scholarly journals The Climatology of Lower Tropospheric Temperature Inversions in China from Radiosonde Measurements: Roles of Black Carbon, Local Meteorology, and Large-Scale Subsidence

2020 ◽  
Vol 33 (21) ◽  
pp. 9327-9350 ◽  
Author(s):  
Jianping Guo ◽  
Xinyan Chen ◽  
Tianning Su ◽  
Lin Liu ◽  
Youtong Zheng ◽  
...  
Keyword(s):  
Black Carbon ◽  
Large Scale ◽  
North China Plain ◽  
North China ◽  
Temperature Inversion ◽  
Tropospheric Temperature ◽  
The North ◽  
Local Meteorology ◽  
Underlying Mechanisms ◽  
Temperature Inversions

AbstractThe variability of the lower tropospheric temperature inversion (TI) across China remains poorly understood. Using seven years’ worth of high-resolution radiosonde measurements at 120 sites, we compile the climatology of lower tropospheric TI in terms of frequency, intensity, and depth during the period from 2011 to 2017. The TI generally exhibits strong seasonal and geographic dependencies. Particularly, the TI frequency is found to be high in winter and low in summer, likely due to the strong aerosol radiative effect in winter. The frequency of the surface-based inversion (SBI) exhibits a “west low, east high” pattern at 0800 Beijing time (BJT), which then switches to “west high, east low” at 2000 BJT. Both the summertime SBI and elevated inversion (EI) reach a peak at 0800 BJT and a trough at 1400 BJT. Interestingly, the maximum wintertime EI frequency occurs over Southeast China (SEC) rather than over the North China Plain (NCP), likely attributable to the combination of the heating effect of black carbon (BC) originating from the NCP, along with the strong subsidence and trade inversion in SEC. Correlation analyses between local meteorology and TI indicate that larger lower tropospheric stability (LTS) favors more frequent and stronger TIs, whereas the stronger EI under smaller LTS conditions (unstable atmosphere) is more associated with subsidence rather than BC. Overall, the spatial pattern of the lower tropospheric TI and its variability in China are mainly controlled by three factors: local meteorology, large-scale subsidence, and BC-induced heating. These findings help shed some light on the magnitude, spatial distribution, and underlying mechanisms of the lower tropospheric TI variation in China.

scholarly journals Vertical profiles of black carbon measured by a micro-aethalometer in summer in the North China Plain

2016 ◽  
Vol 16 (16) ◽  
pp. 10441-10454 ◽  
Author(s):  
Liang Ran ◽  
Zhaoze Deng ◽  
Xiaobin Xu ◽  
Peng Yan ◽  
Weili Lin ◽  
...  
Keyword(s):  
Black Carbon ◽  
North China Plain ◽  
North China ◽  
Ground Level ◽  
Early Morning ◽  
Vertical Profiles ◽  
Large Variability ◽  
Field Campaign ◽  
The North ◽  
The North China Plain

Abstract. Black carbon (BC) is a dominant absorber in the visible spectrum and a potent factor in climatic effects. Vertical profiles of BC were measured using a micro-aethalometer attached to a tethered balloon during the Vertical Observations of trace Gases and Aerosols (VOGA) field campaign, in summer 2014 at a semirural site in the North China Plain (NCP). The diurnal cycle of BC vertical distributions following the evolution of the mixing layer (ML) was investigated for the first time in the NCP region. Statistical parameters including identified mixing height (Hm) and average BC mass concentrations within the ML (Cm) and in the free troposphere (Cf) were obtained for a selected dataset of 67 vertical profiles. Hm was usually lower than 0.2 km in the early morning and rapidly rose thereafter due to strengthened turbulence. The maximum height of the ML was reached in the late afternoon. The top of a full developed ML exceeded 1 km on sunny days in summer, while it stayed much lower on cloudy  days. The sunset triggered the collapse of the ML, and a stable nocturnal boundary layer (NBL) gradually formed. Accordingly, the highest level Cm was found in the early morning and the lowest was found in the afternoon. In the daytime, BC was almost uniformly distributed within the ML and significantly decreased above the ML. During the field campaign, Cm averaged about 5.16 ± 2.49 µg m−3, with a range of 1.12 to 14.49 µg m−3, comparable with observational results in many polluted urban areas such as Milan in Italy and Shanghai in China. As evening approached, BC gradually built up near the surface and exponentially declined with height. In contrast to the large variability found both in Hm and Cm, Cf stayed relatively unaffected through the day. Cf was less than 10 % of the ground level under clean conditions, while it amounted to half of the ground level in some polluted cases. In situ measurements of BC vertical profiles would hopefully have an important implication for accurately estimating direct radiative forcing by BC and improving the retrieval of aerosol optical properties by remote sensing in this region.

Influence of size and mixing state on the wet scavenging of black carbon aerosol in the North China Plain

2020 ◽  
Author(s):  
Xihao Pan ◽  
Nan Ma ◽  
Yaqing Zhou ◽  
Shaowen Zhu ◽  
Long Peng ◽  
...  
Keyword(s):  
Black Carbon ◽  
Radiative Forcing ◽  
North China Plain ◽  
North China ◽  
Mixing State ◽  
Radiation Fog ◽  
The North ◽  
The North China Plain ◽  
Positive Direct ◽  
Scavenging Efficiency

<p>Black carbon (BC) is the most important light-absorbing species in the atmosphere and has a strong positive direct radiative forcing. In-cloud scavenging is the major way to wash out BC from the atmosphere. Understanding the connection between its physico-chemical properties and scavenging efficiency is therefore a key to evaluate its lifetime, atmospheric burden and spatial distribution. During an intensive field campaign conducted in the North China Plain in 2019, a ground-based counterflow virtual impactor was utilized to separate fog droplets in radiation fog events. BC mass and mixing state of fog droplet residues were online measured with a single particle soot photometer (SP2). In a strong radiation fog event with visibility of about 50 m, more than 20% fog droplets are found to contain a BC core. BC scavenging efficiency is found to be strongly determined by its diameter and mixing state. Driven by different mechanisms, higher scavenging efficiencies up to 10% are observed for larger and smaller BC particles, and the minimum efficiency is found at BC diameter of 120 nm. For large core (>120 nm) BC-containing particles, the scavenging efficiency increases significantly with coating thickness (CT), from about 10% for CT<100 nm to 80% for CT>300 nm. Chemical composition may also be a key parameter influencing the scavenging of BC. Based on the observation of 3 fog events, parameterizations of BC scavenging efficiency are also given in this study.</p>

Mass-based mixing state of black carbon measured by a tandem CPMA-SP2 system in wintertime in the North China Plain

2020 ◽  
Author(s):  
Shaowen Zhu ◽  
Nan Ma ◽  
Xihao Pan ◽  
Wenlin Dong ◽  
Jiangchuan Tao ◽  
...  
Keyword(s):  
Black Carbon ◽  
North China Plain ◽  
North China ◽  
Data Retrieval ◽  
Particle Mass ◽  
Radiative Properties ◽  
Mass Analyzer ◽  
Mixing State ◽  
The North ◽  
The North China Plain

<p>Black carbon (BC) is the most important light absorbing component in the atmosphere and has significant impacts on the climate, environment and public health. Its effects depend not only on its spatial-temporal distribution, but also on its physico-chemical characteristics. Mixing state is one of the most important properties of BC and strongly determines its hygroscopicity and radiative properties. During an intensive field campaign conducted in the North China Plain in winter 2018, mass-based mixing state of BC-containing particles were online measured with a Centrifugal Particle Mass Analyzer and Single Particle Soot Photometer (CPMA-SP2) tandem system. This technique directly provides the mass ratio of non-refractory coating matter to BC core (M<sub>R</sub>) in individual particles and does not require to assume the density, morphology and refractive index of BC core and coating in data retrieval, therefore has lower uncertainly compared with leading-edge fit technique. In our measurement, the mean number fraction of uncoated (M<sub>R</sub>=0), thin coated (0<M<sub>R</sub><3) and thick coated (M<sub>R</sub>≥3) BC-containing particle during the campaign were respectively ~10%, ~35% and ~55%, indicating the strong aging process of BC-containing particle in the North China Plain. The median value of M<sub>R</sub> was much higher in polluted days than clean days, for example, the median value of M<sub>R</sub> with a particle mass of 8.56 fg (~220 nm in diameter) for polluted and clean days were ~3.2 and ~1.6, respectively. The mixing state of BC-containing particles obtained by different methods were also compared and evaluated.</p>

A validation of eddy covariance technique for measuring crop evapotranspiration on different time scales in the North China Plain

2020 ◽  
pp. 1-13
Author(s):  
Fangfang Wang ◽  
Donghao Ma ◽  
Wenju Zhao ◽  
Yunxuan Lu ◽  
Ding Zhou ◽  
...  
Keyword(s):  
Energy Balance ◽  
Winter Wheat ◽  
Time Scale ◽  
Large Scale ◽  
North China Plain ◽  
North China ◽  
Summer Maize ◽  
The North ◽  
The North China Plain ◽  
Different Time Scales

Accurate determination of evapotranspiration (ET) has tremendous potential in guiding irrigation and improving the efficiency of water resources utilization in the North China Plain. Eddy covariance (EC) method is currently a popular method for determining field-scale ET. However, due to varying foot print and unclosed energy balance, the applicability of EC in different regions needs to be tested and corrected. In present work, we compared the ET of the winter wheat – summer maize rotation cropland measured by the EC method with the ET measured by large-scale lysimeters on different time scales. The degree of energy balance closure of EC measurements in this region is 78%. After adjusted by using Bowen ratio forced closure method, the ET monitored by EC is comparable with those monitored by large-scale lysimeters. The results also indicated that the consistency of the observed ET by the EC and lysimeters got better with an increasing time scale, especially for the multi-year average ET values with a relative deviation of less than 1%. The short-time events such as irrigation and precipitation and the mismatch of the varying footprint area of the EC and the small fixed source area of the lysimeter should be responsible for the discrepancy of ET in two methods on daily scale. However, the factors of crop biomass, total available water, and local climate condition exert more effects on the observed ET on large time scale. Overall, the EC technique is responsible for ET measurement of winter wheat – summer maize rotation cropland of the North China Plain.

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