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Yang X.,Institute of Meteorological science | Tian Z.,Shanghai Climate Center | Chen B.,Shanghai Typhoon Institute of China Meteorological Administration
International Journal of Climatology

Dense meteorological station network-derived data on daily surface air temperatures over the period 1961-2007 were used to investigate the changes in the thermal growing season (GS) indicators for east China. The 394 stations are classified into six categories: metropolises, large cities, medium-sized cities, small cities, suburbs, and rural area using satellite-measured night-time light imagery and census data. Only the temperature data on 258 small cities and rural stations were used to calculate the GS indicators to reflect more 'natural' changes in thermal GS parameters. During the studied period, the regional mean length of the GS significantly extended by 3.05 and 2.61 d decade-1 for base temperatures of 5 and 10 °C, respectively. This extension is attributed primarily to the GS initiating at an earlier time (2.49 and 2.10 d decade-1 for base temperatures of 5 and 10 °C, respectively), rather than to the delayed end of the GS (0.55 and 0.51 d decade-1 for base temperatures of 5 and 10 °C, respectively). The mean growing degree days (GDD) has increased by 51.84 and 35.89 degree days decade-1 on average at temperatures higher than 5 and 10 °C. When the temperature data from all the 394 stations(including metropolis, large city, medium city, and suburban) were used to calculate the GS indicators, urban heat island (UHI) effects were evident, especially in highly urbanized Yangtze River Delta. The GS extension and GDD increase in metropolises increased by more than onefold over those observed for rural areas. This result indicates significant UHI effects on climatic GS changes. On the basis of the GDD changes, we find that UHI effects contributed to more than 10% in the GDD increase at temperatures higher than 10 °C. Therefore, excluding the urbanization effects from station observational data in evaluating changes in GS indices is necessary, especially for regions characterized by rapid urbanization. © 2012 Royal Meteorological Society. Source

Li L.-G.,Institute of Atmospheric Environment | Xu S.-L.,Tsinghua Holdings Human Settlements Environment Institute Co. | Wang H.-B.,Institute of Atmospheric Environment | Zhao Z.-Q.,Institute of Atmospheric Environment | And 4 more authors.
Chinese Journal of Applied Ecology

Based on the remote images in 2001 and 2010, the source and sink areas of urban heat island (UHI) in Shenyang City, Northeast China were determined by GIS technique. The effect of urban regional landscape pattern on UHI effect was assessed with land surface temperature (LST), area rate index (CI) of the source and sink areas and intensity index (LI) of heat island. The results indicated that the land use type changed significantly from 2001 to 2010, which significantly changed the source and sink areas of UHI, especially in the second and third circle regions. The source and sink areas were 94.3% and 5. 7% in the first circle region, 64.0% and 36.0% in the third circle region in 2001, while they were 93.4% and 6.6%, 70.2% and 29.8% in 2010, respectively. It suggested that the land use pattern extended by a round shape in Shenyang led to the corresponding UHI pattern. The LST in the study area tended to decrease from the first circle region to the third. The UHI intensity was characterized with a single center in 2001 and with several centers in 2010, and the grade of UHI intensity was in a decreasing trend from 2001 to 2010.The absolute value of CI increased from the first circle region to the third, and the LI was close to 1, suggesting the change in land use pattern had no significant influence on UHI in Shenyang. Source

Yang X.,Shanghai Typhoon Institute of China Meteorological Administration | Yang X.,Institute of Meteorological science | Hou Y.,Shanghai Climate Center | Chen B.,Shanghai Typhoon Institute of China Meteorological Administration
Journal of Geophysical Research: Atmospheres

Monthly mean surface air temperature data from 463 meteorological stations, including those from the 1981-2007 ordinary and national basic reference surface stations in east China and from the National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) Reanalysis, are used to investigate the effect of rapid urbanization on temperature change. These stations are dynamically classified into six categories, namely, metropolis, large city, medium-sized city, small city, suburban, and rural, using satellite-measured nighttime light imagery and population census data. Both observation minus reanalysis (OMR) and urban minus rural (UMR) methods are utilized to detect surface air temperature change induced by urbanization. With objective and dynamic station classification, the observed and reanalyzed temperature changes over rural areas show good agreement, indicating that the reanalysis can effectively capture regional rural temperature trends. The trends of urban heat island (UHI) effects, determined using OMR and UMR approaches, are generally consistent and indicate that rapid urbanization has a significant influence on surface warming over east China. Overall, UHI effects contribute 24.2% to regional average warming trends. The strongest effect of urbanization on annual mean surface air temperature trends occurs over the metropolis and large city stations, with corresponding contributions of about 44% and 35% to total warming, respectively. The UHI trends are 0.398°C and 0.26°C decade-1. The most substantial UHI effect occurred after the early 2000s, implying a significant effect of rapid urbanization on surface air temperature change during this period. Copyright 2011 by the American Geophysical Union. Source

Weng Y.,Zhejiang University | Zhao W.,Institute of Meteorological science | Ye Q.,Zhejiang University | Zhang Y.,Zhejiang University | And 2 more authors.
Zhongguo Huanjing Kexue/China Environmental Science

The absorption of carbon dioxide into aqueous blends of 2-amino-2-methyl-1-propanol (AMP) and sodium glycinate (SG) was investigated from 293k to 313k in a double stirred-cell contactor. Five systems of which 1.5 kmol/m3 AMP mixed with various SG concentrations (0.2, 0.4, 0.6 and 0.8 kmol/m3) were studied. The average CO2 absorption rates increased (11.47%, 10.07%, 9.18% and 5.33%) with an increase of SG concentrations (0.2 kmol/m3 SG at a time). Compared to 1.5 kmol/m3 AMP, the blends had an increase of absorption capacity of 11.5%~41.1% within 200 min. The absorption rates increased with an increase of temperature within the temperature range of 293k to 313k. The regenerating performance was also done by heating. The optimum regeneration temperature was 378 K for the mixture of 1.5 kmol/m3 AMP + 0.6 kmol/m3 SG. The aqueous blends of AMP + SG had a higher regenerating efficiency than either single SG or blends of AMP + MEA/DEA. Source

Shen Y.,Chinese Academy of Sciences | Liu C.,Chinese Academy of Sciences | Liu C.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Liu M.,Chinese Academy of Sciences | And 2 more authors.
Hydrological Processes

Pan evaporation, as a surrogate of potential evaporation, is reported to have decreased in different regions of the world since the 1950s. There is much literature to explain the decrease in pan evaporation using the so-called evaporation complimentary relationship hypothesis and it is argued that pan evaporation can be understood as a sign of global warming and indication of an accelerating hydrologic cycle. On the other hand, some scientists insist that the pan evaporation trends may be caused by a global dimming, which effectively reduces the solar radiation to the ground surface. However, few reports are available about the changes in pan evaporation and their implications to water balance in arid regions. In the present study, we investigate the trends in pan evaporation in arid regions of China over the past 50 years and attempt to characterize the changes in water balance in these areas. It is found that pan evaporation in these areas has portrayed a statistically significant decreasing trend, which may be attributed mainly to decreases in wind speed and diurnal temperature range and increase in precipitation. The trends in some major meteorological factors such as pan evaporation, precipitation, temperature, wind speed and others imply an enhanced hydrological cycle in the study area. Copyright © 2009 John Wiley & Sons, Ltd. Source

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