A strong urban heat island （UHI） appeared in a hot weather episode in Suzhou City during the period from 25 July to 1 August 2007. This paper analyzes the urban heat island characteristics of Suzhou City under this ...A strong urban heat island （UHI） appeared in a hot weather episode in Suzhou City during the period from 25 July to 1 August 2007. This paper analyzes the urban heat island characteristics of Suzhou City under this hot weather episode. Both meteorological station observations and MODIS satellite observations show a strong urban heat island in this area. The maximum UHI intensity in this hot weather episode is 2.2℃, which is much greater than the summer average of 1.0℃ in this year and the 37–year （from 1970 to 2006） average of 0.35℃. The Weather Research and Forecasting （WRF） model simulation results demonstrate that the rapid urbanization processes in this area will enhance the UHI in intensity, horizontal distribution, and vertical extension. The UHI spatial distribution expands as the urban size increases. The vertical extension of UHI in the afternoon increases about 50 m higher under the year 2006 urban land cover than that under the 1986 urban land cover. The conversion from rural land use to urban land type also strengthens the local lake-land breeze circulations in this area and modifies the vertical wind speed field.展开更多
Chemical and isotopic compositions have been measured for N2-He-rich bubbling gases discharging from hot springs in the Hainan Island, Southern China. Observed 3He/4He ratios （0.1-1.3 RA） indicate the occurrence of ...Chemical and isotopic compositions have been measured for N2-He-rich bubbling gases discharging from hot springs in the Hainan Island, Southern China. Observed 3He/4He ratios （0.1-1.3 RA） indicate the occurrence of a mantle component throughout the island, which has been highly diluted by a crustal radiogenic 4He component. The occurrence of mantle-derived helium is high in the northern island （12%-16% of total He） and gradually decreases towards southern coast （1%-3% of total He）. Such a distribution pattern is most likely controlled by the Pleocene-Quaternary volcanic activities in the northern island and groundwater circulation along the deep major faults. The 4~Ar/36Ar and N2/Ar ratios suggest that N2 and Ar of the hot spring gases are mostly meteoric. Although 13C values of CO2 （-20%0 to -27%0） with low concentrations are consistent with the biogenic origin, the combination of SHe/4He and 51SCco2 suggests a two end-member mixing of mantle and crustal components with CO2/3He ratios of 2x 109 and 8 1011, respectively. However, the low CO2/3He ratios （1- 22106） can not be ascribed in terms of the simple mixing but has to be explained by the addition of radiogenic 4He and loss of CO2 by calcite precipitation in the hydrothermal system, which is most likely controlled by the degree of gas-water-rock interaction.展开更多
SiCGe ternary alloys have been grown on SiC by hot-wall low-pressure chemical vapour deposition. It has been found that the samples cxhibit an island configuration, and the island growth of SiCGe epilayer depends on t...SiCGe ternary alloys have been grown on SiC by hot-wall low-pressure chemical vapour deposition. It has been found that the samples cxhibit an island configuration, and the island growth of SiCGe epilayer depends on the processing parameters such as the growth temperature. When the growth temperature is comparatively low, the epilayer has two types of islands： onc is spherical island; another is cascading triangular island. With the increase of the growth temperature, the islands change from spherical to cascading triangular mode. The size and density of the islands depend on the growth duration and GeH4 flow-rate. A longer growth time and a larger GeH4 flow-rate can increase the size and density of the island in thc initial stage of the epitaxy. In our case, The optimal growth for a high density of uniform islands occurred at a growth temperature of 1100℃ for l-minute growth, with 10 SCCM GeH4, resulting in a narrow size distribution （about 30nm diameter） and high density （about 3.5 ×10^10 dots/cm2）. The growth follows Stranski- Krastanov modc （2D to 3D modc）, both of the islands and the 2D growth layer have face-centred cubic structure, and the critical thickness of the 2D growth layer is only 2.5 nm.展开更多
India has witnessed tremendous industrialization in the last five decades. This has led to migration of masses from rural areas towards cities for jobs and businesses. With increase in the population, the demand for r...India has witnessed tremendous industrialization in the last five decades. This has led to migration of masses from rural areas towards cities for jobs and businesses. With increase in the population, the demand for residences has also increased which has escalated growth of slum areas and haphazard planning in suburbs. City of Ahmedabad is one such urban metropolis in the state of Gujarat, India. Being the financial capital of Gujarat, population of the city has increased many folds since 1980s. Congested and unsustainable planning and increasing in the emissions from industries and vehicles in certain areas of the city have given birth to many climatic issues. One of these major problems is the Urban Heat Island (UHI) phenomena. This has increased the temperature by four to five degrees and has also severely affected air quality. Satellite based Remote sensing data can provide temperature information of various land use classes. Remote Sensing data along with in-situ surface measurements can help to identify urban heat island intensities and hotspots in the cities. A study on heat island characterization and isotherm mapping was taken up in Ahmedabad City. In the present study, Surface Heat Island (SHI) effect is studied using satellite data along with field measurements. Thermal infrared data from Landsat ETM band-6 have been effectively used for monitoring temperature differences of various land use classes in urban areas. The study aims to identify and study the urban hot spots using the data from LANDSAT-5 and field data collected using IR Gun in various zones of Ahmedabad City. The results of this study indicated that the surface temperature near industrial areas and dense urban areas was higher as compared to other suburban areas in the Ahmedabad City.展开更多
基金sponsored by the National Basic Research Program of China (2010CB428501 and 2011CB952002)National Natural Science Foundation of China (Grant No. 41005008)
文摘A strong urban heat island （UHI） appeared in a hot weather episode in Suzhou City during the period from 25 July to 1 August 2007. This paper analyzes the urban heat island characteristics of Suzhou City under this hot weather episode. Both meteorological station observations and MODIS satellite observations show a strong urban heat island in this area. The maximum UHI intensity in this hot weather episode is 2.2℃, which is much greater than the summer average of 1.0℃ in this year and the 37–year （from 1970 to 2006） average of 0.35℃. The Weather Research and Forecasting （WRF） model simulation results demonstrate that the rapid urbanization processes in this area will enhance the UHI in intensity, horizontal distribution, and vertical extension. The UHI spatial distribution expands as the urban size increases. The vertical extension of UHI in the afternoon increases about 50 m higher under the year 2006 urban land cover than that under the 1986 urban land cover. The conversion from rural land use to urban land type also strengthens the local lake-land breeze circulations in this area and modifies the vertical wind speed field.
基金supported by the China National Key Basic Research and Development Program"973" (No.2009CB219506)
文摘Chemical and isotopic compositions have been measured for N2-He-rich bubbling gases discharging from hot springs in the Hainan Island, Southern China. Observed 3He/4He ratios （0.1-1.3 RA） indicate the occurrence of a mantle component throughout the island, which has been highly diluted by a crustal radiogenic 4He component. The occurrence of mantle-derived helium is high in the northern island （12%-16% of total He） and gradually decreases towards southern coast （1%-3% of total He）. Such a distribution pattern is most likely controlled by the Pleocene-Quaternary volcanic activities in the northern island and groundwater circulation along the deep major faults. The 4~Ar/36Ar and N2/Ar ratios suggest that N2 and Ar of the hot spring gases are mostly meteoric. Although 13C values of CO2 （-20%0 to -27%0） with low concentrations are consistent with the biogenic origin, the combination of SHe/4He and 51SCco2 suggests a two end-member mixing of mantle and crustal components with CO2/3He ratios of 2x 109 and 8 1011, respectively. However, the low CO2/3He ratios （1- 22106） can not be ascribed in terms of the simple mixing but has to be explained by the addition of radiogenic 4He and loss of CO2 by calcite precipitation in the hydrothermal system, which is most likely controlled by the degree of gas-water-rock interaction.
基金Project supported by the National Natural Science Foundation of China （Grant No 60376011） and the Specialized Research Fund for the Doctoral Program of High Education, China （Grant No 20040700001）.
文摘SiCGe ternary alloys have been grown on SiC by hot-wall low-pressure chemical vapour deposition. It has been found that the samples cxhibit an island configuration, and the island growth of SiCGe epilayer depends on the processing parameters such as the growth temperature. When the growth temperature is comparatively low, the epilayer has two types of islands： onc is spherical island; another is cascading triangular island. With the increase of the growth temperature, the islands change from spherical to cascading triangular mode. The size and density of the islands depend on the growth duration and GeH4 flow-rate. A longer growth time and a larger GeH4 flow-rate can increase the size and density of the island in thc initial stage of the epitaxy. In our case, The optimal growth for a high density of uniform islands occurred at a growth temperature of 1100℃ for l-minute growth, with 10 SCCM GeH4, resulting in a narrow size distribution （about 30nm diameter） and high density （about 3.5 ×10^10 dots/cm2）. The growth follows Stranski- Krastanov modc （2D to 3D modc）, both of the islands and the 2D growth layer have face-centred cubic structure, and the critical thickness of the 2D growth layer is only 2.5 nm.
文摘India has witnessed tremendous industrialization in the last five decades. This has led to migration of masses from rural areas towards cities for jobs and businesses. With increase in the population, the demand for residences has also increased which has escalated growth of slum areas and haphazard planning in suburbs. City of Ahmedabad is one such urban metropolis in the state of Gujarat, India. Being the financial capital of Gujarat, population of the city has increased many folds since 1980s. Congested and unsustainable planning and increasing in the emissions from industries and vehicles in certain areas of the city have given birth to many climatic issues. One of these major problems is the Urban Heat Island (UHI) phenomena. This has increased the temperature by four to five degrees and has also severely affected air quality. Satellite based Remote sensing data can provide temperature information of various land use classes. Remote Sensing data along with in-situ surface measurements can help to identify urban heat island intensities and hotspots in the cities. A study on heat island characterization and isotherm mapping was taken up in Ahmedabad City. In the present study, Surface Heat Island (SHI) effect is studied using satellite data along with field measurements. Thermal infrared data from Landsat ETM band-6 have been effectively used for monitoring temperature differences of various land use classes in urban areas. The study aims to identify and study the urban hot spots using the data from LANDSAT-5 and field data collected using IR Gun in various zones of Ahmedabad City. The results of this study indicated that the surface temperature near industrial areas and dense urban areas was higher as compared to other suburban areas in the Ahmedabad City.
