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API Reference


SynopticLabs Data Checks

Seamless integration of data and data checks for the /timeseries, /latest and /nearesttime api services

Data Check API name Description
Range check sl_range_check Identifies physically implausible values. For example, an air temperature of 150 degrees or -80 degree Fahrenheit would be flagged.
Anemometer wind speed vs. wind gust check sl_winddir_windspd_check Determines if the wind speed is greater than the wind gust.
Time rate of change test sl_rate_check Identifies if the absolute difference in two successive values is greater than the maximum plausible rate of change expected for the observed time interval.
Persistence check sl_pers_check Identifies if a sequence of observations appear unchanging. For example, an air temperature sensor reporting the same value every 15 minutes for 24 hours would be labeled as persistent.
UU2DVAR rejection check sl_uu2dvar_rejection Spatial analysis check.
Linear regression check sl_multvariate_lin_reg_check Spatial analysis check.

Introduction

A small set of highly efficient data checks are available for archived data as well as the provisional data continuously being received. Additional data checks are being developed and will be implemented after further testing. The /timeseries, /latest and /nearesttime api services provide these checks as additional attributes delivered along with the data.

All data accessible via the api services must be considered provisional. Official archives for some of the data are available elsewhere. There are many potential causes of erroneous data: sensor failure, transmission errors, or incorrect conversion of the transmitted data arising from invalid metadata. No matter what may have caused erroneous data, the data checks are intended to identify: (1) physically implausible values and (2) values that may not be representative of the conditions prevailing at that time.

Note: Nearly all users will rely on the /timeseries, /latest and /nearesttime api services to identify the values that fail relevant data checks. However, those services rely on code to access the archived data checks that is also available to users via the QC segment api service /qcsegments. For efficient storage and short access times, only the start and end times are stored for each period (referred to as a QC segment) for which any values have failed a data check. For example, if a parameter’s data value falls outside the realistic range for that variable type at one time with realistic values preceding and following, then the QC segment will only be for that single time. However, if the sensor is consistently reporting unrealistic values over many days, then only the beginning and ending times of that segment are stored, thereby reducing the time required for the /timeseries, /latest and /nearesttime services to obtain that information. Further, if the value fails the range check, then any open qc segments for that variable are closed and a range check segment is opened since it is then not necessary to continue to apply the other tests.

Overview of the SynopticLabs data checks

Technical descriptions of the SynopticLabs data checks.

Range check

Is the value physically plausible?

API Name: sl_range_check

Physically implausible values are identified using the SynopticLabs range check. Only if a value passes this check will the remaining checks be applied.

There are situations where physically implausible values may not indicate sensor failure. For example, negative snow depth is considered physically implausible but may result from the height of the sensor above ground changing over the winter season as snow compresses the grass or other underlying obstructions. Further, the maximum relative humidity with respect to water is defined to be 100%, although many research-grade sensors commonly report values in excess of that limit.

Variable Unit Minimum Maximum
Altimeter Pascals 84998.31 108025.75
Pressure Pascals 60000.0 108000.0
Temperature Celsius -59.44 57.22
Dew Point Celsius -59.44 35.0
Relative Humidity % 0.00 100.00
Wind Speed m/s 0.00 200.00
Wind Direction Degrees 0.00 360.00
Wind Gust m/s 0.00 200.00
Solar Radiation W/m**2 0.00 1500.00
Soil Temperature Celsius -58.00 185.00
Sea_level pressure Pascals 850.00 1080.00
Hours of sun Hours 0.00 24.00
Water Temperature Celsius 0.00 135.00
Weather conditions code 0.00 512000.00
Cloud_layer_3 height/coverage code 0.00 8009.00
Low_cloud symbol code 0.00 9.00
Mid_cloud symbol code 10.00 19.00
High_cloud symbol code 20.00 29.00
Pressure Tendency code 0.00 8999.00
Road sensor number 1.00 10.00
Road Temperature Celsius -40.00 150.00
Road_Freezing Temperature Celsius 0.00 40.00
Road_Surface Conditions code 1.00 100.00
Cloud_layer_1 height/coverage code 0.00 18009.00
Cloud_layer_2 height/coverage code 0.00 8009.00
Visibility Statute miles 0.00 200.00
Sonic_Wind Direction Degrees 0.00 360.00
Remarks text NULL NULL
Raw observation text NULL NULL
6 Hr High Temperature Celsius -75.00 135.00
6 Hr Low Temperature Celsius -75.00 135.00
Peak_Wind Speed m/s 0.00 200.00
Fuel Temperature Celsius -40.00 140.00
Fuel Moisture gm 0.00 100.00
Ceiling Meters 0.00 40000.00
Sonic_Wind Speed m/s 0.00 200.00
Pressure change code 0.00 2000.00
IR_Soil Temperature Celsius -75.00 135.00
Temperature in_case Celsius -75.00 135.00
Soil Moisture % 0.00 100.00
Battery voltage volts 0.00 50.00
Data Insert Date/Time minutes 0.00 16000000.00
Data Update Date/Time minutes 0.00 16000000.00
Road Subsurface Temperature Celsius -40.00 150.00
Water Temperature Celsius 0.00 135.00
Evapotranspiration Millimeters 0.00 5.00
24 Hr High Temperature Celsius -75.00 135.00
24 Hr Low Temperature Celsius -75.00 135.00
Peak_Wind Direction Degrees 0.00 360.00
Net Radiation W/m**2 -500.00 1000.00
Soil Moisture tension centibars 0.00 300.00
1500 m Pressure Pascals 700.00 1000.00
Wet bulb temperature Celsius -75.00 135.00
Air_Temperature at_2_meters Celsius -75.00 135.00
Air_Temperature at_10_meters Celsius -75.00 135.00
Pressure Pascals 600.00 1080.00
Temperature Celsius -75.00 135.00
Relative Humidity % 0.00 100.00
Wind Speed m/s 0.00 200.00
Wind Direction Degrees 0.00 360.00
Wind Gust m/s 0.00 250.00
Latitude Degrees -90.00 90.00
Longitude Degrees -180.00 180.00
Elevation Meters -300.00 30000.00
Platform True_Direction Degrees 0.00 360.00
Primary_Swell Wave_Direction Degrees 0.00 360.00
Primary_Swell Wave_Period Seconds 0.00 99.00
Primary_Swell Wave_Height Meters 0.00 33.63
Secondary_Swell Wave_Direction Degrees 0.00 360.00
Secondary_Swell Wave_Period Seconds 0.00 99.00
Secondary_Swell Wave_Height Meters 0.00 33.63
Tide Indicator code 0.00 10.00
Tide Departure Meters 0.00 100.00
Surface Temperature Celsius -58.00 185.00
Platform True_Speed m/s 0.00 125.00
Wave Period Seconds 0.00 99.00
Wave Height Meters 0.00 33.63
Net Shortwave Radiation W/m**2 -500.00 1000.00
Net Longwave Radiation W/m**2 -500.00 1000.00
Sonic Temperature Celsius -75.00 135.00
Vertical_Velocity m/s -2.00 2.00
Zonal_Wind Standard_Deviation m/s 0.00 5.00
Meridional_Wind Standard_Deviation m/s 0.00 5.00
Vertical_Wind Standard_Deviation m/s 0.00 5.00
Temperature Standard_Deviation Centigrade 0.00 5.00
Vertical Heat_Flux m/s C -2.00 2.00
Friction Velocity m/s 0.00 5.00
SIGW/USTR nondimensional 0.00 5.00
Sonic_Obs Total nondimensional 0.00 5000.00
Sonic Warnings nondimensional 0.00 5000.00
Moisture Standard_Deviation g/m**3 0.00 5.00
Vertical Moisture_Flux m/s g/m**3 -1.00 1.00
Dew Point Celsius -75.00 135.00
Virtual Temperature Celsius -75.00 135.00
Geopotential Height Meters -300.00 30000.00
Outgoing Shortwave Radiation W/m**2 0.00 1000.00
Clear Sky Solar Radiation W/m**2 0.00 1500.00
Grip 2 Level of Grip 0.00 1.00
Grip 1 Ice Friction Code 0.00 1.00
Photosynthetically Active Radiation umol/m**2 s 0.00 2500.00
PM_2.5 Concentration ug/m3 0.00 200.00
Flow Rate liters/min 0.00 100.00
Internal Relative_Humidity % 0.00 100.00
Air Flow Temperature Celsius -75.00 135.00
Ozone Concentration ppb 0.00 500.00
Stream flow ft3/s NULL NULL
Gage height ft NULL NULL
Black Carbon Concentration ug/m3 0.00 200.00
Soil Temperature 2 Celsius -58.00 185.00
18_Inch Soil_Temperature Celsius -58.00 185.00
18_Inch Soil_Temperature2 Celsius -58.00 185.00
20_Inch Soil_Temperature Celsius -58.00 185.00
Soil Temperature 3 Celsius -58.00 185.00
Soil Temperature 4 Celsius -58.00 185.00
Soil Moisture 2 % 0.00 100.00
Particulate Concentration ug/m3 0.00 10000.00
Filter Percentage % 0.00 100.00
Sensor Error Code code 0.00 1000.00
Electric Conductivity dS/m 0.00 10.00
Permittivity 0.00 100.00
Past weather code 0.00 9.00
Surface Level Millimeters -100.00 100.00
Incoming Longwave Radiation W/m**2 0.00 1500.00
Outgoing Longwave Radiation W/m**2 0.00 1500.00

Anemometer wind speed vs. wind gust check

Is the wind speed value greater than the wind gust value?

API Name: sl_winddir_windspd_check

If the reported wind speed is greater than the wind gust, then the wind gust is flagged. Note: the conventions for reporting wind speed and wind gust differ among different data providers. The wind gust reported may be a maximum wind within the time interval for that observation.

Time rate of change test

Is the change between two values too large?

API Name: sl_rate_check

For parameters for which it is appropriate to do so, the rate change test compares the absolute difference between two successive observations to the maximum plausible rate of change expected within that time interval.

Variable Name Unit Rules
Pressure Pascals 5 min: 925
15 min: 1000
30 min: 1500
60 min: 1500
Temperature Celsius 1-3 min: 3
4 min: 4
5 min: 5
15 min 7.5
30 min: 15
60 min: 20

Persistence check

Do the values appear to be unchanging?

API Name: sl_pers_check

For parameters for which it is appropriate to do so, the persistence check compares the range of values (difference between the maximum and minimum) within a specified time period relative to the minimum plausible range expected for that parameter.

The following table lists the variable, time period evaluated, and the minimum plausible range expected for that variable..

Variable Name GEMPAK unit Evaluation period Min number of obs Required Change
Altimeter ALTI Pascals 24 hrs 24 5.0
Pressure PRES Pascals 24 hrs 24 5.0
Temperature TMPF Celsius 24 hrs 24 0.1
Dew Point DWPF Celsius 24 hrs 24 0.1
Relative Humidity RELH % 24 hrs 24 0.5
Wind Speed SKNT m/s 24 hrs 24 0.25
Wind Direction DRCT Degrees 24 hrs 24 2.5
Wind Gust GUST m/s 24 hrs 24 0.25
Solar Radiation SOLR W/m**2 48 hrs 48 0.5
Soil Temperature TSOI Celsius 48 hrs 48 0.05
Sea_level pressure PMSL Pascals 24 hrs 24 5.0
Water Temperature TLKE Celsius 48 hrs 48 0.05
Road Temperature TRD Celsius 24 hrs 24 0.1
Sonic_Wind Direction DIRS Degrees 24 hrs 24 1.0
Peak_Wind Speed PEAK m/s 24 hrs 24 0.25
Fuel Temperature FT Celsius 72 hrs 72 0.1
Fuel Moisture FM gm 24 hrs 24 0.1
Sonic_Wind Speed SPDS m/s 24 hrs 24 0.1
IR_Soil Temperature TIR Celsius 24 hrs 24 0.1
Road Subsurface Temperature TSRD Celsius 48 hrs 48 0.05
Water Temperature TLRW Celsius 48 hrs 48 0.05
Peak_Wind Direction PDIR Degrees 24 hrs 24 2.5
Net Radiation NETR W/m**2 48 hrs 48 0.5
Air_Temperature at_2_meters T2M Celsius 24 hrs 24 0.1
Air_Temperature at_10_meters T10M Celsius 24 hrs 24 0.1
Pressure MPRS Pascals 24 hrs 24 5.0
Temperature MTMP Celsius 24 hrs 24 0.1
Relative Humidity MRH % 24 hrs 24 0.5
Wind Speed MSKT m/s 24 hrs 24 0.25
Wind Direction MDIR Degrees 24 hrs 24 2.5
Wind Gust MGST m/s 24 hrs 24 2.5
Surface Temperature TGND Celsius 24 hrs 24 0.1
Net Shortwave Radiation NETS W/m**2 48 hrs 48 0.5
Net Longwave Radiation NETL W/m**2 48 hrs 48 0.5
Sonic Temperature TSNC Celsius 24 hrs 24 0.1
Dew Point MDWP Celsius 24 hrs 24 0.1
Virtual Temperature MTVR Celsius 24 hrs 24 0.1
Outgoing Shortwave Radiation OUTS W/m**2 48 hrs 48 0.5
Photosynthetically Active Radiation SPAR umol/m**2 s 48 hrs 48 0.5
PM_2.5 Concentration PM25 ug/m3 24 hrs 24 0.5
Ozone Concentration OZNE ppb 24 hrs 24 0.5
Black Carbon Concentration BLKC ug/m3 24 hrs 24 0.5
Particulate Concentration PMCN ug/m3 24 hrs 24 0.5