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Revealing the Earth’s water condition from outer space

Meteorology and the Earth’s environment are closely tied to water. By accurately grasping the Earth’s water conditions, more accurate weather predictions are possible, and understanding slight changes to the Earth’s environment.
SHIZUKU(GCOM-W1) plays a key role in collecting various information of Earth’s water from outer space.
Professor Taikan Oki at the Institute of Industrial Science, University of Tokyo and a renowned authority in the field of hydrology, talks on the current situation of Earth’s water and his expectations of satellite SHIZUKU.

Professor Taikan Oki
Institute of Industrial Science, University of Tokyo

Regional water problems impacts the world.

-What is hydrology?

Oki: Just as astronomy is the study of everything about “astron” meaning “star” in Greek, hydrology is the study of everything about “hydro” meaning “water” in Greek.

I focus on 3 major themes- the impact of climate change on fresh water resources, researching the mechanism of flood prediction by clarifying the relationship between precipitation and flooding, and resolving water problems in overseas countries such as Southeast Asia.

Though the population in Japan is decreasing, it is increasing around the world. If the world population grows from the current 7 billion people to reach 9 or 10 billion, what can we do so that people live happily and securely?
This is going to be a mega challenge for humanity.

We should consider such problems from various perspectives such as climate change, social change and demographics.
I would like to contribute to such problems by studying the Earth’s water resources and water cycle.

-What kind of challenges do we have on water?

Oki: Firstly, water for drinking. It is estimated that there are 8 million people who do not have easy access to safe water for drinking. There are some people who need to walk at least 30 minutes to get safe water, or who are forced to drink water possibly including pathogens because of the lack of safe water sources. This poses a major challenge, and there are still many people who are in such situations.

Another problem is how to secure water resources for economic productivity. As the population increases and economic activities progress in many regions, water supplies for agriculture and manufacturing industries are going to be necessary. Securing such water resources without negatively influencing the environment is a big challenge.

Also, climate change is another. Recently in Japan, we had concentrated torrential downpour which we termed as “guerilla-like rainfall”. We think it is being caused by heat island phenomenon in the city and not by global warming for now, but if the global warming becomes worse, it will certainly increase.
To prevent damage due to heavy rain, we need to create a mechanism which can predict rainfall accurately

-The water problem does not appear to be that serious for Japan.

Oki: Perhaps we in Japan do not feel inconvenienced by water including drinking water. However, if we focus on food, the water problem becomes a topic that impacts us.
Food self-sufficiency in Japan is 40%, so we rely on other countries for the remaining 60%. This means, if any water problems such as drought occurs in countries that produces food, it effects food prices immediately, and can de-stabilize the food supply.

It also affects industries. Japanese companies have many factories offshore, so if floods happens there, it greatly impacts the price and supply of Japanese products. We are in a global supply chain, so any water problem in one region or country are likely to affect other regions or countries. That is the present world of global economies.

Combining information of “area” and “points”

-What is the meaning of observing water conditions of the Earth from SHIZUKU?

Oki: We have set many observation points on the ground. However, to set the observation equipment, we need to maintain the power source and network infrastructure at the same time. We risk equipment being stolen or damaged by animals in areas where nobody lives. Also, we need to obtain the data of the sea to know the water conditions on Earth, but it is difficult to set observation equipment at sea. And observation on Earth including on the ground and sea, just provides information by “points”.

Compared to this, SHIZUKU can observe over 99% of the Earth’s area in just 2 days. So we can get data by “area”. Detailed observation on the ground by “points” and an overview from observation by SHIZUKU by “area”. When we combine these two sets of data, we are able to get more accurate data about water and weather. The data contributes to improving forecast accuracy and understanding the current global environment.

-How is SHIZUKU’s data utilized in the study of hydrology?

Oki: Providing information to practical fields such as weather forecasts or fishery has already started. But in the field of research, we are still at the stage of defining how to utilize the data obtained by SHIZUKU.

The microwave sensor “AMSR2” installed in SHIZUKU has a generic function, and can collect various data depending on how it is to be utilized. Now we are collecting data such as precipitation, water vapor, wind speed and water temperature over the sea, water content of soil and depth of snow, and we can know more as we changed the combination of microwave frequency band. We are now considering what kind of data we need to get to know the Earth’s water’s conditions and what knowledge can be gained.

-How do you think SHIZUKU’s data would be useful in improving the Earth’s water challenges?

Oki: Firstly, I think it will be useful in maintaining the information infrastructure so as to prevent water crisis such as floods. The United States launched “GPM/DRP” on 28th February, 2014, to grasp the information of rainfall and snowfall.

We will be able to know the rain and snow conditions of the entire earth in near real time in collaboration with SHIZUKU and the US satellite. If we can announce the warning about rain and snow based on the data, it will help reduce damage.
Also, we anticipate understanding the impact of climate change on the ecosystem by continuing to observe over a long period of time. For this, SHIZUKU is needed to be in service continuously and climate change observed dynamically. The current SHIZUKU is the first satellite of Global Change Observation Mission (G-COM). The 2nd and 3rd satellites that succeeds it should carry on the activities. We hope that they continue to provide water information to us for decades to come.

Catching earth’s changes from outer space

-Have satellite technologies been used previously to grasp global environmental changes?

Oki: The Aral Sea salt lake spans Kazakhstan and Uzbekistan. In 1973, the satellite first observed that the water in this lake was beginning to decrease. In 2009, 36 years later, the water had decreased so much that there was almost no lake. Such changes become known because the satellite is continuing to observe.

The reason why the water of the Aral Sea salt lake had almost disappeared was obvious. It was because a lot of cotton farms had been set up upstream of the river which goes into the lake, using large amounts of water for irrigation. The image obtained by this satellite clearly showed that human activities can almost dry up a huge lake.

State of the Aral Sea
Right:2012 Left:2000

Oki: Also, satellite observations that began around 1979 revealed that ice of the Arctic Ocean had decreased in September 2012 by data obtained by SHIZUKU.
Without continuous satellite observations we would not have known about that too.

Changes in sea ice distribution of the Arctic Ocean.
Right: 16th September, 2012
Left: Average distribution during the period of smallest sea ice distribution in September 1980s

Oki: The information which we can get on the ground is really limited. On the Earth, there are many places that human eyes cannot reach. However, if we always have a perspective from space, we can catch the Earth’s change quickly and take actions against problems. Only earth observation satellites make this possible.

-What do you think is the meaning of Japan taking an active role in developing satellites?

Oki: In order to continue to make observations by satellites needs technology, funds and human resources. However there are not so many countries which have enough of them. Japan is one of the countries which have such resources.

The countries which have such capabilities should not only collect data from each satellites, but share the information globally, and contribute to resolving global problems such as environment, weather, food and disasters. Such a framework of international cooperation will become more important in the coming future. Japan must continue its commitment to the framework with pride. It is my belief that these are the most important meanings behind developing satellites.

-Could you describe your future research activities?

Oki: The Earth is being exposed to various risks now. Clarifying each risk and contributing to the environment so that human can live stably. I think we can establish a field like “Global risk management “. Such efforts would not be possible without the information from satellites. I have high hopes of satellite activities such as SHIZUKU.

Translated article originally written by Sho Nikaido April 9th, 2013

Taikan Oki

Professor at Institute of Industrial Science, University of Tokyo
Born in Tokyo in 1964, raised in Nishinomiya, Hyogo Prefecture.
Since 2006, professor at Institute of Industrial science, University of Tokyo.
Specializing in hydrology, especially climate change and global water cycle, and world water resource assessment considering virtual water trade.
Chief Author of the 5th Assessment report of the intergovernmental Panel on Climate Change (IPCC) and a member of the National Land Council.

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