scholarly journals Seasonal and Regional Variations of Long-Term Changes in Upper-Tropospheric Jets from Reanalyses

2017 ◽  
Vol 31 (1) ◽  
pp. 423-448 ◽  
Author(s):  
Gloria L. Manney ◽  
Michaela I. Hegglin
Keyword(s):  
Seasonal Variations ◽  
Asian Monsoon ◽  
Human Impacts ◽  
Wind Speeds ◽  
Subtropical Jet ◽  
Long Term Changes ◽  
Poleward Shift ◽  
Annual Means ◽  
Good Agreement

Abstract Long-term changes in upper-tropospheric jet latitude, altitude, and strength are assessed for 1980–2014 using five modern reanalyses: MERRA, MERRA-2, ERA-Interim, JRA-55, and NCEP CFSR. Changes are computed from jet locations evaluated daily at each longitude to analyze regional and seasonal variations. The changes in subtropical and polar (eddy driven) jets are evaluated separately. Good agreement among the reanalyses in many regions and seasons provides confidence in the robustness of the diagnosed trends. Jet shifts show strong regional and seasonal variations, resulting in changes that are not robust in zonal or annual means. Robust changes in the subtropical jet indicate tropical widening over Africa except during Northern Hemisphere (NH) spring, and tropical narrowing over the eastern Pacific in NH winter. The Southern Hemisphere (SH) polar jet shows a robust poleward shift, while the NH polar jet shifts equatorward in most regions/seasons. Both subtropical and polar jet altitudes typically increase; these changes are more robust in the NH than in the SH. Subtropical jet wind speeds have generally increased in winter and decreased in summer, whereas polar jet wind speeds have weakened (strengthened) over Africa and eastern Asia (elsewhere) during winter in both hemispheres. The Asian monsoon has increased in area and appears to have shifted slightly westward toward Africa. The results herein highlight the importance of understanding regional and seasonal variations when quantifying long-term changes in jet locations, the mechanisms for those changes, and their potential human impacts. Comparison of multiple reanalyses is a valuable tool for assessing the robustness of jet changes.

scholarly journals Measurement report: Long-term changes in black carbon and aerosol optical properties from 2012 to 2020 in Beijing, China

2022 ◽  
Vol 22 (1) ◽  
pp. 561-575
Author(s):  
Jiaxing Sun ◽  
Zhe Wang ◽  
Wei Zhou ◽  
Conghui Xie ◽  
Cheng Wu ◽  
...  
Keyword(s):  
Optical Properties ◽  
Black Carbon ◽  
Seasonal Variations ◽  
Radiative Forcing ◽  
Action Plan ◽  
Aerosol Optical Properties ◽  
Long Term Changes ◽  
Clean Air ◽  
Beijing China

Abstract. Atmospheric aerosols play an important role in the radiation balance of the earth–atmosphere system. However, our knowledge of the long-term changes in equivalent black carbon (eBC) and aerosol optical properties in China is very limited. Here we analyze the 9-year measurements of eBC and aerosol optical properties from 2012 to 2020 in Beijing, China. Our results showed large reductions in eBC by 71 % from 6.25 ± 5.73 µg m−3 in 2012 to 1.80 ± 1.54 µg m−3 in 2020 and 47 % decreases in the light extinction coefficient (bext, λ = 630 nm) of fine particles due to the Clean Air Action Plan that was implemented in 2013. The seasonal and diurnal variations of eBC illustrated the most significant reductions in the fall and at nighttime, respectively. ΔeBC / ΔCO also showed an annual decrease from ∼ 7 to 4 ng m−3 ppbv−1 and presented strong seasonal variations with high values in spring and fall, indicating that primary emissions in Beijing have changed significantly. As a response to the Clean Air Action Plan, single-scattering albedo (SSA) showed a considerable increase from 0.79 ± 0.11 to 0.88 ± 0.06, and mass extinction efficiency (MEE) increased from 3.2 to 3.8 m2 g−1. These results highlight the increasing importance of scattering aerosols in radiative forcing and a future challenge in visibility improvement due to enhanced MEE. Brown carbon (BrC) showed similar changes and seasonal variations to eBC during 2018–2020. However, we found a large increase of secondary BrC in the total BrC in most seasons, particularly in summer with the contribution up to 50 %, demonstrating an enhanced role of secondary formation in BrC in recent years. The long-term changes in eBC and BrC have also affected the radiative forcing effect. The direct radiative forcing (ΔFR) of BC decreased by 67 % from +3.36 W m−2 in 2012 to +1.09 W m−2 in 2020, and that of BrC decreased from +0.30 to +0.17 W m−2 during 2018–2020. Such changes might have important implications for affecting aerosol–boundary layer interactions and the improvement of future air quality.

Changes of the nutrient loads of the Danube since the late eighties: an analysis based on long term changes along the whole Danube River and its main tributaries

2005 ◽  
Vol 51 (11) ◽  
pp. 205-212 ◽  
Author(s):  
J. van Gils ◽  
H. Behrendt ◽  
A. Constantinescu ◽  
F. Laszlo ◽  
L. Popescu
Keyword(s):  
Human Impacts ◽  
Inorganic Nitrogen ◽  
Danube River ◽  
The Black Sea ◽  
Nutrient Loads ◽  
Economic Changes ◽  
Long Term Changes ◽  
Eastern European Countries ◽  
River Loads

The Danube nutrient loads are affected by human impacts mainly from agriculture and wastewater discharges. Knowledge about the Danube nutrient loads and the changes of these loads over time is essential for understanding the changes within the ecosystem of the Black Sea, induced by these loads. The paper shows the long term changes of the nutrient load along the Danube estimated by measurements from different countries and institutions. The results show large differences between Dissolved Inorganic Nitrogen (DIN) and Total Phosphorus (TP). For TP, the Danube River loads show a strong decrease since 1988–1992, especially in the Middle and Lower basin. This change is probably partly connected to the dramatic economic changes in the Middle and Eastern European countries following the collapse of the communist system. The DIN load does not show a decreasing trend in the last decade. The data indicate that there may be a decreasing trend in the anthropogenic emissions, but that such a trend is counteracted by a significantly increasing trend of the Danube discharge in the last decade. The accuracy of the available data is analysed in the paper as well.

Long-term changes of fisheries landings in enclosed gulf lagoons (Amvrakikos gulf, W Greece): Influences of fishing and other human impacts

2013 ◽  
Vol 131 ◽  
pp. 31-40 ◽  
Author(s):  
George N. Katselis ◽  
Dimitrios K. Moutopoulos ◽  
Evagelos N. Dimitriou ◽  
Constantin Koutsikopoulos
Keyword(s):  
Human Impacts ◽  
Long Term Changes

scholarly journals Measurement report: Long-term changes in black carbon and aerosol optical properties from 2012 to 2020 in Beijing, China

2021 ◽  
Author(s):  
Jiaxing Sun ◽  
Zhe Wang ◽  
Wei Zhou ◽  
Conghui Xie ◽  
Cheng Wu ◽  
...  
Keyword(s):  
Optical Properties ◽  
Black Carbon ◽  
Seasonal Variations ◽  
Radiative Forcing ◽  
Aerosol Optical Properties ◽  
Seasonal And Diurnal Variations ◽  
Long Term Changes ◽  
Clean Air ◽  
Beijing China

Abstract. Atmospheric aerosols play an important role in radiation balance of the earth-atmosphere system. However, our knowledge of the long-term changes in black carbon (BC) and aerosol optical properties in China are very limited. Here we analyze the nine-year measurements of BC and aerosol optical properties from 2012 to 2020 in Beijing, China. Our results showed large reductions in eBC by 67 % from 5.54 ± 5.25 µg m−3 in 2012 to 1.80 ± 1.54 µg m−3 in 2020, and 47 % decreases in light extinction coefficient (bext, λ = 630 nm) of fine particles due to clean air action plan since 2013. The seasonal and diurnal variations of eBC illustrated the most significant reductions in the fall and night time, respectively. ΔeBC/ΔCO also showed an annual decrease from ~6 to 4 ng m−3 ppbv−1 and presented strong seasonal variations with high values in spring and fall, indicating that primary emissions in Beijing have changed significantly. As a response to clean air action, single scattering albedo (SSA) showed a considerable increase from 0.79 ± 0.11 to 0.88 ± 0.06, and mass extinction efficiency (MEE) increased from 3.2 to 3.8 m2 g−1. These results highlight an increasing importance of scattering aerosols in radiative forcing, and a future challenge in visibility improvement due to enhanced MEE. Brown carbon (BrC) showed similar changes and seasonal variations to eBC during 2018–2020. However, we found a large increase of secondary BrC in the total BrC in most seasons, particularly in summer with the contribution up to 50 %, demonstrating an enhanced role of secondary formation in BrC in recent years. The long-term changes in eBC and BrC have also affected the radiative forcing effect. The direct radiative forcing (ΔFR) of BC decreased by 64 % from +3.00 W m−2 in 2012 to +1.09 W m−2 in 2020, and that of BrC decreased from +0.30 to +0.17 W m−2 during 2018–2020. Such changes might have important implications in affecting aerosol and boundary-layer interactions and the future air quality improvement.

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