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Zacari Jardak
260327978
Major: Atmospheric and Oceanic Science
Japan 2011: Predicting Weather Patterns to Predict Radioactive Dispersion
The March 11th Honshu earthquake off Japan’s North-Eastern coast produced a large
tsunami that crippled much of the region. One of the most severe problems to emerge from
the event was the damage to the Fukushima nuclear power station, in Japan’s Fukushima
prefecture. As of March 14th, explosions began occurring at several of the plant’s reactors,
threatening to release radioactive material into the ground, air, and sea. In the following days,
the situation remained tense, as up to four of the plant’s six reactors were malfunctioning.
Reactor 2 was in the worse situation, with officials saying that it could even partially melt down.
With growing fears of a major nuclear accident at the Fukushima plant, Japan and to a
lesser extent, the rest of The World began fearing the possible consequences of such an
occurrence. More specifically, if radioactive material was released, how and where would it be
transported? What are the atmospheric (and oceanic) mechanisms that could transport this
material across an already suffering nation? Could the material travel overseas, and how?
These are the questions that were answered in my March 16th presentation, which
focused on the atmospheric and oceanic implications of the disaster at Fukushima. First I
outlined the geography of Japan and the surrounding areas, noting that the major Japanese
population centres lie to the Southwest of the ravished Fukushima reactors. Furthermore, major
international centres such as Seoul and Shanghai are in close proximity to Japan and may be
affected, were radiation to be spread. It is also important to note the nuclear plant’s extreme
proximity to the Pacific Ocean, facilitating the transportation of radioactive materials overseas
via the strong ocean current, Kuroshiro, that envelops the Northern Hemisphere portion of the
Pacific Ocean. Next, I gave a brief overview of the atmospheric mechanisms that could transport
radiation. More specifically, these are upper-level winds (including the jetsteam) surface winds,
and precipitation. Lastly, I focused my presentation on the practical application of this
knowledge, making qualitative weather forecasts for a five day period, to determine where any
radiation would be transported.
This paper will be divided into four sections, of which three will elaborate on the
meteorological subsections of my presentation as described above, including a description of
what was forecast, using tools provided by National Oceanic and Atmospheric Administration
(NOAA) and the Japanese Meteorological Agency (JMA). NOAA’s NCEP GFS Model provided a
forecast for both surface and upper-level winds, as well as precipitation. NOAA’s HYSPLIT
trajectory model calculated an integrated path that an air parcel would take, taking into account
meteorological variations that could influence the circulation of air. JMA provided local forecasts
for areas in Japan, that might be affected. Lastly, I will conclude with a brief follow-up looking at
the past ten days to see the outcome, in hindsight. A complete guide of meteorological
references as well as other references will be listed, after the conclusion.
1) Upper Level Winds:
Understanding how upper-level winds could transport radiation is relatively simple. Due
in part to the absence of friction (caused by topography, among other things) near the surface,
upper-level winds travel much faster than surface winds. They have the ability to transport
atmospheric material long distances, with little impediment. The most obvious upper-level wind
pattern to look at is commonly known as the jetstream. In reality, there is more than one, of
which Japan is directly affected by the polar jet, a large conveyor belt pattern that influences
global weather patterns in the Northern-hemisphere mid-latitudes. If any radioactive material
was able to ascend to the troposphere-stratosphere boundary, it would surely be transported by
upper-level winds. In the case of the upper-level patterns that affect Japan, the predominant
circulations are westerly (originating from the west, travelling to the east). That said, low levels
of radiation would be thought to be carried out to the Pacific Ocean, dissipating over time
(Cesium has a biological half-life of 70 days (Hyperphysics)). Higher doses of radiation, however,
could be transported across the ocean to the North-American West coast. In order to forecast
the upper-level wind tendency, I analyzed the GFS model’s forecasts over Asia, at the 250 hPa
level for both streamlines and wind and height (corresponding to the upper-troposphere,
roughly at jet-level). The analysis of the streamline map showed that air parcels generally had a
westerly trajectory over Japan. That said, I looked at upper-level winds and heights for further
evidence of a westerly upper-level trajectory. This map shows individual wind barbs, as well as
the location and movement of the polar jet. The upper-level winds and jet both propagated in a
westerly trajectory, over the 5-day period, analyzed. This was regarded as good news, suggesting
that any radiation, which at the time was fairly low, would be carried out to sea, had it reached
the upper-levels.
2) Surface Winds:
The effects of surface winds are slightly more complicated. Lower-level circulations are
susceptible to pressure systems that are in constant movement with the advection of warm or
cold air. They are affected by local geography and as previously mentioned, travel at slower
speeds than upper-level winds. Their effects, therefore, can be thought of as relatively smaller
in scale, compared to upper-level winds. Therefore, the best case scenario for the
transportation of radioactive material would be that none of it be spread to the surrounding
population centres. As mentioned before, the major Japanese population centres are located to
the southwest (with smaller ones such as Kyoto, to the northwest) of the Fukushima plant, and
Mainland Asia is located to the West. Therefore, it is desirable for surface winds to blow at a
straight westerly trajectory. To forecast the surface-level winds, I once again consulted NOAA’s
NCAR GFS model, this time at the 850 hPa level. This time, I looked at 3 maps, one for
streamlines, one of temperature, wind, and height, and one for vorticity. As was the case for the
upper-level winds, the surface-level streamlines revealed largely westerly flow, out of Japan,
which was regarded as good news. Upon analyzing the temperature, wind, and height map, I
observed that the general wind pattern was westerly, with the exception of a surface low
pressure system, moving over Japan, in the later stages of the forecast. This was supported by
the analysis of the map of vorticity, which showed cyclonic vorticity being advected into the
region. It is important to note that circulation around a low pressure system is clockwise. This is
slightly worrisome, as a wind that is initially westerly could be deflected either to the north or
the south (depending on where it is relative to the low) by the clockwise circulation of the low
pressure system. Nonetheless, this was generally seen as a minor problem. For another analysis
of the surface winds, I analyzed NOAA’s HYSPLIT trajectory model. The goal behind this was to
retrieve a more definitive integrated trajectory for an air parcel. The idea behind this particular
model, as explained in my presentation, was that the path of an air parcel is variable with time.
Its instantaneous trajectory is subject to change. I used the example of a low pressure system
tracking along an arbitrary route, influencing the path of an arbitrary air parcel. The HYSPLIT
model takes these variations into account and outputs a vector-like trajectory. The output given
during the presentation was favourable. I input the damaged reactors’ coordinates into the
model and it output a favourable trajectory that showed an air parcel (possibly carrying
radioactive material) being advected out to the Pacific Ocean, after initially dipping South, but
not far enough to reach Tokyo.
3) Precipitation:
Precipitation is generally not desired, for a situation involving radioactive particles. More
specifically, radioactive particles can mix with water vapour particles and can then be
transported by various weather systems. Once saturation has occurred, these particles are
scavenged and redistributed in the form of precipitation (usually rain). A low pressure system
moved over Japan, during the latter stages of the forecast period, as was observed when
forecasting the surface winds. It is important to note that cyclonic vorticity (as mentioned
above) acts to intensify a low pressure system. Generally, low pressure systems are favourable
to precipitation, as they can promote convection through the ascent of moisture. It was
therefore important to diagnose how much available moisture there was, over Japan. Once
again I used the GFS model, this time analyzing the relative humidity and precipitable water
maps. Unfortunately, the model forecast high relative humidity and significant amounts of
precipitable water in the region, during the latter stages of the forecast. To corroborate this, I
retrieved the local forecast, for the Fukushima prefecture, from the JMA. The forecast for the
March 21st did indeed call for rain in the area. The good news was still that the precipitation, for
the most part was due to leave the region.
4) Follow-up and conclusion:
The goal of my presentation was to see where any radiation released by the damaged
Fukushima nuclear power plant would go, by forecasting and interpreting various metrological
phenomena. I concluded that the short range outcome was reasonably favourable. Both upper
and lower-level winds were generally forecast to blow out to sea, away from major population
centres. The precipitation that was predicted wasn’t forecast to linger in the area, minimizing
any possible negative outcomes. Unfortunately, in the time that has passed since my
presentation, the situation has not improved. Traces of radiation have been detected in the local
water supply and contaminated vegetables grown in the Fukushima region are no longer being
exported to many countries (CBC, 2011), and just recently, traces of plutonium were found in
the ground, at the embattled power station (The Guardian, 2011), indicating that the
containment vessels have likely been breached. Negligible levels of radiation have also been
detected in British Columbia (The Province, 2011).
References:
Meteorogical References:
NOAA NCEP:
National Centres for Environmental Prediction (2011). Model Analysis and Guidance. Retrieved
on March 16th 2011, from
http://mag.ncep.noaa.gov/NCOMAGWEB/appcontroller?prevPage=Model&MainPage=index&model=GF
S&area=&areaDesc=&page=Model&prevModel=&prevArea=&currKey=model&prevKey=model&cat=MO
DEL+GUIDANCE
NOAA HYSPLIT:
Air Resources Laboratory (2011). HYSPLIT Trajectory Model. Retrieved on March 16th, 2011, from
http://ready.arl.noaa.gov/hysplit-bin/trajtype.pl
JMA:
Justin Meteorological Agency. Weather Forecasts and Analysis. Retrieved on March 16th, 2011,
from http://www.jma.go.jp/en/yoho/313.html
News References:
Hyperphysics. Biological Half-life.
http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/biohalf.html
(accessed on March 31st, 2011)
McCurry, Justin. (2011, March 29). Fukushima Soil Contains Plutonium Traces, According to
Japanese Officials. The Guardian.
http://www.guardian.co.uk/world/2011/mar/29/japan-fukushima-plutonium-traces-soil (accessed on
March 31st, 2011).
Staff Reporter. (2011, March 22). ‘Negligible’ Amounts of Radiation Detected in B.C. The
Province.
http://www.theprovince.com/news/Negligible+amount+radiation+detected/4480058/story.html
(accessed on March 31, 2011).
CBC News. (2011, March 23). Japan Radiation Fears Limit Food Exports.
http://www.cbc.ca/news/world/story/2011/03/23/japan-food-water-safety.html
(accessed on March 31st, 2011).