A Global Land-Surface Climate Reference Network: Technical Reflections Thank you! To Michael Palleckiand Mark Hall from US CRN for extended conversations AOPC Exeter 30 th March 2017 Michael de Podesta
A Global Land-Surface Climate Reference Network 1. Who am I? What is NPL? 2. Climate Monitoring Principles and Choices 3. The US Climate Reference Network 4. A Global Climate Reference Network
Michael de Podesta Most accurate measurement of the Boltzmann constant. The basis of the new definition of the kelvin and the degree Celsius (2018) Most accurate temperature measurements in human history. Details the errors in every temperature measurement made on Earth New technique for measurement of air temperature and humidity Non-contact Representative of the BIPM on WMO CIMO Expert Teams on operational metrology and in-situ observations
What is the temperature? User 1 User 2 User 3 Calibration Lab NIM NIST NPL PTB LNE-CNAM International Bureau of Weights and Measures, BIPM
What am I doing here?
A Global Land-Surface Climate Reference Network 1. Who am I? What is NPL? 2. Climate Monitoring Principles and Choices 3. The US Climate Reference Network 4. A Global Climate Reference Network
10 Climate Monitoring Commandments 1. Management of Network Change Think before you change anything 2. Parallel Testing Check what you thought would happen does actually happen 3. Metadata Critical element missing from current records 4. Data Quality and Continuity Continually evaluate station and network performance 5. Integrated Environment Assessment Make sure data is suitable for direct use 6. Historical Significance Sites with the longest records are most valuable 7. Complementary Data Improve the weakest parts of the network 8. Climate Requirements Stations must be suitable 9. Continuity of purpose Long term commitment 10. Data and Metadata Access Get it out there in ways people can use and understand Adequacy of Climate Observing Systems Panel on Climate Observing Systems Status, Climate Research Committee, National Research Council ISBN 0-309-57074-3 (1999) http://www.nap.edu/catalog/6424.html
Choices $$$$$$$$$$$$$ $$$$$$$$$$$$$ $$$$$$$$$$$$$ Expensive Cheap $$$$$ Many different measurands Complexity Simplicity Temperature only Different (traceable) technology in each station Diversity Homogeneity Identical stations Centrally planned, funded and maintained Top Down Bottom up Diverse (quality controlled) voluntary contributions
A Global Land-Surface Climate Reference Network 1. Who am I? What is NPL? 2. Climate Monitoring Principles and Choices 3. The US Climate Reference Network 4. A Global Climate Reference Network
US Climate Reference Network
US Climate Reference Network
US Climate Reference Network
US Climate Reference Network 114 stations in the contiguous United States, 18 stations Alaska (plans to expand to 36) 2 stations in Hawaii.
Primary Mission Air Temperature Thermometrics Corporation Platinum Resistance Thermometer Met One Instruments Fan Aspirated Shield Model 076B Precipitation Geonor Precipitation Gauge Model T-200B Data Acquisition Campbell Scientific CR3000 Micrologger Support Precipitation Vaisala DRD11A Rain Detector Hydrological Services America Tipping Bucket Rain Gauge Model TB-3 Solar Radiation Kipp& Zonen, Inc., SP Lite2 Pyranometer Ground Surface Infrared Temperature Apogee Instruments, Inc. SI-111: Standard Field of View Infrared Radiometer Sensor Wind Speed @1.5 m Met One Instruments Wind Speed Sensor Model 014A Drought (Since 2011) Soil Moisture and Temperature Stevens Water Monitoring Systems, Inc., Hydra Probe II Soil Sensor Model SDI-12 Relative Humidity Vaisala HMT337 Humidity and Temperature Transmitter
US Climate Reference Network Lessons Careful Choice of sites Distribution Locale Pairing Studies Altitude Studies Metadata Thorough Available Annual Photographs Data Availability Rapid Open Access Resilience Technical Human Political None of these are technicalfeatures
US Climate Reference Network Strengths It exists. It has demonstrated its value in just over 10 years. New data have given extra value to historical data.
US Climate Reference Network Weaknesses Generally few: the system is technically excellent Top down approach Suitable for a national system in a rich nation: centralised control Requires large capital and labour resource Maintenance is $2.3M/annum: ~$17k per station per year Working for 12 years is good: is it sustainable for 100 years? RH Measurements Single sensor added as part of drought assessment. Should be in triplicate as part of main package. Data Transmission 20 second burst of data every hour One way transmission only Unable to update software remotely or send commands
A Global Land-Surface Climate Reference Network 1. Who am I? What is NPL? 2. Climate Monitoring Principles and Choices 3. The US Climate Reference Network 4. A Global Climate Reference Network
US CRN versus Global CRN US CRN Global CRN Structure of US CRN unlikely to be suitable for a global CRN
You have been here before Initial Selection of a GCOS Surface Network: 1997 ~940 Stations @1 site per 250,000 km2 Scored existing sites with multiple criteria. Emphasised long existing records Included extra sites for additional studies (e.g. versus altitude)
Global CRN: Station Density US CRN Global CRN Mean separation 241 km At US-CRN density : 8780 stations GCOS-34 ~940 Minimum requirement ~150 stations. The thick black line shows CRUTEM 4.5 annual anomalies taken from the Hadobswebsite, along with the 95% confidence limits from the same source (shaded grey). The coloured lines show the smoothed annual griddedanomalies from the respective hemispherical component of five unique 163-member global subsets of CRUTEM 4.5.
Global CRN: Station Density Global CRN At US-CRN density : 8780 stations GCOS-34 ~940 Minimum requirement ~150 stations. Land surface of the Earth ~ 150 x 10 6 km 2 @ 1 site per 10 6 km 2 (separation ~1000 km) South America :~ 18 sites North America :~ 25 sites USA ~10 Africa:~ 30 sites Europe:~ 10 sites European Countries ~ 0, 1 sites Asia ~45 sites China:~ 10 sites Russia ~30 sites India~3 Oceania :~ 9 sites Australia ~8 sites Antarctica:~ 14 sites A low-density network would be adequate Multiply by n for redundancy and extra studies
Global Climate Reference Network How to begin? You need to decide that. How to select sites Follow US CRN procedures or similar procedure used by GCOS-34 Joint CCL/CBS Expert Meeting on the GCOS Surface Network No problem to start with existing sites But US CRN shows there is no need to prefer sites with long records
Technical Details
Primary Mission Air Temperature Thermometrics Corporation Platinum Resistance Thermometer Met One Instruments Fan Aspirated Shield Model 076B Precipitation Geonor Precipitation Gauge Model T-200B Data Acquisition Campbell Scientific CR3000 Micrologger Support Precipitation Vaisala DRD11A Rain Detector Hydrological Services America Tipping Bucket Rain Gauge Model TB-3 Solar Radiation Kipp& Zonen, Inc., SP Lite2 Pyranometer Ground Surface Infrared Temperature Apogee Instruments, Inc. SI-111: Standard Field of View Infrared Radiometer Sensor Wind Speed @1.5 m Met One Instruments Wind Speed Sensor Model 014A Drought (Since 2011) Soil Moisture and Temperature Stevens Water Monitoring Systems, Inc., Hydra Probe II Soil Sensor Model SDI-12 Relative Humidity Vaisala HMT337 Humidity and Temperature Transmitter
Global CRN: Triple Redundancy Triple redundancy Enables early detection of a faulty sensor Enables detection of conditions in which sensors misread E.g. evaporative cooling after mist One out of three sensors replaced each year Even though PRTs are highly reproducible, triple-redundancy is strongly recommended. An alternative would be to recalibrate after use to monitor in-service drift, but this is not as smart as the US CRN scheme Triple redundancy is strongly recommended
Global CRN: Platinum Resistance Thermometers Platinum Resistance Thermometers 100 year old technology. Old. But well understood. Electrical resistance almost Subject to radiative and evaporative cooling Easy to Interface IMHO unlikely to ever be replaced Non-contact Thermometers Unlikely to achieve acceptance in the near future PRT measurements strongly recommended
Global CRN: PRT Measurement Standard Resistance In addition to three PRTs, system reads a temperature-independent resistor Tests the functioning of the data acquisition system Wiring Circuitry 4-wire measurement eventually adopted This is essential. Is current reversal used? 4-wire measurement strongly recommended PT100 or PT1000? Choice between 100 Ω(@ 0 C) and 1000 Ω(@ 0 C) should be reviewed. PT100 standard: thicker wires: more robust PT1000: larger signal to noise; thinner wire; more fragile 1 ma for PT100 0.1 ma for PT1000 100 Ωor 1000 Ω:Choice ~108 mv @20 C
Global CRN: Screen Either screen (or mixture of screens) would be acceptable Aspirated Enclosures Generally superior to passive screen But requires ~ 3 W of power per screen Requires monitoring of fan speed Passive Screens Well-characterised Three thermometers in one screen?
Primary Mission Air Temperature Thermometrics Corporation Platinum Resistance Thermometer Met One Instruments Fan Aspirated Shield Model 076B Precipitation Geonor Precipitation Gauge Model T-200B Data Acquisition Campbell Scientific CR3000 Micrologger Support Precipitation Vaisala DRD11A Rain Detector Hydrological Services America Tipping Bucket Rain Gauge Model TB-3 Solar Radiation Kipp& Zonen, Inc., SP Lite2 Pyranometer Ground Surface Infrared Temperature Apogee Instruments, Inc. SI-111: Standard Field of View Infrared Radiometer Sensor Wind Speed @1.5 m Met One Instruments Wind Speed Sensor Model 014A Drought (Since 2011) Soil Moisture and Temperature Stevens Water Monitoring Systems, Inc., Hydra Probe II Soil Sensor Model SDI-12 Relative Humidity Vaisala HMT337 Humidity and Temperature Transmitter
Global CRN: Precipitation Tipping Bucket Rain gauge Triplicate counters could be installed No need for a human to empty More complex for solid precipitation Either type (or alternatives) would be acceptable with appropriate wind screens Weighing Rain Gauge Redundancy through three wire suspensions Needs a human to empty it Procedure to put in antifreeze Validated equation for precipitation rate Tipping Bucket Resonant frequency related to load Bucket Two extra sensors Install additional tipping counters Wire Tray
Primary Mission Air Temperature Thermometrics Corporation Platinum Resistance Thermometer Met One Instruments Fan Aspirated Shield Model 076B Precipitation Geonor Precipitation Gauge Model T-200B Data Acquisition Campbell Scientific CR3000 Micrologger Support Precipitation Vaisala DRD11A Rain Detector Hydrological Services America Tipping Bucket Rain Gauge Model TB-3 Solar Radiation Kipp& Zonen, Inc., SP Lite2 Pyranometer Ground Surface Infrared Temperature Apogee Instruments, Inc. SI-111: Standard Field of View Infrared Radiometer Sensor Wind Speed @1.5 m Met One Instruments Wind Speed Sensor Model 014A Drought (Since 2011) Soil Moisture and Temperature Stevens Water Monitoring Systems, Inc., Hydra Probe II Soil Sensor Model SDI-12 Relative Humidity Vaisala HMT337 Humidity and Temperature Transmitter
Global CRN: RH Measurement Technology Polymer (alumina sensor) capacitance sensor. Capacitance depends on number of water molecules adsorbed on sensor This depends on the rate balance between molecules arriving and leaving Saturated Vapour Pressure of H 2 O varies as ~exp(rt/l) Desorption rate of H 2 O from sensor varies as ~exp(αt) Amount of H 2 O left on sensor in equilibrium depends on relative humidity Additional knowledge of temperature yields dewpoint. Drawbacks Significant drifts in service many % at high RH Affected by contaminants (Dust, Pollen, Condensation) RH measurement would benefit from triple redundancy. Recent Developments Heated sensor prevents condensation on sensor and improves recovery from wetting Alternatives Wet and Dry bulb measurements require too much attention TDLAS technology would be an improvement but is currently too expensive.
A Global Land-Surface Climate Reference Network 1. Who am I? What is NPL? 2. Climate Monitoring Principles and Choices 3. The US Climate Reference Network 4. A Global Climate Reference Network The End
The End
Power Requirements Power requirements: The normal station draws around 1.5-2 amps continuous at 12 volts and can draw more if a heater is running on the precipitation gauge inlet. This is controlled by several variables to keep the current requirements as low as possible. We have a lower power design we use at some remote Alaska sites that draws 1-1.2 amps. We are working to decrease this even more 18 W to 24 W + heater Low Power 12 W -15 W 1 day = 18 W x 24 hours = 432 Wh(36 Ah at 12 V)