Record-breaking lack of sunshine in the Kanto region in 2019

This July, the Kanto region is suffering from a record-breaking lack of sunshine due to the rainy season in full swing, and there are concerns about the impact on vegetables and other crops. Observation data from Global Change Observation Mission – Climate “SHIKISAI” (GCOM-C) and Meteorological Satellite “Himawari-8” also indicated that solar irradiance was lower this year than last year.

Figure 1 shows the spatial distribution of photosynthetically active radiation, PAR (unit; Ein/m²/day) around Japan averaged over the 10-day period from July 1 to 10, 2018 (left) and 2019 (right) by GCOM-C. PAR is the sum of solar irradiance in visible wavelengths reaching the Earth’s surface that is used by plants for photosynthesis. We can see that PAR in the early July of 2019 around the Kanto area is about half that of 2018.

Figure 1. Photosynthetically active radiation averaged in early July (10 days from 1 to 10) in 2018 (left) and 2019 (right) by GCOM-C (unit; Ein/m²/day).

Figure 2 shows the solar irradiance around Japan in early July (10-day average from the 1st to the 10th) generated from the Himawari-8 observation data for the 5-year period from 2015 to 2019 (lower right: 5-year average; unit W/m²) and the spatial distribution of the ratio of solar irradiance to the 5-year average for each year. These figures clearly show the low amount of solar irradiance this year on the Pacific side of Japan, including the Kanto region where the amount of solar irradiance in the early July of 2019 was about half of the average of the past five years.

Figure 2. 5-year average solar irradiance in early July (10-day average from the 1st to the 10th) by Himawari-8 (lower right; unit W/m²) and the ratio of solar irradiance from each year to the 5-year average solar irradiance.

These annual variations in solar irradiance are closely related to the growth of vegetables and other agricultural products, as well as the amount of electricity generated by solar power and other renewable energy sources, and should be closely monitored in the future. Once the long rainy season is over, Japan may return to its extremely hot climate. It is still fresh in our memories that the Japan Islands was hit by an extreme heat wave on August 1, 2018. JAXA/EORC will continue to monitor the solar environment around Japan.

Observation images around Japan by GCOM-C are available on the “JASMES SGLI Near-Realtime Monitor”, a global environmental monitoring website. Observation images by Himawari are also available at “JAXA Himawari monitor“.

Explanation of the Images

Figure 1

Satellite	Global Change Observation Mission – Climate “SHIKISAI” (GCOM-C)
Sensor	Second generation GLobal Imager (SGLI)
Date	July 1-10, 2018 (left) July 1-10, 2019 (right)