing on effective sampling area calculation.
- Propagation of sampling area errors to rainfall intensity and reflectivity factor.
- Examination of a specific rain event on April 16, 2006.
Main Results:
- The effective sampling area can be significantly smaller than the nominal area for large raindrops (>6 mm), potentially halving it.
- Uncorrected sampling areas lead to underestimation of rainfall intensity (up to 50%) and reflectivity factor (up to 100%).
- Z-R relationships showed minimal dependence on sampling area due to proportional error propagation.
Conclusions:
- Accurate determination of the effective sampling area is essential for reliable disdrometer measurements.
- Failure to correct for sampling area leads to systematic underestimation of key rainfall parameters.
- The findings highlight the need for improved disdrometer calibration and data processing techniques.
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