A Rain Gauge for the Measurement of Finescale Temporal Variations

C. David Stow University of Auckland, Auckland, New Zealand

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Stuart G. Bradley University of Auckland, Auckland, New Zealand

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Keith E. Farrington University of Auckland, Auckland, New Zealand

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Kim N. Dirks University of Auckland, Auckland, New Zealand

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Warren R. Gray University of Auckland, Auckland, New Zealand

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Abstract

A rain gauge is described that quantizes rainwater collected by a funnel into equal-sized drops. Using a funnel of 150-mm diameter, the quantization corresponds to 1/160 mm of rainfall, enabling the measurement of low rainfall rates and the attainment of a fine temporal resolution on the order of 15 s without unduly large sampling errors. Two drop-producing units are compared and an operational rain gauge design is presented. Field comparisons with conventional rain gauges are made, showing excellent correlations for daily rain totals, and intercomparisons between clusters of dropper gauges are also given. Examples of highly resolved rainfall events are shown demonstrating the ability to measure low rainfall accumulations and also coherent high intensity events of short duration, which are not detectable with conventional rain gauges.

* Current affiliation: National Institute of Water and Atmospheric Research, Wellington, New Zealand.

Corresponding author address: C. D. Stow, Dept. of Physics, University of Auckland, Private Bag 92019, Auckland, New Zealand.

Email: d.stow@auckland.ac.nz

Abstract

A rain gauge is described that quantizes rainwater collected by a funnel into equal-sized drops. Using a funnel of 150-mm diameter, the quantization corresponds to 1/160 mm of rainfall, enabling the measurement of low rainfall rates and the attainment of a fine temporal resolution on the order of 15 s without unduly large sampling errors. Two drop-producing units are compared and an operational rain gauge design is presented. Field comparisons with conventional rain gauges are made, showing excellent correlations for daily rain totals, and intercomparisons between clusters of dropper gauges are also given. Examples of highly resolved rainfall events are shown demonstrating the ability to measure low rainfall accumulations and also coherent high intensity events of short duration, which are not detectable with conventional rain gauges.

* Current affiliation: National Institute of Water and Atmospheric Research, Wellington, New Zealand.

Corresponding author address: C. D. Stow, Dept. of Physics, University of Auckland, Private Bag 92019, Auckland, New Zealand.

Email: d.stow@auckland.ac.nz

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