Steady growth in accumulated temperature, approaching the “600°C rule” of cherry blossoms in Tokyo – Weather News

2023/03/11 12:29 Weather news

In Tokyo, cherry blossoms are expected to bloom as early as next week.

While this winter has been severely cold, the temperature rises suddenly in March, and the spring weather continues. The average daily maximum temperature in Tokyo in early March was 18.4°C. This number corresponds to the first half of April, indicating that the warmth continues following the cherry blossoms fall.

The growth of the cherry blossom buds is progressing rapidly, but it is expected that there will be many warm days next week, and it seems that we will receive news of the cherry blossoms from Tokyo.

This time, we will introduce the “600°C rule” that can be used to estimate the flowering time with a simple calculation.

Flowering mechanism of cherry blossoms

Cherry blossom buds are formed in the summer of the year before flowering. From autumn to winter, it enters a dormant state to prevent growth and passes the year. Then, following receiving sufficient cold stimulation, the temperature rises a lot and wakes up from dormancy. This is called “breaking dormancy”.

Mechanism of breaking dormancy

In the flowering forecasts made by meteorological information companies, the day when the dormancy is broken is used as the starting date, and the number of days for temperature conversion is calculated.

How to predict easily by yourself

Even without such a complicated method, you can easily predict when the cherry blossoms will bloom by using a procedure called the “600°C rule” for the cherry blossom specimens at Yasukuni Shrine in Tokyo. The content is very simple.

[Law of 600°C]
Blooms when the total daily maximum temperature following February 1 reaches 600°C

In other words, you can predict the blooming of cherry blossoms simply by assuming February 1 as “the day when dormancy is broken” and setting it as the starting point for the flowering forecast, and then adding the maximum temperature of each day from that point.

For the 13 years from 2010 to 2022, we examined the accuracy of the 600°C law in Tokyo from the data of the Japan Meteorological Agency, and found that “the day when the temperature exceeded 600°C” and “the day when flowering was actually observed”. The maximum error was only 3 days. Isn’t it pretty accurate?

What is this year’s “Law of 600°C”?

This February, there were slightly more warm days than usual, and the cumulative temperature remained slightly higher. However, from the end of February, the number of days with extremely high temperatures increased, so the slope of the graph suddenly became steeper. Cumulative weekly forecast temperatures suggest reaching 600°C on March 15th.

If the law of 600°C is followed, the flowers may bloom as early as 2021 (March 14th) and 2020 (March 14th: leap year), the earliest ever. According to Weathernews’ cherry blossom forecast, March 15 is expected to be the blossoming date in Tokyo.

Please note that the “600°C rule” is only an empirical rule for sample trees in Tokyo, so please use Weather News’ Sakura Ch.

Reference materials, etc.

Shinagawa Environmental Information Activity Center