scholarly journals The Large‐Scale Circulation Patterns Responsible for Extreme Precipitation Over the North China Plain in Midsummer

2019 ◽  
Vol 124 (23) ◽  
pp. 12794-12809 ◽  
Author(s):  
Yang Zhao ◽  
Xiangde Xu ◽  
Jiao Li ◽  
Rong Zhang ◽  
Yanzhen Kang ◽  
...  
Keyword(s):  
Extreme Precipitation ◽  
Large Scale ◽  
North China Plain ◽  
North China ◽  
Large Scale Circulation ◽  
The North ◽  
The North China Plain ◽  
Circulation Patterns

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

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.

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.

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