Editorial Type:
Article
Article Type:
Research Article

A Study of the Error Covariance Matrix of Radar Rainfall Estimates in Stratiform Rain. Part II: Scale Dependence

Marc Berenguer J. S. Marshall Radar Observatory, McGill University, Montreal, Quebec, Canada

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Isztar Zawadzki J. S. Marshall Radar Observatory, McGill University, Montreal, Quebec, Canada

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Print Publication:
01 Jun 2009
DOI:
https://doi.org/10.1175/2008WAF2222210.1
Page(s):
800–811
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Abstract

The contribution of various physical sources of uncertainty affecting radar rainfall estimates at the ground has been recently quantified at a resolution typically used in schemes assimilating rainfall at the ground onto mesoscale models. Here, the contribution of the two most important sources of uncertainty at nonattenuating wavelengths (the range-dependent error and the uncertainty due to the Z–R transformation) and their interaction are studied as a function of the resolution of radar observations.

The analysis is carried out using a large dataset of collocated reflectivity profiles from the McGill S-band radar and disdrometric measurements obtained in stratiform rainfall at resolutions of 1 × 1, 5 × 5, and 15 × 15 km2. Results show that the errors affecting radar quantitative precipitation estimation (QPE) have a strong dependence with range, and that their structure is scale dependent. At the analyzed resolutions, QPE errors are significantly correlated in time and over several grid points.

Corresponding author address: Marc Berenguer, J. S. Marshall Radar Observatory, McGill University, 805 Sherbrooke St. W, Montreal, QC H3A2K6, Canada. Email: berenguer@meteo.mcgill.ca

Abstract

The contribution of various physical sources of uncertainty affecting radar rainfall estimates at the ground has been recently quantified at a resolution typically used in schemes assimilating rainfall at the ground onto mesoscale models. Here, the contribution of the two most important sources of uncertainty at nonattenuating wavelengths (the range-dependent error and the uncertainty due to the Z–R transformation) and their interaction are studied as a function of the resolution of radar observations.

The analysis is carried out using a large dataset of collocated reflectivity profiles from the McGill S-band radar and disdrometric measurements obtained in stratiform rainfall at resolutions of 1 × 1, 5 × 5, and 15 × 15 km2. Results show that the errors affecting radar quantitative precipitation estimation (QPE) have a strong dependence with range, and that their structure is scale dependent. At the analyzed resolutions, QPE errors are significantly correlated in time and over several grid points.

Corresponding author address: Marc Berenguer, J. S. Marshall Radar Observatory, McGill University, 805 Sherbrooke St. W, Montreal, QC H3A2K6, Canada. Email: berenguer@meteo.mcgill.ca

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