Chein-Jung Shiu

Temperature dependence of global precipitation extremes

[1] Data from the Global Precipitation Climatology Project (GPCP) covering the period 1979-2007 are examined for changes of precipitation extremes as a function of global mean temperature by using a new method which focuses on interannual differences rather than time series. We find that the top 10% bin of precipitation intensity increases by about 95% for each degree Kelvin (K) increase in global mean temperature, while 30%-60% bins decrease by about 20% K -1 . The global average precipitation intensity increases by about 23% K -1 , substantially greater than the increase of about 7% K -1 in atmospheric water-holding capacity estimated by the Clausius-Clapeyron equation. The large increase of precipitation intensity is qualitatively consistent with the hypothesis that the precipitation intensity should increase by more than 7% K -1 because of the additional latent heat released from the increased moisture. Our results also provide an independent evidence in support for significant increases in the number and/or size of strong global tropical cyclones. However an ensemble of 17 latest generation climate models estimates an increase of only about 2% K -1 in precipitation intensity, about one order of magnitude smaller than our value, suggesting that the risk of extreme precipitation events due to global warming is substantially greater than that estimated by the climate models.

Diurnally Asymmetric Trends of Temperature, Humidity, and Precipitation in Taiwan

In this work, 45 years (1961‐2005) of hourly meteorological data in Taiwan, including temperature, humidity, and precipitation, have been analyzed with emphasis on their diurnal asymmetries. A long-term decreasing trend for relative humidity (RH) is found, and the trend is significantly greater in the nighttime than in the daytime, apparently resulting from a greater warming at night. The warming at night in three large urban centers is large enough to impact the average temperature trend in Taiwan significantly between 1910 and 2005. There is a decrease in the diurnal temperature range (DTR) that is largest in major urban areas, and it becomes smaller but does not disappear in smaller cities and offshore islands. The nighttime reduction in RH is likely the main cause of a significant reduction of fog events over Taiwan. The smaller but consistent reductions in DTR and RH in the three off-coast islands suggests that, in addition to local land use changes, a regional-scale process such as the indirect effect of anthropogenic aerosols may also contribute to these trends. A reduction in light precipitation (, 4m m h 21 ) and an increase in heavy precipitation (.10 mm h 21 ) are found over Taiwan and the offshore islands. The changes in precipitation are similar to the changes of other areas in Asia, but they are different from those of the United States, Europe, and the tropical oceans. The latter do not show any reduction in light precipitation.

IL28B genetic variations are associated with high sustained virological response (SVR) of interferon-α plus ribavirin therapy in Taiwanese chronic HCV infection

Chronic hepatitis C virus (HCV) infection patients exhibit different sustained virological responses (SVRs) following the treatment with pegylated interferon-α (IFN-α) and ribavirin. Genome-wide association studies consistently linked SVR of IFN-α-based therapy to the IL28B single-nucleotide polymorphisms (SNPs) on chromosome 19q.13 in various populations. This study was undertaken to investigate the association of IL28B SNPs with SVR in a cohort of Taiwanese chronic HCV patients. Ten SNPs of IL28B were genotyped in 728 chronic HCV patients and 960 healthy controls. Genotype distributions, allele frequencies and haplotypes were tested for SVR and susceptibility in Taiwanese chronic HCV patients. Non-genotype 1 infection (adjusted P=3.3 × 10−12, odds ratio (OR) 0.179; 95% confidence interval (CI): 0.110–0.290) and low HCV viral load (<400 000 IU ml–1) (adjusted P=3.5 × 10−9, OR 0.299; 95% CI: 0.200–0.446) were two major factors identified for high SVR. Notably, eight IL28B SNPs including previously described disease-associated SNPs (Trend test P=0.005) were significantly associated with SVR. Our data indicate that IL28B polymorphisms are the essential contributing factors for high SVR in Taiwanese chronic HCV patients. Combination of virus genotyping and host genetic data may be used to select the optimal treatment regimes in IFN-based therapy.

Trends of extreme precipitation in eastern China and their possible causes

Significant increases of heavy precipitation and decreases of light precipitation have been reported over widespread regions of the globe. Global warming and effects of anthropogenic aerosols have both been proposed as possible causes of these changes. We examine data from urban and rural meteorological stations in eastern China (1955–2011) and compare them with Global Precipitation Climatology Project (GPCP) data (1979–2007) and reanalysis data in various latitude zones to study changes in precipitation extremes. Significant decreases in light precipitation and increases in heavy precipitation are found at both rural and urban stations, as well as low latitudes over the ocean, while total precipitation shows little change. Characteristics of these changes and changes in the equatorial zone and other latitudes suggest that global warming rather than aerosol effects is the primary cause of the changes. In eastern China, increases of annual total dry days (28 days) and ≥10 consecutive dry days (36%) are due to the decrease in light precipitation days, thereby establishing a causal link among global warming, changes in precipitation extremes, and higher meteorological risk of floods and droughts. Further, results derived from the GPCP data and reanalysis data suggest that the causal link exists over widespread regions of the globe.

Trends in aerosol optical depth in northern China retrieved from sunshine duration data

A new method has been developed to retrieve aerosol optical depth (AOD) from sunshine duration (SSD). Retrieved AODs from SSD at the six stations in northern China in 2003–2005 agree reasonably well with AODs retrieved from Moderate Resolution Imaging Spectroradiometer observations near the six stations. Values and trends in AOD retrieved from SSD in Beijing and Tianjin in the period 1961–2005 also agree with those retrieved from solar radiation and visibility. These agreements allow the retrieval of credible upper and lower limits for anthropogenic AODs from SSD at the six stations during 1961–2005. The trends in anthropogenic AODs are approximately a factor of 3 to 5 lower than the trends in emissions of gas-phase precursors of aerosols in 1973–2005, implying a significant sublinear relationship between the level of aerosols and emissions of their gas phase precursors. This finding has important implications for formulating a control strategy for PM2.5 or haze pollution in northern China.

Trends of Regional Precipitation and Their Control Mechanisms during 1979-2013

Trends in precipitation are critical to water resources. Considerable uncertainty remains concerning the trends of regional precipitation in response to global warming and their controlling mechanisms. Here, we use an interannual difference method to derive trends of regional precipitation from GPCP (Global Precipitation Climatology Project) data and MERRA (Modern- Era Retrospective Analysis for Research and Applications) reanalysis in the near-global domain of 60°S–60°N during a major global warming period of 1979–2013. We find that trends of regional annual precipitation are primarily driven by changes in the top 30% heavy precipitation events, which in turn are controlled by changes in precipitable water in response to global warming, i.e., by thermodynamic processes. Significant drying trends are found in most parts of the U.S. and eastern Canada, the Middle East, and eastern South America, while significant increases in precipitation occur in northern Australia, southern Africa, western India and western China. In addition, as the climate warms there are extensive enhancements and expansions of the three major tropical precipitation centers–the Maritime Continent, Central America, and tropical Africa–leading to the observed widening of Hadley cells and a significant strengthening of the global hydrological cycle.

Correlation between aerosol optical depth derived from CIMEL sunphotometer and surface particulate concentration in Northern and Southern Taiwan

Three years (2003-2005) of aerosol optical depths (AOD) measured with CIMEL sunphotometer were compared to the surface concentrations of PM10 and PM2.5 in Northern (i.e. Taipei) and Southern (i.e. Tainan) Taiwan. The correlation between AOD and PM10 is higher in Taipei than in Tainan. Additional chemical compositions of PM10 and PM2.5 in these two sites, including ionic component, sea salt, OC/EC and crustal components, were also examined to find their relationship with the AOD. These analyses indicate that aerosols in Taipei are mainly composed of fine aerosols, whereas in Tainan more crustal material and OC exist in the coarse mode, which partially explain the higher correlation of PM10 and AOD in Taipei. Closure calculations are carried out by combining data from lidar, sunphotometer, nephelometer, aethalomter, SMPS and APS size spectrometers, as well as chemical analyses of aerosols from PM10 and PM2.5 samplers and MOUDI impactor to investigate their consistency. The observed surface single scattering albedo was also compared to that retrieved by CIMEL sunphotometer, with additional discussion on the possible explanation to the discrepancies of the comparisons. Then, lidar measurement is applied to relate aerosols at the surface to those aloft.

Response to comments by Yuan Wang on “Trends of extreme precipitation in Eastern China and their possible causes”

In his comments, Wang cites a number of works to dispute the conclusion in our previous work, which attributes the observed decreases/increases in light/heavy precipitation in eastern China primarily to global warming rather than the regional aerosol effect. However, most of the cited works (admittedly, including our previous work), employ correlation analysis, which has little bearing on the cause–effect relationship. Theoretical analyses and/or modeling studies are needed to ascertain the cause–effect relationship. We argue that theoretical analyses and modeling results show that global warming is the primary cause of the widely observed phenomena of suppression of light precipitation and enhancement of heavy precipitation across the globe, including in eastern China.