Data and variables

The LI-710 begins measuring parameters and recording raw data in its volatile memory almost immediately after it is powered on. After it has recorded about 30 minutes of data (around 18,000 data points) it computes results for that time period. These results represent the first computed output from the device - evapotranspiration and other computed parameters for the previous 30 minutes. The results will be reported until the next results are ready. See The XT (trigger) command for more details.

Fluxes - ET, LE, and H (evapotranspiration, latent energy, or heat) - represent a quantity of something exchanged over a time period, over an area. Evapotranspiration is reported as mm. It is the total (millimeters) water vapor exchanged over the measurement period, over the fetch footprint around the sensor for a 30-minute period. Other computed parameters - VPD, PA, TA, RH, SVP, and TD (vapor pressure deficit, atmospheric pressure, air temperature, relative humidity, saturation vapor pressure, and dewpoint temperature) are the average for the measurement period.

The LI-710 sends up to four packets of results, each including up to nine variables.

Group 0: Results

Group 0 is the main set of measurements, including actual evapotranspiration, a set of measured and computed parameters, the sequence number, and diagnostic information for the measurement period.

Table 8‑1. Data group 0 includes results for a measurement period.
Output Label Units Precision
Actual Evapotranspiration ET mm 3
Latent Energy Flux LE W m-2 1
Heat Flux H W m-2 1
Vapor Pressure Deficit VPD kPa 2
Atmospheric Pressure PA kPa 2
Air Temperature (not sonic) TA °C 2
Relative Humidity Ambient RH percent 2
Sequence Number SEQ # 0
Diagnostic Value DIAG # (0 - 65535) 0

Group 1: Results and sample count

Group 1 represents results and the total number of samples used in the measurement.

Table 8‑2. Data group 1 includes results and the sample count.
Output Label Units Precision
Actual Evapotranspiration ET mm 3
Latent Energy Flux LE W m-2 1
Heat Flux H W m-2 1
Atmospheric Pressure PA kPa 2
Air Temperature (not sonic) TA °C 2
Relative Humidity Ambient RH percent 2
Sequence Number SEQ # 0
Sample Count SAMP_CNT # (up to 18000) 0
Diagnostic Value DIAG # (0 - 65535) 0

Group 2: Air, humidity, and instrument information

Group 2 includes measurements of environmental characteristics without any flux results.

Table 8‑3. Data group 2 has environmental information without any flux results.
Output Label Units Precision
Absolute Humidity Ambient AH g m-3 2
Relative Humidity Ambient RH percent 2
Saturated Vapor Pressure Ambient SVP kPa 2
Vapor Pressure Deficit VPD kPa 2
Atmospheric Pressure PA kPa 2
Air Temperature (not sonic) TA °C 2
Dewpoint Temperature TD °C 2
Tilt TILT degrees (0 - 180) 0

Group 3: Performance information and diagnostics

Group 3 includes diagnostic and performance information for the LI-710. The Data QC parameter may be of interest. It indicates how many points were discarded in the processing of the raw data. A high percentage of excluded data indicates that the measurement has poor quality.

Table 8‑4. Data group 3 presents diagnostic information and details that can assist with diagnostics.
Output Label Units Precision
Pump Voltage PUMP_V V 2
Cell Pressure PA_CELL kPa 2
Cell RH RH_CELL % 2
Cell Temperature TA_CELL C 2
Enclosure RH RH_ENCL percent 2
Flow FLOW cm3 min-1 0
Input Voltage INPUT_V V 2
Data QC DATA_QC percent 0