deposed on the ground (“ground-shine”). The plume-shine usually
is responsible for peak values (high but during a short time),
whereas the ground-shine corresponds to the gamma dose-rate
measured after the plume departure. Hence, the most numerous
gamma-dose rate observations correspond to ground-shine, which
decreases slowly due to radioactive decay. The decrease rate of
this residual gamma dose rate depends on the radioisotopes
deposed on the ground, and on their respective half-life times.
Therefore, “classical” indicators such as FAC2 and FAC5 mainly
depend on the simulation’s ability to forecast deposition, isotopic
composition and subsequent decay. In case of an accidental release
of radionuclides, an operational simulation should be able to
forecast peak values, since they represent an important part of
human exposure (through direct radiation and inhalation), and
plume arrival times (i.e. the first date when the gamma dose rate
value is higher than background value). In the following, we will
focus on (1) bias on peak values, (2) plume arrival times and (3)
FAC2, FAC5 and FMT. Comparisons are made on hourly-averaged
values.
Table 2 gives an overview of the model’s performance for each
station. Peak values are within less than a factor of two, except for
Iwaki, Daini and Minamisoma, where it is overestimated by a factor
of five. These three stations are located close to the coast,
where the meteorological model often has difficulties forecasting
the wind field. Besides, for the two events responsible for the
peaks (event 1 for Minamisoma and event 4 for Daini and Iwaki),
the meteorological conditions were very stable. Thus, the plume
was very thin, and uncertainties in the wind field, station location,
and/or release height would have a large impact on the result. At
Minamisoma and Iwaki, gamma dose-rate measurements are only
available every hour during the main releases periods (prior to
March 16). Simulations show a high temporal variability, especially
during the plume passage, indicating that the temporal frequency
of observations may not be sufficient. The temporal resolution of
the wind field (3 h) is also too coarse to account for the wind
variability.
On the other stations, the peak values are very well reproduced,
although a delay of 6 h in the plume arrival time is
observed on the northwestern stations Iitate and Fukushima. At
Funehiki, there were no observations at the simulated peak
times, and the air dose-rate due to deposition is overestimated
by more than a factor of five. For all other stations except Iwaki,
more than 80% of simulated values are within a factor 5 of the
observations, and the FAC2 is also very good, especially at the
northwestern stations. Fig. 4 shows the model-to-data comparisons
of gamma dose rate values, for the eight monitoring stations,
hour-by-hour. A few singular values are underestimated,
especially at Iitate and Fukushima, due to the delay in the plume
arrival time.
3.1.2. Temporal analysis on stations
Fig. 5 shows the temporal evolution on four of these stations:
two are representative of a high contamination level due to wet
deposition (Iitate and Fukushima), and two stations where little
wet deposition occurs (Minamisoma and Kawauchi). The latter
show a time series with several peaks corresponding to plumes
coming through the station, and little deposition, while the former
show a high contamination by deposition, with a decrease rate
over time essentially due to radioactive decay of the deposed
isotopes.
At Minamisoma and Kawauchi (Fig. 5(a) and (b)), most peaks
are simulated, with a small delay and some overestimation at
Kawauchi. Missing peaks are probably due to inaccuracies in the
source term, but are small compared to the initial contamination.
These two stations illustrate the difficulty to correctly
represent both peak values and deposition: at
Minamisoma, the peak value is overestimated but the deposition
is correctly forecast, while at Kawauchi, the peak value is much
better reproduced but the deposition is overestimated after
March 22nd. At Iitate and Fukushima, the dose rates are well
reproduced, except for the initial delay in the plume arrival (6 h).
This delay is also found by other simulations (Katata et al., 2012).
Fig. 6 illustrates the contamination processes at two ty
deposed on the ground (“ground-shine”). The plume-shine usually
is responsible for peak values (high but during a short time),
whereas the ground-shine corresponds to the gamma dose-rate
measured after the plume departure. Hence, the most numerous
gamma-dose rate observations correspond to ground-shine, which
decreases slowly due to radioactive decay. The decrease rate of
this residual gamma dose rate depends on the radioisotopes
deposed on the ground, and on their respective half-life times.
Therefore, “classical” indicators such as FAC2 and FAC5 mainly
depend on the simulation’s ability to forecast deposition, isotopic
composition and subsequent decay. In case of an accidental release
of radionuclides, an operational simulation should be able to
forecast peak values, since they represent an important part of
human exposure (through direct radiation and inhalation), and
plume arrival times (i.e. the first date when the gamma dose rate
value is higher than background value). In the following, we will
focus on (1) bias on peak values, (2) plume arrival times and (3)
FAC2, FAC5 and FMT. Comparisons are made on hourly-averaged
values.
Table 2 gives an overview of the model’s performance for each
station. Peak values are within less than a factor of two, except for
Iwaki, Daini and Minamisoma, where it is overestimated by a factor
of five. These three stations are located close to the coast,
where the meteorological model often has difficulties forecasting
the wind field. Besides, for the two events responsible for the
peaks (event 1 for Minamisoma and event 4 for Daini and Iwaki),
the meteorological conditions were very stable. Thus, the plume
was very thin, and uncertainties in the wind field, station location,
and/or release height would have a large impact on the result. At
Minamisoma and Iwaki, gamma dose-rate measurements are only
available every hour during the main releases periods (prior to
March 16). Simulations show a high temporal variability, especially
during the plume passage, indicating that the temporal frequency
of observations may not be sufficient. The temporal resolution of
the wind field (3 h) is also too coarse to account for the wind
variability.
On the other stations, the peak values are very well reproduced,
although a delay of 6 h in the plume arrival time is
observed on the northwestern stations Iitate and Fukushima. At
Funehiki, there were no observations at the simulated peak
times, and the air dose-rate due to deposition is overestimated
by more than a factor of five. For all other stations except Iwaki,
more than 80% of simulated values are within a factor 5 of the
observations, and the FAC2 is also very good, especially at the
northwestern stations. Fig. 4 shows the model-to-data comparisons
of gamma dose rate values, for the eight monitoring stations,
hour-by-hour. A few singular values are underestimated,
especially at Iitate and Fukushima, due to the delay in the plume
arrival time.
3.1.2. Temporal analysis on stations
Fig. 5 shows the temporal evolution on four of these stations:
two are representative of a high contamination level due to wet
deposition (Iitate and Fukushima), and two stations where little
wet deposition occurs (Minamisoma and Kawauchi). The latter
show a time series with several peaks corresponding to plumes
coming through the station, and little deposition, while the former
show a high contamination by deposition, with a decrease rate
over time essentially due to radioactive decay of the deposed
isotopes.
At Minamisoma and Kawauchi (Fig. 5(a) and (b)), most peaks
are simulated, with a small delay and some overestimation at
Kawauchi. Missing peaks are probably due to inaccuracies in the
source term, but are small compared to the initial contamination.
These two stations illustrate the difficulty to correctly
represent both peak values and deposition: at
Minamisoma, the peak value is overestimated but the deposition
is correctly forecast, while at Kawauchi, the peak value is much
better reproduced but the deposition is overestimated after
March 22nd. At Iitate and Fukushima, the dose rates are well
reproduced, except for the initial delay in the plume arrival (6 h).
This delay is also found by other simulations (Katata et al., 2012).
Fig. 6 illustrates the contamination processes at two ty
การแปล กรุณารอสักครู่..
deposed on the ground (“ground-shine”). The plume-shine usually
is responsible for peak values (high but during a short time),
whereas the ground-shine corresponds to the gamma dose-rate
measured after the plume departure. Hence, the most numerous
gamma-dose rate observations correspond to ground-shine, which
decreases slowly due to radioactive decay. The decrease rate of
นี้เหลืออัตราปริมาณรังสีแกมมาขึ้นอยู่กับไอโซโทปกัมมันตรังสี
อดีตบนพื้นดินและบนเวลาครึ่งชีวิตของตน .
ดังนั้นตัวบ่งชี้ " คลาสสิก " เช่น fac2 fac5
และส่วนใหญ่ขึ้นอยู่กับการเลียนแบบของความสามารถในการคาดการณ์การสะสม องค์ประกอบของไอโซโทป
และภายหลังการสลายตัว ในกรณีของการเกิดอุบัติเหตุของ
ปล่อยสารกัมมันตรังสี , การจำลองการดำเนินงานควรจะ
ค่า peak คาดการณ์ เนื่องจากพวกเขาเป็นส่วนสำคัญของการเป็นมนุษย์
( ผ่านรังสีโดยตรง และสูดดม ) และ
ขนนกมาถึงครั้ง ( เช่นวันแรกเมื่อค่าอัตราปริมาณรังสีสูงกว่าค่า
พื้นหลัง ) ในต่อไปนี้เราจะ
เน้น ( 1 ) มีอคติกับคุณค่าสูงสุด ( 2 ) ขนนกมาถึงครั้ง และ ( 3 )
fac2 fac5 FMT , และ . การเปรียบเทียบจะทำในแบบรายชั่วโมงเฉลี่ย
ค่าTable 2 gives an overview of the model’s performance for each
station. Peak values are within less than a factor of two, except for
Iwaki, Daini and Minamisoma, where it is overestimated by a factor
of five. These three stations are located close to the coast,
where the meteorological model often has difficulties forecasting
the wind field. Besides, for the two events responsible for the
ยอด ( 1 minamisoma เหตุการณ์และเหตุการณ์ที่ 4 และ อิวากิ ไดนิ )
เงื่อนไขทางอุตุนิยมวิทยามีเสถียรภาพมาก ดังนั้น ขนนก
ผอมมาก และความไม่แน่นอนของลมในเขตที่ตั้งสถานี
และ / หรือความสูงปล่อยจะมีผลกระทบมากต่อผล ที่ minamisoma
และวัดอัตราปริมาณรังสีแกมมา อิวากิ เท่านั้น
ใช้ได้ทุกชั่วโมงในช่วงระยะเวลารุ่นหลัก ( ก่อน
16 มีนาคม )จำลองแสดงความแปรปรวนสูงชั่วคราว โดยเฉพาะ
ในระหว่างขนนกเรียง แสดงว่าเวลาความถี่
สังเกตอาจไม่เพียงพอ ความละเอียดที่ขมับของ
สนามลม ( 3 ชั่วโมง ) ยังหยาบเกินไปที่จะบัญชีสำหรับลม
ในความผันแปร สถานี อื่น ๆ , ยอดค่าเป็นอย่างดีถึงแม้ว่าการทำซ้ำ
6 H ในขนนกมาถึงเวลา
observed on the northwestern stations Iitate and Fukushima. At
Funehiki, there were no observations at the simulated peak
times, and the air dose-rate due to deposition is overestimated
by more than a factor of five. For all other stations except Iwaki,
more than 80% of simulated values are within a factor 5 of the
observations, and the FAC2 is also very good, especially at the
สถานีวิทยุภาคตะวันตกเฉียงเหนือ รูปที่ 4 แสดงรูปแบบข้อมูลการเปรียบเทียบอัตราปริมาณรังสีแกมมา
ของค่านิยม ในแปดตรวจสอบสถานี
ชั่วโมงโดยชั่วโมง เป็นค่าเอกพจน์น้อยจะ underestimated ,
โดยเฉพาะไอ ตาเตะจากเนื่องจากความล่าช้าในการมาถึงขนนก
.
3.1.2 . การวิเคราะห์ชั่วคราวสถานี
รูปที่ 5 แสดงให้เห็นถึงวิวัฒนาการ และสี่ จากสถานีเหล่านี้ :
two are representative of a high contamination level due to wet
deposition (Iitate and Fukushima), and two stations where little
wet deposition occurs (Minamisoma and Kawauchi). The latter
show a time series with several peaks corresponding to plumes
coming through the station, and little deposition, while the former
show a high contamination by deposition, with a decrease rate
over time essentially due to radioactive decay of the deposed
isotopes.
At Minamisoma and Kawauchi (Fig. 5(a) and (b)), most peaks
are simulated, with a small delay and some overestimation at
Kawauchi. Missing peaks are probably due to inaccuracies in the
source term, but are small compared to the initial contamination.
These two stations illustrate the difficulty to correctly
represent both peak values and deposition: at
Minamisoma, the peak value is overestimated but the deposition
is correctly forecast, while at Kawauchi, the peak value is much
better reproduced but the deposition is overestimated after
March 22nd. At Iitate and Fukushima, the dose rates are well
reproduced, except for the initial delay in the plume arrival (6 h).
This delay is also found by other simulations (Katata et al., 2012).
Fig. 6 illustrates the contamination processes at two ty
การแปล กรุณารอสักครู่..