SURF: Understanding and Predicting Urban Convection and Haze

Abstract

34Urbanization modifies atmospheric energy and moisture balances, forming distinct 35 features, e.g., urban heat islands (UHIs) and enhanced or decreased precipitation. 36These produce significant challenges to science and society, including rapid and incudes complex topography with mountains, plains, and coastal areas (Fig. 1a), and 261 seven of the 10 most polluted Chinese cities, with 40% of days during 2013 (mostly in 262 winter) having "very hazardous" air quality (CMEP 2014 adaptation, air quality, planning, and emergency-response management. 298The critical science needed to achieve these goals was identified as increased WUQ), and one rural (SDZ) tower (all PBL observational sites are shown in Fig. 1). 335Other operational PBL sensors ( conditions. Photos of a selection of these instruments and sites are shown in Fig. 2. flown over pre-approved flight paths (Fig. 1) at altitudes from 600 to 3 600 m (at 300 357 m intervals). The aircraft is equipped with atmospheric gas and aerosol instrumenta- Additional observation data (e.g., weather radar, aircraft, and lightning) will be added. BTH area centered on Beijing (a somewhat larger area than in Fig. 1a). 439Additional details on all of these steps are provided by Zhang et al. (2017a (Fig. 1) were used to show that the dominant linear relationship between * and also 494 exists over urban canopies. The strong wind shear from the rough urban surfaces produces 495 turbulence in near neutral urban stability conditions, shown by Bornstein 1968 to exist over 496 NYC, as stable boundary layers over urban canopies are thus hard to maintain. The role of 497 surface roughness on turbulent mixing is also reflected in the increasing slope (Fig. 4) Table 4a shows the average midday (1000-1400 LST) radiative and energy fluxes 515Although MIY has higher outgoing longwave radiation, the net all-wave radiations 516 are nearly equal. Significant differences existed, however, in the surface energy 517 partitions, as IAP has smaller turbulent sensible and latent heat fluxes, and thus a 518 larger (estimated) residual heat storage. Another contributing factor to urban heat 519 storage is its anthropogenic heat flux source (discussed below). 520Daily mean Bowen ratios (ratio of turbulent sensible to latent-heat flux; Table 4b Normalized relative backscatter (NRB) data from two MPL lidar (in a vertical to 545 zenith scan mode) were also used to concurrently estimate midday PBL heights on 11 546August 2015 from 1250-1402 LST, both alone a mobile route (Fig. 1b) and at a fixed 547 site (adjacent to the urban IAP tower). As MPL instruments cannot be absolutely Beijing and fluxes from the 140-m level of the IAP tower (Fig. 1b). The modeling 574 period was 4-11 July 2015, which included dry (6 th -11 th ) and wet (4 th -5 th ) days. 575Results show major improvement for daytime "total" sensible plus latent heat flux 576 values ( Fig. 7a and b), although the timing of its peak was about 2 h too late. The 577 increased latent heat flux during the EC simulation (ac...

Simulation of the radiative effect of haze on the urban hydrological cycle using reanalysis data in Beijing

“…In recent decades rapid economic development and the acceleration of urbanization and industrialization have led to many environmental problems in China, such as increased atmospheric aerosol concentrations, water pollution, and soil contamination (e.g. Kulmala, 2015;Liao et al, 2015;Shao et al, 2006;Sun et al, 2014;Xia et al, 2011). As a consequence of urbanization and industrialization, north-east China is one of the most populated and polluted areas in the world (HEI International Scientific Oversight Committee, 2010).…”

Observational Analyses of Dramatic Developments of A Severe Air Pollution Event in the Beijing Area

“…8g). The strong wind shear relative to the rough urban surface generated strong turbulent mixing (e.g., Sun et al, 2017), and resulted in the strong upward transport of the polluted air and the downward transport of 25 the less-polluted air from northwest, leading to the decrease of PM 2.5 , q, and CO 2 (marked 1 in Figs.8a, 8b, and 8c). Thus, the shear-generated turbulent mixing contributed the reduction of the surface PM 2.5 concentration in the afternoon of 29 November.…”

“…During this event, the PM 2.5 concentration oscillated dramatically 12 hours before the final rapid increase on 30 November (Fan et al, 2015). This event happened to occur during the three-year field campaign of the Study of Urban Rainfall and Fog/Haze (SURF-15) (Liang et al, 2017), which started in the spring of 2015. Using extra measurements from SURF-15 as well as routine measurements spread around Beijing described in section 2, we investigate 35 2 Atmos.…”

“…Meanwhile, the PM 2.5 concentration at Beijing increased dramatically from 0500 LST to 1100 LST, and its development was faster than its surrounding area (Fig. 5), for which, the rough surface of the 10 urban area might have contributed additional turbulent mixing (Sun et al, 2017).…”

New Evidences on Anomalous Phenomenon of Buildings in Regulating Urban Climate From Observations in Beijing, China

“…By 2050, approximately 66% of global population will be expected to live in urban areas (United Nations, Department of Economic and Social Affairs, Population Division, ). As the two most important underlying elements of urban area, urban buildings and parks have substantially different effects on momentum, heat, and water vapor exchanges in land‐atmosphere interactions (Grimmond et al, ; Kuang, Liu, et al, ; Kuang et al, ; Liang et al, ; Oke et al, , ). Therefore, buildings and parks have different contributions in regulating urban microclimate phenomena, such as urban heat island (UHI; Grimm et al, ; Intergovernmental Panel on Climate Change, ; Kuang, Dou, et al, ).…”