Guoyu Ren | China University of Geosciences(Wuhan) (original) (raw)
Papers by Guoyu Ren
Bulletin of the American Meteorological Society
he long-term variation in precipitation and drought frequency in the past centuries is key to und... more he long-term variation in precipitation and drought frequency in the past centuries is key to understanding current impacts of climate change. However, high-resolution proxy records are scarce in some of the humid large river basins, such as the upper reaches of the Yangtze River. Near the Three Gorges, close to the boundary between the upper and middle Yangtze, an enormous rock, the White Crane Ridge (WCR), or Baiheliang, lies below the surface of the river. The 1,600-m-long and 15-m-wide ridge was exposed to air only during the middle winter to early spring seasons of drier years. Its emergence from the waters has had special significance in this area of China; early drought in the upper Yangtze was most likely followed by favorable weather and a bumper harvest in the following growing season in the WCR area.
Journal of Geophysical Research: Atmospheres
Bulletin of the American Meteorological Society
Capsule summary Rock Fishes at White Crane Ridge record extreme Low water levels of the Yangtze, ... more Capsule summary Rock Fishes at White Crane Ridge record extreme Low water levels of the Yangtze, showing more droughts in the MCA, less droughts during the LIA, and once again more droughts in the last century.
Journal of Applied Meteorology and Climatology
Sea-effect precipitation (SEP) over the Shandong Peninsula is a unique climatological phenomenon ... more Sea-effect precipitation (SEP) over the Shandong Peninsula is a unique climatological phenomenon in mainland China, and it exerts a considerable impact on the southern shore of the Bohai Sea. From observed data from 123 stations for the period 1962–2012, the characteristics of cold-season (November–February) SEP in this area were analyzed. Results showed that SEP occurred throughout the late autumn and winter. In all, 1173 SEP days were identified during the 51 years, of which snow days accounted for 73.7% and rain and snow–rain days accounted for 16.1% and 10.1%, respectively. December had the largest number of SEP snow days, followed by January and November. November was the most productive month in terms of SEP rain and snow–rain days. Intense SEP snowfall mainly affected the inland hill area of the peninsula, whereas light SEP snowfall reached farther inland. SEP rainfall shared a similar pattern with snowfall. The SEP frequency showed a significant interannual variability and a...
Journal of Applied Meteorology and Climatology
Typical rain gauge measurements have long been recognized to underestimate actual precipitation. ... more Typical rain gauge measurements have long been recognized to underestimate actual precipitation. Long-term daily precipitation records during 1961–2013 from a dense national network of 2379 gauges were corrected to remove systematic errors caused by trace precipitation, wetting losses, and wind-induced undercatch. The corrected percentage was higher in cold seasons and lower in warm seasons. Both trace precipitation and wetting loss corrections were more important in arid regions than in wet regions. A greater correction percentage for wind-induced error could be found in cold and arid regions, as well as high wind speed areas. Generally, the annual precipitation amounts as well as the annual precipitation intensity increased to varying degrees after bias correction with the maximum percentage being about 35%. More importantly, the bias-corrected snowfall amount as well as the rainstorm amount increased remarkably by percentages of more than 50% and 18%, respectively. Remarkably, th...
Journal of Applied Meteorology and Climatology
Hourly datasets obtained by automatic weather stations in Beijing, China, are developed and emplo... more Hourly datasets obtained by automatic weather stations in Beijing, China, are developed and employed to analyze the spatial and temporal characteristics of relative humidity (RH) and urban dryness island intensity (UDII) over built-up areas. A total of 36 stations inside the sixth ring road are considered as urban sites, while six stations in suburban belts surrounding the built-up areas are taken as reference sites. Results show that the RH is obviously smaller in urban areas than in suburban areas, indicating the effect of urbanization on near-surface atmospheric moisture and RH. A further analysis of relations between RH and temperature on varied time scales shows that the variations in RH in the urban areas are not due solely to changes in temperature. The annual and seasonal mean UDII are high in central urban areas, with the strongest UDII values occurring in autumn and the weakest values occurring in spring. The diurnal UDII variations are characterized by a steadily strong U...
Environmental Research Letters
Based on the satellite-derived global daily sea surface temperature (SST) data set with high reso... more Based on the satellite-derived global daily sea surface temperature (SST) data set with high resolution (0.25° by 0.25°), we analyzed changes in annual mean SST and extreme SSTs over the China Seas since 1982. Results show that the annual mean SST in the China Seas has experienced a remarkable declining trend during the global warming hiatus (1998–2013), which was dominated by the striking cooling of SST in boreal winter. Despite annual mean SST experienced warming hiatus after 1998, the regional averaged SST for 1998–2013 was still 0.5 °C above that for 1982–1997. The statistical distributions show that there are not only significant warmer climate shift in annual mean SSTs but also in annual extreme hot SSTs and cold SSTs. These changes can increase the likelihood of extreme oceanic warming events, known as marine heatwaves (MHWs). Further analyses reveal that, from 1982 to present, the MHW frequency increases at a rate of 1.13 events per decade, 2.5 times the global mean rate. Fo...
Applied Geography
Abstract The Weather Research and Forecasting model (WRF) includes a wildland fire-behavior modul... more Abstract The Weather Research and Forecasting model (WRF) includes a wildland fire-behavior module, WRF-Fire, which simulates wildland fire interactions with the atmosphere. Combining the WRF model with the coupled weather–wildland fire model allows simulations of wildland fire propagation. In this paper, we have chosen the method that performs simulation of wildfire spread progress coupled with prepared weather data as soon as a wildfire is found. In simulation of the weather field data, a one-way nest model is used with a grid resolution of 1 km. The high-resolution Digital Elevation Model (DEM) data (0.002° × 0.002°) and fuel distribution maps based on forest type data were used. We demonstrated the potential for establishing a real-time wildland fire forecasting system using WRF-Fire model based on the existing conditions and computing resources for weather condition at fire monitoring stations, which can be applied in monitoring and forecasting of the wildland fire disasters in the area of the country.
Meteorology and Atmospheric Physics
Based on a homogenized data set of monthly mean temperature, minimum temperature, and maximum tem... more Based on a homogenized data set of monthly mean temperature, minimum temperature, and maximum temperature at Shijiazhuang City Meteorological Station (Shijiazhuang station) and four rural meteorological stations selected applying a more sophisticated methodology, we reanalyzed the urbanization effects on annual, seasonal, and monthly mean surface air temperature (SAT) trends for updated time period 1960–2012 at the typical urban station in North China. The results showed that (1) urbanization effects on the long-term trends of annual mean SAT, minimum SAT, and diurnal temperature range (DTR) in the last 53 years reached 0.25, 0.47, and − 0.50 °C/decade, respectively, all statistically significant at the 0.001 confidence level, with the contributions from urbanization effects to the overall long-term trends reaching 67.8, 78.6, and 100%, respectively; (2) the urbanization effects on the trends of seasonal mean SAT, minimum SAT, and DTR were also large and statistically highly significant. Except for November and December, the urbanization effects on monthly mean SAT, minimum SAT, and DTR were also all statistically significant at the 0.05 confidence level; and (3) the annual, seasonal, and monthly mean maximum SAT series at the urban station registered a generally weaker and non-significant urbanization effect. The updated analysis evidenced that our previous work for this same urban station had underestimated the urbanization effect and its contribution to the overall changes in the SAT series. Many similar urban stations were being included in the current national and regional SAT data sets, and the results of this paper further indicated the importance and urgency for paying more attention to the urbanization bias in the monitoring and detection of global and regional SAT change based on the data sets.
Theoretical and Applied Climatology
Land surface air temperature (SAT) change is one of the core issues in monitoring and assessing r... more Land surface air temperature (SAT) change is one of the core issues in monitoring and assessing regional climate change. In this study, the characteristics of SAT change over DPR Korea for the period 1918–2015 were investigated using a high-quality historical dataset. Results show that the region-averaged annual mean SAT increased 0.21 °C/decade for the period 1918–2015 on the basis of data from four stations and 0.19 °C/decade for the period 1941–2015 as estimated based on data from nine stations. Before the 1970s, Pyongyang station in the central region experienced the largest warming trend. Linear trends of seasonal mean SAT during 1941–1970 were negative for all seasons in eastern coast and for summer and autumn in western coast and northern inland areas. Since 1971, however, the annual and seasonal mean SAT trends have shifted to positive values in all regions, with winter experiencing the most rapid warming. During the period of global warming slowdown since 1998 or 2000, no significant seasonal warming trend of wintertime was detectable, and this caused the smallest winter warming for the last 45 years. Other seasons also witnessed a generally weakened warming during 1971–2015 compared to that of 1971–2000. The results of the study will help in understanding regional climate change and in assessing the impacts of climate change on economic and natural ecosystems in the country.
Urbanization has led to a significant urban heat island (UHI) effect in Beijing in recent years. ... more Urbanization has led to a significant urban heat island (UHI) effect in Beijing in recent years. At the same time, air pollution caused by a large number of fine particles significantly influences the atmospheric environment, urban climate, and human health. The distribution of fine particulate matter (PM 2.5) concentration and its relationship with the UHI effect in the Beijing area are analyzed based on station-observed hourly data from 2012 to 2016. We conclude that, (1) in the last five years, the surface concentrations of PM 2.5 averaged for urban and rural sites in and around Beijing are 63.2 and 40.7 µg m −3 , respectively, with significant differences between urban and rural sites (PM 2.5) at the seasonal, monthly and daily scales observed; (2) there is a large correlation between PM 2.5 and the UHI intensity defined as the differences in the mean (T ave), minimum (T min), and maximum (T max) temperatures between urban and rural sites. The correlation between PM 2.5 and T mi...
Boundary-Layer Meteorology
While the land-surface temperature (LST) observed at meteorological stations has significantly in... more While the land-surface temperature (LST) observed at meteorological stations has significantly increased over the previous few decades, it is still unclear to what extent urbanization has affected these positive trends. Based on the LST data recorded at an urban station in Shijiazhuang in North China, and two rural meteorological stations, the effect of urbanization at the Shijiazhuang station for the period 1965–2012 is examined. We find, (1) a statistically-significant linear trend in annual mean urban–rural LST difference of 0.27\,^{\circ }\hbox {C}$$0.27∘C$$\hbox {(10 year)}^{-1}$$(10year)-1, with an urbanization contribution of 100% indicating that the increase in the annual mean LST at the urban station is entirely caused by urbanization. The urbanization effects in spring, summer and autumn on the trends of mean LST are also significant; (2) the urbanization effect is small for time series of the annual mean minimum LST, and statistically marginal for the trend in annual mean maximum LST [$$0.19\,^{\circ }\hbox {C}\,\hbox {(10 year)}^{-1}$$0.19∘C(10year)-1]; (3) the urbanization effect on the annual mean diurnal LST range ($$\Delta {LST}$$ΔLST) at the urban station is a strongly significant trend of 0.23\,^{\circ }\hbox {C (10\,year)}^{-1}$$0.23∘C (10year)-1, with an urbanization contribution of 21%. The urbanization effects on trends in the spring and autumn mean \Delta {LST}$$ΔLST are also larger and more significant than for the other seasons; (4) the urbanization effects on the long-term LST trends are remarkably different from those on the near-surface air temperature at the same urban station. Nonetheless, the significant warming of the urban boundary layer is expected to affect the urban environment and ecosystems. However, the problem of data representativeness at an urban station for the monitoring and investigation of large-scale climate change remains.
Datasets of daily precipitation, wind speed, and weather phenomena of 71 stations during 1960-200... more Datasets of daily precipitation, wind speed, and weather phenomena of 71 stations during 1960-2009 and experimental observations of precipitation from three stations are used to estimate wind-induced errors in winter snowfall records over northeastern China, and to analyze the effects of wind-induced under-catch on long-term winter snowfall trends. The results show that winter snowfall is generally undervalued. Although the region’s average annual snowfall was measured at 15.1 mm, the corrected snowfall was 22.5 mm, which indicates an average error of 7.5 mm, or relative error of approximately 34.1%. In recent years, the gauge catch rate has increased due to the weakening of surface wind speed resulting from urbanization and micro-environmental change surrounding the stations, which have led to an overestimate of winter snowfall trends in the study region. This analysis shows a trend of winter snowfall of 0.4mm/10yr for the past 50 years when the original precipitation data are used...
Geophysical Research Letters
Heavy PM 2.5 (particulate matter with aerodynamic diameter equal to or less than 2.5 μm) pollutio... more Heavy PM 2.5 (particulate matter with aerodynamic diameter equal to or less than 2.5 μm) pollution and urban heat island (UHI) pose increasing threats to human health and living environment in populated cities. However, how PM 2.5 pollution affects the UHI intensity (UHII) has not been fully understood. The impacts of PM 2.5 on the wintertime UHII in the Beijing-Tianjin-Hebei megalopolis of China are explored during 2013-2017. The results show that the UHII at the time of daily maximum/minimum temperature (UHII max /UHII min) exhibits a decreasing/increasing tendency as PM 2.5 concentration increases, causing a continuous decrease in the diurnal temperature range. These effects are mediated via aerosol-radiation interaction (aerosol-cloud interaction) under clear-sky (cloudy) condition. The changes in PM 2.5 concentration further cause different relative trends of UHII max /UHII min /diurnal temperature range across different cities in the Beijing-Tianjin-Hebei region, which are likely related to the differences in both the PM 2.5 composition and city size. This study provides insights on how air pollution affects urban climate and would help to design effective mitigation strategies. Plain Language Summary A detailed understanding of the relationship between PM 2.5 (particulate matter with aerodynamic diameter equal to or less than 2.5 μm) and the urban heat island (UHI) effect is significant for climate change adaption, planning, and sustainable development in urban regions. While the Beijing-Tianjin-Hebei (BTH) megalopolis of China is among the areas with the highest population densities and fastest urbanization rates in the world, the impacts of PM 2.5 pollution on UHI, along with their regional differences in the BTH megalopolis, remain unclear. This study demonstrates that different PM 2.5 concentrations in the BTH region pose various influences on the UHI intensities and their change rates in different cities of varying sizes. The UHI intensities during daytime and nighttime, respectively, exhibit weakening and strengthening tendency as PM 2.5 concentration increases. These effects are mediated via aerosol-radiation interaction under clear-sky condition and aerosol-cloud interaction in cloudy weather. The relative changes in the UHI magnitudes were mainly determined by PM 2.5 composition and city size. The asymmetrical influences of PM 2.5 on the daytime and nighttime UHI intensities caused continuous decreases in the diurnal temperature ranges in the urban areas as the pollution level increased. Our study improves the understanding of urban climate affected by air pollution and provides a scientific basis for the mitigation of UHI impacts.
Journal of Chemical Research
A coordination compound constructed from a nitronyl nitroxide biradical NITPh(3-NIT) and CuII(hfa... more A coordination compound constructed from a nitronyl nitroxide biradical NITPh(3-NIT) and CuII(hfac)2(H2O)2 building blocks [NITPh(3-NIT) = 1,3-bis(1′-oxyl-3′-oxido-4′,4′, 5′, 5′-tetramethyl-4,5-dihydro-1 H-imidazol-2-y1)-benzene, hfac = hexafluoroacetylacetonato] is successfully synthesized. The crystal structure is determined by X-ray single-crystal diffraction. The asymmetric complex {[(NITPh(3-NIT)]Cu(hfac)2} consists of one Cu(II) ion and two >N–O• groups and adopts a distorted triangular bipyramid with a penta-coordinated central copper(II) atom and three hfac oxygen atoms at the base and a >N–O• oxygen atom and one hfac oxygen atom at the apices. Intramolecular O. . .O bonding and π–π stacking interactions are observed between molecules. A magnetic susceptibility study of the coordination compound shows antiferromagnetic interactions between Cu(II) ions and >N–O• groups and very weak ferromagnetic interactions between Cu(II) ions and the free >N–O• group through O....
Hydrology
The Haihe River basin of North China is characterized by extremely low per capita water resources... more The Haihe River basin of North China is characterized by extremely low per capita water resources and a consistently long-term decreasing trend of precipitation and runoff over the last few decades. This study analyzes the climatological features of rainy season (May–September) precipitation in the Haihe River basin and its branch systems based on a high-density hourly observational dataset during 2007–2017. We show that there are two high-rainfall zones in the basin, with one along the south of the Yanshan Mountains to Taihang Mountains and another along the Tuma River in the south. Rainstorm centers exist amidst the two zones. July generally sees the highest precipitation, followed by August, and May has the lowest precipitation. The major flood season is reached between the third pentad of July and the fourth pentad of August. The precipitation is high at night but low in the daytime. In the pre-flood season before early July, rainfalls mostly arrive at 16:00–21:00 h. After enter...
Bulletin of the American Meteorological Society
he long-term variation in precipitation and drought frequency in the past centuries is key to und... more he long-term variation in precipitation and drought frequency in the past centuries is key to understanding current impacts of climate change. However, high-resolution proxy records are scarce in some of the humid large river basins, such as the upper reaches of the Yangtze River. Near the Three Gorges, close to the boundary between the upper and middle Yangtze, an enormous rock, the White Crane Ridge (WCR), or Baiheliang, lies below the surface of the river. The 1,600-m-long and 15-m-wide ridge was exposed to air only during the middle winter to early spring seasons of drier years. Its emergence from the waters has had special significance in this area of China; early drought in the upper Yangtze was most likely followed by favorable weather and a bumper harvest in the following growing season in the WCR area.
Journal of Geophysical Research: Atmospheres
Bulletin of the American Meteorological Society
Capsule summary Rock Fishes at White Crane Ridge record extreme Low water levels of the Yangtze, ... more Capsule summary Rock Fishes at White Crane Ridge record extreme Low water levels of the Yangtze, showing more droughts in the MCA, less droughts during the LIA, and once again more droughts in the last century.
Journal of Applied Meteorology and Climatology
Sea-effect precipitation (SEP) over the Shandong Peninsula is a unique climatological phenomenon ... more Sea-effect precipitation (SEP) over the Shandong Peninsula is a unique climatological phenomenon in mainland China, and it exerts a considerable impact on the southern shore of the Bohai Sea. From observed data from 123 stations for the period 1962–2012, the characteristics of cold-season (November–February) SEP in this area were analyzed. Results showed that SEP occurred throughout the late autumn and winter. In all, 1173 SEP days were identified during the 51 years, of which snow days accounted for 73.7% and rain and snow–rain days accounted for 16.1% and 10.1%, respectively. December had the largest number of SEP snow days, followed by January and November. November was the most productive month in terms of SEP rain and snow–rain days. Intense SEP snowfall mainly affected the inland hill area of the peninsula, whereas light SEP snowfall reached farther inland. SEP rainfall shared a similar pattern with snowfall. The SEP frequency showed a significant interannual variability and a...
Journal of Applied Meteorology and Climatology
Typical rain gauge measurements have long been recognized to underestimate actual precipitation. ... more Typical rain gauge measurements have long been recognized to underestimate actual precipitation. Long-term daily precipitation records during 1961–2013 from a dense national network of 2379 gauges were corrected to remove systematic errors caused by trace precipitation, wetting losses, and wind-induced undercatch. The corrected percentage was higher in cold seasons and lower in warm seasons. Both trace precipitation and wetting loss corrections were more important in arid regions than in wet regions. A greater correction percentage for wind-induced error could be found in cold and arid regions, as well as high wind speed areas. Generally, the annual precipitation amounts as well as the annual precipitation intensity increased to varying degrees after bias correction with the maximum percentage being about 35%. More importantly, the bias-corrected snowfall amount as well as the rainstorm amount increased remarkably by percentages of more than 50% and 18%, respectively. Remarkably, th...
Journal of Applied Meteorology and Climatology
Hourly datasets obtained by automatic weather stations in Beijing, China, are developed and emplo... more Hourly datasets obtained by automatic weather stations in Beijing, China, are developed and employed to analyze the spatial and temporal characteristics of relative humidity (RH) and urban dryness island intensity (UDII) over built-up areas. A total of 36 stations inside the sixth ring road are considered as urban sites, while six stations in suburban belts surrounding the built-up areas are taken as reference sites. Results show that the RH is obviously smaller in urban areas than in suburban areas, indicating the effect of urbanization on near-surface atmospheric moisture and RH. A further analysis of relations between RH and temperature on varied time scales shows that the variations in RH in the urban areas are not due solely to changes in temperature. The annual and seasonal mean UDII are high in central urban areas, with the strongest UDII values occurring in autumn and the weakest values occurring in spring. The diurnal UDII variations are characterized by a steadily strong U...
Environmental Research Letters
Based on the satellite-derived global daily sea surface temperature (SST) data set with high reso... more Based on the satellite-derived global daily sea surface temperature (SST) data set with high resolution (0.25° by 0.25°), we analyzed changes in annual mean SST and extreme SSTs over the China Seas since 1982. Results show that the annual mean SST in the China Seas has experienced a remarkable declining trend during the global warming hiatus (1998–2013), which was dominated by the striking cooling of SST in boreal winter. Despite annual mean SST experienced warming hiatus after 1998, the regional averaged SST for 1998–2013 was still 0.5 °C above that for 1982–1997. The statistical distributions show that there are not only significant warmer climate shift in annual mean SSTs but also in annual extreme hot SSTs and cold SSTs. These changes can increase the likelihood of extreme oceanic warming events, known as marine heatwaves (MHWs). Further analyses reveal that, from 1982 to present, the MHW frequency increases at a rate of 1.13 events per decade, 2.5 times the global mean rate. Fo...
Applied Geography
Abstract The Weather Research and Forecasting model (WRF) includes a wildland fire-behavior modul... more Abstract The Weather Research and Forecasting model (WRF) includes a wildland fire-behavior module, WRF-Fire, which simulates wildland fire interactions with the atmosphere. Combining the WRF model with the coupled weather–wildland fire model allows simulations of wildland fire propagation. In this paper, we have chosen the method that performs simulation of wildfire spread progress coupled with prepared weather data as soon as a wildfire is found. In simulation of the weather field data, a one-way nest model is used with a grid resolution of 1 km. The high-resolution Digital Elevation Model (DEM) data (0.002° × 0.002°) and fuel distribution maps based on forest type data were used. We demonstrated the potential for establishing a real-time wildland fire forecasting system using WRF-Fire model based on the existing conditions and computing resources for weather condition at fire monitoring stations, which can be applied in monitoring and forecasting of the wildland fire disasters in the area of the country.
Meteorology and Atmospheric Physics
Based on a homogenized data set of monthly mean temperature, minimum temperature, and maximum tem... more Based on a homogenized data set of monthly mean temperature, minimum temperature, and maximum temperature at Shijiazhuang City Meteorological Station (Shijiazhuang station) and four rural meteorological stations selected applying a more sophisticated methodology, we reanalyzed the urbanization effects on annual, seasonal, and monthly mean surface air temperature (SAT) trends for updated time period 1960–2012 at the typical urban station in North China. The results showed that (1) urbanization effects on the long-term trends of annual mean SAT, minimum SAT, and diurnal temperature range (DTR) in the last 53 years reached 0.25, 0.47, and − 0.50 °C/decade, respectively, all statistically significant at the 0.001 confidence level, with the contributions from urbanization effects to the overall long-term trends reaching 67.8, 78.6, and 100%, respectively; (2) the urbanization effects on the trends of seasonal mean SAT, minimum SAT, and DTR were also large and statistically highly significant. Except for November and December, the urbanization effects on monthly mean SAT, minimum SAT, and DTR were also all statistically significant at the 0.05 confidence level; and (3) the annual, seasonal, and monthly mean maximum SAT series at the urban station registered a generally weaker and non-significant urbanization effect. The updated analysis evidenced that our previous work for this same urban station had underestimated the urbanization effect and its contribution to the overall changes in the SAT series. Many similar urban stations were being included in the current national and regional SAT data sets, and the results of this paper further indicated the importance and urgency for paying more attention to the urbanization bias in the monitoring and detection of global and regional SAT change based on the data sets.
Theoretical and Applied Climatology
Land surface air temperature (SAT) change is one of the core issues in monitoring and assessing r... more Land surface air temperature (SAT) change is one of the core issues in monitoring and assessing regional climate change. In this study, the characteristics of SAT change over DPR Korea for the period 1918–2015 were investigated using a high-quality historical dataset. Results show that the region-averaged annual mean SAT increased 0.21 °C/decade for the period 1918–2015 on the basis of data from four stations and 0.19 °C/decade for the period 1941–2015 as estimated based on data from nine stations. Before the 1970s, Pyongyang station in the central region experienced the largest warming trend. Linear trends of seasonal mean SAT during 1941–1970 were negative for all seasons in eastern coast and for summer and autumn in western coast and northern inland areas. Since 1971, however, the annual and seasonal mean SAT trends have shifted to positive values in all regions, with winter experiencing the most rapid warming. During the period of global warming slowdown since 1998 or 2000, no significant seasonal warming trend of wintertime was detectable, and this caused the smallest winter warming for the last 45 years. Other seasons also witnessed a generally weakened warming during 1971–2015 compared to that of 1971–2000. The results of the study will help in understanding regional climate change and in assessing the impacts of climate change on economic and natural ecosystems in the country.
Urbanization has led to a significant urban heat island (UHI) effect in Beijing in recent years. ... more Urbanization has led to a significant urban heat island (UHI) effect in Beijing in recent years. At the same time, air pollution caused by a large number of fine particles significantly influences the atmospheric environment, urban climate, and human health. The distribution of fine particulate matter (PM 2.5) concentration and its relationship with the UHI effect in the Beijing area are analyzed based on station-observed hourly data from 2012 to 2016. We conclude that, (1) in the last five years, the surface concentrations of PM 2.5 averaged for urban and rural sites in and around Beijing are 63.2 and 40.7 µg m −3 , respectively, with significant differences between urban and rural sites (PM 2.5) at the seasonal, monthly and daily scales observed; (2) there is a large correlation between PM 2.5 and the UHI intensity defined as the differences in the mean (T ave), minimum (T min), and maximum (T max) temperatures between urban and rural sites. The correlation between PM 2.5 and T mi...
Boundary-Layer Meteorology
While the land-surface temperature (LST) observed at meteorological stations has significantly in... more While the land-surface temperature (LST) observed at meteorological stations has significantly increased over the previous few decades, it is still unclear to what extent urbanization has affected these positive trends. Based on the LST data recorded at an urban station in Shijiazhuang in North China, and two rural meteorological stations, the effect of urbanization at the Shijiazhuang station for the period 1965–2012 is examined. We find, (1) a statistically-significant linear trend in annual mean urban–rural LST difference of 0.27\,^{\circ }\hbox {C}$$0.27∘C$$\hbox {(10 year)}^{-1}$$(10year)-1, with an urbanization contribution of 100% indicating that the increase in the annual mean LST at the urban station is entirely caused by urbanization. The urbanization effects in spring, summer and autumn on the trends of mean LST are also significant; (2) the urbanization effect is small for time series of the annual mean minimum LST, and statistically marginal for the trend in annual mean maximum LST [$$0.19\,^{\circ }\hbox {C}\,\hbox {(10 year)}^{-1}$$0.19∘C(10year)-1]; (3) the urbanization effect on the annual mean diurnal LST range ($$\Delta {LST}$$ΔLST) at the urban station is a strongly significant trend of 0.23\,^{\circ }\hbox {C (10\,year)}^{-1}$$0.23∘C (10year)-1, with an urbanization contribution of 21%. The urbanization effects on trends in the spring and autumn mean \Delta {LST}$$ΔLST are also larger and more significant than for the other seasons; (4) the urbanization effects on the long-term LST trends are remarkably different from those on the near-surface air temperature at the same urban station. Nonetheless, the significant warming of the urban boundary layer is expected to affect the urban environment and ecosystems. However, the problem of data representativeness at an urban station for the monitoring and investigation of large-scale climate change remains.
Datasets of daily precipitation, wind speed, and weather phenomena of 71 stations during 1960-200... more Datasets of daily precipitation, wind speed, and weather phenomena of 71 stations during 1960-2009 and experimental observations of precipitation from three stations are used to estimate wind-induced errors in winter snowfall records over northeastern China, and to analyze the effects of wind-induced under-catch on long-term winter snowfall trends. The results show that winter snowfall is generally undervalued. Although the region’s average annual snowfall was measured at 15.1 mm, the corrected snowfall was 22.5 mm, which indicates an average error of 7.5 mm, or relative error of approximately 34.1%. In recent years, the gauge catch rate has increased due to the weakening of surface wind speed resulting from urbanization and micro-environmental change surrounding the stations, which have led to an overestimate of winter snowfall trends in the study region. This analysis shows a trend of winter snowfall of 0.4mm/10yr for the past 50 years when the original precipitation data are used...
Geophysical Research Letters
Heavy PM 2.5 (particulate matter with aerodynamic diameter equal to or less than 2.5 μm) pollutio... more Heavy PM 2.5 (particulate matter with aerodynamic diameter equal to or less than 2.5 μm) pollution and urban heat island (UHI) pose increasing threats to human health and living environment in populated cities. However, how PM 2.5 pollution affects the UHI intensity (UHII) has not been fully understood. The impacts of PM 2.5 on the wintertime UHII in the Beijing-Tianjin-Hebei megalopolis of China are explored during 2013-2017. The results show that the UHII at the time of daily maximum/minimum temperature (UHII max /UHII min) exhibits a decreasing/increasing tendency as PM 2.5 concentration increases, causing a continuous decrease in the diurnal temperature range. These effects are mediated via aerosol-radiation interaction (aerosol-cloud interaction) under clear-sky (cloudy) condition. The changes in PM 2.5 concentration further cause different relative trends of UHII max /UHII min /diurnal temperature range across different cities in the Beijing-Tianjin-Hebei region, which are likely related to the differences in both the PM 2.5 composition and city size. This study provides insights on how air pollution affects urban climate and would help to design effective mitigation strategies. Plain Language Summary A detailed understanding of the relationship between PM 2.5 (particulate matter with aerodynamic diameter equal to or less than 2.5 μm) and the urban heat island (UHI) effect is significant for climate change adaption, planning, and sustainable development in urban regions. While the Beijing-Tianjin-Hebei (BTH) megalopolis of China is among the areas with the highest population densities and fastest urbanization rates in the world, the impacts of PM 2.5 pollution on UHI, along with their regional differences in the BTH megalopolis, remain unclear. This study demonstrates that different PM 2.5 concentrations in the BTH region pose various influences on the UHI intensities and their change rates in different cities of varying sizes. The UHI intensities during daytime and nighttime, respectively, exhibit weakening and strengthening tendency as PM 2.5 concentration increases. These effects are mediated via aerosol-radiation interaction under clear-sky condition and aerosol-cloud interaction in cloudy weather. The relative changes in the UHI magnitudes were mainly determined by PM 2.5 composition and city size. The asymmetrical influences of PM 2.5 on the daytime and nighttime UHI intensities caused continuous decreases in the diurnal temperature ranges in the urban areas as the pollution level increased. Our study improves the understanding of urban climate affected by air pollution and provides a scientific basis for the mitigation of UHI impacts.
Journal of Chemical Research
A coordination compound constructed from a nitronyl nitroxide biradical NITPh(3-NIT) and CuII(hfa... more A coordination compound constructed from a nitronyl nitroxide biradical NITPh(3-NIT) and CuII(hfac)2(H2O)2 building blocks [NITPh(3-NIT) = 1,3-bis(1′-oxyl-3′-oxido-4′,4′, 5′, 5′-tetramethyl-4,5-dihydro-1 H-imidazol-2-y1)-benzene, hfac = hexafluoroacetylacetonato] is successfully synthesized. The crystal structure is determined by X-ray single-crystal diffraction. The asymmetric complex {[(NITPh(3-NIT)]Cu(hfac)2} consists of one Cu(II) ion and two >N–O• groups and adopts a distorted triangular bipyramid with a penta-coordinated central copper(II) atom and three hfac oxygen atoms at the base and a >N–O• oxygen atom and one hfac oxygen atom at the apices. Intramolecular O. . .O bonding and π–π stacking interactions are observed between molecules. A magnetic susceptibility study of the coordination compound shows antiferromagnetic interactions between Cu(II) ions and >N–O• groups and very weak ferromagnetic interactions between Cu(II) ions and the free >N–O• group through O....
Hydrology
The Haihe River basin of North China is characterized by extremely low per capita water resources... more The Haihe River basin of North China is characterized by extremely low per capita water resources and a consistently long-term decreasing trend of precipitation and runoff over the last few decades. This study analyzes the climatological features of rainy season (May–September) precipitation in the Haihe River basin and its branch systems based on a high-density hourly observational dataset during 2007–2017. We show that there are two high-rainfall zones in the basin, with one along the south of the Yanshan Mountains to Taihang Mountains and another along the Tuma River in the south. Rainstorm centers exist amidst the two zones. July generally sees the highest precipitation, followed by August, and May has the lowest precipitation. The major flood season is reached between the third pentad of July and the fourth pentad of August. The precipitation is high at night but low in the daytime. In the pre-flood season before early July, rainfalls mostly arrive at 16:00–21:00 h. After enter...