MIT Regional Warming

MIT Regional Warming - Click Here GEOPHYSICAL RESEARCH...

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Long-term changes in summer weekend effect over northeastern China and the connection with regional warming Chang-Hoi Ho, 1 Yong-Sang Choi, 2 and Sun-Kyong Hur 1 Received 6 June 2009; accepted 21 July 2009; published 13 August 2009. [ 1 ] The 7-day cycle of human activities may lead to the ‘‘weekend effect’’ in climate variables and air pollutants. The weekend effect is defined as the average value (e.g., the diurnal temperature range) for Saturday through Monday minus the average value for Wednesday through Friday. A composite of the ground observations over northeastern China presents that, during 26-year (1980–2005) summers, the weekend effect in the diurnal temperature range increased by 1.2 ° C. Conversely, the weekend effects in the relative humidity, cloud amount, and light rain ( ± 5mm day ² 1 ) events decreased. These changes are due to a shifted phase of the weekly cycle of the meteorological variables. The long-term change in weekend effects have a high correlation coefficient ( j r 0.8) with the decrease in relative humidity over the region, which is likely induced by regional warming. The results suggest that regional warming is a possible factor in a transition of dominant aerosol effects in the weekend effect. Citation: Ho, C.-H., Y.-S. Choi, and S.-K. Hur (2009), Long-term changes in summer weekend effect over northeastern China and the connection with regional warming, Geophys. Res. Lett. , 36 , L15706, doi:10.1029/ 2009GL039509. 1. Introduction [ 2 ] A 7-day cycle of human activities may produce weekly variation in air quality and the weather. To date, researchers have suggested that the aerosol-meteorology interaction is the most probable process behind this phenom- enon [ Cerveny and Balling , 1998; Forster and Solomon , 2003; Jin et al. , 2005; Gong et al. , 2006, 2007; Bell et al. , 2008; Choi et al. , 2008a]. The increased aerosol emissions during the workweek and the decreased aerosol emissions during the weekend [ Delene and Ogren , 2002; Marr and Harley , 2002; Beirle et al. , 2003; Gong et al. , 2007] may give rise to considerable external forcing that affects the climate processes involved with radiation, clouds, precipi- tation, and other conditions, and conversely respond to them. This so-called weekend effect is defined as the average values of meteorological variables for Saturday through Monday minus those for Wednesday through Friday. Applying this definition in China, the most signif- icant weekend effect has been detected in the diurnal temperature range (DTR), that is, the daily maximum temperature minus daily minimum temperature [ Gong et al. , 2006, 2007; Choi et al. , 2008a]. [ 3 ] The DTR weekend effect in China was found to be either negative or positive, depending on the season [ Gong et al. , 2006] and the region [ Choi et al. , 2008a]. This variety suggests that complex mechanisms are factored in the DTR weekend effect [ Ba ¨umer and Vogel ,2 0 0 7
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This note was uploaded on 10/21/2011 for the course ATMOSPHERI Research taught by Professor V.ram during the Spring '11 term at UCSD.

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MIT Regional Warming - Click Here GEOPHYSICAL RESEARCH...

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