NANJING UNIVERSITY OF INFORMATION SICENCE & TECHNOLOGY

Eddy Covariance measurement on Lake Taihu

Wei Xiao, Xuhui Lee, Jingming ChenShoudong Liu, Wei Wang

Motivation of the research

• As a big shallow lake (~2m depth & ~2460 km2), Lake Taihu should have significant effect on regional weather processes and climate change.

• The surface parameterization in weather forecasting model was not validated due to the lack of detailed measurement.

• Algae bloom is a big environmental problem for Lake Taihu and the basin, but the meteorological and ecological mechanisms controlling the algae bloom were not clearly identified.

• As a powerful tool in land ecosystem research, only a few papers reports the use of eddy covariance method in lake ecosystem.

History meteorology in the Taihu Basin

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 201015

15.5

16

16.5

17

17.5

18

Year

Air

tem

pera

ture

at 2

m, d

eg C

58358Dongshan

31.04N,120.2 6E

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 20102.8

3

3.2

3.4

3.6

3.8

4

4.2

4.4

Year

Win

d sp

eed,

m s

-2

58358 Dongshan

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 20100

200

400

600

800

1000

1200

1400

1600

1800

Year

Pre

cipi

tatio

n, m

m

58358 Dongshan Temperature increased and wind speed decreased in the past 50 years.

Similar trends were found in almost all the land meteorology site.

Buoy

Eddy covarince

In-lake platform

Microwave radar/Lidar

Surface Met station

Ship-borne isotopemeasurement

Helicopter profiling

Automated surface station

Buoy

Eddy covariance system

Microwave radar/lidar

Helicopter Profiling Ship-borne isotope measurement

Data Center

NUIST & other collaborators

Suzhou Met Bureau

In-lake platform

Our Experimental Site

NANJING UNIVERSITY OF INFORMATION SICENCE & TECHNOLOGY

EC

microclimate

raingaugedataloggerAC

water temp

EC and microclimate measurement at Taihu site

NANJING UNIVERSITY OF INFORMATION SICENCE & TECHNOLOGYEC installation

NANJING UNIVERSITY OF INFORMATION SICENCE & TECHNOLOGY

EC system

south

southeast

3.57m

EC system

NANJING UNIVERSITY OF INFORMATION SICENCE & TECHNOLOGY

Microclimate system

Total radiation

Temp and humidity

Wind speed and direction

Solar power

NANJING UNIVERSITY OF INFORMATION SICENCE & TECHNOLOGYWater temp

NANJING UNIVERSITY OF INFORMATION SICENCE & TECHNOLOGY

Water surface

20cm100cm

50cm

Water temp

Wind direction

160 180 200 220 240 260 280 300 320 3400

50

100

150

200

250

300

350

DOY of 2010

Win

d di

rect

ion,

deg

Good fetch: wind direction 90~270o, 48%

Energy budget

0 4 8 12 16 20 240

20

40

60

80

100

120

140

160

180

200

Time (hour)

Late

nt h

eat f

lux,

W m

-2

JuneJulyAugustSeptemberOctoberNovember

0 4 8 12 16 20 24-5

0

5

10

15

20

25

30

35

40

45

Time (hour)

Sen

sibl

e he

at fl

ux, W

m-2

JuneJulyAugustSeptemberOctoberNovember

June 0.25July 0.19August 0.17September 0.30October 0.17November 0.18

Monthly Bowen ratio

Lake-land CO2 exchange

0 4 8 12 16 20 24-0.2

-0.1

0

0.1

Time (hour)

Net

CO

2 exc

hang

e, m

g m

-2 s

-1

JuneJulyAugustSeptemberOctoberNovember

229 230 231 232 233 234 235 236 237-0.2

-0.15

-0.1

-0.05

0

DOY of 2010

NE

E, m

g m

-2 s

-1

Solar angle and cloudiness are the main drivers of abledo variations. We need to identify the effect of water quality on water suface albedo.

Water albedo

-10 0 10 20 30 40 50 60 70 80 900

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Solar elevation angle, rad

Alb

edo

JuneJulyAugustSeptemberOctoberNovemberHenderson-sellers Simulation

223 224 225 226 227 228 229 230 231 232 23329

30

31

32

33

34

35

36

DOY of 2010

Tem

pera

ture

, deg

C

20cm depth50cm depth100cm depth150cm depthLake bottom

160 180 200 220 240 260 28020

22

24

26

28

30

32

34

DOY of 2010

Wat

er te

mpe

ratu

re, d

eg C

Water temperature

164 166 168 170 172 174 176 178

22

24

26

28

30

32

Wat

er te

mpe

ratu

re, d

eg C

184 186 188 190 192 194 196 198

22

24

26

28

30

32

DOY of 2010

Wat

er te

mpe

ratu

re, d

eg C

100cm depth50cm depth20cm depth

Net radiation siteNet radiation site