scholarly journals Effect of rainfall-induced diabatic heating over southern China on the formation of wintertime haze on the North China Plain

2021 ◽  
Author(s):  
Xiadong An ◽  
Lifang Sheng ◽  
Chun Li ◽  
Wen Chen ◽  
Yulian Tang ◽  
...  
Keyword(s):  
Rossby Wave ◽  
Large Scale ◽  
North China Plain ◽  
North China ◽  
Diabatic Heating ◽  
Southern China ◽  
Wave Source ◽  
Anticyclonic Circulation ◽  
The North ◽  
The North China Plain

Abstract. During the winters (December–February) between 1985 and 2015, the North China Plain (NCP) suffered many periods of heavy haze, and these episodes were contemporaneous with extreme rainfall over southern China; i.e., South Rainfall−North Haze events. The formation of such haze events depends on meteorological conditions, which are controlled by the atmospheric circulation associated with rainfall over southern China, but the underlying physical mechanism remains unclear. This study uses observations and model simulations to demonstrate that haze over the NCP is modulated by anomalous anticyclonic circulation caused by the Rossby wave train, in conjunction with the north−south circulation system (NSC), which ascends over southern China, moves north into northern China near 200–250 hPa, and then descends in the study area. Moreover, in response to rainfall heating, southern China is an obvious Rossby wave source, supporting waves along the subtropical westerly jet waveguide and finally strengthening anticyclonic circulation over the NCP. Composite analysis indicates that these changes lead to a stronger descending motion, higher relative humidity, and a weaker northerly wind, which favors the production and accumulation of haze over the NCP. A linear baroclinic model (LBM) simulation reproduced the observed NSC reasonably well and supports the diagnostic analysis. Quasi-geostrophic (QG) vertical pressure velocity (ω) diagnostics were used to quantify the contributions to the NSC made by large-scale adiabatic forcing and diabatic heating. The results indicated that the NSC is induced mainly by diabatic heating related to precipitation over southern China, and the effect of large-scale circulation is negligible. These results provide the basis for a more comprehensive understanding of the mechanisms that drive the formation of haze over the NCP.

scholarly journals The combined effect of two westerly jet waveguides on heavy haze in the North China Plain in November and December 2015

2019 ◽  
Author(s):  
Xiadong An ◽  
Lifang Sheng ◽  
Qian Liu ◽  
Chun Li ◽  
Yang Gao ◽  
...  
Keyword(s):  
East Asia ◽  
Rossby Wave ◽  
South China ◽  
North China Plain ◽  
North China ◽  
Combined Effect ◽  
The North ◽  
Westerly Jet ◽  
The North China Plain ◽  
Subtropical Westerly Jet

Abstract. Severe haze occurred in the North China Plain (NCP) from November to December 2015, with a wide spatial range and long duration. In this paper, the combined effect of two westerly jet waveguides on haze in the NCP was investigated based on visibility observational data and NCEP/NCAR reanalysis data. The results showed that the two Rossby waveguides within the westerly jet originating from the Mediterranean were responsible for the haze formation in the NCP. The Rossby wave propagated eastward along the subtropical westerly jet and the polar front jet, causing an anomalous anticyclone over the Sea of Japan and anticyclonic wind speed shear at 850 hPa over the NCP, which enhanced the anomalous descending air motion in the middle and lower troposphere and subsequently resulted in a stable atmosphere. Furthermore, the Rossby wave weakened the East Asia trough and Ural ridge, and strengthened the anomalous southerly wind at 850 hPa over the coastal areas of east China, decelerating the East Asia winter monsoon. The above meteorological conditions modulated haze accumulation in November and December 2015. Meanwhile, continuous rainfall related to ascending motion due to Rossby wave propagation along the subtropical westerly jet occurred in a large area of southern China. The latent heat released by rainfall acted as a heat source, inducing convection over South China. This further strengthened the ascending motion over South China so that the descending motion over the NCP was maintained, favoring the maintenance of severe haze. This study is of great significance to elucidate the formation and maintenance mechanism of large-scale haze in the NCP in late fall and boreal winter.

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.

Emergy analysis of grain production systems on large-scale farms in the North China Plain based on LCA

2014 ◽  
Vol 128 ◽  
pp. 66-78 ◽  
Author(s):  
Xiaolong Wang ◽  
Yuanquan Chen ◽  
Peng Sui ◽  
Wangsheng Gao ◽  
Feng Qin ◽  
...  
Keyword(s):  
Large Scale ◽  
North China Plain ◽  
North China ◽  
Production Systems ◽  
Emergy Analysis ◽  
Grain Production ◽  
The North ◽  
The North China Plain

Possible Relationship between the Chukchi Sea Ice in the Early Winter and the February Haze Pollution in the North China Plain

2019 ◽  
Vol 32 (16) ◽  
pp. 5179-5190 ◽  
Author(s):  
Zhicong Yin ◽  
Huijun Wang ◽  
Xiaohui Ma
Keyword(s):  
Sea Ice ◽  
Large Scale ◽  
North China Plain ◽  
North China ◽  
Chukchi Sea ◽  
Early Winter ◽  
Atmospheric Circulations ◽  
The North ◽  
The North China Plain ◽  
Haze Pollution

AbstractHaze pollution is among the most serious disasters in the North China Plain, dramatically damaging human health and the social economy. The frequency of haze events in February typically varies from the number of haze days in the winter. To improve the understanding of haze pollution in February, this study not only showed the large-scale atmospheric circulations associated with the variation in the haze, but also analyzed its connection with Arctic sea ice. The observational and large ensemble model results both illustrated that the preceding increase in the early-winter Chukchi Sea ice might intensify the February haze pollution. The accumulated sea ice over the Chukchi Sea resulted in a steeper meridional sea surface temperature gradient and a significant and persistent westerly thermal wind. In February, the responsive pattern in the atmosphere developed into a Rossby wave–like pattern, linking the Chukchi Sea ice and the February haze pollution. Modulating by the induced large-scale atmospheric circulations, the horizontal and vertical atmospheric ventilation conditions and the hygroscopic growth conditions enhanced the frequency of haze pollution events.

scholarly journals Lower tropospheric ozone over the North China Plain: variability and trends revealed by IASI satellite observations for 2008–2016

2018 ◽  
Vol 18 (22) ◽  
pp. 16439-16459 ◽  
Author(s):  
Gaëlle Dufour ◽  
Maxim Eremenko ◽  
Matthias Beekmann ◽  
Juan Cuesta ◽  
Gilles Foret ◽  
...  
Keyword(s):  
Linear Regression ◽  
Large Scale ◽  
North China Plain ◽  
North China ◽  
Satellite Observations ◽  
Negative Trend ◽  
Nox Emissions ◽  
Emission Reductions ◽  
The North ◽  
The North China Plain

Abstract. China is a highly polluted region, particularly the North China Plain (NCP). However, emission reductions have been occurring in China for about the last 10 years; these reduction measures have been in effect since 2006 for SO2 emissions and since 2010 for NOx emissions. Recent studies have shown a decrease in the NO2 tropospheric column since 2013 that has been attributed to the reduction in NOx emissions. Quantifying how these emission reductions translate regarding ozone concentrations remains unclear due to apparent inconsistencies between surface and satellite observations. In this study, we use the lower tropospheric (LT) columns (surface – 6 km a.s.l. – above sea level) derived from the IASI-A satellite instrument to describe the variability and trend in LT ozone over the NCP for the 2008–2016 period. First, we investigate the IASI retrieval stability and robustness based on the influence of atmospheric conditions (thermal conditions and aerosol loading) and retrieval sensitivity changes. We compare IASI-A observations with the independent IASI-B instrument aboard the Metop-B satellite as well as comparing them with surface and ozonesonde measurements. The conclusion from this evaluation is that the LT ozone columns retrieved from IASI-A are reliable for deriving a trend representative of the lower/free troposphere (3–5 km). Deseasonalized monthly time series of LT ozone show two distinct periods: the first period (2008–2012) with no significant trend (<−0.1 % yr−1) and a second period (2013–2016) with a highly significant negative trend of −1.2 % yr−1, which leads to an overall significant trend of −0.77 % yr−1 for the 2008–2016 period. We explore the dynamical and chemical factors that could explain these negative trends using a multivariate linear regression model and chemistry transport model simulations to evaluate the sensitivity of ozone to the reduction in NOx emissions. The results show that the negative trend observed from IASI for the 2013–2016 period is almost equally attributed to large-scale dynamical processes and emissions reduction, with the large El Niño event in 2015–2016 and the reduction of NOx emissions being the main contributors. For the entire 2008–2016 period, large-scale dynamical processes explain more than half of the observed trend, with a possible reduction of the stratosphere–troposphere exchanges being the main contributor. Large-scale transport and advection, evaluated using CO as a proxy, only contributes to a small part of the trends (∼10 %). However, a residual significant negative trend remains; this shows the limitation of linear regression models regarding their ability to account for nonlinear processes such as ozone chemistry and stresses the need for a detailed evaluation of changes in chemical regimes with the altitude.

scholarly journals The combined effect of two westerly jet waveguides on heavy haze in the North China Plain in November and December 2015

2020 ◽  
Vol 20 (8) ◽  
pp. 4667-4680 ◽  
Author(s):  
Xiadong An ◽  
Lifang Sheng ◽  
Qian Liu ◽  
Chun Li ◽  
Yang Gao ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Rossby Waves ◽  
Southern China ◽  
Polar Front ◽  
The North ◽  
Westerly Jet ◽  
The North China Plain ◽  
Polar Front Jet ◽  
Subtropical Westerly Jet

Abstract. Severe haze occurred in the North China Plain (NCP) from November to December 2015, with a wide spatial range and long duration. In this paper, the combined effect of the anomalous stationary Rossby waves within two westerly jet waveguides on this haze event in the NCP is investigated based on observational visibility data and NCEP/NCAR reanalysis data. The results show that circulation anomalies in Eurasia caused by the propagation of anomalous stationary Rossby wave energy along two waveguides within the westerly jet originating from the Mediterranean were responsible for haze formation in the NCP. The Rossby waves propagated eastward along the subtropical westerly jet and the polar front jet, causing an anomalous anticyclone over the Sea of Japan and anticyclonic wind shear at 850 hPa over the NCP, which enhanced the anomalous descent in the middle and lower troposphere and subsequently resulted in a stable lower atmosphere. Furthermore, the anomalous stationary Rossby waves propagating along the polar front jet weakened the East Asia trough and Ural ridge and strengthened the anomalous southerly wind at 850 hPa over the coastal areas of eastern China, decelerating the East Asia winter monsoon. The above meteorological conditions modulated haze accumulation in November and December 2015. Meanwhile, continuous rainfall related to ascending motion due to Rossby wave propagation along the waveguide provided by the subtropical westerly jet occurred in a large area of southern China. The associated latent heat release acted as a heat source, intensifying the ascending motion over southern China so that the descending motion over the NCP was strengthened, favoring the maintenance of severe haze. This study elucidates the formation and maintenance mechanism of large-scale haze in the NCP in late fall and boreal winter.

scholarly journals Prediction of migratory routes of the invasive fall armyworm in eastern China using a trajectory analytical approach

2019 ◽  
Author(s):  
Xi-Jie Li ◽  
Ming-Fei Wu ◽  
Jian Ma ◽  
Bo-Ya Gao ◽  
Qiu-Lin Wu ◽  
...  
Keyword(s):  
Northeast China ◽  
North China Plain ◽  
North China ◽  
Southern China ◽  
Eastern China ◽  
Fall Armyworm ◽  
Invasive Pest ◽  
The North ◽  
The North China Plain ◽  
Migration Pathways

AbstractBACKGROUNDThe fall armyworm (FAW), an invasive pest from the Americas, is rapidly spreading through the Old World, and has recently invaded the Indochinese Peninsula and southern China. In the Americas, FAW migrates from winter-breeding areas in the south into summer-breeding areas throughout North America where it is a major pest of corn. Asian populations are also likely to evolve migrations into the corn-producing regions of eastern China, where they will pose a serious threat to food security.RESULTSTo evaluate the invasion risk in eastern China, the rate of expansion and future migratory range was modelled by a trajectory simulation approach, combined with flight behaviour and meteorological data. Our results predict that FAW will migrate from its new year-round breeding regions into the two main corn-producing regions of eastern China (the North China and Northeast China Plains), via two pathways. The western pathway originates in Myanmar and Yunnan, and FAW will take four migration steps to reach the North China Plain by July. Migration along the eastern pathway from Indochina and southern China progresses faster, with FAW reaching the North China Plain in three steps by June and reaching the Northeast China Plain in July.CONCLUSIONOur results indicate that there is a high risk that FAW will invade the major corn-producing areas of eastern China via two migration pathways, and cause significant impacts to agricultural productivity. Information on migration pathways and timings can be used to inform integrated pest management strategies for this emerging pest.

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