Nanjing University of Information Science and Technology

About: Nanjing University of Information Science and Technology is a education organization based out in Nanjing, China. It is known for research contribution in the topics: Precipitation & Aerosol. The organization has 14129 authors who have published 17985 publications receiving 267578 citations. The organization is also known as: Nan Xin Da.

Role of intraseasonal oscillation in asymmetric impacts of El Niño and La Niña on the rainfall over southern China in boreal winter

Abstract: The impacts of El Nino and La Nina on the rainfall over southern China in winter half year (November–April) are investigated diagnostically. It is found that positive rainfall anomalies with statistical significance appear over southern China in El Nino winter but no reversed significant rainfall anomalies in La Nina winter. The asymmetry of the rainfall anomalies are related with the asymmetry in anomalous circulation over western North Pacific (WNP) in lower troposphere, with a strong anomalous anticyclone in El Nino winter but a weak anomalous cyclone in La Nina winter. It is revealed that the asymmetric responses in anomalous circulation to El Nino and La Nina are affected by the intraseasonal oscillation (ISO). In El Nino winter the interannual variation is dominant and the ISO is weak, and the strong interannual variation leads to a strong response of the anomalous anticyclone over WNP in winter half year. However, in La Nina winter the ISO is dominant and the interannual variation is weak, and the weak interannual variation results in a weak response of the anomalous cyclone over WNP.

PM2.5 Pollution Modulates Wintertime Urban‐Heat‐Island Intensity in the Beijing‐Tianjin‐Hebei Megalopolis, China

Abstract: Heavy PM2.5 (particulate matter with aerodynamic diameter equal to or less than 2.5 mu m) pollution and urban heat island (UHI) pose increasing threats to human health and living environment in populated cities. However, how PM2.5 pollution affects the UHI intensity (UHII) has not been fully understood. The impacts of PM2.5 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 (UHIImax/UHIImin) exhibits a decreasing/increasing tendency as PM2.5 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 PM2.5 concentration further cause different relative trends of UHII(ma)x/UHIImin/diurnal temperature range across different cities in the Beijing-Tianjin-Hebei region, which are likely related to the differences in both the PM2.5 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 PM2.5 (particulate matter with aerodynamic diameter equal to or less than 2.5 mu m) 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 PM2.5 pollution on UHI, along with their regional differences in the BTH megalopolis, remain unclear. This study demonstrates that different PM2.5 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 PM2.5 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 PM2.5 composition and city size. The asymmetrical influences of PM2.5 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.

Spatial variations of methane emission in a large shallow eutrophic lake in subtropical climate

Abstract: Subtropical lakes are an important source of atmospheric methane (CH4). This study aims to investigate spatial variations of the CH4 flux in Lake Taihu, a large (area 2400 km2) and shallow (mean depth 1.9 m) eutrophic lake in Eastern China. The lake exhibited high spatial variations in pollution level, macrophyte vegetation abundance, and algal growth. We measured the diffusion CH4 flux via the transfer coefficient method across the whole lake. In addition, data obtained with the flux-gradient and the eddy-covariance methods were used in conjunction with the data on the diffusion flux to estimate the contribution by ebullition. Results from three years’ measurements indicate high spatial variabilities in the diffusion CH4 flux. The spatial pattern of the diffusion CH4 emission was correlated with water clarity, and dissolved oxygen concentration, and with the spatial distributions of algal and submerged vegetation. In comparison to the transfer coefficient method, the eddy covariance and the flux-gradient method observed a lake CH4 flux that was 3.39 ± 0.58 (mean ± one standard deviation) and 1.95 ± 0.36 times higher in an open-water eutrophic zone and in a habitat of submerged macrophytes, respectively. The result implied an average of 71% and 49% ebullition contribution to the total CH4 flux in the two zones. The annual mean diffusion CH4 flux of the whole lake was 0.54 ± 0.30 g m-2 year-1. Our CH4 emission data suggest that the average CH4 emission reported previously for lakes in Eastern China was overestimated.