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Is Climate Change in Asia-Pacific Attributed to Human Activities?. Chang-Hoi Ho School of Earth and Environmental Sciences Seoul National University. Acknowledgments. Main collaborators
School of Earth and Environmental Sciences
Seoul National University
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.
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.
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.
(Cases for 30 mm/day)
(Cases for 0.1 mm/day)
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.
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.
Recent summer-mean 500-hPa 5870m gpm
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.
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).
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.
BC aerosols heat up the low-level atmosphere, and stabilize it
Burn cloud droplets by UV absorption
1) suppress warm precipitation
Increase cloud droplets
Reduce cloud droplet size
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
The increase in aerosol concentrations in China, via aerosol indirect and semi-direct effects, may affectthe long-term variations in precipitation
Southern China (Cheng et al. 2005 JC)
Eastern-central China (Zhao et al. 2006 GRL)
Increased aerosol reduced precipitation
(Zhao et al. 2006 GRL)
Less precipitation more aerosol in the air
PM10 and precipitation station
The significant correlation suggests that the increase in aerosol concentrationincreases rainfall frequency, which in turn removes aerosols from the atmosphere. This process is referred to “aerosol self-cleansing effect”.
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.
enhances moderate rain
suppresses light rain
Additional moisture & aerosols
Rainfall event (in days/10-yr)
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.
6 ~ 3
3 ~ 0
0 ~ 3
3 ~ 6
Relative humidity (in %/10-yr), NCEP
Relative humidity (in %/10-yr), observation
Specific humidity (in g/10-yr), observation
Local sources of aerosoldue to industrialization
Regional climate variationson decadal time scale
An increase in aerosols
A decrease in rain frequency
Aerosol self-cleansing system
An increase in rain frequencydue to cloud ice nuclei
An increase in wet scavenging
due to a increase in rain frequency
A decrease in wet scavenging
due to a decrease in rain frequency
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.
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.
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).
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
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).