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Commercial weather systems, data loggers, and weather databases
Ned Bair US Army Corps of Engineers Cold Regions Research and Engineering
LaboratoryEarth Research Institute, UC - Santa Barbara
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Weather systems
• Some companies offer “one stop” shopping, e.g. Campbell offers instruments, logger, and software packages.
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Two US companies that offer commercial systems
• Campbell Scientific– Scientific applications, remote (no power)
installations– Campbell makes instruments, loggers, and
software• Andover – Facilities system– provides controllers– SQL Server interface
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Data loggers
• Record measurements from instruments into tables
• Often convert a voltage into a physical quantity using a linear equation
• Also can use serial protocols • Use a simple high level programming
language, e.g. Edlog for Campbell
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Weather databases
• What is a relational database?• What is the difference between databases and
spreadsheets?• When should one use a database versus a
spreadsheet?
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Getting logger data into a database
• This is the hard part!• Commercial solutions• Campbell LNDB• Vista Datavision• Roll your own (e.g. UNIX shell scripting or
Python)
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What is UNIX/LINUX
• A plain text operating system. Linux (1991) is based on UNIX, developed in 1969 by Bell Labs.
• Tons of text tools, makes it great for processing scientific data
• Cygwin is unix emulator for PCs.
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In practice
• Each table should contain as few columns as possible
• Converting a table from more columns to more rows usually results in a more normalized form
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How much time should I spend dealing with database issues?
• It depends on the scale of your system. • If you only have a few instruments, then a
basic system that spits out logger tables, e.g. Campbell is fine.
• If you have lots of instruments and things change frequently, then you need a database system, e.g. Andover.
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Why spend the effort of normalizing?
• For more complex systems you will spend much less time overall with an efficient and normalized DB.
• E.g. adding deleting columns in a flat file sucks. It’s not an issue with a transaction table.
• For the bigger systems I suggest becoming good friends with a DBA, preferably one who works for the same employer and likes patrol/avalanche work/etc.
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Wind heads
• “Birds” - RM Young– Pros: Cheap– Cons: Rime and break easily, no heat.
• Cylindrical - Phil Taylor– Pros: can accurately measure very strong peak winds (220
mph); great heaters.– Cons: Spin-down time; expensive; phil will retire soon
• Sonic – Campbell, Lufft– Pros: No moving parts; not too expensive for 2d version– Cons: arms can rime up and break, but heated version is
offered
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Temperature/RH sensors
• usually combo probes• simple install, but MUST be shielded from
radiation.• Mammoth’s super signs, bank signs, and high
school signs are often not shielded.• e.g. Campbell HMP45C
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Tipping Buckets
– Work by filling a small bucket with melted precip until it tips, tips are counted by the gauge.
– e.g. MetOne– Pros: accuracy, cost– Cons: clogging by ice; undercatch bias
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Weighing gauges
– Precip falls into an antifreeze/water mixture on top of a pressure transducer.
– Increases in transducer weight correspond to precip increases.
– e.g Noah, Sutron– Pros: accuracy, cost; – Cons: clogging by ice; undercatch bias; need to be
emptied, sometimes 2X or more a season.
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Undercatch
Goodison, B., Louie, P. Y. T., and Yang, D.: WMO Solid precipitation measurement intercomparison, World Meteorological Organization, 1998.
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Snow pillows
• Custom-made deals, e.g. CA DWR• Stainless steel, usually 2 x 2 filled with
antifreeze (ethylene glycol)• Antifreeze is piped to a pressure transducer, e.g.
GE Druck that outputs a voltage, eg. 0-5 V, 0-100 in water– Pros – only decent measure of SWE on the ground– Cons – not very sensitive; expensive and hard to get– Custom rigs
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Radiometers
• Shortwave– Clear (200-1200nm) and nIR (1200-1500nm), e.g.
Eppley labs– Direct and diffuse (e.g. auto shadow band,
Sunshine pyranometer)• Longwave
– 3.5 µm
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Depth pingers
• Ultrasonic– Send a ultrasonic chirp down to snow surface,
then calculate depth based on its return time back to the sensor
– E.g. Judd, Campbell• Pros– cheap, accurate, durable
• Cons– Can give null readings during heavy snow
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Cool shit• Gamma ray SWE detectors
– Measure SWE via attenuation of gamma radiation emitted from earth’s core.– Campbell makes a commercial sensor– Pros: no moving parts– Cons: water kills signal, low SWE limit, expensive
• FMCW radar– Measures stratigraphy by scanning through radars frequencies – Pros: nondestructive stratigraphy– Cons: expensive and needs modeled grain sizes
• Lysimeters– Tipping buckets buried in the ground– Measure melt water– Pros: cheap, great way to measure when water 1st gets through pack– Cons: not commercial systems available, get silted up.
• Capacitance probes– Measure SWE via dielectric constant– Pros: very accurate– Cons: water kills signal
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Instrument calibration
• All instruments require maintenance and calibration.
• Some instruments are more robust than others, e.g. Phil Taylor wind heads versus sonic anemometers.
• This is an integral part of your budget that you can’t skimp on.
• Cap-Ex’s are usually easier sells than other budget items like pay raises.