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Gaseous hydrochloric (HCl) and hydrobromic acid (HBr) are vital halogen species that play essential roles in tropospheric physicochemical processes. Yet, the majority of the current studies on these halogen species were conducted in marine or coastal areas. Detection and source identification of HCl and HBr in inland urban areas remain scarce, thus limiting the full understanding of halogen chemistry and potential atmospheric impacts in the environments with limited influence from the marine sources. Here, both gaseous HCl and HBr were concurrently measured in urban Beijing, China, during winter and early spring of 2019. We observed significant HCl and HBr concentrations ranging from a minimum value at 1 × 10 8 molecules cm -3 (4 ppt) and 4 × 10 7 molecules cm -3 (1 ppt) up to 6 × 10 9 molecules cm -3 (222 ppt) and 1 × 10 9 molecules cm -3 (37 ppt), respectively. The HCl and HBr concentrations are enhanced along with the increase of atmospheric temperature, UVB and levels of gaseous HNO 3. Based on the air mass analysis and high correlations of HCl and HBr with the burning indicators (HCN and HCNO), gaseous HCl and HBr are found to be related to anthropogenic burning aerosols. The gas–particle partitioning may also play a dominant role in the elevated daytime HCl and HBr. During the daytime, the reactions of HCl and HBr with OH radicals lead to significant production of atomic Cl and Br, up to 2 × 10 4 molecules cm -3 s -1 and 8 × 10 4 molecules cm -3 s -1 , respectively. The production rate of atomic Br (via HBr + OH) is 2–3 times higher than that of atomic Cl (via HCl + OH), highlighting the potential importance of bromine chemistry in the urban area. On polluted days, the production rates of atomic Cl and Br are faster than those on clean days. Furthermore, our observations of elevated HCl and HBr may suggest an important recycling pathway of halogen species in inland megacities and may provide a plausible explanation for the widespread halogen chemistry, which could affect the atmospheric oxidation in China. [ABSTRACT FROM AUTHOR]

Surface air temperature (Ta), as an important climate variable, has been used in a wide range of fields such as ecology, hydrology, climatology, epidemiology, and environmental science. However, ground measurements are limited by poor spatial representation and inconsistency, while reanalysis and meteorological forcing datasets suffer from coarse spatial resolution and inaccuracy. Previous studies using satellite data have mainly estimated Ta under clear-sky conditions, or with limited temporal and spatial coverage. In this study, an all-sky daily mean Ta product at 1 km spatial resolution over mainland China for 2003-2019 has been generated mainly from the Moderate Resolution Imaging Spectroradiometer (MODIS) products and the Global Land Data Assimilation System (GLDAS) dataset. Three Ta estimation models based on random forest were trained using ground measurements from 2384 stations for three different clear-sky and cloudy-sky conditions. The validation results showed that R2 and root mean square error (RMSE) values of the three models ranged from 0.984 to 0.986 and 1.342 K to 1.440 K, respectively. We examined the spatiotemporal patterns and land cover type dependences of model accuracy. The relative contributions of different features to models were also quantitatively analysed. Finally, values of our Ta product in 2010 were validated and compared with the China Land Data Assimilation System (CLDAS) dataset at 0.0625° spatial resolution, China Meteorological Forcing Data (CMFD) dataset at 0.1° spatial resolution and GLDAS dataset at 0.25° spatial resolution. The R2 and RMSE values of our product were 0.992 and 1.010 K, respectively, indicating this high-resolution satellite product has significantly higher accuracy. In summary, the all-sky daily mean Ta dataset developed in this study has achieved satisfactory accuracy and high spatial resolution simultaneously, which fills the current dataset gap in this field and plays an important role in the studies of climate change and hydrological cycle. This dataset is freely available at http://doi.org/10.5281/zenodo.4399453 (Chen et al., 2021b) and the University of Maryland (http://glass.umd.edu/Ta%5FChina/) currently. A sub-dataset that covers Beijing generated from this dataset is publicly available at http://doi.org/10.5281/zenodo.4405123 (Chen et al., 2021a). [ABSTRACT FROM AUTHOR]

Extreme air temperature directly affected human health. However, the short-term effect of extreme air temperature on the incidence of cardiovascular diseases has rarely been reported in China. In this study, we focused on Beijing, China, and assessed the effects of cold/warm days and nights on the number of hospital emergency room (ER) visits for cardiovascular diseases from 2009 to 2012. We used a generalized additive model (GAM) to estimate the association between extreme air temperature and the number of hospital ER visits for cardiovascular diseases. We divided the entire study group into two gender subgroups and three age subgroups. The results showed that the short-term effect of extreme air temperature on hospital ER visits for cardiovascular diseases was more profound in females and the elderly (aged ≥ 75 years). Among all the study subgroups, the highest relative risk (RR) of cardiovascular diseases associated with extremely cold days, warm days, cold nights, and warm nights was 3.0% (95% CI, 1.6%–4.4%), 0.8% (95% CI, − 0.9%–2.6%), 2.8% (95% CI, 1.6%–4.2%), and 1.8% (95% CI, 0.6%–4.3%), respectively. Overall, the effect of extremely low air temperature (during both days and nights) on the incidence of cardiovascular diseases was stronger and more acute than that of extremely high air temperature. [ABSTRACT FROM AUTHOR]

The production of Chinese chives is reduced throughout China due to a root-feeding dipteran pest Bradysia odoriphaga Yang et Zhang (Diptera: Sciaridae), therefore deciphering the conditions influencing its growth and development are important in developing ecological control strategies. A study was conducted from 2014 to 2017 to determine the relationship between the abundance of B. odoriphaga and temperature (atmospheric and soil), soil water content, and atmospheric humidity in a Chinese chive field in Beijing City, China. Numbers of adults peaked in March and October to November and were lowest in July to August and December to next February; numbers of larvae were highest in December to next February and lowest in July to August. From 2014 to 2017, the numbers of adults and larvae were significantly correlated with monthly mean atmospheric temperatures and soil temperatures, but were not significantly correlated with monthly mean atmospheric relative humidity and soil water content. However, for both adults and larvae, numbers were significantly greater with high soil water contents compared with drought treatment. The results of this study suggest that the very low soil water contents, high atmospheric temperatures, and high soil temperatures were critical for regulating field populations of B. odoriphaga. [ABSTRACT FROM AUTHOR]

Urban heat island (UHI) can be characterized and quantified to understand the modification of urban surfaces on the local and regional climate. This study examines UHI variation across three megacities that are located in rapid urbanization regions in eastern China (Beijing, Shanghai and Guangzhou). These cities are located within a warm temperate climate zone, north subtropical climate zone, and lower subtropical climate zone, respectively. Satellite-based land surface temperature (LST) data and air temperature records from 2003 to 2016 were used to identify surface urban heat island (SUHI) and canopy urban heat island (CUHI), respectively. Generally, the average annual SUHI is higher than the CUHI, with the greatest UHIs appearing in Beijing (SUHI: 2.33 ± 0.18 °C, CUHI: 1.45 ± 0.54 °C). UHI changes across latitudes were negatively related to humidity variation, with higher UHI in drier climates. Seasonal UHI analysis suggests that a lower SUHI would occur in winter and a higher UHI in spring and summer, except for Guangzhou. CUHI in dry season was higher than in wet season for all three megacities, and the largest CUHI (2.10 ± 0.33 °C) appeared in winter in Beijing. Various patterns of seasonal cycles of SUHI and CUHI were related to monthly precipitation and solar insolation. Annual average daytime SUHI was higher than the nighttime SUHI, and larger daytime SUHI appeared in Guangzhou, contrasting with Shanghai and Beijing. The difference between SUHI and CUHI for all seasons was also high in Guangzhou. UHI changes were considered to be altered by warm and wet conditions in mega-cities of eastern China, and heat transportation from urban surface to urban canopy provided some possible understanding of the UHI change. [ABSTRACT FROM AUTHOR]

• 7 phases of leafing and 6 phases of flowering of Chinese pine can be identified. • Leaf and male cone phenophases advanced along rural-urban gradients. • The influence of urbanization on phenology depended on plant growth stage. • The timing of leaf phenophases was negatively related with minimum air temperature. Numerous studies have shown that plant phenology has advanced due to urbanization. However, large uncertainties remain because different indicators and methods have been used to characterize plant phenology. In this study, by means of photograph identification and logistic curve fitting, the phenophases of leaves and male cones of Chinese pine (Pinus tabuliformis Carr.) were divided into seven and six phases, respectively. The rural-urban gradient in phenology of leaves and male cones varied significantly in ranges of 0.36–1.92 and 0.41–0.66 days/km, respectively, depending on the phenophase defined. Interestingly, the rural-urban gradient of leaf phenology increased with leaf development. Thus, fine separation of phenophases is necessary to provide more precise criterion for assessing urbanization-induced plant phenology across different studies or regions. For Chinese pine, the timings of maximum leaf elongation rate achievement and male cones maturation were key phenophases for investigating the effect of urbanization. [ABSTRACT FROM AUTHOR]

Measurements of speciated atmospheric mercury play a key role in identifying mercury behavior in the atmosphere. In this study, we measured speciated atmospheric mercury, including gaseous elemental mercury (GEM), reactive gaseous mercury (RGM), and particulate bound mercury (PBM) (<2.5 μm), in 2015 and 2016 at an urban site in Beijing, China. The mean concentrations of GEM, RGM, and PBM were 4.70 ± 3.53 ng m−3, 18.47 ± 22.27 pg m−3, and 85.18 ± 95.34 pg m−3, respectively. The concentration of PM 2.5 significantly affected the distribution of reactive mercury between the gaseous and particulate phases. With the raising of PM 2.5 levels, PBM concentrations increased, on the contrary, the concentrations of RGM decreased gradually. The mean concentration of PBM during air-pollution events was more than three times that during clear days. During days with air pollution, the relative humidity significantly affected the gas-particle partitioning of reactive mercury. The linear relationships between gas-particle partitioning coefficient and meteorological factors (air temperature and relative humidity) were obtained over the four seasons. The data also showed that the gas-particle partitioning coefficient of reactive mercury was related to particle composition (e.g., Cl−, BC). The data present in this paper suggested the influence of anthropogenic emissions on reactive mercury in Beijing urban. And the findings will contribute to understand the gas-particle partitioning of reactive mercury and its influencing factors with complex urban pollution. Image 1 • Three speciated atmospheric mercury exhibited obviously seasonal and diurnal variations. • Increasing PM 2.5 led to a decrease in RGM levels and an increase in PBM levels. • Temperature, relative humidity, and particle composition were important factors in determining the reactive mercury gas-particle partitioning. PM 2.5 levels influenced the RGM and PBM concentrations, and the important factors that affect the reactive mercury gas-particle partitioning were discussed. [ABSTRACT FROM AUTHOR]

A new type of roof structure was developed for the shade room in a double-slope greenhouse used for mushroom-vegetable planting. A simulation model was developed to evaluate the thermal performance of the new roof with an insulation thickness of 0.12 m in Beijing, China. The results showed that (1) the indoor air temperature of the shade room with the newly implemented shade roof was 2.7°C-4.9°C higher than that of an ordinary shade room during the winter months; (2) The indoor air temperature of the solar room adjacent to the shade room with the new roof was higher than that of the ordinary solar room and the minimum indoor air temperature of the solar room was increased 1.9°C at winter night; (3) the indoor temperature of the shade room with the new roof design was 2°C-4°C lower than that of the ordinary shade room during the summer months; (4) Under factory production conditions, which were conducted in a controlled environment to promote the annual growth of the edible fungus, the heating energy consumption of the shade room after the implementation of the new roof structure was reduced by 69.3%, the amounted to total energy savings of 61.3% per year. The new roof structure provided a significant improvement in the thermal environment compared to an ordinary shade room, improved the vegetable growth in the winter, and also significantly reduced the energy consumption and production costs. [ABSTRACT FROM AUTHOR]

Urban buildings and parks play an important role in regulating urban climate and ecosystem services. Diurnal air temperature range (DTRa) of rocklike buildings is commonsensically regarded as higher due to no latent heat from evapotranspiration and its smaller thermal inertia compared to wet soil. Therefore, the building DTRa is supposed to be higher than that of parks due to its building fabric. However, we found an opposite phenomenon (smaller building DTRa than that of parks), and the underlying mechanisms explaining this phenomenon are unclear. Here we conducted, in Beijing (China), a long‐term observational campaign of standard meteorological variables and radiation/energy fluxes to provide a new valuable evidence (a part of external energy) to explain this phenomenon. The observations indicated external heat energies from horizontal advection and anthropogenic heat sources. We found a significantly lower building DTRa than that of parks (ΔDTRa =2.53±1.93 °C), with a maximum difference of 3.54±1.96 °C in autumn; which was mainly attributed to higher daily minimum air temperature. We also found the large differences in air temperature contribution between the buildings and the parks happened mainly at night. The external heat sources of the building contributed 16.71% to the nighttime air temperature, which was higher than that of the parks (8.39%). The more indoor and outdoor anthropogenic heat sources in the building footprints were the major cause of the slower decrease in Tmin. The comparison between buildings and parks can be extensively applied to analyzing the effects of urbanization on climate. Plain Language Summary: An effective mosaic of buildings and parks, as the two core elements of cities, plays an important role in regulating urban climate and providing ecosystem services. A comfortable urban environment is becoming the pivotal theme for the United Nations Sustainable Development Goals 2030 related to resilient and sustainable cities and to mitigate climate change. While the urbanization effect on the diurnal air temperature range (DTRa) is still being debated within the climate community, we, surprisingly, found a significantly lower DTRa of buildings than of parks, which contradicts our common knowledge. The observations showed that nocturnal radiation cooling did not result in a decrease of air temperature, largely due to external heat input (60.17±22.98 W/m2). Heat fluxes of both the building roofs from their large indoor heat sources and the mixed peripheral advection with anthropogenic heat discharges contributed to a higher minimum air temperature. In daytime, despite additional input from human‐induced energy, neighboring vegetation transpiration and building/tree shadows offset those heat fluxes and slowed down the air temperature increase. The findings provide new knowledge on urban heat island mitigation and climate change adaptation. Key Points: The diurnal air temperature range of buildings is significantly lower than that of parks (ΔDTRa = 2.53±1.93 °C)The lower diurnal air temperature range of buildings compared to parks is attributed to a higher daily minimum air temperatureThe contribution of external heat sources by buildings (16.71%) to the nighttime air temperature was twice that of the park (8.39%) [ABSTRACT FROM AUTHOR]

To evaluate the contribution of urban surface expansion to regional warming using different methods to calculate the daily mean surface air temperature (SAT), satellite-based images displaying urban surface expansion over the past 37 years (1980-2016) across China were collected for use in nested numerical experiments using the weather research and forecasting (WRF) regional climate model. The contribution of urban surface expansion to urban-related warming was determined using the daily mean SAT averages based on four time records each day (00, 06, 12, and 18 h UTC, T4) and averages of the SAT maximum (Tmax) and minimum (Tmin) (Txn). The contribution of urban surface expansion to urban-related warming (relative value) in Beijing was 0.110°C per decade (22.8% of total warming) for T4 and 0.094°C per decade (20.2%) for Txn. The values obtained when using T4 were larger than those obtained when using Txn. Differences in the urban-related warming calculated using T4 and Txn could be attributed to the smaller changing trends in Txn in the urban-surface expansion experiment, which resulted from a large changing trend in Tmin and a much smaller changing trend in Tmax. The changes in the diurnal cycle of the energy budget due to urban surface expansion induced changes in the diurnal cycle of SAT, as evidenced by the four time records each day, as well as Tmax and Tmin. This was especially true for periods of intense urban surface expansion, although the annual mean SAT calculated using Txn was larger than that calculated using T4. The increase in impervious area (walls, streets, etc.) due to urban surface expansion, as well as the widespread use of building materials with a large heat capacity resulted in a marked increase in ground heat flux in the daytime. This restricted the increase in SAT in the daytime, but promoted it at night. The increases in SAT due to urban surface expansion were not symmetrical, being smaller in the daytime and larger at night. [ABSTRACT FROM AUTHOR]

• The urban forest was a C sink, which was dominated by changes in R e rather than GEP. • Annual GEP and R e were primarily controlled by summer SWC. • Summer T a impacted annual NEE through the suppression of R e , rather than GEP. • Drought decreased both GEP and R e , with greater reduction in R e relative to GEP. Afforestation projects in urban areas have generally prospered in China. Although urban forests play an important role in sequestering carbon (C) at local to regional scales, understanding the current role of C-sink strength in urban forests is generally absent. We used continuous eddy-covariance and hydrometeorological data from 2012 to 2020 acquired from an urban forest reserve in Beijing to assess the interannual variability (IAV) in C-fluxes, as well as their key controlling factors. Over the study period, the urban forest was mostly a C-sink, maintaining a mean net ecosystem exchange (NEE) of -195 ± 98 g C m−2 yr−1. Interannual variability in NEE was largely due to variation in ecosystem respiration (R e). Interannual variation in annual gross ecosystem production (GEP) and R e were controlled to a large extent by summer soil water content (SWC). Since the effects of SWC on GEP and R e partially offset their individual responses, IAV in annual NEE was seen as being less influenced by summer SWC. Annual NEE was constrained by changes in summer air temperature (T a). Residuals based on a R e -to- SWC regression exhibited significant decreases with increasing summer T a , appreciably more than the residuals based on GEP- to -SWC regressions. This underscored the importance of summer T a in impacting annual NEE through the suppression of R e , rather than through GEP. Our analysis also revealed that R e was more affected by drought than GEP. Long-lasting drought, greater than one month, was seen to impact GEP and R e more than short-term drought. Our study might imply that irrigation by elevating SWC was not be an effective strategy improving NEE of urban forest. Under anticipated climate change, drought and attendant high temperatures would impact C-fluxes more in the future. Land-surface models should adequately address the inhibitive characteristics of high temperatures on C-fluxes to improve simulations. [ABSTRACT FROM AUTHOR]

• We examined environmental controls on ecosystem RUEs in a young, urban plantation. • Upward trends in RUEs corresponded with increases in NDVI. • Duration and timing of drought played a significant role in regulating RUEs. • Ample mid-summer rainfall lessened the impact early, spring drought had on RUEs. Understanding the long-term trends and interannual variability in ecosystem resource use efficiencies (RUEs) and their controlling factors is central to the prediction of ecosystem response to climate change. However, knowledge in this area, particularly as it pertains to young urban plantations, remains largely absent. In this study, we used continuous eddy covariance and site-specific climatic data collected from a 12-year-old mixedwood plantation in Beijing, China, to assess (i) long-term trends, (ii) interannual variability, and (iii) key controlling factors of RUEs with respect to plantation use of carbon (i.e., CUE), water (WUE) and light (LUE). On average, annual CUE and WUE over the 2012–2020 growing seasons increased by about 5.2 and 7.6%. Trends in RUEs corresponded with increases in normalized difference vegetation index (NDVI) when the plantation transitioned from a carbon source to a sink. Analysis of controlling factors indicated that RUEs were regulated by NDVI and other environmental factors at varying degrees dependent on season. Interannual variability in (i) CUE was largely controlled by spring soil temperature, (ii) WUE by summer water vapor pressure deficit and spring soil water content (SWC), and (iii) LUE by photosynthetically active radiation, summer SWC and spring air temperature. Relative seasonal changes in paired RUEs were positively correlated, with soil water availability being the most limiting. Long-term summer drought was shown to evoke severe and persistent decline in same-year RUEs. Ample mid-summer rainfall lessened the impact of early spring drought on plantation performance. Our results emphasized the need to account for the combined effects of climatic controls and canopy-physiological characteristics in the management of young plantations. [ABSTRACT FROM AUTHOR]

To obtain a better understanding of the behaviour of the energy balance, CO2 fluxes and the turbulence characteristics in cities, eddy covariance (EC) measurements of turbulent fluxes and variances were collected continuously during the entire year of 2009 at three levels, 47, 140 and 280m, over an urban landscape in Beijing. The results showed that the summer daytime maximum of the sensible heat (105W m-2) was similar to the winter value (102W m-2), although the summer daytime maximum of the latent heat (167W m-2) was greater than the winter value (23W m-2). The heat storage as the residual of the energy balance ranged from -145 to 404W m-2 and from -95 to 90W m-2 in summer months and winter months, respectively. The annual CO2 emissions were estimated at 32.6, 34.6 and 34.2 kg CO2 m-2 yr-1 at 47, 140 and 280m, respectively, which is considerably higher than the yearly emissions obtained for other urban and suburban landscapes. The variation of turbulence characteristics supported the well-known empirical formulation. [ABSTRACT FROM AUTHOR]

Abstract: Temporal variations of organochlorine pesticides (OCPs) were determined in precipitation and monthly depositional fluxes were calculated in Beijing from February 2009 to March 2011. Compounds which were detected most often included α-HCH and β-HCH, and the volume-weighted mean (VWM) concentration of hexachlorocyclohexanes (HCHs) was 33.0 ng L−1, accounting for 72.3% of the ∑OCPs in precipitation. The total concentrations of OCPs ranged from 3.73 to 152 ng L−1 (mean: 29.7 ± 3.5 ng L−1) for dissolved phase and from 1.61 to 114 ng L−1 (mean: 15.9 ± 2.0 ng L−1) for particulate phase, respectively. OCPs in dissolved phase dominated sampled concentrations in precipitation (HCHs: 71.8%, Chlordane: 77.7%, dichlorodiphenyltrichloroethanes-DDTs: 50.1%) with an exception of hexachlorobenzene–HCB (26.3%). Furthermore, the distribution coefficient, K pd, was generally large in low temperature, especially in spring. The abundance of ∑OCPs in the precipitation fluctuated monthly, with high value in late winter and spring. The past farmland near the sampling site was under construction during sampling, which may be an important local re-emission source in this study. The elevated wet deposition flux of 11 selected OCPs was 14.9 μg m−2 yr−1 in Beijing. [Copyright &y& Elsevier]

Abstract: This study investigates the weekly periodicity of PM10 (aerosol particulate matter with a diameter <10 μm) mass concentrations over Beijing and Tianjin as well as its relationship with synoptic-scale weather variability. The two cities are large air pollutant source regions that are often affected by the same weather system due to their close proximity. Comparison of the two cities, therefore, advances our understanding of the contributions of the weather variability (or anthropogenic emissions) to the weekly periodicity of PM10. Here we analyze PM10 anomalies against weekly means over the past 10 years (2000–2009) on the frequency domain using a fast Fourier transform. Results show that the interannual variabilities of PM10 weekly periodicity, defined as the ratio of 6–8-day variance to 2–14-day variance, between Beijing and Tianjin are correlated in the summer and fall, but are uncorrelated in the spring. In the fall, the higher correlation of PM10 weekly periodicity between the two cities may be associated with strong influence of the natural weather variability as represented by 850-hPa geopotential height, surface diurnal temperature range, and 1000-hPa wind. However, in the spring and summer, the influence of the weather variability on the PM10 weekly periodicity was not identified. The weather variability accounts for 0–85% of the PM10 weekly periodicity variation, with the maximal value in Beijing in the fall. These findings suggest that contribution of the weather variability to shaping the PM10 weekly periodicity over Beijing and Tianjin is restrictive and transient. [Copyright &y& Elsevier]

Abstract: A high-resolution and absolute-dated stalagmite record from Kulishu Cave, Beijing characterizes Asian Monsoon (AM) history in northern China between ca 14 and 10.5 ka BP (thousand yrs before present, present = 1950), including the entire Younger Dryas (YD) event. Using 230Th dates and counting of annual-layers, the shift into the YD began at 12,850 ± 40 yr BP and took ∼340 yrs and the shift out of the YD began at 11,560 ± 40 yr BP and took <38 yrs (best estimate ∼20 yrs), broadly similar to previously reported AM records from central and southeastern China. The more gradual nature of the start of the YD event as observed in the AM records appears to contrast with the more abrupt beginning observed in the Greenland ice records. The total amplitude of the AM YD event is also smaller than the amplitude of the AM Heinrich Stadial 1 event. In addition, the general rising trend of the AM during the Bølling-Allerød period contrasts with the general cooling trend in Greenland temperature during that time. The influence of rising insolation on the AM may explain this observation. [Copyright &y& Elsevier]

Abstract: Understanding theimpact of urban underlying surfaces on the urban local climate is very important. The analysis on climatic characteristics of different urban landscape communities can play an important part in understanding the urban surface – atmosphere interaction, urban planning and landscape design. In this study, meteorology and radiation observation data of two typical urban landscape communities (a typical architectural complex and a green park) in Beijingwere used to analyze the climate differences and energy budget items differences with alocalscaleurban meteorological parameterization scheme (LUMPS). The results showed that: 1) Comparison with the green park, the architectural complexwas more hot-dry climatic conditions than the green park.The difference value of air temperature and relative humidity of the two communities were 0.30°C and 2.0% separately. 2) The changes of energy budget items could explain the change process of air temperature. The heat budget of different landscape communities existed differences, especially net radiation and latent heat flux, which displayed a marked difference. Therein, the annual mean net radiation and the latent heat flux of the green park were 14.33W/m2and 14.56W/m2 higher than the architectural complex area, respectively. While the sensible heat flux of the green park was 2.9W/m2 lower than the architectural complex area. 3) The latent heat flux had close relationship with air temperature, and had a lag effect. The correlation coefficient between latent heat flux and temperature could reach 0.633 from the initial 0.513 after about 2-hour delay. All these demonstrated the important effects of latent heat on temperature. [Copyright &y& Elsevier]

Ground-based microwave radiometer profilers (MWRPs) are widely used to provide high-temporal resolution atmospheric temperature and humidity profiles. The quality of the observed brightness temperature (TB) from MWRPs is key for retrieving accurate atmospheric profiles. In this study, TB simulations derived from a radiative transfer model (RTM) were used to assess the quality of TB observations. Two types of atmospheric profile data (conventional radiosonde and ERA5 reanalysis) were combined with the RTM to obtain TB simulations, then compared with corresponding observations from three MWRPs located in different places in North China to investigate the influence of input atmospheric profiles on TB simulations and evaluate the quality of TB observations from the three MWRPs. The comparisons of the matching samples under clear-sky conditions showed that TB simulations derived from both radiosonde and ERA5 profiles were very close to the TB observations from most of the MWRP channels; however, the correlation was lower and the bias was obvious at 51.26 GHz and 52.28 GHz, which indicates that the oxygen absorption component in the RTM needs to be improved for lower-frequency temperature channels. The difference in location of the radiosonde and MWRP sites affected the TB simulations for the water vapor channels, but had little impact on temperature channels that are insensitive to humidity. Comparisons of both simulations (ERA5 and Radiosonde) and the corresponding TB observations from the three sites indicated that the water vapor channels observation quality for the MWRP located in southern Beijing needs improvement. For the two types of profile data, ERA5 profiles have a more positive effect on TB simulations in the water vapor channels, such as enhanced consistence, reduced bias and standard deviation between simulations and observations for those MWRPs located away from the radiosonde station. Therefore, hourly ERA5 data are an optimal option in terms of compensating for limited radiosonde measurements and enhancing the monitoring quality of MWRP observations within 24 h. [ABSTRACT FROM AUTHOR]

Based on 139 nights of observational data of the Rayleigh lidar site in Beijing, China (40.5° N, 116.2° E), typical lower MIL cases and their temperature inversion evolution process were reported and compared with the SABER data from the same time. Meanwhile, the seasonal distribution of lower MIL cases over North China was also statistically analyzed. The average inversion temperature of the low MIL is 23.4 K, and the average layer thickness is 4.78 km with an average MIL bottom altitude of 68.2 km. Meanwhile, 65% of the MIL propagates vertically, most of which goes downward. These results show the temperature behavior properties of the lower MIL over North China, which may be helpful for us to further understand middle atmosphere chemical and dynamics processes. [ABSTRACT FROM AUTHOR]

In this study, a one-dimensional variational (1D-VAR) retrieval system is proposed to simultaneously retrieve temperature and humidity atmospheric profiles under clear-sky conditions. Our technique requires observations from the Fengyun-3D Hyperspectral Infrared Radiation Atmospheric Sounding (HIRAS) satellite combined with the Weather Research and Forecast (WRF) model. In the method, the radiative transfer for the TIROS Operational Vertical Sounder (TOVS (RTTOV) model is also used as a forward observation operator. The accuracy of our approach was evaluated using as a case study the region of Beijing in China. Predicted temperature and humidity profiles were compared against ERA-Interim data, which was used as reference. Mean bias (MB) of the temperature profiles varied between −0.8 K to 0.9 K, while the root-mean-square error (RMSE) ranged from 0.5 K to 2.6 K. In the boundary layer, the 1D-VAR algorithm performed better compared with the first guess. In the middle troposphere, the retrievals were more dependent on the first guess. With respect to relative humidity predictions, the accuracy of the evaluation of the whole troposphere was improved with the inclusion of the satellite observations, reporting an MB varying from −5.68% to 2.83%. Compared with Atmospheric Infrared Sounder's (AIRS') products, our predicted temperature profiles showed a very good consistency and the humidity predictions were also of an acceptable prediction accuracy. All in all, results clearly evidenced the promising potential of our proposed approach for retrieving temperature and humidity profiles under clear-sky conditions. [ABSTRACT FROM AUTHOR]

Glyoxal (CHOCHO) and formaldehyde (HCHO) trace gases were successfully retrieved from a multi-axis differential optical absorption spectroscopy (MAX-DOAS) system in Beijing (39.95°N, 116.32°E) and Baoding (39.15°N, 115.40°E), China. The measurements of these trace gases span the period from May 2017 to April 2018. Higher levels of trace gases were observed in Beijing most likely due to increased transport and industrial activities compared to Baoding. Different time scales were analyzed from seasonal to daily levels. Seasonal variation categorized by wintertime maximum and summertime minimum was observed for CHOCHO, while for HCHO maximum values were recorded during summer at both observation points. Variations in the diurnal cycle of trace gases were examined. The results are consistent with strong links to photo-oxidations of VOCs for HCHO production, whereas the CHOCHO diurnal variation can be related to anthropogenic effects in the evening. Weekends didn't have any significant effect on both HCHO and CHOCHO. We investigated the temperature dependency of HCHO and CHOCHO. HCHO shows positive correlation with air temperature, which strengthened the argument that HCHO production is linked to photo-oxidation of VOCs. CHOCHO is anti-correlated with air temperature. This suggests that photolysis is a major sink for CHOCHO in Beijing and Baoding. We also investigated the relationship between CHOCHO and HCHO VCDs with enhanced vegetation index (EVI) data obtained from MODIS, which represents a direct relation with biogenic emissions. The positive correlations were observed among monthly mean HCHO VCDs and monthly mean EVI at both monitoring stations. The strong correlation of HCHO with EVI found, suggests that oxidation of isoprene and HCHO production is strongly related, while negative correlation was observed among CHOCHO VCDs and EVI. [ABSTRACT FROM AUTHOR]