Cloudiness and Solar Radiation During the Longest Total Solar Eclipse of the 21st Century at Tianhuangping (Zhejiang), China

Abstract

The lack of comprehensive solar radiation monitoring during the longest total solar eclipse of the 21st century at Tianhuangping (Zhejiang), China, on 22 July 2009, has led to this investigation in order to evaluate the cloudiness contribution in estimating the impact on global solar radiation throughout this phenomenon. In doing so, we applied a cloud cover empirical model to obtain the global solar radiation and, at the same time, we deduced a theoretical model to get the direct solar radiation in which both the occultation and obscuration functions of this eclipse are included. We took limb darkening and atmospheric transmission into account. Though the weather during our eclipse observations agreed with the forecasts for that day, clouds and some rain, we were nonetheless able to observe all phases of the eclipse from our observation site at Tianhuangping. This experience suggests that for coming eclipses a record of the in situ observation protocol of cloudiness is mandatory. Our results for comparing global solar radiation models indicate that our total solar eclipse radiation model is quite acceptable and representative of that which could have happened at that time.Plain Language Summary A total solar eclipse is a situation where the Sun is obscured by the Moon viewed from Earth. In this particular arrangement in space a shadow is cast over a particular region. Thus, the ideal circumstances to observe a total solar eclipse are those in which the sky is cloudless in that region or zone. Yet from time to time this phenomenon occurs in the presence of interfering clouds preventing a direct observation of the event. However, under these adverse circumstances effects over the environment can still be felt and measured as, for example, the rapid reduction of solar energy reaching the surface. In that case such measurements would be lacking, but with some information about cloudiness one can have an idea of how the variation of this energy during the eclipse took place. In the procedure a quantitative knowledge of how the Moon disk is going to progressively cut the Sun's brightness during the eclipse is necessary. From an environmental point of view it is shown that a scientific observation of a total solar eclipse matters even though it was made under the influence of blocking clouds.

Anatomy of the Annular Solar Eclipse of 26 December 2019 and Its Impact on Land– Atmosphere Interactions Over an Arid Region

“…At higher latitudes, Kameda et al [13] noted a decrease in the 1.5-m temperature of about 3 • C during the 23 November 2003 TSE at Dome Fuji, Antarctica, whereas for the 20 March 2015 TSE in Svalbard, a drop smaller than the 0.5 • C uncertainty of the sensor was recorded [14]. It is important to note that the eclipse signal can still be detected even when the atmospheric conditions are not at all favorable (i.e., cloudy skies) [15].…”

Anomalies and Fluctuations of Near-surface Air Temperature at Tianhuangping (Zhejiang), China, Produced by the Longest Total Solar Eclipse of the 21st Century Under Cloudy Skies

“…It is based on a sort of calibration curve of the type "air temperature vs. solar radiation" from which we can extract the air temperature during the phenomenon. In this case, clouds of different types and heights affected the solar radiation before, during, and after the eclipse (Peñaloza-Murillo & Pasachoff, 2018). Therefore, our first task, of this part of the investigation, was to formulate a solar-radiation model under cloudy conditions, as if the occultation had not happened, in order to be taken subsequently as such in the eclipse situation, as was obtained by Peñaloza-Murillo & Pasachoff (2018) (see Fig.…”

“…4. For these goals it was necessary first to get the occultation and obscuration function, via limb-darkening integration as was done by Peñaloza-Murillo & Pasachoff (2018) and to which the reader is referred for details. Our challenge now is to apply the pioneering Phillips's method (Phillips, 1969), in combination with that of Peñaloza-Murillo & Pasachoff (2018), to retrieve the temperature profile directly from a radiative model of the solar radiation's collapse and recovery during the eclipse process, this time total, but under cloudy conditions.…”

“…Despite the cloudy conditions (Peñaloza-Murillo & Pasachoff, 2018), the method applied in this investigation turns out to be practical and it is affordable to be repeated and rechecked in future similar conditions. In other words, using a simple set of NSAT measurements obtained during solar eclipses even under adverse weather allows a mathematical analysis of these measurements and its relation to changes and fluctuations of it can still be attempted following the methods presented here (Phillips, 1969;Szałowski, 2002) along with that presented by Peñaloza-Murillo & Pasachoff (2018) in which an analysis of the cloudiness and solar radiation during this eclipse was undertaken.…”

“…According to Meeus (2002) and Espenak (2014) between 2001 and 2100, there are eleven TSEs with maximum duration greater than five minutes, with none more than seven minutes [see Table 1 of Peñaloza-Murillo & Pasachoff (2018) for TSEs with maximum totality duration greater than five minutes during this century]. The longest one, with up to 6' 40" of totality, took place on 22 July 2009, with its longest duration somewhere in the western Pacific Ocean.…”