2012/5/22 1

Analyzing the impact of climate change on seagrass and coral by using remote sensing techniques

South china sea institute of oceanology

Yang Dingtian

dtyang@scsio.ac.cn; dtdang@tom.com

013710103198

2012/5/22 2

1、questions

Greenhouse effect Sea level change

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Coral in Sanya Bay

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Coral in Yalong Bay

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Coral in little east sea

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Coral Reef Bleaching

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Temperature and coral calcification

Left coordinate is sea surface temperature; right is calcification rate

8

Remote sensing techniques

jidi

si

z z, limlim

ji

00

ijdi

iz

j

water

u zlimlim,ji

00

dzdzzkzzEzzdE surfsurfdsurfwateru ,2exp,,

2

324

00 8350190 cos.,,

.

ww

),(~

)(b),( ppp

2/32

2

cos21

1

4

1~

HG

2

1

2/12

23

32.4

00

cos21

1

2cos

3

835.0cos,902

2

12exp

),(

,,0

gg

g

g

b

k

zzkQ

zzE

zzEQR p

wsurf

surfd

surfwateruwater

rs

1 RTE model

θ0

ψ1

ψ2

waterEu

(z,λ)

c

o

α0

△Z

Y

z

layer_S

Ed(z,λ)

FOV

Assumption: multi-layer system, each layer of which was described by different optical characteristics. The effect of each water layer on its bottom substrate is determined by flux of multiple scattering and absorption.

1 RTE model

p

O

C

△Ωj

ω

n

Ψ

△zi

φdi

φsi

jidi

si

z z, limlim

ji

00

ijdi

iz

j

water

u zlimlim,ji

00

We assume the layer is divided into innumerable infinitesimals.

And, the jth infinitesimal scattering volume

The spectral volume scattering function

The scattered flux

1 RTE 模型

dzdzzkzzEzzdE surfsurfdsurfwateru ,2exp,,

2

324

00 8350190 cos.,,

.

ww

),(~

)(b),( ppp

2/32

2

cos21

1

4

1~

HG

2

1

2/12

23

32.4

00

cos21

1

2cos

3

835.0cos,902

2

12exp

),(

,,0

gg

g

g

b

k

zzkQ

zzE

zzEQR p

wsurf

surfd

surfwateruwater

rs

Figure (a) Comparison of the in situ measured bottom reflectance with subsurface reflectance;

X-axis shows the reflectance of coral reef measured in Sanya Bay in 2011; Y-axis shows the

subsurface reflectance in situ measured. (b) The experimental reflectance of coral reefs, plotted

with the corresponding values retrieved by the semi-empirical model; X-axis shows the

reflectance of coral reef measured in Sanya Bay in 2011; Y-axis shows the bottom reflectance

calculated with equation (4) following the procedure mentioned in water column correction

algorithm section.

seagrass

Normalized Difference Vegetation Index

RNDVI=(NIR-Red)/(NIR+Red)

NIR-740 nm， Red-660 nm;

GNDVI=(NIR-Green)/(NIR+Green)

Green-550 nm

BNDVI=(NIR-Blue)/(NIR+Blue)

Blue-450 nm

BNDVI,GNDVI和RNDVI increased with LAI

sensitivity of different indexes to LAI is different

LAI

0 1 2 3 4 5 6

VN

DV

I

-1.0

-.8

-.6

-.4

-.2

0.0

.2

R NDVI

B NDVI

G NDVI

R NDVI

G NDVI

B NDVI

r2=0.6705

r2=0.6729

r2=0.7357

coefficient of determination between GNDVI and LAI is relatively larger.

LAI

0 1 2 3 4 5 6

VN

DV

I

-1.0

-.8

-.6

-.4

-.2

0.0

.2

R NDVI

B NDVI

G NDVI

R NDVI

G NDVI

B NDVI

r2=0.6705

r2=0.6729

r2=0.7357

校正模型在海草遥感监测中的应用

summarize

leaving a plateau-like shape between 600 and 650 nm

triple-peaked pattern

2 1

2

st st

rs rs

st

rs

R RPRI

R

The most probable values of the index occupy the range from -0.15 to -0.05 (85.8 %). ). For

comparison, PRI for sand has a value of 0.18, for seagrass is -0.038, and for deep water is -

8.48.

75% of the healthy coral second derivative values at 556 nm were positive which was validated by in situ visual assessment.

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Sanya bay

GuangX

i GuangDong

HaiNa

n Sanya

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Distribution of coral reef in sanya bay

109.35 109.4 109.45 109.5 109.55

18.15

18.2

18.25

18.3

S01

S03 S04

S05

S07

S08

S09

S11

S12S13S14

S15

S16

S17

S18

S19

S20

S31

站位图例

一般珊瑚礁调查

鱼类调查

浮游生物调查

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DISTRIBUTION OF CORAL REEF

b3

East island - sanyabay

West island-sanya bay

1990 2004

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Coral cover

1990 1993-941998-99 2001 2002 2002~04 2007

15

20

25

30

35

40

45

cora

l cov

erag

e(%

)

In situ observation year

;但在1998年依然受到很大影响,出现明显的下降.之后一直下降.

National Nature Conservation

was established in 1990

el nino

Coral species

1962-65 1975 1992-93 2006 2010

50

60

70

80

90

100

110

120

Cor

al s

peci

es

In situ observation year

1990年建立自然保护区

the number of coral species

increased

1 Remote sensing technique can be an effective tool to analyze the impact of climate change on seagrass or coral reef.

2 water column corrections are needed to be done before bottom mapping.

3 RTE model can be used to remove the water column effects

4 NDVI can be used to retrieve seagrass informations

5 coral coverage decreased in sanya bay

summary

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thank you