Abstract
In line with the critical comments formulated in relation to the S-shape global solar radiation estimation method, the original formula was improved via a 5-step procedure. The improved method was compared to four-reference methods on a large North-American database. According to the investigated error indicators, the final 7-parameter S-shape method has the same or even better estimation efficiency than the original formula. The improved formula is able to provide radiation estimates with a particularly low error pattern index (PIdoy) which is especially important concerning the usability of the estimated radiation values in crop models. Using site-specific calibration, the radiation estimates of the improved S-shape method caused an average of 2.72 ± 1.02 (α = 0.05) relative error in the calculated biomass. Using only readily available site specific metadata the radiation estimates caused less than 5% relative error in the crop model calculations when they were used for locations in the middle, plain territories of the USA.
Highlights
Solar radiation is the main driving force of the processes in the atmosphere, as well as in the biosphere, including the rhizosphere
We investigated the model proposed by [21] and found more than 2500 days when the estimated radiation value was greater than the physical upper limit calculated with the formula proposed by [23]
The improved method was tested on a large North-American database along with four reference methods
Summary
Solar radiation is the main driving force of the processes in the atmosphere, as well as in the biosphere, including the rhizosphere. Measured daily global solar radiation is an important factor in most cropping systems and water balance models. The scarcity of good quality solar radiation data series can be a major limitation to the use of crop models. To circumvent this problem, numerous radiation estimation methods were developed using commonly measured meteorological variables, such us sunshine hours, temperature, and precipitation [1], as well as [2] gave a comprehensive overview and carried out an in-depth analysis of the temperature and precipitation based global radiation models
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