Abstract. A tree-ring δ18O chronology of Linzhi spruce, spanning from AD 1781 to 2005, was developed in Bomi, Southeast Tibetan Plateau (TP). During the period with instrumental data (AD 1961–2005), this record is strongly correlated with regional CRU (Climate Research Unit) summer cloud data, which is supported by a precipitation δ18O simulation conducted with the isotope-enabled atmospheric general circulation model LMDZiso. A reconstruction of a regional summer cloud index, based upon the empirical relationship between cloud and diurnal temperature range, was therefore achieved. This index reflects regional moisture variability in the past 225 yr. The climate appears drier and more stable in the 20th century than previously. The drying trend in late 19th century of our reconstruction is consistent with a decrease in the TP glacier accumulation recorded in ice cores. An exceptional dry decade is documented in the 1810s, possibly related to the impact of repeated volcanic eruptions on monsoon flow.

Using a portable emissions measurement system, 16 gasoline passenger cars were tested on a fixed route consisting of different types of roads in Macao and the data were normalized with the vehicle-specific power bin method. The normalized HC, CO and NO X emission levels of the seven passenger car samples with model year older than 2000 were 3.19 ± 5.04, 14.59 ± 22.88, 2.57 ± 2.12 g/km, respectively. The HC, CO and NO X emission levels of other newer samples were 0.02 ± 0.02, 0.23 ± 0.29 and 0.10 ± 0.13 g/km, respectively. The scrappage of old passenger cars in Macao should be a high priority to control the total emissions of motor vehicles. Based on relative emission levels, a clear and similar pattern for gaseous pollutants and fuel consumption with driving conditions was identified. The emissions of HC, CO and NO X are best fitted to average speed with inverse functions. Fuel consumption is best fitted to average speed with a power function. Compared to the average driving conditions, the emission factors of HC, CO and NO X and fuel consumption of gasoline passenger cars during the rush hours on the Macau Peninsula will be increased by 61, 55, 45 and 90 %, respectively. This situation will deteriorate by 2015 if no further transportation management strategies are implemented in Macao. To save energy and mitigate the air pollutant emissions in the urban area, improved traffic planning and travel demand management are also necessary.

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Abstract. In this study, we report on the development of a lamp-based vacuum ultraviolet photoionization mass spectrometer (VUV-PIMS) in our laboratory; it is composed of a radio-frequency-powered VUV lamp, a VUV photoionizer, an ion-migration lens assembly, and a reflection timeof-flight mass spectrometer. By utilizing the novel photoionizer consisting of a photoionization cavity and a VUV light baffle, the baselines of the mass spectra decreased from 263.6 ± 15.7 counts to 4.1 ± 1.8 counts. A detection limit (2σ ) of 3 pptv was achieved for benzene after an acquisition time of 10 s. To examine its potential for real-time monitoring applications of samples, the developed VUV-PIMS was employed for the continuous measurement of urban air for 6 days in Beijing, China. Strong signals of trace-level volatile organic compounds, such as benzene and its alkylated derivatives, were observed in the mass spectra. These initial experimental results reveal that the instrument can be used for the online monitoring of trace-level species in the atmosphere.