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| Titel |
Automatic Extraction of High-Resolution Rainfall Series from Rainfall Strip Charts |
| VerfasserIn |
Antonio Saá-Requejo, Jose Luis Valencia, Alberto Garrido, Ana M. Tarquis |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250113409
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| Publikation (Nr.) |
 EGU/EGU2015-14950.pdf |
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| Zusammenfassung |
| Soil erosion is a complex phenomenon involving the detachment and transport of soil
particles, storage and runoff of rainwater, and infiltration. The relative magnitude and
importance of these processes depends on a host of factors, including climate, soil,
topography, cropping and land management practices among others. Most models for soil
erosion or hydrological processes need an accurate storm characterization. However, this data
are not always available and in some cases indirect models are generated to fill this gap. In
Spain, the rain intensity data known for time periods less than 24 hours back to 1924 and
many studies are limited by it. In many cases this data is stored in rainfall strip
charts in the meteorological stations but haven’t been transfer in a numerical form.
To overcome this deficiency in the raw data a process of information extraction
from large amounts of rainfall strip charts is implemented by means of computer
software.
The method has been developed that largely automates the intensive-labour extraction
work based on van Piggelen et al. (2011). The method consists of the following five basic
steps: 1) scanning the charts to high-resolution digital images, 2) manually and visually
registering relevant meta information from charts and pre-processing, 3) applying automatic
curve extraction software in a batch process to determine the coordinates of cumulative
rainfall lines on the images (main step), 4) post processing the curves that were not
correctly determined in step 3, and 5) aggregating the cumulative rainfall in pixel
coordinates to the desired time resolution. A colour detection procedure is introduced that
automatically separates the background of the charts and rolls from the grid and
subsequently the rainfall curve. The rainfall curve is detected by minimization of a cost
function.
Some utilities have been added to improve the previous work and automates some
auxiliary processes: readjust the bands properly, merge bands when those have been scanned
in two parts, detect and cut the borders of bands not used (demanded by the software). Also
some variations in which colour system is tried basing in HUE or RGB colour have been
included.
Thanks to apply this digitization rainfall strip charts 209 station-years of three locations in
the centre of Spain have been transformed to long-term rainfall time series with 5-min
resolution.
References
van Piggelen, H.E., T. Brandsma, H. Manders, and J. F. Lichtenauer, 2011: Automatic
Curve Extraction for Digitizing Rainfall Strip Charts. J. Atmos. Oceanic Technol., 28,
891–906.
Acknowledgements
Financial support for this research by DURERO Project (Env.C1.3913442) is greatly
appreciated. |
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