BANGLADESH RESEARCH PUBLICATIONS JOURNAL ISSN: 1998-2003, Volume: 2, Issue: 4, Page: 754-758, July - August, 2009 DISPARITY OF TEMPERATURE GRADIENT IN NET COVERED AND FAN AND PAD COOLED GREENHOUSES IN THE STIFLING CLIMATE OF CENTRAL THAILAND Mst. Meherunnahar ∗ 1 , D.N.R Paul 2 Mst. Meherunnahar, D.N.R Paul. (2009). Disparity of Temperature Gradient in Net Covered and Fan and Pad Cooled Greenhouses in the Stifling Climate of Central Thailand. Bangladesh Res. Pub. J. 2(4): 754-758. Retrieve from http://www.bdresearchpublications.com/admin/journal/upload/08092/08092.pdf A b stra c t Effects of naturally ventilated or net covered greenhouse (NC) with 52 mesh net and fan & pad cooling greenhouse (FPC) were examined for the air temperature gradients, contained by the greenhouses throughout the dry season in the stifling climate of central Thailand. Air temperature was determined along with the greenhouses as a function of height and space. It was revealed that, in FPC greenhouse, the inside air temperature remained lower to both the ambient air temperature and NC greenhouse air temperature on most of the days because of cooling and airflow. Main air temperature gradient was found in the vertical –Z direction from bottom to top. Relative humidity, contained by the FPC greenhouse, was always higher than the ambient relative humidity and NC greenhouse. Air temperature was substandard near pad side and it was higher near the fan side in FPC greenhouse; and the reverse behavior was experienced in NC greenhouse. Key words: Fry collector, Ban, Shrimp fry, Livelihood, Alternative Livelihood, Dadonder. Intro d uc tio n Thailand lies on the arid part of the world where summer is very hot with high air temperature that can reach 54º C (Britannica, 2005) and winter is warm and sunny. Air temperature, heavy rainfall, solar radiation and/or unfavorable high levels of air humidity are a major constraint for the production of vegetables in the tropics where mean daily Ta of 27 to 33 °C is considered to be optima (Abdul-Baki and Stommel, 1995; Sato et al., 2000). In addition to this adverse and harsh weather Net covered (NC) greenhouse, fan and pad cooling greenhouse (FPC), misting or fogging systems (e.g. Baille et al., 2001; Arbel et al., 2003; Kittas et al., 2003) play an important role to manage microclimate. In general, fan and pad cooling is a process of reducing air temperature by evaporation of water into air stream. It usually tends to be high due to crop transpiration that depends on solar radiation, CO2 concentration, temperature and relative humidity. Sato et al., 2000 also mentioned that fan and pad cooling under hot weather conditions is an operation in which latent heat is converted to sensible heat. And net covered greenhouse is an attractive method for controlling greenhouse microclimate because of its economic advantages, Zhao e t a l. (2001). Bucklin e t a l., 1993 informed that the temperature gradient across the greenhouse at plant level are the most important concern, but the accurate prediction of temperature gradient across the house was difficult because of their nature and steepness. It was concluded that air might heat up as rapidly as 0·5 °C for ∗ Corresponding Author’s Address: mnahar_bcas@yahoo.com 1 Masters of Engineering, Department of Agricultural Systems and Engineering (ASE), School of Environment Resources and Development (SERD), Asian Institute of Technology (AIT), Klong Luang, PathumThani, Thailand-12120. 2 Professor, Department of Agricultural Business, Atish Dipankar University of Science and Technology (ADUST), Faisal Tower, Gulshan-2, Dhaka-1212.