Microclimate conditions in ventilated wet-walled greenhouses in a subtropical climate: spatial variability

Figures & data

Table 1 Details of the equipment used

Environment	Greenhouse (polycarbonate) unit 4	Greenhouse (polycarbonate) unit U
Sensors	Hobo^1 units (model H8 Temp or RH/Temp) in seven-plate Gill-radiation shields	Eleven needle anemometers^6; three-dimensional sonic anemometer^7 (model SWS-211/3V) and digitalanalogue converter (SA-4); three-dimensional propeller anemometer8 (model 0207)
	Solar irradiance (CM3^2), RH and air temperature (HMP45C^3 in 12-plate shield), wind speed and direction^4 (model 03001), 16 type-E 24-gauge thermocouples^5 for air temperature in seven-plate shields
Logging equipment: power details	21X and CR7X dataloggers^9 and SM192 storage module^9 connected to two 14 A h batteries and 40 W solar panel	CR7X and SM192 storage module^9

¹Onset Computer Corporation, Bourne, MA, USA

²Kipp & Zonen BV, Delft, The Netherlands

³Vaisala Oyj, Helsinki, Finland

⁴RM Young Company, Traverse City, MI, USA

⁵Omega Engineering, Stamford, CT, USA

⁶Soiltronics, Burlington, WA, USA

⁷Applied Technologies, Boulder, CO, USA

⁸WeatherTronics, Division of Qualimetrics, Inc., Sacremento, CA, USA

⁹Campbell Scientific, Inc., Logan, UT, USA

Figure 1 Typical measured (Hobo) east–west air temperature differences for the north (furthest from the wet-wall), middle and south (nearest the wet-wall) positions in greenhouse unit 4 (a) for a hot cloudless day, with mid-position air temperatures (right-hand y-axis) and (b) for a cool cloudless day, with outside air temperatures (right-hand y-axis)

Figure 2 Half-hourly average (thermocouple; TC) air temperatures for north, middle and south (near the wet-wall) positions in greenhouse unit 4 for a typical summer day

Figure 3 Two-minute propeller wind speed for 3 d showing the influence of temperature-controlled fans and reasonable agreement between three-dimensional sonic and needle anemometer wind speed in greenhouse U (maize experiment)

Figure 4 Spatial variation in needle anemometer wind speed at distances near the wet-wall and 6 and 12 m away (greenhouse unit U, mid-position) for a day when fans were on (upper set of three) and for a day when fans were off for most of the day (lower set)

Figure 5 Measured (Hobo) east and west relative humidity (RH) differences for mid-position (ME–MW) and north–south (N–S; nearest the wet-wall) positions of greenhouse unit 4 for a spring day. (a) RH inside (mid-position) and outside; (b) RH differences for ME–MW and N–S positions; (c) water vapour pressure inside (middle-position), outside, S (near wet-wall) and N positions; (d) water vapour pressure differences for ME–MW and N–S positions