Instantaneous global horizontal irradiance and clearness index data with high temporal resolution for 1016 days

Global Horizontal Irradiance was measured using a thermopile-type pyranometer during more than three years using a sample time of two seconds, with the purpose of capturing fast transient events of irradiance which are notable in tropical regions as the one where these data were collected: Bogotá, Colombia. The date and time of each measurement were registered along with the irradiance values. In addition, other related quantities were calculated and included for each one of the measurement instants: Optical Air Mass, Zenith angle, Extraterrestrial Solar Irradiance, and Clearness Index. Daily aggregated statistics of irradiance were calculated and are provided here too. Data points corresponding to nights were discarded. The raw data was analyzed to remove incomplete days, to guarantee that daily statistics are accurate and meaningful. After this data cleaning process, 1016 complete days remain, having a total of 21,959,912 data points. These data are useful for studying the effect of irradiance transients over photovoltaic systems, including power electronics, batteries and electric loads; it can also be used in studies about the stability of the radiative regime or the variability of irradiance such as Avila et al. (2019) (where part of these data was effectively used) and other related works cited there.


a b s t r a c t
Global Horizontal Irradiance was measured using a thermopile-type pyranometer during more than three years using a sample time of two seconds, with the purpose of capturing fast transient events of irradiance which are notable in tropical regions as the one where these data were collected: Bogotá, Colombia. The date and time of each measurement were registered along with the irradiance values. In addition, other related quantities were calculated and included for each one of the measurement instants: Optical Air Mass, Zenith angle, Extraterrestrial Solar Irradiance, and Clearness Index. Daily aggregated statistics of irradiance were calculated and are provided here too. Data points corresponding to nights were discarded. The raw data was analyzed to remove incomplete days, to guarantee that daily statistics are accurate and meaningful. After this data cleaning process, 1016 complete days remain, having a total of 21,959,912 data points. These data are useful for studying the effect of irradiance transients over photovoltaic systems, including power electronics, batteries and electric loads; it can also be used in studies about the stability of the radiative regime or the variability of irradiance such as Avila

Value of the Data
• The data was measured using a high sampling rate, which allowed to capture many fast transient behaviors of received irradiance, produced by atmospheric phenomena. Also, longer term phenomena are present in the data since it was taken over a period of more than three years. • Researchers working on photovoltaic systems, testing of power electronics for energy conversion, or the modelling of the solar resource can find these data useful. • From these data, the transient behavior of irradiance can be characterized and its impact in photovoltaic systems can be assessed, including power electronics, battery systems, electric loads, etc. • By Integration of the data, it is possible to obtain energy totals, needed in the sizing of solar energy systems. • Also, it can be used to create statistical models of irradiance levels, or synthesis of new irradiance signals; as done, for example, in [2] .

Data Description
Solar irradiance at the surface of the earth is heavily influenced by atmospheric phenomena like clouds, which can produce fast and considerable variations in the received irradiance [3] , this is more notable in tropical regions. Therefore, to be able to account for these sudden changes, data measured with a high sample rate (i.e., low sample time) is necessary [4] .
These data are provided here on the table "irradiance_data", along with other useful quantities. Daily aggregated statistics are calculated on the table "daily_stats". Both tables can be found on [5] .
An example of the data available for one single day (of the 1016 available) including only Global Horizontal Irradiance (blue) and Extraterrestrial Solar Irradiance (red) is shown in Fig. 1 .

Experimental Design, Materials and Methods
The thermopile-type pyranometer was used to measure Global Horizontal Irradiance between the dates 2016-08-19 and 2019-11-10. Specifications of this instrument are shown in Fig. 2. To capture fast transient phenomena, a sampling time of 2 s was used, which is considered appropriate for instantaneous irradiance measurements [4] .
Raw data registered by the recording software, was transformed to a standard format much more accessible for data analysis tools. For each data point three values were recorded: date, time, and Global Horizontal Irradiance ( I s ).
The Zenith angle, Air Mass, and Extraterrestrial Solar Irradiance ( I 0 h ) were calculated for each data point, based on the geographical coordinates, date and time of the measurement, using the formulas available at Sections 3.6 and 3.11 of [6] . This was also used to calculate the Instantaneous Clearness Index as defined in [3] : k t = I S /I 0h .
Data corresponding to non-positive values of I 0 h were discarded, since this corresponds to negligible values of measured I s , below the accuracy of the pyranometer.
Days with any missing data were completely removed since this would create defective irradiance signals or daily statistics. Afterwards, aggregated statistics were calculated for each one of the 1016 days, as given in table "daily_stats ".

Ethics Statements
The presented data involved none of the following: human subjects, animal experiments, or data collected from social media platforms.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: There are not any other interests to declare.