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Japan - Introduction

Japan was the worst-hit country by extreme weather in 2018. Japan experienced record torrential downpours and prolonged heat waves last year. Germanwatch released the information to reporters on 04 December 2019 at the UN climate change conference, COP25, in Madrid, Spain. The think tank's report ranks countries according to their vulnerability to extreme weather events. Japan ranked first in terms of fatalities and economic loss. The ranking is a result of deadly torrential downpours that pounded western Japan in July 2018, as well as Typhoon Jebi, that made landfall in western Japan in September 2018 while maintaining extreme strength. In addition, much of Japan was hit by persistent extreme heat in July and August, with the mercury soaring to a record 41.1 degrees Celsius in Kumagaya City near Tokyo in July. The think tank officials note that multiple extreme weather occurrences in a single year would not have happened if it were not for global warming.

The World Meteorological Organization reported extreme weather conditions dealt a deadly blow in many places in 2018, with blistering heatwaves and disastrous precipitation. Global warning does't always mean hot weather, but some times it does. Hotter than average days began in late June 2018 in eastern Japan, and on around the 9th of July in the west of the country. The highest-ever temperature in Japan was recorded in Kumagaya City, Saitama Prefecture, amid an extreme heat wave that continues to plague wide areas of the country. The mercury rose to 41.1 degrees Celsius on 23 July 2018 in the city, located north of Tokyo. This is the first time the temperature has hit the 40-degree mark at an observation point in Tokyo since recordkeeping began. They are the highest averages for the period since record-keeping began in 1961.

Japanese weather officials warned people to take strict precautions against heatstroke, as the country remained in the grip of a deadly heat wave. More than 22,000 people with symptoms of heatstroke were rushed to hospitals across Japan in the third week of July. The figure was 3.1 times that of the same period last year, and 2.3 times that of the previous week. More than 1,800 people with symptoms of heatstroke were rushed to hospitals across Japan on 24 July 2018 alone, and eight of them died. Over 90 percent of those who died in rooms with air conditioners were not using them. About 80 percent of the victims were aged 70 or older.

Hospitals across Japan have treated more than 78,000 people for symptoms of heatstroke from late April to mid-August 2018. The Fire and Disaster Management Agency said 78,345 people were treated for heatstroke symptoms between the end of April and last Sunday. That's nearly double the total in the same period in 2017. The agency saif it was the largest number on record for a single year. The previous high was reached in 2013, when hospitals treated more than 58,000 people for heatstroke symptoms between June and September.

Many parts of Japan saw record high temperatures and heavy rains in July. The Meteorological Agency called the month's weather conditions "abnormal". Meteorological Agency officials said the torrential rains and fierce heat seen in July were conditions that come along "less than once in 30 years." The death toll among Tokyo residents from suspected heatstroke hit 96 during July. The Tokyo Metropolitan Police Department and others said the victims were in their 40s through 90s. The figure is nearly 4 times that of last year's toll of 25.

The July 2018 catastrophic flooding in Japan, the worst in decades, claimed over 200 lives. WMO spokeswoman, Claire Nullis, says the death toll is likely to climb. This, in what she calls one of the world’s best prepared countries when it comes to tackling disasters. “They are supremely well prepared," said Nullis. "And, so the magnitude of the casualties, of the destruction that we are seeing now really is an indication of just how big and how extreme this was and how heavy the rainfall was in such a short period of time.”

Following the disaster, questions began to emerge. Some wondered whether people were given enough warning to leave areas threatened by rising waters. Others asked whether the high loss of life could have been avoided. This was Japan's worst weather-related disaster in more than 3 decades. Experts are looking into why so many people failed to flee.

The Japanese archipelago has a temperate marine climate. Though they may differ depending on the effects of seasonal winds and ocean currents, the changes in the four seasons are distinct. Japan typically experiences hot, humid summers and cold, dry winters. The topography of Honshu, however, features a series of major mountain ranges running from north to south. Because of this feature, the northwest monsoon in the winter brings humid conditions with heavy precipitation (snow) to the Sea of Japan side of Honshu but comparatively dry weather with low precipitation to the Pacific Ocean side. In summer, the winds blow mainly from the southeast, giving rise to hot and humid weather.

Another unique characteristic of Japan's climate is that it has two long spells of rainy seasons, one in early summer when the southeast monsoon begins to blow, and the other in autumn when the winds cease. From summer to autumn, tropical cyclones generated in the Pacific Ocean to the south develop into typhoons and hit Japan, sometimes causing storm and flood damage.

In spring (March-April-May), migratory cyclones and anticyclones that alternately move eastward prevail across Japan. Temperature increases (decreases) in front (back) of cyclonic systems due to warm southerly (cold northerly) flow. Temperature rises gradually with large short-term variations. Sunshine duration is long in the second half of spring due to the predominance of anticyclonic systems.

The rainy season (known as the Baiu) begins in early May in Okinawa and in mid-May in Amami. Early summer is the rainy season, known as the Baiu, in Japan. Its precipitation is caused by a stationary front, called the Baiu front, which forms where a warm maritime tropical air mass meets a cool polar maritime air mass.

In the second half of summer (June-July-August), the North Pacific High extends northwestward around Japan, bringing hot and sunny conditions to the country. Western Japan sometimes experiences temperatures of 35°C or above. On the other hand, the Okhotsk High sometimes appears over the Sea of Okhotsk and causes cool and moist easterly winds (known as Yamase), which bring cloudy and rainy conditions to the Pacific side of northern and eastern Japan. The number of tropical cyclones approaching Okinawa/Amami peaks in August.

In autumn (September-October-November), temperatures fall gradually. Monthly precipitation amounts are large in September due to the active autumnal rain front and tropical cyclones. In October, the frequent passage of anticyclonic systems brings sunny conditions and refreshing air to Japan. The frequency of cold northwesterly flows across Japan and precipitation (rainfall or snowfall) on the Sea of Japan side of the country show an increasing tendency in November.

In winter (December-January-February), the Siberian High develops over the Eurasian Continent and the Aleutian Low develops over the northern North Pacific. Prevailing northwesterly winds cause the advection of cold air from Siberia to Japan and bring heavy snowfall to Japan's Sea of Japan side (upstream of mountainous land) and sunny weather to its Pacific side (downstream of mountainous land). Temperatures as low as -20°C are frequently observed in inland areas of Hokkaido, while Okinawa and Amami have mild winters due to their subtropical location.

Japan’s average temperature varies widely from year to year, but over the long term, it has been on an upward trend, rising at a rate of 1.15°C per 100 years, which is higher than the global average of 0.68°C per 100 years. Both the number of extremely hot days with maximum temperature of 35°C and higher and tropical nights with minimum temperatures of 25°C and higher appear to be on the rise.

There is a large area of land at 0m above sea level along Japan’s three major bays (Tokyo Bay, Ise Bay and Osaka Bay), but assuming a sea level rise of 60cm, the area of land at 0m above sea level and the population in those zones would both increase by as much as 50%; therefore, future sea level rise has the potential to cause serious problems. Furthermore, changes in the course and intensity of typhoons could lead to an increased risk of high waves in coastal areas along the Pacific Ocean.

Changes in precipitation are also evident, with the number of days with rainfall of 1mm or more declining while the number of days with rainfall of 100 mm or more is on the rise. According to the Automated Meteorological Data Acquisition System (AMeDAS) observations, the frequency of hourly heavy rains of 50mm or more is extremely likely to have increased.

If CO2 concentrations increase in line with Scenarios B1, A1B and A2, Japan’s average temperature is projected to increase by 2.1 - 4.0°C, which exceeds the global average of 1.8 - 3.4°C. Based on climate change model projections, temperature increases will be larger in Northern Japan, while the number of extremely hot days and tropical nights will increase significantly in Okinawa and Amami, Western Japan, and Eastern Japan. Meanwhile, the number of cold and extremely cold days will decline primarily in Northern Japan. Furthermore, the frequency of hourly heavy rains will increase in all regions, while the number of dry days with daily precipitation less than 1mm is expected to increase in almost every region.

In addition to the increase in drought risk, the risk of disaster due to heavy rain could also increase. One study of class A rivers throughout the country predicts the probability of floods exceeding the rivers’ prescribed target flood safety levels to be 1.8 to 4.4 times the current value. In addition, there is a possibility that the risk of mass movement in mountainous areas will also increase. Some slopes in hilly and mountainous areas have experienced considerably large deep-seated landslides, which are landslides in which the underlying bedrock collapses along with the topsoil, and the risk of these landslides may increase.

Having faced a drastic change in its circumstances with regard to energy due to the Great East Japan Earthquake and the accident at the Tokyo Electric Power Company’s Fukushima Dai-ichi Nuclear Power Station, Japan decided the new Strategic Energy Plan as a starting point for reviewing and rebuilding our energy strategy from scratch.

Japan’s INDC towards post-2020 GHG emission reductions is at the level of a reduction of 26.0% by fiscal year (FY) 2030 compared to FY 2013 (25.4% reduction compared to FY 2005) (approximately 1.042 billion t-CO2 eq. as 2030 emissions), ensuring consistency with its energy mix1, set as a feasible reduction target by bottom-up calculation with concrete policies, measures and individual technologies taking into adequate consideration, inter alia, technological and cost constraints, and set based on the amount of domestic emission reductions and removals assumed to be obtained.

Japan witnessed record-breaking weather in the first ten days of July 2020, with destructive and sometimes deadly consequences. Some places had been lashed with more than three times the average rainfall for the entire month. The island of Kyushu, located in the southwest of Japan and sandwiched between warm ocean fronts, is the wettest place in the archipelago. And its mountainous terrain makes it the most disaster-prone area. Around 60% of the landslides that occur in the country are in Kyushu.

Heavy rain is common there, but the downpours in early July 2020 broke records. They also cost the lives of at least 66 people. The Japan Meteorological Agency issued an emergency warning – the highest possible level of alert – for much of the island. It was the first time the warning had been issued for Kumamoto and Kagoshima prefectures since the alert system was introduced in 2013.

From July 3rd to 9th, the city of Kanoya in Kagoshima Prefecture received more than a meter of rain. That's three times the average for all of July. Even more astonishing is that most of it fell within just half a day. Kanoya and the city of Minamata in Kumamoto Prefecture saw 415 millimeters in just 12 hours, while Ashikita, also in Kumamoto Prefecture, recorded 326 millimeters in six hours. All of these far exceeded previous records. This extreme rain caused many rivers, including the Kuma River, one of the three most rapid in Japan, to overflow. The rain quickly ran downstream, breached levees and caused deadly flooding.

In June and July, humid maritime air and dry continental air collide, creating a seasonal rain front in and around Japan. The front usually moves northward as the season progresses. However, a Pacific high-pressure system normally responsible for pushing the front along has not done so this month. That left it stalled in the same area for more than a week. Officials at the Japan Meteorological Agency say they cannot recall the last time this occurred. In addition, a plume of unusually strong water vapor called a "wet tongue" surged into Kyushu and strengthened the stalled rain front.

And much narrower bands of rain called "trainings" developed over Kyushu. A training is a series of thunderclouds that forms over the same area for an extended period of time. The thunderclouds are often short-lived, lasting only about 30 minutes, but inside the training the clouds are continuously forming, and that means extended periods of rain in one location.

The wet period typically lasts through mid-July in Kyushu, and until late-July in central Japan. Over the past 100 years, global temperatures have risen by 0.73°, while the temperature in Japan has gone up by 1.13°. The rapid rise has increased the amount of moisture in the air, resulting in an increase in rainfall. Studies suggest the frequency of heavy rain at a rate of at least 50mm per hour has increased by 40% over the last decade. Some scientists even believe the length of the rainy season could increase. On top of all that, Japan is physically vulnerable to natural disasters. Some 70% of the land is mountainous and around 1,000 landslides occur every year. Around 10% of the land is flood-prone and half of the population lives in these areas. With rising temperatures, an increase in rain is unavoidable.

The rainy season, which brings with it river spills, landslides and floods, is a common thing for the first half of the Japanese summer. However, every year the situation worsens, increasingly going beyond what Japan is accustomed to as a natural disaster. Many local meteorologists attribute this alarming trend to global warming, the process of which in the area of ??the Japanese islands, in their opinion, was proceeding faster than global rates.

Local meteorologists admit that the country has not seen heavy rains of such power and intensity for several decades - in some areas up to 100 mm of rain fell per hour. It is also worth noting that the number of heavy rainfall with rainfall from 80 mm per hour in Japan over the past 40 years has increased by almost 1.7 times. About 100 thousand inhabitants of these regions were instructed to immediately evacuate to special centers and still as many strongly recommended to leave their homes. The reason for this was the formation of the so-called long rainfall belt over the southwestern Japanese island of Kyushu - the concentration of cumulonimbus clouds dropping huge volumes of water.

Unlike typhoons, with dozens of landfalls in Japan every year and also bringing heavy rains, it is very difficult to predict the appearance of a belt of prolonged rainfall. A typhoon is formed hundreds of kilometers from the main territory of the country and gradually moves towards it for several days. But an area of ??prolonged rainfall can form almost instantly, in just a few hours, over any region. And almost overnight, a huge amount of rainfall will be shed there, which will inevitably lead to tragic consequences.

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Page last modified: 06-07-2021 16:52:20 ZULU