Mareile Wolff, Norwegian Meteorological Service

Transcription

1 C Mareile Wolff, Norwegian Meteorological Service Eumetnet WG-INS, Wien September 2013

2 Status and Benefits Status started to work with the classification scheme as recommended from CIMO in 2010 Translation of the document and distribution, both as a simplified and a complete version. Suitable tools for field measurements were considered and tested. For the present, a laser distance meter with tilt function was chosen (though not perfect). Tests with a fisheye camera have been performed Step by step manual and forms for field work were developed, tested and improved Classification of precipitation stations have started in 2012; Ca. 140 (40%-50%) of the precipitation stations will be classified by the end of Classification of temperature stations have started in 2013; ca 20 stations (5%) will be classfied by the end of 2013 Wind and Radiation will follow eventually, Benefits a more objective method to characterize the exposure of a site easier and better understandable communication, both internal and external possible to follow development of a station easy to identify measures to improve the exposure of a site, also motivation a quality measure to differentiate between stations of the Norwegian Meteorological Institute and stations of cooperation partners also applicable for finding new places for stations

3 Precipitation Challenges and Questions: Tool (Leica Disto D8) does not work reliable on very bright days Difficulties to judge if the natural relief is representative or not ( does a move of the station by 500 m change the class obtained? )* How accurate is the description of natural shielding ( surrounded by obstacles of uniform height, seen under an elevation angle between 14 to 26 )* : Class jump from 1 to 3 when surrounding trees higher than 26.5

4 Tool: Leica Disto D8 +Cheap (6500 NOK + tax) +tilt sensor +Image targeting possible +Bluetooth data transfer +Possible to use without tripod Data transfer not sufficient Tripod improves results significantly No camera, no compass

5 Statistics 140 of ca. 300 stations classified in 2013 average class: of 140 (22%) can be improved

6 Temperature Challenge: Method does not consider the duration of possible shading, depending on the obstacle s width and location. That aspect is especially important for locations with high variation of sun elevation and azimuth throughout a year (high latitude countries).

7 Example: Ørlandet

8 N NW E SE W

9 N NW E SE W

10 Example: Flisa

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14 valuated Tools Tool Parameters Advantages Disadvantages Triangles (wood, metal, plastic) with three angles Leica Disto D8 determination if all obstacles are lower than the maxelevation angle defined for each class elevation angle height distance (<100 m) almost no costs easy to use relatively cheap easy to use measurements in multiple directions necessary only classification of precipitation sensors possible compass and GPS needed measurements in multiple directions necessary no usable datatransfer compass and GPS needed limited range under very bright conditions Smartphone application (Theodolite, GeoCam, ) elevation angle position azimuth angle distance internal compass and GPS reporting function not reliable accuracy measurements in multiple directions necessary Fisheye camera elevation angle relative azimuth angle (absolute requires external compass or camera with GPS) 360 picture GPS and compass required no distances GPS and compass required manual analysis afterwards low accuracy on low elevation angles Suneye 210 Shade Tool (incl. GPS) elevation angle position azimut angle one picture captures 360 internal GPS analysis software which produces data of elevation of shadowing objects no distances manual analysis afterwards low accuracy on low elevation angles Laser Rangefinder and Land Survey Tools elevation angle position azimut angle height distance often with internal GPS and/or compass datatransfer possible rather expensive more accurate than necessary? high user threshold measurements in multiple directions necessary Aerial photos & maptools distance internal GPS and compass also surface roughness lengths can be determined no information on height-of-obstacles available picture might be outdated

15 ome questions and thoughts Are there other tools which are easy to use and accurate enough (Disto not perfect)? Simplification for the actual fieldwork is needed.schemes, diagrams, Smartphone apps, Excel sheets - What are you using? Difficulties to judge if the natural relief is representative or not ( does a move of the station by 500m change the class obtained? )* How accurate is the description of natural shielding ( surrounded by obstacles of uniform height, seen under an elevation angle between 14 to 26 )* : Class jump from 1 to 3 when surrounding trees higher than 26.5 The shading duration due to one obstacle depends on its width and its location. That aspect is especially important for locations with high variation of sun elevation and azimuth throughout a year (high latitude countries) Weighting of shadowing effect by itself, monthly evaluation? Weighting of effect compared to distance of heat source/water extent? Complete classification of an existing network will take a couple of years if no extra classification resources are available Archiving and maintaining good and usable documentation of classification results needs good planning and extra resources How to further use the results (statistics, quality stamp of station, external cooperation)? How to improve the scheme without overloading it?

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