scholarly journals Diurnal and seasonal variation of planetary boundary layer height over East Asia and its climatic change as seen in the ERA-5 reanalysis data

2022 ◽  
Vol 4 (2) ◽  
Author(s):  
Kwang-Yul Kim
Keyword(s):  
Boundary Layer ◽  
East Asia ◽  
Sensible Heat Flux ◽  
Reanalysis Data ◽  
Minor Role ◽  
The Tibetan Plateau ◽  
Regional Warming ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Continental Area

AbstractThe diurnal/seasonal structure of the boundary layer height (BLH) is investigated over East Asia by using the hourly synoptic monthly ERA5 reanalysis variables from 1979 to 2019. Sensible heat flux (SHF) is the major factor in the temporal and spatial variation of the BLH. Although BLH, in general, is positively correlated with SHF throughout the year, BLH-SHF relationship varies significantly based on the surface type, latitude and time of the year. Analysis also reveals that stability is an important parameter controlling the diurnal maximum BLH. The growth of BLH is strongly limited by the presence of a stable layer. On the other hand, BLH increases abruptly in the presence of a weakly stratified residual layer. In addition, regional warming tends to increase the BLH in the mid- to high-latitude continental area. In the low-latitude continental area, the sign of anomalous SHF varies seasonally and regionally. Stability plays only a minor role in the BLH change except over the Tibetan Plateau, where the increased stability at the top of boundary layer due to warming reduces BLH rather significantly.

scholarly journals Diurnal and Seasonal Variation of Planetary Boundary Layer Height  over East Asia and Its Climatic Change as Seen in the ERA-5 Reanalysis Data

2021 ◽  
Author(s):  
Kwang-Yul Kim
Keyword(s):  
Boundary Layer ◽  
East Asia ◽  
Sensible Heat Flux ◽  
Reanalysis Data ◽  
Minor Role ◽  
The Tibetan Plateau ◽  
Regional Warming ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Continental Area

Abstract The diurnal/seasonal structure of the boundary layer height (BLH) is investigated over East Asia by using the hourly synoptic monthly ERA5 reanalysis variables from 1979–2019. Sensible heat flux (SHF) is the major factor in the temporal and spatial variation of the BLH. Although BLH, in general, is positively correlated with SHF throughout the year, BLH-SHF relationship varies significantly based on the surface type, latitude and time of the year. Analysis also reveals that stability is an important parameter controlling the diurnal maximum BLH. The growth of BLH is strongly limited by the presence of a stable layer. On the other hand, BLH increases abruptly in the presence of a weakly stratified residual layer. In addition, regional warming tends to increase the BLH in the mid- to high-latitude continental area. In the low-latitude continental area, the sign of SHF differs seasonally and regionally. Stability plays only a minor role in the BLH change except over the Tibetan Plateau, where the increased stability at the top of boundary layer due to warming reduces BLH rather significantly.

scholarly journals Boundary Layer Height as Estimated from Radar Wind Profilers in Four Cities in China: Relative Contributions from Aerosols and Surface Features

2020 ◽  
Vol 12 (10) ◽  
pp. 1657 ◽  
Author(s):  
Boming Liu ◽  
Jianping Guo ◽  
Wei Gong ◽  
Yifan Shi ◽  
Shikuan Jin
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Vertical Structure ◽  
Sensible Heat Flux ◽  
Adaptive Method ◽  
Dry Mass ◽  
Atmospheric Environment ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Wind Profilers

The turbulent mixing and dispersion of air pollutants is strongly dependent on the vertical structure of the wind, which constitutes one of the major challenges affecting the determination of boundary layer height (BLH). Here, an adaptive method is proposed to estimate BLH from measurements of radar wind profilers (RWPs) in Beijing (BJ), Nanjing (NJ), Chongqing (CQ), and Wulumuqi (WQ), China, during the summer of 2019. Validation against simultaneous BLH estimates from radiosondes (RSs) yielded a correlation coefficient of 0.66, indicating that the method can be used to derive BLH from RWPs. Diurnal variations of BLH and the ventilation coefficient (VC) at four sites were then examined. A distinct diurnal cycle of BLH was observed over all four cities; BLH gradually increased from sunset, reached a maximum in the afternoon, and then dropped sharply after sunset. The maximum hourly average BLH (1.426 ± 0.46 km) occurred in WQ, consistent with the maximum hourly mean VC larger than 5000 m2/s observed there. By comparison, the diurnal variation of VC was not strong, with values ranging between 2000 and 3000 m2/s, likely owing to the high-humidity environment. Furthermore, surface sensible heat flux, latent heat flux, and dry mass of particulate matter with aerodynamic diameter ≤2.5 µm (PM2.5) concentrations were found to somehow affect the vertical structure of wind and thermodynamic features, leading to a difference between RS and RWP BLH estimates. This indicates that the atmospheric environment can affect BLH estimates using RWP data. The BLH results from RWPs were better in some specific cases. These findings show great potential of RWP measurements in air quality research, and will provide key data references for policy-making toward emission reductions.

scholarly journals The climatology of planetary boundary layer height in China derived from radiosonde and reanalysis data

2016 ◽  
Author(s):  
Jianping Guo ◽  
Yucong Miao ◽  
Yong Zhang ◽  
Huan Liu ◽  
Zhanqing Li ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Reanalysis Data ◽  
Near Surface ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Early Afternoon ◽  
Fine Resolution

Abstract. The important roles of planetary boundary layer (PBL) in climate, weather and air quality have long been recognized, but little has been known about the PBL climatology in China. Using the fine-resolution sounding observations made across China and a reanalysis data, we conducted a comprehensive investigation of the PBL in China from January 2011 to July 2015. The boundary layer height (BLH) is found to be generally higher in spring and summer than that in fall and winter. The comparison of seasonally averaged BLH derived from observations and reanalysis shows good agreement. The BLH derived from three- or four-times-daily soundings in summer tends to peak in the early afternoon, and the diurnal amplitude of BLH is higher in the northern and western sub-regions of China than other sub-regions. The meteorological influence on the annual cycle of BLH are investigated as well, showing that BLH at most sounding sites is negatively associated with the surface pressure and lower tropospheric stability, but positively associated with the near-surface wind speed and temperature. This indicates that meteorology plays a significant role in the PBL processes. Overall, the key findings obtained from this study lay a solid foundation for us to gain a deep insight into the fundamentals of PBL in China, which helps understand the roles of PBL playing in the air pollution, weather and climate of China.

scholarly journals Turbulent and boundary layer characteristics during VOCALS-REx

2021 ◽  
Vol 21 (3) ◽  
pp. 1937-1961
Author(s):  
Dillon S. Dodson ◽  
Jennifer D. Small Griswold
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Sensible Heat Flux ◽  
Cloud Layer ◽  
Cloud Base ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Turbulent Characteristics

Abstract. Boundary layer and turbulent characteristics (surface fluxes, turbulent kinetic energy – TKE, turbulent kinetic energy dissipation rate – ϵ), along with synoptic-scale changes in these properties over time, are examined using data collected from 18 research flights made with the CIRPAS Twin Otter Aircraft. Data were collected during the Variability of the American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study Regional Experiment (VOCALS-REx) at Point Alpha (20∘ S, 72∘ W) in October and November 2008 off the coast of South America. The average boundary layer depth is found to be 1148 m, with 28 % of the boundary layer profiles analyzed displaying decoupling. Analysis of correlation coefficients indicates that as atmospheric pressure decreases, the boundary layer height (zi) increases. As has been shown previously, the increase in zi is accompanied by a decrease in turbulence within the boundary layer. As zi increases, cooling near cloud top cannot sustain mixing over the entire depth of the boundary layer, resulting in less turbulence and boundary layer decoupling. As the latent heat flux (LHF) and sensible heat flux (SHF) increase, zi increases, along with the cloud thickness decreasing with increasing LHF. This suggests that an enhanced LHF results in enhanced entrainment, which acts to thin the cloud layer while deepening the boundary layer. A maximum in TKE on 1 November (both overall average and largest single value measured) is due to sub-cloud precipitation acting to destabilize the sub-cloud layer while acting to stabilize the cloud layer (through evaporation occurring away from the surface, primarily confined between a normalized boundary layer height, z/zi, of 0.40 to 0.60). Enhanced moisture above cloud top from a passing synoptic system also acts to reduce cloud-top cooling, reducing the potential for mixing of the cloud layer. This is observed in both the vertical profiles of the TKE and ϵ, in which it is found that the distributions of turbulence for the sub-cloud and in-cloud layer are completely offset from one another (i.e., the range of turbulent values measured have slight or no overlap for the in-cloud and sub-cloud regions), with the TKE in the sub-cloud layer maximizing for the analysis period, while the TKE in the in-cloud layer is below the average in-cloud value for the analysis period. Measures of vertical velocity variance, TKE, and the buoyancy flux averaged over all 18 flights display a maximum near cloud middle (between normalized in-cloud height, Z*, values of 0.25 and 0.75). A total of 10 of the 18 flights display two peaks in TKE within the cloud layer, one near cloud base and another near cloud top, signifying evaporative and radiational cooling near cloud top and latent heating near cloud base. Decoupled boundary layers tend to have a maximum in turbulence in the sub-cloud layer, with only a single peak in turbulence within the cloud layer.

Factors influencing the boundary layer height and their relationship with air quality in the Sichuan Basin, China

2020 ◽  
Author(s):  
Bangjun Cao
Keyword(s):  
Boundary Layer ◽  
Air Quality ◽  
Sichuan Basin ◽  
Wind Shear ◽  
Sensible Heat Flux ◽  
Sensible Heat ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Factors Influencing ◽  
The Sichuan Basin

<p>We investigated the factors influencing the daily maximum boundary layer height (h<sub>max</sub>) and their relationship with air quality in the Sichuan Basin, China. We analyzed the factors influencing h<sub>max</sub> on cloudy and sunny days in winter using five years of observational data and a reanalysis dataset and investigated the relationship between h<sub>max</sub> and air quality. The inversion layer in the lower troposphere has a critical impact on h<sub>max</sub> on cloudy days. By contrast, the sensible heat flux and wind shear are the main influencing factors on sunny days, although the contribution of the sensible heat flux to h<sub>max</sub> is less than that of the wind shear. This is because the turbulence is mainly affected by mechanical mixing induced by the topographic effect of the Tibetan Plateau to the west of the Sichuan Basin. The secondary circulation over the Sichuan Basin is weaker on cloudy days than on sunny days. These results are important for understanding the dispersion of air pollutants over the Sichuan Basin.</p>

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