GREENWORLD SECTOR-7 // METRICS // VC-MET-111
ALL SYSTEMS NOMINAL · —
METRICS · ENVIRONMENT & CLIMATE

Canopy Airflow Velocity

VC-MET-111 — the air speed moving across the canopy plane, which thins the leaf boundary layer and governs heat, humidity, and CO₂ exchange between leaf and air.

Metric ID VC-MET-111 Category Environment & Climate Unit m·s⁻¹ Type Direct Source PhytoSense Mesh Sampling 1 min Owner Metrology & Telemetry Standards Rev C · Effective 2089-06-01
Current 0.52 m·s⁻¹ Nominal 0.3–0.8 m·s⁻¹ 1-min cadence PhytoSense Mesh

Definition

Canopy Airflow Velocity is the speed of air moving horizontally across the canopy plane, in metres per second. It is sensed directly by low-threshold thermal-anemometer or ultrasonic nodes on the PhytoSense Mesh, distributed across the bench so that dead zones are detectable. Airflow is the variable that sets leaf boundary-layer thickness — the still film of air over each leaf through which heat, water vapour, and CO₂ must diffuse — and so it modulates the effective transpiration and gas exchange the other climate metrics assume.

Why it matters

Without airflow the canopy suffocates in its own microclimate: a stagnant leaf sits in a saturated, CO₂-depleted, overheated film regardless of what the bulk-air sensors report. Adequate airflow keeps the leaf coupled to the controlled bulk air, sharpening the response to VPD (VC-MET-102) and CO₂ delivery, and suppressing the leaf wetness that drives fungal disease. Too much airflow, though, mechanically stresses tissue and drives excess transpiration. CHLORA modulates the internal-circulation fans against this metric to hold a gentle, uniform flow field.

Formula

A directly measured signal. Zone airflow is the spatial mean of the anemometer grid, with a uniformity statistic that matters as much as the mean:

v_zone = mean( { v_i : i ∈ grid } )

  v_i   anemometer speed (m·s⁻¹), node i (omnidirectional)

Dead-zone detection:
  uniformity U = v_min / v_mean
  U < 0.4 raises a stagnation advisory even when v_mean is
  in band — pockets of still air invite disease.

Boundary-layer context (advisory):
  thinner boundary layer ⇒ stronger coupling of leaf to
  bulk-air VPD (VC-MET-102) and CO₂ (VC-MET-103).

Inputs

ChannelSensorPlacementReference BandSource
V1–V5Thermal/ultrasonic anemometer (±0.05 m·s⁻¹)Canopy plane grid, 5× per zone0.3 → 0.8 m·s⁻¹PhytoSense Mesh
F_cmdCirculation-fan commandFan telemetry (cross-check)0 → 100 %PhytoSense Mesh
RHRelative humidityBoundary-layer contextVC-MET-101PhytoSense Mesh
VPDVapour pressure deficitCoupling contextVC-MET-102CHLORA

Units & Scale

Reported in metres per second to two decimal places. Airflow is intensive and not summed; the zone figure is the grid mean, but the uniformity ratio (min/mean) is reported with it because a healthy mean can hide a dangerous stagnant pocket. Confidence degrades to DEGRADED when fewer than three nodes report, or when measured flow diverges sharply from commanded fan output (a slipping belt or fouled impeller).

Sampling & Source

Thresholds

Nominal · 0.3–0.8 m·s⁻¹

OK

Gentle, uniform flow; boundary layer well coupled. No action.

Warning · < 0.1 / > 1.2 m·s⁻¹

WARN

Stagnation/disease risk (low) or mechanical stress & over-drying (high); airflow review.

Critical · < 0.05 / > 1.8 m·s⁻¹

CRIT

Dead-air microclimate (low) or wind damage / desiccation (high); auto-escalation.

Stagnation override. A low-side < 0.05 m·s⁻¹ CRIT — or an in-band mean with a uniformity ratio < 0.4 — arms the circulation fans and flags the zone for a leaf-wetness and disease-scouting pass, since dead air plus high RH is the classic Botrytis setup. A high-side > 1.8 m·s⁻¹ CRIT points to a stuck-open fan and is throttled back to prevent mechanical canopy damage. Recovery from a low WARN requires ≥ 0.2 m·s⁻¹ across all nodes.

Recent Trend

Zone-A canopy-grid airflow, last 14 sampling roll-ups (m·s⁻¹):

Airflow · 14-period trend (current 0.52 m·s⁻¹)

Interpretation Guidance

BandReadingLikely DriverAction
0.3–0.8 m·s⁻¹OptimalCirculation fans at set-pointNone; log uniformity as reference.
0.1–0.29 m·s⁻¹Sluggish driftLow fan level, obstructed flow pathRaise circulation; watch RH (VC-MET-101) & wetness.
0.8–1.2 m·s⁻¹Brisk driftOver-driven fans, duct imbalanceTrim fans; watch VPD (VC-MET-102) rising.
< 0.1 / > 1.2 m·s⁻¹WARNFan fault or imbalanceAirflow review; CHLORA advisory.
< 0.05 / > 1.8 m·s⁻¹CRITDead air or wind damageAuto-dispatch; restore/throttle fans, scout disease.
VC-MET-102

VPD

Airflow couples leaf to bulk-air deficit.

 VC-MET-101

Relative Humidity

Flow disperses boundary-layer moisture.

 VC-MET-103

Atmospheric CO₂

Flow delivers CO₂ to the leaf surface.

 VC-MET-100

Air Temperature

Flow removes heat & limits stratification.

 VC-MET-104

PAR / PPFD

Radiant heat airflow must carry off.

 VC-MET-001

Canopy Vitality Index

Stagnation suppresses gas exchange it scores.

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