1. Summary of 2023 Pollen Dispersion (compared to previous years)
The amount of cedar and cypress pollen dispersed in 2023 was the highest in the past three years in both Tokyo and Osaka, and as of now (until April 10), the amount of pollen dispersed has already exceeded the average value for the past 10 years.
The best weather conditions for cedar flower bud formation are “high temperature, high sunshine, and low rainfall” in the first half of the previous summer.
In the summer of 2022, the above conditions were fulfilled, and it promoted the formation of cedar flower buds.
In addition, the amount of cedar scattering over the past three years (2020-2022) has been similar to or lower than usual, which has allowed the cedar trees to store up the energy necessary for flower bud formation.
Also, from late December to the beginning of the new year, Western and Eastern part of Japan were affected by cold air and cooler-than-normal temperatures, which is considered to have allowed the flower buds to go dormant for a longer period.
In February, cedar pollen began to be dispersed in Kyushu and other regions. Compared to 2022, the start of scattering was 10 days to 2 weeks earlier. In late February, cedar pollen peaked over a wide area from Kyushu to Kanto. Especially in Tokyo, cedar pollen counts of 500 pollen/㎠ or more were observed for three days straight from February 28, resulting in a large amount of pollen dispersion. In Osaka, the peak of cedar pollen continued for about two weeks from February 28.
In March, the dispersal of cypress pollen was confirmed to have begun in the Kyushu region. The dispersion of cypress pollen instantly spread to many areas and reached its peak in mid to late March.
2. Outlook for the End of Pollen Dispersion
In Tokyo, scattering of cedar pollen has been decreasing in April and is expected to end by the end of this month. In Osaka, the scattering of cedar pollen ended on April 9.
As for cypress pollen, it is likely to remain intermittently scattered in Tokyo until around the Golden Week, but in Osaka, it is expected to be over by the end of this month.
In Hokkaido, where birch pollen will begin to be scattered from late April, it is anticipated to continue until mid-May.
3. JWA’s Pollen Dispersal Forecast:
For more detailed information about JWA’s Pollen Dispersal Forecast, please find the link below:
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Originally released in Japanese: 2023/4/25
PDF DOWNLOAD：Cedar Pollen Forecast 2023 (Apr 25th, 2023)