Air Temperature

Definition

Air Temperature is the dry-bulb temperature of the bulk air mass within a defined cultivation zone, measured in degrees Celsius. It is a directly sensed quantity, not a derived one: each zone carries a redundant cluster of aspirated, radiation-shielded thermistors on the PhytoSense Mesh, and the reported zone value is the trimmed mean of the cluster after outlier rejection. Temperature is referenced to the canopy-height plane (1.0 m above bench surface), not to floor or duct, so the figure reflects what the plants experience.

Why it matters

Air temperature is the master climate lever. It sets the saturation vapour pressure that, with humidity, determines Vapour Pressure Deficit (VC-MET-102) — the leading environmental driver CHLORA watches for canopy decline. It governs reaction kinetics of photosynthesis and respiration, drives or starves transpiration, and at the extremes causes heat shock or chilling injury. Because every other climate metric is read against it, a drifting zone temperature degrades confidence across the whole environmental panel on the Operations Dashboard.

Formula

A directly measured signal. The zone value is a robust aggregate of the sensor cluster with a two-stage calibration applied at the node:

T_zone = trimmed_mean( { T_i · g_i + b_i  :  i ∈ cluster } )

  T_i   raw thermistor reading (°C), node i
  g_i   span-calibration gain   (annual NIST-traceable bath)
  b_i   zero offset             (annual two-point calibration)

Outlier rejection:
  drop any T_i where |T_i − median| > 0.8 °C  before averaging.

Aspiration / radiation correction:
  shielded + fan-aspirated probes; no solar-load correction
  required. Spot probes (unaspirated) carry +0.0/−1.2 °C bias
  flag and are excluded from the zone trimmed mean.

Inputs

Units & Scale

Reported in degrees Celsius to one decimal place. Zone temperature is an instantaneous spatial aggregate; it is never summed. Facility roll-up is the area-weighted mean of zone values, reported with a 24-hour min/max envelope. A confidence flag degrades to DEGRADED when fewer than two canopy-plane probes report, or when canopy and return-air values diverge by > 3 °C (indicating stratification or a stuck probe).

Sampling & Source

• Sampled every 1 minute from the PhytoSense Mesh aspirated cluster.
• Zone value is the outlier-trimmed mean of the canopy-plane probes; return-air RTD is advisory only.
• Stale handling: a probe silent > 3 min is dropped; if all canopy probes drop, the zone falls back to return-air RTD with a DEGRADED flag.
• Calibration: annual NIST-traceable bath check; drift > 0.3 °C raises a metrology work order.

Thresholds

Recent Trend

Zone-A canopy-plane temperature, last 14 sampling roll-ups (°C):

Interpretation Guidance

Related Metrics

Related SOPs

• SOP Library — climate control & HVAC response procedures.
• Heat-shock and chilling-injury response on CRIT — see Environment SOP set in the SOP Library.
• Alarm escalation & HVAC interlocks — Monitoring Systems.