This study summarizes the 2021 ground level solar irradiance figures in the Eastern Mediterranean and makes a preliminary estimate for 2022. Regional solar irradiance data is analyzed in order to estimate and project the normalized output of solar power facilities in the region, considering the strong link between the two variables. The average solar energy cumulative flux, measured at the IMS station in Bet Dagan in Israel's Central Coastal Plane during 2021, was 5,556 Wh/m^2 per day, which is 8.6% higher than the 1965-2014 multi-year annual solar flux average. The anomaly was out of the standard annual deviation of ±4.0% during the reference period and the highest annual average to date. An estimate for 2022 based on measurements during the first nine months of the year is 5,430±55 Wh/m^2 per day. Hence, 2022 is also expected to show above average solar irradiance figures in the Eastern Mediterranean region, continuing the high-level solar irradiance trend, though not as extreme as during 2021.
Bet Dagan is the longest operating Israel Meteorological Service (IMS) station which has been measuring solar energy flux on ground level since 1965. The station is thus very suitable for long-term analysis of ground level solar energy flux in the Eastern Mediterranean. Regional solar irradiance data is analyzed in order to estimate the normalized output of individual solar power facilities in the region, considering the strong link between the two variables. It should be emphasized that variance in solar flux on the ground level is mostly a result of regional weather and climate influenced by long-term trends in solar activity, planetary climatic shifts and more recently by anthropogenic causes; only to small degree variance in measured solar flux is a direct result of sun's solar output, which is relatively stable.
Figure 1. Solar irradiance measured at Bet Dagan in central Israel in monthly resolution during 2021 (orange) vs. the average solar flux for respective months obtained during 1965-2014 (blue).
Historically, the 2014 solar energy cumulative flux was at 5,399 Wh/m^2 per day. In 2015, the solar flux was at 5,269 Wh/m^2 per day. In 2016, solar flux was at 5,520 Wh/m^2 per day, 7.6% higher than the multi-year flux average. In 2017, solar flux figure was at 5,453 Wh/m^2 per day, 6.3% higher than the multi-year average. In 2018, solar flux was at 5,339 Wh/m^2 per day, which was 4.0% higher than the multi-year average. In 2019, solar flux was 5,543 Wh/m^2 per day, which was 8.1% higher than the multi-year solar flux average. In 2020, solar flux was 5,354 Wh/m^2 per day, which was 4.4% higher than the multi-year average at Bet Dagan IMS station since it began operating since 1965.
The average solar energy cumulative flux, measured at the IMS station in Bet Dagan in Israel's Central Coastal Plane during 2021 was record 5556 Wh/m^2 per day, which was 8.6% higher than 1965-2014 multi-year annual solar flux average. The anomaly was significantly outside of the standard annual deviation of ±4.0% during the 1965-2014 period.
Figure 2. Solar irradiance measured at Bet Dagan in central Israel in yearly resolution during 1965-2021 (blue) and an estimate for 2022.
An estimate for 2022, based on the first nine months of the year, is 5,430±55 Wh/m^2 per day, which is higher than multi-year average. Hence, 2022 is also expected to show above average solar irradiance figures in the Eastern Mediterranean region, continuing the high-level solar irradiance trend - similar to the period of late 1960s and early 1970s. Increased solar irradiance on ground level is driving increased performance figures for PV facilities in the region - a phenomenon which may continue for some time. Among possible factors to alter this projection is an unexpected change in solar activity or a powerful volcanic eruption in Equatorial regions at an intensity of VEI 5.0 or above. Indeed, we are obesrving a certain trend change, possibly linked to the higher than expected solar activity during Cycle 25. Despite the exceptionally high intensity of the Hunga Tonga Hunga Haapai eruption in January 2022 at VEI 5-6, the eruption effect on global weather is not presumed to be substantial due to the relatively small ejecta of sulfur into stratosphere; on the other hand, the global mid-term weather effect of unusually high water vapor ejecta into stratosphere is not yet known.
