scholarly journals Aircraft observations since the 1990s reveal increases of tropospheric ozone at multiple locations across the Northern Hemisphere

2020 ◽  
Vol 6 (34) ◽  
pp. eaba8272 ◽  
Author(s):  
Audrey Gaudel ◽  
Owen R. Cooper ◽  
Kai-Lan Chang ◽  
Ilann Bourgeois ◽  
Jerry R. Ziemke ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Temporal Variability ◽  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Monitoring Network ◽  
Spatial And Temporal Variability ◽  
Commercial Aircraft ◽  
Aircraft Observations ◽  
Ozone Precursor ◽  
Satellite Product

Tropospheric ozone is an important greenhouse gas, is detrimental to human health and crop and ecosystem productivity, and controls the oxidizing capacity of the troposphere. Because of its high spatial and temporal variability and limited observations, quantifying net tropospheric ozone changes across the Northern Hemisphere on time scales of two decades had not been possible. Here, we show, using newly available observations from an extensive commercial aircraft monitoring network, that tropospheric ozone has increased above 11 regions of the Northern Hemisphere since the mid-1990s, consistent with the OMI/MLS satellite product. The net result of shifting anthropogenic ozone precursor emissions has led to an increase of ozone and its radiative forcing above all 11 study regions of the Northern Hemisphere, despite NOx emission reductions at midlatitudes.

scholarly journals Chemical and climatic drivers of radiative forcing due to changes in stratospheric and tropospheric ozone over the 21<sup>st</sup> century

2017 ◽  
Author(s):  
Antara Banerjee ◽  
Amanda C. Maycock ◽  
John A. Pyle
Keyword(s):  
Greenhouse Gas ◽  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Radiative Forcings ◽  
Climatic Drivers ◽  
Ozone Precursor ◽  
Ozone Depleting Substances ◽  
Projected Changes

Abstract. The ozone radiative forcings (RFs) resulting from projected changes in climate, ozone-depleting substances (ODSs), non-methane ozone precursor emissions and methane between the years 2000 and 2100 are calculated using simulations from the UM-UKCA chemistry-climate model. Projected measures to improve air-quality through reductions in tropospheric ozone precursor emissions present a co-benefit for climate, with a net global mean ozone RF of −0.09 Wm−2. This is opposed by a positive ozone RF of 0.07 Wm−2 due to future decreases in ODSs, which is mainly driven by an increase in tropospheric ozone through stratosphere-to-troposphere exchange. An increase in methane abundance by more than a factor of two (as projected by the RCP8.5 scenario) is found to drive an ozone RF of 0.19 Wm−2, which would greatly outweigh the climate benefits of tropospheric non-methane ozone precursor reductions. A third of the ozone RF due to the projected increase in methane results from increases in stratospheric ozone. The sign of the ozone RF due to future changes in climate (including the radiative effects of greenhouse gas concentrations, sea surface temperatures and sea ice changes) is shown to be dependent on the greenhouse gas emissions pathway, with a positive RF (0.06 Wm−2) for RCP4.5 and a negative RF (−0.07 Wm−2) for the RCP8.5 scenario. This dependence arises from differences in the contribution to RF from stratospheric ozone changes.

scholarly journals Estimation of the aerosol radiative forcing at ground level, over land, and in cloudless atmosphere, from METEOSAT-7 observation: method and case study

2008 ◽  
Vol 8 (3) ◽  
pp. 625-636 ◽  
Author(s):  
T. Elias ◽  
J.-L. Roujean
Keyword(s):  
Optical Thickness ◽  
Temporal Variability ◽  
Radiative Forcing ◽  
Ground Level ◽  
Aerosol Optical Thickness ◽  
Reference Level ◽  
Urban Site ◽  
Spatial And Temporal Variability ◽  
Aerosol Radiative Forcing ◽  
Aerosol Radiative

Abstract. A new method is proposed to estimate the spatial and temporal variability of the solar radiative flux reaching the surface over land (DSSF), as well as the Aerosol Radiative Forcing (ARF), in cloud-free atmosphere. The objective of regional applications of the method is attainable by using the visible broadband of METEOSAT-7 satellite instrument which scans Europe and Africa on a half-hourly basis. The method relies on a selection of best correspondence between METEOSAT-7 radiance and radiative transfer computations. The validation of DSSF is performed comparing retrievals with ground-based measurements acquired in two contrasted environments: an urban site near Paris and a continental background site located South East of France. The study is concentrated on aerosol episodes occurring around the 2003 summer heat wave, providing 42 cases of comparison for variable solar zenith angle (from 59° to 69°), variable aerosol type (biomass burning emissions and urban pollution), and variable aerosol optical thickness (a factor 6 in magnitude). The method reproduces measurements of DSSF within an accuracy assessment of 20 W m−2 (5% in relative) in 70% of the situations, and within 40 W m−2 in 90% of the situations, for the two case studies considered here. Considering aerosol is the main contributor in changing the measured radiance at the top of the atmosphere, DSSF temporal variability is assumed to be caused only by aerosols, and consequently ARF at ground level and over land is also retrieved: ARF is computed as the difference between DSSF and a parameterised aerosol-free reference level. Retrievals are linearly correlated with the ground-based measurements of the aerosol optical thickness (AOT): sensitivity is included between 120 and 160 W m−2 per unity of AOT at 440 nm. AOT being an instantaneous measure indicative of the aerosol columnar amount, we prove the feasibility to infer instantaneous aerosol radiative impact at the ground level over land with METEOSAT-7 visible channel.

scholarly journals Chemical and climatic drivers of radiative forcing due to changes in stratospheric and tropospheric ozone over the 21st century

2018 ◽  
Vol 18 (4) ◽  
pp. 2899-2911 ◽  
Author(s):  
Antara Banerjee ◽  
Amanda C. Maycock ◽  
John A. Pyle
Keyword(s):  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Radiative Forcings ◽  
The United Kingdom ◽  
Climatic Drivers ◽  
Ozone Precursor ◽  
Ozone Depleting Substances ◽  
Projected Changes

Abstract. The ozone radiative forcings (RFs) resulting from projected changes in climate, ozone-depleting substances (ODSs), non-methane ozone precursor emissions and methane between the years 2000 and 2100 are calculated using simulations from the UM-UKCA chemistry–climate model (UK Met Office's Unified Model containing the United Kingdom Chemistry and Aerosols sub-model). Projected measures to improve air-quality through reductions in non-methane tropospheric ozone precursor emissions present a co-benefit for climate, with a net global mean ozone RF of −0.09 W m−2. This is opposed by a positive ozone RF of 0.05 W m−2 due to future decreases in ODSs, which is driven by an increase in tropospheric ozone through stratosphere-to-troposphere transport of air containing higher ozone amounts. An increase in methane abundance by more than a factor of 2 (as projected by the RCP8.5 scenario) is found to drive an ozone RF of 0.18 W m−2, which would greatly outweigh the climate benefits of non-methane tropospheric ozone precursor reductions. A small fraction (∼ 15 %) of the ozone RF due to the projected increase in methane results from increases in stratospheric ozone. The sign of the ozone RF due to future changes in climate (including the radiative effects of greenhouse gases, sea surface temperatures and sea ice changes) is shown to be dependent on the greenhouse gas emissions pathway, with a positive RF (0.05 W m−2) for RCP4.5 and a negative RF (−0.07 W m−2) for the RCP8.5 scenario. This dependence arises mainly from differences in the contribution to RF from stratospheric ozone changes. Considering the increases in tropopause height under climate change causes only small differences (≤ |0.02| W m−2) for the stratospheric, tropospheric and whole-atmosphere RFs.

Controls on Spatial and Temporal Variability in Northern Hemisphere Terrestrial Snow Melt Timing, 1979–2012

2015 ◽  
Vol 28 (6) ◽  
pp. 2136-2153 ◽  
Author(s):  
J. R. Mioduszewski ◽  
A. K. Rennermalm ◽  
D. A. Robinson ◽  
L. Wang
Keyword(s):  
Energy Balance ◽  
North America ◽  
Northern Hemisphere ◽  
Temporal Variability ◽  
Longwave Radiation ◽  
Spatial And Temporal Variability ◽  
Radiative Processes ◽  
Central Russia ◽  
Modern Era ◽  
Spring Snowmelt

Abstract Spring snowmelt onset has occurred earlier across much of the Northern Hemisphere land area in the last four decades. Understanding the mechanisms driving spring melt has remained a challenge, particularly in its spatial and temporal variability. Here, melt onset dates (MOD) obtained from passive microwave satellite data are used, as well as energy balance and meteorological fields from NASA’s Modern-Era Retrospective Analysis for Research and Applications, to assess trends in the MOD and attribute melt onset across much of Arctic and sub-Arctic Eurasia and North America during the spring snowmelt season from 1979 to 2012. Across much of the Northern Hemisphere MOD has occurred 1–2 weeks earlier over this period, with the strongest trends in western and central Russia and insignificant trends across most of North America. Trends in MOD are reflected by those in energy balance terms, with energy advection providing an increasing proportion of melt energy in regions with the strongest MOD trends. Energy advection plays a larger role in melt onset in regions where snow begins melting in March and April, while insolation and longwave radiation drives melt where the MOD occurs in May and June. This implies that there is a potential shift in snowmelt drivers toward those involved in advective processes rather than radiative processes with an earlier MOD. As the high latitudes warm and terrestrial snow cover continues to melt and disappear earlier in the spring, it is valuable to elucidate regional snowmelt sensitivities to better understand regional responses to changing climatological processes.

scholarly journals Growing season CH<sub>4</sub> and N<sub>2</sub>O fluxes from a sub-arctic landscape in northern Finland

2016 ◽  
Author(s):  
Kerry J. Dinsmore ◽  
Julia Drewer ◽  
Peter E. Levy ◽  
Charles George ◽  
Annalea Lohila ◽  
...  
Keyword(s):  
Spectral Data ◽  
Temporal Variability ◽  
Radiative Forcing ◽  
Growing Season ◽  
Spatial And Temporal Variability ◽  
N2o Emissions ◽  
Feedback Mechanisms ◽  
Ch4 And N2o ◽  
Subarctic Forest ◽  
Chamber Measurements

Abstract. Subarctic and boreal emissions of CH4 are important contributors to the atmospheric greenhouse gas (GHG) balance and subsequently the global radiative forcing. Whilst N2O emissions may be lower, the much greater radiative forcing they produce justifies their inclusion in GHG studies. In addition to the quantification of flux magnitude, it is essential that we understand the drivers of emissions to be able to accurately predict climate-driven changes and potential feedback mechanisms. Hence this study aims to increase our understanding of what drives fluxes of CH4 and N2O in a subarctic forest/wetland landscape, exploring both spatial and temporal variability, and uses satellite derived spectral data to extrapolate from chamber scale fluxes to a 2 × 2 km landscape area. From static chamber measurements made during summer and autumn campaigns in 2012 in the Sodankylä region of Northern Finland, we concluded that wetlands represent a significant source of CH4 (3.35 ± 0.44 mg C m−2 h−1 during summer campaign and 0.62 ± 0.09 mg C m−2 h−1 during autumn campaign), whilst the surrounding forests represent a small sink (−0.06 ± 

Spatial and Temporal Variability of Tropospheric Ozone over Europe

1997 ◽  
pp. 35-64 ◽  
Author(s):  
H. E. Scheel ◽  
G. Ancellet ◽  
H. Areskoug ◽  
J. Beck ◽  
J. Bösenberg ◽  
...  
Keyword(s):  
Temporal Variability ◽  
Tropospheric Ozone ◽  
Spatial And Temporal Variability

scholarly journals Multi-decadal surface ozone trends at globally distributed remote locations

Elem Sci Anth ◽  
2020 ◽  
Vol 8 ◽  
Author(s):  
Owen R. Cooper ◽  
Martin G. Schultz ◽  
Sabine Schröder ◽  
Kai-Lan Chang ◽  
Audrey Gaudel ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Tropospheric Ozone ◽  
Surface Ozone ◽  
Positive Trend ◽  
Remote Locations ◽  
Ozone Trends ◽  
Ozone Precursor ◽  
Globally Distributed

Extracting globally representative trend information from lower tropospheric ozone observations is extremely difficult due to the highly variable distribution and interannual variability of ozone, and the ongoing shift of ozone precursor emissions from high latitudes to low latitudes. Here we report surface ozone trends at 27 globally distributed remote locations (20 in the Northern Hemisphere, 7 in the Southern Hemisphere), focusing on continuous time series that extend from the present back to at least 1995. While these sites are only representative of less than 25% of the global surface area, this analysis provides a range of regional long-term ozone trends for the evaluation of global chemistry-climate models. Trends are based on monthly mean ozone anomalies, and all sites have at least 20 years of data, which improves the likelihood that a robust trend value is due to changes in ozone precursor emissions and/or forced climate change rather than naturally occurring climate variability. Since 1995, the Northern Hemisphere sites are nearly evenly split between positive and negative ozone trends, while 5 of 7 Southern Hemisphere sites have positive trends. Positive trends are in the range of 0.5–2 ppbv decade–1, with ozone increasing at Mauna Loa by roughly 50% since the late 1950s. Two high elevation Alpine sites, discussed by previous assessments, exhibit decreasing ozone trends in contrast to the positive trend observed by IAGOS commercial aircraft in the European lower free-troposphere. The Alpine sites frequently sample polluted European boundary layer air, especially in summer, and can only be representative of lower free tropospheric ozone if the data are carefully filtered to avoid boundary layer air. The highly variable ozone trends at these 27 surface sites are not necessarily indicative of free tropospheric trends, which have been overwhelmingly positive since the mid-1990s, as shown by recent studies of ozonesonde and aircraft observations.

scholarly journals Spatial and temporal variability of urban soil water dynamics observed by a soil monitoring network

2016 ◽  
Vol 16 (11) ◽  
pp. 2523-2537 ◽  
Author(s):  
Sarah Wiesner ◽  
Alexander Gröngröft ◽  
Felix Ament ◽  
Annette Eschenbach
Keyword(s):  
Soil Water ◽  
Temporal Variability ◽  
Urban Soil ◽  
Monitoring Network ◽  
Water Dynamics ◽  
Spatial And Temporal Variability ◽  
Soil Monitoring ◽  
Soil Water Dynamics

scholarly journals Estimation of the aerosol radiative forcing at ground level, over land, and in cloudless atmosphere, from METEOSAT-7 observation: method and first results

2007 ◽  
Vol 7 (5) ◽  
pp. 13503-13535
Author(s):  
T. Elias ◽  
J.-L. Roujean
Keyword(s):  
Optical Thickness ◽  
Temporal Variability ◽  
Radiative Forcing ◽  
Ground Level ◽  
Aerosol Optical Thickness ◽  
Reference Level ◽  
Urban Site ◽  
Spatial And Temporal Variability ◽  
Aerosol Radiative Forcing ◽  
Aerosol Radiative

Abstract. A new method is proposed to estimate the spatial and temporal variability of the solar radiative flux reaching the surface (DSSF) over land, as well as the Aerosol Radiative Forcing (ARF), in cloud-free atmosphere. The objective of global applications of the method is fulfilled by using the visible broadband of METEOSAT-7 satellite which scans Europe and Africa on a half-hourly basis. The method relies on a selection of best correspondence between METEOSAT-7 radiance and DSSF computed with a radiative transfer code. The validation of DSSF is performed comparing retrievals with ground-based measurements acquired in two contrasted environments, i.e. an urban site near Paris and a continental background site in South East of France. The study is concentrated on aerosol episodes occurring around the 2003 summer heat wave, providing 42 cases of comparison for variable solar zenith angle (from 59° to 69°), variable aerosol type (biomass burning emissions and urban pollution), and variable aerosol optical thickness (a factor 6). The method reproduces measurements of DSSF within an accuracy assessment of 20 Wm−2 (5% in relative) in 70% of the cases, and within 40 Wm−2 in 90% of the cases. Considering aerosol is the main contributor in changing the measured radiance at the top of the atmosphere, DSSF temporal variability is assumed to be caused only by aerosols, and consequently the ARF at ground level and over land is also retrieved: ARF is computed as the difference between DSSF and a parameterised aerosol-free reference level. Retrievals are linearly correlated with the ground-based measurements of the aerosol optical thickness (AOT): sensitivity is included between 120 and 160 Wm−2 per unity of AOT at 440 nm. AOT being an instantaneous measure indicative of the aerosol columnar amount, we therefore prove the feasibility to infer instantaneous aerosol radiative impact at the ground level over land with METEOSAT-7 visible channel.

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