Rungrat Wattan

A semi-empirical model for estimating surface solar radiation from satellite data

This paper presents a semi-empirical model for estimating surface solar radiation from satellite data for a tropical environment. The model expresses solar irradiance as a semi-empirical function of cloud index, aerosol optical depth, precipitable water, total column ozone and air mass. The cloud index data were derived from MTSAT-1R satellite, whereas the aerosol optical depth data were obtained from MODIS/Terra satellite. The total column ozone data were derived from OMI/AURA satellite and the precipitable water data were obtained from NCEP/NCAR. A five year period (2006-2010) of these data and global solar irradiance measured at four sites in Thailand namely, Chiang Mai (18.78 °N, 98.98 °E), Nakhon Pathom (13.82 °N, 100.04 °E), Ubon Ratchathani (15.25 °N, 104.87 °E) and Songkhla (7.20 °N, 100.60 °E), were used to derive the coefficients of the model. To evaluate its performance, the model was used to calculate solar radiation at four sites in Thailand namely, Phisanulok (16.93 °N, 100.24 °E), Kanchanab...

An investigation of solar erythemal ultraviolet radiation at two sites in tourist attraction areas of Thailand

Islands on the southern coasts of Thailand are famous attractions for local and foreign tourists. Tourists usually expose their skins to solar radiation for tanning. Thus information on solar ultraviolet radiation (UV) is of importance for tourists to protect themselves from adverse effects of UV. In this work, solar erythemal ultraviolet radiation (EUV) at two touristic sites namely Samui island (9.451°N, 100.033°E) and Phuket island (8.104°N, 98.304°E) was investigated. In investigating EUV, broadband UV radiometers (Kipp & Zonen, model UVS-B-C) were installed at existing meteorological stations in Samui and Phuket islands. A one-year period of EUV data from these two sites was analyzed. The level of UV index at these sites was studied. The values of UV index higher than 12 at noon time of clear days are usually found in the summer at both sites. Seasonal variation of EUV at both sites was investigated. It was found that the tropical monsoons have strong influence on this variation. Finally, global broa...

Statistical models for estimating hourly diffuse solar radiation in different regions of Thailand

In this study, four statistical models for estimating diffuse solar radiation from global solar radiation in different regions of Thailand have been developed. In developing the models, a 12-year period of global and diffuse solar radiation measured at four of our solar radiation monitoring stations, situated in different regions of Thailand have been analyzed. The statistical models estimate diffuse fraction from clearness index at the hourly scale. The performance of these models have been compared with that of other models. The models developed in this study performed best for most cases.

Development of a Luminous Efficacy Model Using Ground and Satellite-Based Data from the Tropics

In this work, a global luminous efficacy model was developed. The formulation of the model was based on global illuminance and global irradiance measured at four tropical sites in Thailand. The model expresses luminous efficacy as an empirical function of aerosol optical depth, precipitable water, satellite-derived cloud index and cosine of solar zenith angle. The aerosol optical depth and precipitable water were obtained from Aerosol Robotic Network (AERONET) of NASA, and cloud index was derived from multifunctional transport satellite (MTSAT)-1R satellite. The model coefficients were calculated using a 4-year period of hourly data (2007–2010), and the model was validated against an independent data set for 2011. The model predicted well the global illuminance with a root mean square difference (RMSD) of 3.6 % and a mean bias difference (MBD) of 0.3 %. In addition, the model was compared favourably with most existing models when tested against this independent data set.