Microsoft PowerPoint - RS環境情報学 I 掲載用.pptx

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Optical remote sensing

of atmospheric pollutants

大気汚染物質の光学的リモートセンシング

Center for Environmental Remote Sensing

(CEReS), Chiba University

Hiroaki Kuze, Professor, Dr.Sc.

[email protected]

1

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衛星画像の色の違い

110818 111007 130118 130131

（

AQUA/MODIS 500 m RGB）

違いの原因 Why these images look different -① 太陽高度が季節によって違う Solar elevation ② 地表面状態が違う（植生や積雪など） Ground coverage ③ 大気中の微粒子であるエアロゾルの量と性質が違う Cloud and aerosol 2

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吸収率％黒体放射

放射収支

_{(radiation budget) と大気の吸収}

窓領域入射 Incoming 5800 K 出射 Outgoing 280 K 平衡状態入射と出射のエネルギーのつり合い地表面 11 km 550 nm 10 m 3

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120913 15:14 130104 11:27

130112 12:30 121129 09:22

Change of sky color

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Rayleigh scattering and Mie scattering

clear sky cloud Mie scattering Rayleigh scattering - Air molecules (N₂, O₂, ..) - radius r <<  -- Scattering due to

induced electric dipole moment

4

1 /

)

(

Intensity





- Liquid or solid particles

(aerosol)

- radius r ~ 

-- Including refraction,

reflection, diffraction, etc.

p

)

/

(

Intensity



1 

5 p: Angstrom exponent

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レイリー散乱とミー散乱（

_{Rayleigh and Mie scattering）}

青空 (clear sky) 曇天（cloudy sky) Mie scattering Rayleigh scattering - 大気分子 (N₂, O₂, ..) - 半径 r << 波長  - 強度は - 光の電場によって誘起された電気双極子モーメントによる散乱 4

)

/

1 (





- 液体または固体粒子（エアロゾルと総称） - 半径 r ~ 波長  - 強度は - 反射、屈折、回折など複雑な効果を含んだ散乱 p

)

/

1 (





6 p: Angstrom指数

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Questions

Q1 Why colors are different from image to image?

Q2 Why distant mountains look blue?

Q3 Describe scattering processes in the atmosphere.

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2. Air pollution

大気汚染

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Vertical

structure of the

atmosphere

Thermosphere 熱圏 Mesosphere 中間圏 Stratosphere 成層圏 Troposphere 対流圏 ➣ Stratosphere is formed due to UV absorption of O₃. ➣ Molecular composition up to 80 km: N₂ (78 %) O₂ (21 %) H₂O (0.1 – 3 %) Ar (0.93 %) CO₂ (0.038 %) 380ppm Ne (0.0014 %) CH₄ (0.00017 %) 9

大気の鉛直構造

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航空機から見た雲

Encyclopedia Britannica 2007 Altitude (km) cirrus 巻雲 cirrocumulus cirrostratus altocumulus 高積雲 altostratus 高層雲 cumulonimbus 積乱雲 10

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The moderately long-lived species contribute to regional and urban air pollution and smog.

Space and time scales of atmospheric trace gases

大気汚染物質の時空間スケール

http://oceanworld.tamu.edu/resources/oceanography-book/atmosphere.html

The long-lived species contribute to the ozone hole and greenhouse warming.

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Urban smog: PM2.5

Los Angels Alberta, Canada

Beijing

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PM2.5, PM10 and SPM

➣ In USA, a new environmental standard of PM2.5 was added in 1997 to the existing standard of PM10.

➣ In Japan, the standard for PM10 was established in 1972. The

suspended particulate matter (SPM) was defined as particles with diameters less than 10 m.

http://www.nies.go.jp/kanko/news/20/20-5/20-5-05.html

Collection Efficiency

Particle Diameter (m)

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Andersen Sampler (Multi-stage cascade impactor)

http://www.h2.dion.ne.jp/~yokke/study/atmosphere/air_pm/air_pm.html Aerosol particles accumulate on a filter paper. 14

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Long-term trend of NO

₂

and SPM concentration

NO₂ concentration SPM concentration Roadside Roadside General General ppm mg/m 3

Ground sampling measurement at around 2000 stations (roadside: 500)

Environmental standard

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SO

₂

emission

1970-2010 0.035 ppm → 0.003 ppm (sampling station measurement) http://www.nies.go.jp/kanko/tokubetu/setsumei/sr-065-2006b.html kilo-ton SO₂ in 0.5o_×_0.5o mesh (2000) 16

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Global distribution of PM2.5

(g/m3₎

Donkelaar et al., http://ehp.niehs.nih.gov/0901623/

➣The global ground-level PM2.5 concentrations are mapped using total column aerosol optical depth (AOD) from the MODIS and MISR satellite instruments and coincident aerosol vertical profiles from the GEOS-Chem global chemical

transport model. Global estimates of long-term average (1 January 2001 to 31 December 2006) PM2.5 concentrations at approximately 10 km × 10 km

resolution indicate a global population-weighted geometric mean PM2.5 concentration of 20 µg/m3_.

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Asian dust event observed

on April 8, 2006

Aqua/MODIS visible band (RGB)

http://fujin.geo.kyushu-u.ac.jp/~hayasaki/

SPM distribution on the same day, (11:00, 14:00, and 23:00) observed at 1500 General (non-roadside) Stations.

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3. Solar radiation and

Rayleigh scattering

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Atmospheric perspective

大気遠近法

Solar spectrum – visible spectrum peaked at around 550 nm

(Blackbody Radiation at 5800 K)

Molecular Rayleigh scattering – enhanced blue color

Spectral reflectance of vegetation – in the

visible range, R_max ~ 15% (not very high) Observer

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分光反射率

_{Spectral reflectance}

・カオリナイト (Kaolinite) は陶磁器の材料となる白色の粘土質鉱物 ・オーク (Oak) とトウヒ (Spruce) 植生は、可視域では緑 (波長0.55 m付近) の反射を示し、その反射率は10 - 20%程度である。一方、波長0.7-1.3 mの近赤外での反射率は50-90%と 非常に大きくなっている。図は米国地質調査所のデータベースのデータによる： http://speclab.cr.usgs.gov/spectral.lib06/ds231/datatable.html Oak Spruce 21

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Irradiance and radiance

放射照度と放射輝度

E

[W/m

2

]

irradiance

Photon flux J = E / h



s-1m-2

Incident light beam

scattered light

L

[W m

-2

sr

-1

]

radiance

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立体角

_{solid angle}

○ In the case of plane the

angle is measured with the

length of the corresponding arc.

○ Since the periphery of a circle with radius r is 2



r, the

angle for the total plane can be calculated to be 2



(rad).

○ Since the total area of a sphere with radius

r is 4



r2, the solid

angle for total space is calculated to be 4



(sr).





d

r

dS

d





₂



sin

23

○ Solid angle is measured with the area subtended at the surface of a sphere.

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Questions

Q1 Why colors are different from image to image?

Q2 Why distant mountains look blue?

Q3 Describe scattering processes in the atmosphere.

Q4 Why the temperature increases in the stratosphere?

Q5 Describe species that are important for environmental pollution.

Q6 What is the difference between irradiance and radiance?

Q7 What’s new? – New concepts and facts you have learned from today’s lecture.