## 4 Conclusions  
The aim of this study was to assess the spatial, vertical, and temporal variability of environmental variables in CSGs in winter and to provide basic information that could be used to aid the monitoring and control of environmental factors in CSGs. The average minimum and maximum temperatures inside the CSG without crops were 8.84 \({}^{\circ}\)C (5:00 h) and 30.3 \({}^{\circ}\)C (12:00 h), respectively; the average minimum and maximum humidity were 25.63% (12:00 h) and 94.26% (15:00 h), respectively. The average minimum and maximum temperatures inside the CSG with crops were 9.96 \({}^{\circ}\)C (4:00 h) and 24.5 \({}^{\circ}\)C (12:00 h), respectively; the average minimum and maximum humidity were 32.6% (12:00 h) and 92.1% (5:00 h), respectively. The temperature difference between layers in the CSG without crops was approximately 2.2 \({}^{\circ}\)C, and the difference between layers in the CSG with crops was approximately 1.4 \({}^{\circ}\)C. The temperature increased during the day, and the temperature of the top layer was higher than the temperature of the bottom layer inside the greenhouse without crops. In addition, air mobility within the greenhouse was limited by the effect of crops; consequently, the bottom layer was warmer in the greenhouse without crops. The concentration of CO\({}_{2}\) in the different layers inside the solar greenhouse with crops was highest at night. The average maximum solar radiation was 222.24 Wm\({}^{-2}\) (12:00 h to 13:00 h). The average maximum light intensity in the CSG without crops was 38,612.5 lx, 44,412.5 lx, and 48,612.5 lx (12:00 h to 13:00 h) in the bottom, middle, and top layers, respectively. The average maximum light intensity inside the CSG with crops was 32,660.19 lx, 36,618.12 lx, and 40,660.48 lx from 12:00 h to 13:00 h in the bottom, middle, and top layers, respectively. The crops affected the light intensity inside the greenhouse. At midday, the maximum average wind speed was 8.3 ms\({}^{-1}\) from the NE. Variability in the ambient conditions in the greenhouse should be considered for sensor placement and sensor-based monitoring, as well as for effective control of the ambient conditions in CSGs. Future research should focus on long-term monitoring, crop-specific effects, the integration of advanced control systems, and emerging technologies so as to enhance crop productivity and environmental sustainability in CSGs.  
Conceptualization, M.N.R. and S.-O.C.; methodology, M.N.R. and S.-O.C.; software, M.N.R., M.N.I. and M.Z.I.; validation, M.N.R., M.S.N.K., M.C., M.-K.J. and S.-O.C.; formal analysis, M.N.R., M.N.I., M.C., M.A.G. and M.A.; investigation, M.S.N.K., M.-K.J. and S.-O.C.; resources, M.-K.J. and S.-O.C.; data curation, M.N.R., M.N.I, M.C. and M.Z.I.; writing--original draft preparation, M.N.R.; writing--review and editing, M.N.R., M.S.N.K. and S.-O.C.; visualization, M.N.R., M.N.I., M.A.G. and M.A.; supervision, S.-O.C.; project administration, S.-O.C.; funding acquisition, S.-O.C. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the Korea Institute of Planning and Evaluation for Technology in Food, Agriculture, Forestry and Fisheries (IPET) through the Technology Commercialization Support Program, funded by the Ministry of Agriculture, Food and Rural Affairs (MAFRA) (project No. 821051-03), Republic of Korea.  
Not applicable.  
The authors declare no conflict of interest.