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The focus of this study is an intense heat episode that occurred on 9–13 July 2017 in Beijing, China, that resulted in severe impacts on natural and human variables, including record-setting daily electricity consumption levels. This event was observed and analyzed with a suite of local and mesoscale instruments, including a high-density automated weather station network, soil moisture sensors, and ground-based vertical instruments (e.g., a wind profiler, a ceilometer, and three radiometers) situated in and around the city, as well as electric power consumption data and analysis data from the U.S. National Centers for Environmental Prediction. The results show that the heat wave originated from dry adiabatic warming induced by the dynamic downslope and synoptic subsidence. The conditions were aggravated by the increased air humidity during subsequent days, which resulted in historically high records of the heat index (i.e., an index representing the apparent temperature that incorporates both air temperature and moisture). The increased thermal energy and decreased boundary layer height resulted in a highly energized urban boundary layer. The differences between urban and rural thermal conditions throughout almost the entire boundary layer were enhanced during the heat wave, and the canopy-layer urban heat island intensity (UHII) reached up to 8°C at a central urban station at 2300 local standard time 10 July. A double-peak pattern in the diurnal cycle of UHIIs occurred during the heat wave and differed from the single-peak pattern of the decadal average UHII cycles. Different spatial distributions of UHII values occurred during the day and night. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive approach to renovating and optimizing balconies in old residential buildings in Beijing. Firstly, it explores residential balconies' evolution, characteristics, and development trends to identify various sample types and understand the associated problems and residents' needs related to balconies through investigation. Secondly, the Rhino/Grasshopper parametric platform is employed to simulate the performance and analyze data from standard balcony types, resulting in five qualitative and four quantitative renovation strategies and methods. Subsequently, these comprehensive renovation and optimization design strategies are implemented in the renovation process, and their performance is simulated. The daylight autonomy (DA), universal daylight indicator (UDI), and spatial daylight autonomy (sDA) metrics experienced significant increases of 16.56, 20.12, and 0.13, respectively, indicating improved light environment and functionality. Notably, the proposed strategies maintain consistent energy consumption and thermal comfort levels. Both PMV and PPD have improved, but the improvement is not significant, only by 0.01. The window-to-wall ratio has been increased by 0.1, and insulation has been added. The overall thermal comfort value is stable. These findings validate the practicality and effectiveness of the proposed approach and methods. This study provides valuable references for renovating and optimizing balconies in old residential buildings, contributing to problem-solving efforts and enhancing living quality. [ABSTRACT FROM AUTHOR]

Fourteen-month precipitation measurements from a second-generation PARSIVEL disdrometer deployed in Beijing, northern China, were analyzed to investigate the microphysical structure of raindrop size distribution and its implications on polarimetric radar applications. Rainfall types are classified and analyzed in the domain of median volume diameter D 0 and the normalized intercept parameter N w . The separation line between convective and stratiform rain is almost equivalent to rain rate at 8.6 mm h−1 and radar reflectivity at 36.8 dBZ. Convective rain in Beijing shows distinct seasonal variations in log 10 N w – D 0 domain. X-band dual-polarization variables are simulated using the T-matrix method to derive radar-based quantitative precipitation estimation (QPE) estimators, and rainfall products at hourly scale are evaluated for four radar QPE estimators using collocated but independent rain gauge observations. This study also combines the advantages of individual estimators based on the thresholds on polarimetric variables. Results show that the blended QPE estimator has better performance than others. The rainfall microphysical analysis presented in this study is expected to facilitate the development of a high-resolution X-band radar network for urban QPE applications. [ABSTRACT FROM AUTHOR]

Regional raindrop size distribution (DSD) features are poorly understood due to the lack of observations. Here we investigate the regional variability of summertime DSD in Beijing, using the DSD observations from ten disdrometer sites from April to September 2017. The characteristics of DSD are analyzed for both convective and stratiform precipitation, mainly classified by rain rate (R). The shape (μ) and slope (λ) parameters follow a second-degree polynomial regression relationship for both stratiform and convective precipitation. On average, stratiform precipitation is found to have larger values of μ and λ than convective precipitation, whereas convective precipitation has a larger mass-weighted mean diameter (D m) and a generalized intercept parameter (N w). Interestingly, the north of Beijing has larger values of μ and λ , as opposed to D m and N w that exhibit greater values in the south, which could probably be attributed to terrain differences. The rain rate dependence on DSD is analyzed as well. In general, the D m -R and N w -R relationships follow a power-law distribution, and both D m and N w increase significantly with R. As the rain rate increases, D m keeps increasing to around 1.5 mm until an equilibrium state is reached. The findings obtained here could provide useful reference for better estimations of rainfall using the remote sensing techniques. • Raindrop size distribution is reported from a network of disdrometers in Beijing. • Convective DSDs have larger D m and N w as compared to stratiform DSDs. • DSDs show variablity over space and dependence on precipitation regimes. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) and odors are two important gaseous pollutants escaped from landfill, which are harmful to human health and the surrounding environment. In this study, biofilter was used to control VOCs and odors from an actual landfill. The operating efficiency and mechanism of biofilters on the sealing zone and leachate treatment zone were respectively analyzed and compared. The results found that components of gaseous pollutants from these two zones are different. Hydrogen sulfide (572.96 μg/m3), ammonia (479.28 μg/m3), and dimethyl sulfide (279.81 μg/m3) were mainly detected in sealing zone, and dichloromethane (3573.97 μg/m3), triethylamine (1818.21 μg/m3), benzene (1809.11 μg/m3), and chlorobenzene (1286.81 μg/m3) were main components of gaseous pollutants in leachate treatment zone. Although the types and concentrations of gaseous pollutants in these two zones were significantly different, the biofilters showed good removal efficiencies. The average removal rate of the total VOC (TVOC), sulfides, and amines in both biofilters exceeded 80%. The outlet concentrations meet the level-3 standard of the Emission standards for odor pollutants (GB 14544–93). This is mainly related to the evolution of bacterial population during the operation of biofilters. In the inoculums, the dominant bacterial genus is Brevibacillus (58.84%), and bacteria with Bacillus and Pseudomonas only occupied 2.67% and 1.77%. With the extension of operation time, the dominant bacteria of biofilter in the sealing zone gradually evolved into Mycobacterium (67.82%) and Bacillus (27.90%), while the dominant bacteria of biofilter in the leachate treatment zone evolved into Bacillus (72.69%) and Pseudomonas (21.59%). These results indicated that identification of gaseous pollutant components and design of appropriate treatment systems based on their components will further improve the operating efficiency of biofilters in the actual landfill. Image 1 • Treatment of volatile organic compounds (VOCs) and odors by biofilters was studied. • Two biofilters were constructed in an actual landfill in Beijing. • Variation in waste gas concentrations and bacterial populations were analyzed. • The biofilters showed good removal efficiencies. • Scientific basis for co-treatment of VOCs and odors in landfills by biofilters provided. [ABSTRACT FROM AUTHOR]

Based on total lightning location data from the Beijing Lightning Network (BLNET) and hailfall reports from 2015 to 2017 in Beijing, as well as S-band radar data from the Beijing Meteorological Observation Center, the total lightning activities for 148 hailfall events are analyzed with the identification method of strong convective cells (CCs) (similar to Thunderstorm Identification Tracking Analysis and Nowcasting, TITAN). Most of the hailstorms have a very high flash rate (FR), and a significant increase in FR is observed before hailfall events. The 2σ lightning jump (LJ) algorithm (with 4 and 10 flashes/min activation thresholds for different districts of Beijing) is tested as a hailfall nowcasting predictor. The average LJ lead time is 27.1 min. LJs precede 81.8% of all hailfall events, and 38.6% of LJs are not followed by hailfall reports within one hour. The merging of two adjacent strong CCs usually forms hail-bearing severe thunderstorms producing a sudden increase in total lightning. In addition, most hailfall events occurred at the boundary of strong CCs instead of at the cell centers. This study shows that the total LJ is a potentially useful predictor for hail nowcasts in the Beijing area. • Detailed analysis on operational feasibility of the 2σ lightning jump algorithm for the hail nowcast in Beijing. • Hails usually occur in the vertical convection decline stage with the maximum VCS intensity exceeding 55 dBZ. • Hailstones are usually generated after two cells merge, except for isolated storms. [ABSTRACT FROM AUTHOR]