Distribution of the monthly global solar irradiation in the State of Tabasco, Mexico

Abstract

Objective: The objective was to estimate the mean monthly global solar irradiation (Rg), using observed data on cloudiness (% of cloudy days), as well as its spatial distribution for the state of Tabasco.

Design / Methodology / Approach: The model proposed by Tejeda-Martínez et al. (1999) was adjusted to estimate the Rg of 35 meteorological stations in the state of Tabasco. The adjustment was done with daily observed Rg data from eight automated meteorological stations and with cloud cover data from eight ordinary weather stations.

Results: The proposed model presented a good fit, since its prediction was optimal according to the Willmott comparison parameter (c = 0.89), and excellent based on the Nash-Sutcliffe efficiency index (E = 0.99); and it had a high adjusted coefficient of determination Rc² = 0.87.

Study limitations / implications: The number of automated stations needs to be increased in the state of Tabasco, as well as to provide technical maintenance to existing stations.

Findings / conclusions: The estimated Rg is statistically reliable. The highest Rg values were shown in the dry season, with a maximum of 22.99 MJ m^-2 d^-1, mainly distributed in the northern part of the state. The minimum Rg values were obtained in the cold-rainy season (12.52 MJ m^-2 d^-1) distributed in more than 80% of the total surface of the state.

Key words: Willmott's index, cloud cover, transmissibility, heliophany