Is Climate Change in Asia-Pacific Attributed to Human Activities?Is Climate Change in Asia-Pacific Attributed to Human Activities?

Chang-Hoi HoSchool of Earth and Environmental Sciences

Seoul National University

Chang-Hoi HoSchool of Earth and Environmental Sciences

Seoul National University

2

AcknowledgmentsAcknowledgments

Main collaborators Climate Physical Laboratory, Seoul National

University, Korea: Drs. Y.-S. Choi, J.-H. Kim, J.-H. Jeong- Website: http://cpl.snu.ac.kr

Bejing Normal University, China: Prof. D.-Y. Gong National Central University, Taiwan: Prof. C.-H. Sui Ewha Womans University, Korea: Prof. Seon-Ki Park University of California, Los Angeles, USA: Dr. J. Kim Seoul National University, Korea: Prof. R. J. Park

3

Ho, C.-H., J.-Y. Lee, M.-H Ahn, and H.-S. Lee, 2003: A sudden change in summer rainfall characteristics in Korea during the late-1970s. International Journal of Climatology, 23, 117−128.

Changes in the rainfall distribution of KoreaChanges in the rainfall distribution of Korea

4

5-year average precipitation and number of rainy days during summer for rain rate 1 mm day-1 (a) and rain rate 30 mm day-1 (b). Solid line indicates the number of rainy days and bar represents the summer total precipitation.

5

Daily precipitation contributed by typhoonDaily precipitation contributed by typhoon

0

100

200

300

1950 1960 1970 1980 1990 2000Year

Pre

cipitation (

mm

/day)

1 0 0 E 1 2 0 E 1 4 0 E 1 6 0 E 1 8 0 E

0 N

2 0 N

4 0 N

6 0 N

E q

Kim, J.-H., C.-H. Ho, M.-H. Lee, J.-H. Jeong, and D. Chen, 2006: Large increase in heavy rainfall associated with tropical cyclone landfalls in Korea after the late 1970s. Geophysical Research Letters, 33, L18706, doi:10.1029/2006GL027430.

6

Long-term change in summer rainfallLong-term change in summer rainfall

Ho, C.-H., J.-H. Kim, K.-M. Lau, K.-M. Kim, D.-Y. Gong, and Y.-B. Lee, 2005: Interdecadal changes in heavy rainfall in China during the northern summer. The Journal of Terrestrial, Atmospheric and Oceanic Sciences, 16, 1163−1176.

100E 105E 110E 115E 120E 125E 130E20N

25N

30N

35N

40N

45N

Latitu

de

Longitude100E 105E 110E 115E 120E 125E 130E

20N

25N

30N

35N

40N

45N

Longitude

Latitu

de

(a) Total rainfall (b) Accumulative rainfall(≥30mm/day)

Difference (1980-95 minus 1961-79)

100E 105E 110E 115E 120E 125E 130E20N

25N

30N

35N

40N

45N

Latit

ude

Longitude100E 105E 110E 115E 120E 125E 130E

20N

25N

30N

35N

40N

45N

Longitude

Latit

ude

(a) Total rainfall (b) Accumulative rainfall(≥30mm/day)

Difference (1980-95 minus 1961-79)

(Cases for (Cases for 0.1 mm/day) 0.1 mm/day) (Cases for (Cases for 30 mm/day) 30 mm/day)

7

1 0 0 E 1 2 0 E 1 4 0 E 1 6 0 E 1 8 0 E0 N

1 0 N

2 0 N

3 0 N

4 0 N( a) 1 9 5 8 -7 9

1 0 0 E 1 2 0 E 1 4 0 E 1 6 0 E 1 8 0 E0 N

1 0 N

2 0 N

3 0 N

4 0 N(b ) 1 9 8 0 -9 9

Gong, D.-Y. and C.-H. Ho, 2002: Shift in the summer rainfall over the Yangtze river valley in the late 1970s, Geophysical Research Letters, 29, 78.

5870 gpm contour lines for each summer5870 gpm contour lines for each summer

8

-11 to -7

-7 to -4

-4 to -2

-2 to -1

1 to 2

2 to 4

4 to 7

< -7

1980- 2001 minus 1951- 1979 (%)

Recent summer-mean 500-hPa 5870m gpm

Previous one

Increase

decrease

decreaseIncrease

Interdecadal variability of TC tracksInterdecadal variability of TC tracks

Ho, C.-H., J.-J. Baik, J.-H. Kim, D.-Y. Gong, and C.-H. Sui, 2004: Interdecadal changes in summertime typhoon tracks. Journal of Climate, 17, 1767−1776.

9

SummarySummary

A number of our findings indicate the presence of considerable changes in summertime rainfall, typhoon, and large-scale circulation over East Asia.

However, the periods of the data are limited to the past few decades. Thus it remains insoluble whether these changes are due to climate change or climate variation.

Is there any decisive evidence showing that human activities alter the climate system?

Some studies on rain-aerosol relation over ChinaSome studies on rain-aerosol relation over China

Choi, Y.-S., C.-H. Ho, D.-Y. Gong, R. J. Park, and J. Kim, 2007, The Impact of Aerosols on the Summer Rainfall Frequency in China, Journal of Applied Meteorology and

Climatology (in press).

Choi, Y.-S., C.-H. Ho, D.-Y. Gong, R. J. Park, and J. Kim, 2007, The Impact of Aerosols on the Summer Rainfall Frequency in China, Journal of Applied Meteorology and

Climatology (in press).

11Long-term trend of the rainfall event in summer

and the increase in air pollution

Long-term trend of the rainfall event in summer

and the increase in air pollution

80E 90E 100E 110E 120E 130E

20N

30N

40N

50N

80E 90E 100E 110E 120E 130E

20N

30N

40N

50N

1955 1979

1980 2005

< 6 6 ~ 3 3 ~ 0

0 ~ 33 ~ 66

-16 to -6 -6 to -3 -3 to 0 0 to 3 3 to 6 6 to 16

80E 90E 100E 110E 120E 130E

20N

30N

40N

50N

80E 90E 100E 110E 120E 130E

20N

30N

40N

50N

1955 1979

1980 2005

< 6 6 ~ 3 3 ~ 0

0 ~ 33 ~ 66

-16 to -6 -6 to -3 -3 to 0 0 to 3 3 to 6 6 to 16

< 6 6 ~ 3 3 ~ 0

0 ~ 33 ~ 66

-16 to -6 -6 to -3 -3 to 0 0 to 3 3 to 6 6 to 16

Southern China (from Cheng et al. 2005)

Long-term trend of the number of rainfall event (in days/10-yr) in summer for 1955−1979 (upper) and 1980−2005 (lower).

The red (blue) circle indicates positive (negative) value. Stations significant at the 90% level are indicated by filled circles. In contrast to the situation before 1979, the number of rainfall event has rapidly decreased since 1980.

12

Different aerosol effects on precipitationDifferent aerosol effects on precipitation

Indirect Effect

OHSO2 + H2SO4

Increase cloud droplets

Reduce cloud droplet

sizeBrighter Cloud

Semi-direct Effect

Burn cloud droplets by UV absorption

2) increase cloud lifetime, suppress warm precipitation

3) more aerosols and moisture are allowed to reach higher altitudes by updrafts, more cold precipitation from intense convective storms

BC aerosols heat up the low-level atmosphere, and stabilize

it 1) suppress

warm precipitation

13The increase in aerosol concentrations in China, via aerosol indirect and semi-direct effects, may

affectthe long-term variations in precipitation

The increase in aerosol concentrations in China, via aerosol indirect and semi-direct effects, may

affectthe long-term variations in precipitationEastern-central China (Zhao et al. 2006 GRL)Eastern-central China (Zhao et al. 2006 GRL)Southern China (Cheng et al. 2005 JC)Southern China (Cheng et al. 2005 JC)

14The long-term trend of precipitation and aerosol

and scientific question

The long-term trend of precipitation and aerosol

and scientific question

Question

Increased aerosol reduced precipitation

(Zhao et al. 2006 GRL)

Or

Less precipitation more aerosol in the air

15

Employed surface PM10 observationsEmployed surface PM10 observations

Air pollution Index (API) data Period: June 5, 2000 to July 31, 2006 (summers only) Available online at http://www.sepa.gov.cn/quality/air.php3

90E 100E 110E 120E 130E

20N

30N

40N

50N

Beijing

Shanghai

Guangzhou

Chengdu

PM10 station

PM10 and precipitation station

16

Aerosol-precipitation interactionAerosol-precipitation interaction

The significant correlation suggests that the increase in aerosol concentration

increases rainfall frequency, which in turn removes aerosols from the atmosphere. This process is referred to “aerosol self-cleansing

effect”.

17

Relation with MODIS cloud propertiesRelation with MODIS cloud properties

Aerosol concentration (g/m3)

0 40 80 120 160 200

Clo

ud

co

ver

(%)

0

10

20

30

4060

80

Total R = 0.95

Water R = 0.95

Ice R = 0.68

Mixed R = 0.85

Aerosol concentration (g/m3)

0 40 80 120 160 200

Ice

clou

d e

ffec

tive

radi

us ( m

)

23

24

25

26

27

28

Wat

er c

loud

eff

ect

ive

rad

ius

(m

)

14

15

16

17

18

19

Water

Ice

a

d

c

e f

b

18

Rainfall intensity-aerosol relationshipRainfall intensity-aerosol relationship

Difference of the rain-day frequencies in terms of rainfall intensity in between the cases of high (100190 g m3) and low aerosol concentrations (090 g m3).

A positive anomaly indicates that the frequency associated with the high aerosol cases dominates that associated with the low aerosol concentration. The error bar corresponds to the standard error of the anomaly. Bars significant at the 90% levels are indicated by red and blue colors.

RC*R

-5

0

5

RCCC*R

-5

0

5

RCC*R

-5

0

5

90%

95%

< 5 5 10 10 20 20Rainfall (mm/day)

Diff

eren

ce o

f ra

in-d

ay

fre

quen

cie

s (%

)

90%

Large smallaerosol concentrations

RC*R

-5

0

5

RCCC*R

-5

0

5

RCC*R

-5

0

5

90%

95%

< 5 5 10 10 20 20Rainfall (mm/day)

Diff

eren

ce o

f ra

in-d

ay

fre

quen

cie

s (%

)

90%

Large smallaerosol concentrations

19

The possible role of aerosols in precipitationThe possible role of aerosols in precipitation

Hei

ght

(km

)

1

2

3

4

5

6

7

SEEDERZONE

FEEDERZONE

IN CCN

Warm-rain processsuppresses light rain

Cold-rain processenhances moderate rain

Additional moisture & aerosols

20

The self-cleansing system of aerosolsThe self-cleansing system of aerosols

A self-cleansing system

Ice cloudFormationIce cloudFormation

Airpollutants

Airpollutants

Rainfrequency

Rainfrequency

Wet scavenging

IncreaseIncrease

21Contradictory long-term trend in rainfall event

Contradictory long-term trend in rainfall event

80E 90E 100E 110E 120E 130E

20N

30N

40N

50N

80E 90E 100E 110E 120E 130E

20N

30N

40N

50N

< 66 ~ 33 ~ 0 0 ~ 3 3 ~ 6 6

19501979

19802006

Rainfall event (in days/10-yr)

-1.3

-2.8

Despite the aerosol self-cleansing effect, aerosol concentration has been increasing in China, accompanied by a decrease in rainfall events, over the last few decades.

22

Long-term trends in RH and SHLong-term trends in RH and SH

19501979

19802006

Relative humidity (in %/10-yr), NCEP

7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0

2 0

3 0

4 0

5 0

- 5 ~ - 2 . 5 - 2 . 5 ~ 0 0 ~ 2 . 5 2 . 5 ~ 5

Relative humidity (in %/10-yr), observation

19802006

7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0

2 0

3 0

4 0

5 0

- 2 0 ~ - 0 . 5 - 0 . 5 ~ - 0 . 2 5 - 0 . 2 5 ~ 0 0 ~ 0 . 2 5 0 . 2 5 ~ 0 . 5 0 . 5 ~ 0 . 7 5

Specific humidity (in g/10-yr), observation

19802006

23Detrainmental effect of human activities on the nature over East Asia

Detrainmental effect of human activities on the nature over East Asia

Aerosol self-cleansing system

A decrease in wet scavengingdue to a decrease in rain frequency

An increase in wet scavengingdue to a increase in rain frequency

An increase in rain frequencydue to cloud ice nuclei

AerosolsRain

frequency

Local sources of aerosoldue to industrialization

Regional climate variationson decadal time scale

A decrease in rain frequencyAn increase in aerosols

24

SummarySummary

The aerosol self-cleansing effect is another important mechanism involved in aerosol-cloud-rainfall interaction in the summertime in China.

Despite the presence of aerosol self-cleansing effect, aerosol concentration has been increasing in China, accompanied by a decrease in rainfall events, over the last few decades.

These results show that the impact of reduced RH dominates the aerosol self-cleansing mechanism in determining the long-term trend in rainfall frequency, and additionally contributing to the increase in aerosol concentrations since the beginning of the industrialization of China in 1980s.

A weekly cycle of aerosol-meteorology interaction over China

A weekly cycle of aerosol-meteorology interaction over China

1. Gong, D.-Y., G. Dong, and C.-H. Ho, 2006: Weekend effect in diurnal temperature range in China: Opposite signals between winter and summer. Journal of Geophysical Research, 111, D18113.

2. Gong, D.-Y., C.-H. Ho, D. Chen, Y. Qian, Y.-S. Choi, and J. Kim, 2007: A weekly cycle of aerosol-meteorology interaction over China. Journal of Geophysical Research, 112, D22202.

3. Choi, Y.-S., C.-H. Ho, D. Chen, Y.-H. Noh, and C.-K. Song, 2007, Spectral analysis of weekly variation in PM10 mass concentration and environment conditions over China, Atmospheric Environment (in press).

1. Gong, D.-Y., G. Dong, and C.-H. Ho, 2006: Weekend effect in diurnal temperature range in China: Opposite signals between winter and summer. Journal of Geophysical Research, 111, D18113.

2. Gong, D.-Y., C.-H. Ho, D. Chen, Y. Qian, Y.-S. Choi, and J. Kim, 2007: A weekly cycle of aerosol-meteorology interaction over China. Journal of Geophysical Research, 112, D22202.

3. Choi, Y.-S., C.-H. Ho, D. Chen, Y.-H. Noh, and C.-K. Song, 2007, Spectral analysis of weekly variation in PM10 mass concentration and environment conditions over China, Atmospheric Environment (in press).

26Weekly cycle of aerosol-meteorology interaction

Weekly cycle of aerosol-meteorology interaction

Scientists began to pay attention to find more clear evidence of anthropogenic effect.

Weekly cycle of aerosol and meteorology is only a clear evidence of anthropogenic effect on the nature.

Satellite-observed gas/aerosol (Delene and Ogren 2002; Beirle et al. 2003)

Surface-observed gas/aerosol: carbon oxide (Hies et al. 2000; Cerveny and Coakley 2002), nitrogen oxide (Marr and Harley 2002), and PM (Jin et al. 2005; Gong et al. 2007)

DTR (Forster and Solomon 2003; Gong et al. 2006) Cloud and precipitation (Cerveny and Balling Jr. 1998; Jin et al.

2005)

27

Evidences of weekly cycles in urban regionEvidences of weekly cycles in urban region

Jin et al. (2005), Urban aerosols and their variations with clouds and rainfall: A case study for New York and Houston, JGR

Cerveny and Balling (1998), Weekly cycles ofair pollutants, precipitation and tropical cyclones

in the coastal NW Atlantic region, Nature

1946-96

1970-96

28

Evidences of weekly cycles in the globeEvidences of weekly cycles in the globe

Weekend effect for stations outside the U.S., using 1980–1999 data. Filled circles are temporally significant at the 95% confidence level. The diameter of the circle is related to the size of the DTR weekend effect in Kelvin (Forster and Solomon, 2003 PNAS).

weekend-weekday

29

Scientific questionScientific question

Why do aerosol concentrations show a maximum on Wednesday or Thursday in China?

30

Relation with low-level wind fieldRelation with low-level wind field

31

Relation with temperature profileRelation with temperature profile

32

Relation with DTR and rain frequencyRelation with DTR and rain frequency

33

SummarySummary

The PM10 (aerosol particulate matters of diameter < 10 m) concentrations in China show significant weekly cycles with the largest values around midweek and smallest values in weekend.

Accompanying this weekly PM10 cycle, the meteorological variables such as wind speed, air temperature, show notable and consistent weekly cycles.

We hypothesize that the changes in the atmospheric circulation may be triggered by the accumulation of PM10 through diabatic heating of the lower troposphere.

34

Concluding RemarksConcluding Remarks

The impact of aerosols on the regional hydroclimate, as a part of anthropogenic effects together with greenhouse gases, involves a number of processes on a wide range of time scales

Aerosol-cloud interaction (hourly or shorter) Aerosol-accumulation-rainfall and wet scavenging (a few

days) Aerosol-meteorology interaction (weekly) Long-term variations in the atmospheric RH modulate the

formal effects (decadal or longer)

We believe that these processes are going on, and will be clearer, at least over East Asia, in the future.