scholarly journals Understanding the influence of combustion on atmospheric CO<sub>2</sub> over Europe by using satellite observations of CO<sub>2</sub> and reactive trace gases

2021 ◽  
Author(s):  
Mehliyar Sadiq ◽  
Paul I. Palmer ◽  
Mark F. Lunt ◽  
Liang Feng ◽  
Ingrid Super ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Atmospheric Carbon Dioxide ◽  
Transport Model ◽  
Trace Gases ◽  
Satellite Observations ◽  
Secondary Source ◽  
Combustion Emissions ◽  
Full Complement ◽  
Reactive Trace Gases ◽  
Carbon Dioxide Co2

Abstract. We assess how nitrogen oxides (NOx = NO + NO2), carbon monoxide (CO) and formaldehyde (HCHO) can be used as proxies to determine the combustion contribution to atmospheric carbon dioxide (CO2) using satellite observations. We focus our analysis on 2018 when there is a full complement of column data from the TROPOspheric Monitoring Instrument (NO2, CO, and HCHO) and the Orbiting Carbon Observatory-2 (CO2). We use the nested GEOS-Chem atmospheric chemistry model to relate high-resolution emission inventories over Europe to these atmospheric data, taking into account scene-dependent averaging kernels. We find that that NO2 and CO are the better candidates to identify incomplete combustion and fingerprints of different combustion sectors, but both have their own challenges associated with properly describing their atmospheric chemistry. The secondary source of HCHO from oxidation of biogenic volatile organic compounds, particularly over southern European countries, compromises its use as a proxy for combustion emissions. We find a weak positive correlation between the CO : CO2 inventory ratio and observed column enhancements of ΔCO : ΔCO2 (R < 0.2), suggesting some consistency and linearity in CO chemistry and transport. However, we find a stronger negative correlation between the NOx : CO2 inventory ratio and observed column enhancements of ΔNO2 :ΔCO2 (R < 0.50), driven by non-linear photochemistry. Both of these observed ratios are described well by the GEOS-Chem atmospheric chemistry transport model, providing confidence of the quality of the emission inventory and that the model is a useful tool for interpreting these tracer-tracer ratios. Our results also provide some confidence in our ability to develop a robust method to infer combustion CO2 emission estimates using satellite observations of reactive trace gases that have up until now mostly been used to study surface air quality.

scholarly journals Stratospheric lifetime ratio of CFC-11 and CFC-12 from satellite and model climatologies

2014 ◽  
Vol 14 (11) ◽  
pp. 16865-16906 ◽  
Author(s):  
L. Hoffmann ◽  
C. M. Hoppe ◽  
R. Müller ◽  
G. S. Dutton ◽  
J. C. Gille ◽  
...  
Keyword(s):  
Global Warming ◽  
Atmospheric Chemistry ◽  
Climate Model ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Michelson Interferometer ◽  
Coupled Model ◽  
Model System ◽  
Satellite Observations ◽  
The Impact

Abstract. Chlorofluorocarbons (CFCs) play a key role in stratospheric ozone loss and are strong infrared absorbers that contribute to global warming. The stratospheric lifetimes of CFCs are a measure of their global loss rates that are needed to determine global warming and ozone depletion potentials. We applied the tracer-tracer correlation approach to zonal mean climatologies from satellite measurements and model data to assess the lifetimes of CFCl3 (CFC-11) and CF2Cl2 (CFC-12). We present estimates of the CFC-11/CFC-12 lifetime ratio and the absolute lifetime of CFC-12, based on a reference lifetime of 52 yr for CFC-11. We analyzed climatologies from three satellite missions, the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS), the HIgh Resolution Dynamics Limb Sounder (HIRDLS), and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). We found a CFC-11/CFC-12 lifetime ratio of 0.47±0.08 and a CFC-12 lifetime of 111(96–132) yr for ACE-FTS, a ratio of 0.46±0.07 and a lifetime of 112(97–133) yr for HIRDLS, and a ratio of 0.46±0.08 and a lifetime of 112(96–135) yr for MIPAS. The error-weighted, combined CFC-11/CFC-12 lifetime ratio is 0.47±0.04 and the CFC-12 lifetime estimate is 112(102–123) yr. These results agree with the recent Stratosphere-troposphere Processes And their Role in Climate (SPARC) reassessment, which recommends lifetimes of 52(43–67) yr and 102(88–122) yr, respectively. Having smaller uncertainties than the results from other recent studies, our estimates can help to better constrain CFC-11 and CFC-12 lifetime recommendations in future scientific studies and assessments. Furthermore, the satellite observations were used to validate first simulation results from a new coupled model system, which integrates a Lagrangian chemistry transport model into a climate model. For the coupled model we found a CFC-11/CFC-12 lifetime ratio of 0.48±0.07 and a CFC-12 lifetime of 110(95–129) yr, based on a ten-year perpetual run. Closely reproducing the satellite observations, the new model system will likely become a useful tool to assess the impact of advective transport, mixing, and photochemistry as well as climatological variability on the stratospheric lifetimes of long-lived tracers.

scholarly journals Estimated regional CO<sub>2</sub> flux and uncertainty based on an ensemble of atmospheric CO<sub>2</sub> inversions

2021 ◽  
Author(s):  
Naveen Chandra ◽  
Prabir K. Patra ◽  
Yousuke Niwa ◽  
Akihiko Ito ◽  
Yosuke Iida ◽  
...  
Keyword(s):  
Atmospheric Carbon Dioxide ◽  
Transport Model ◽  
Carbon Sink ◽  
A Priori ◽  
Inversion Method ◽  
Co2 Fluxes ◽  
Emission Mitigation ◽  
Regional Sources ◽  
Carbon Dioxide Co2 ◽  
Riverine Export

Abstract. Global and regional sources and sinks of carbon across the earth’s surface have been studied extensively using atmospheric carbon dioxide (CO2) observations and chemistry-transport model (ACTM) simulations (top-down/inversion method). However, the uncertainties in the regional flux (+ve: source to the atmosphere; −ve: sink on land/ocean) distributions remain unconstrained mainly due to the lack of sufficient high-quality measurements covering the globe in all seasons and the uncertainties in model simulations. Here, we use a suite of 16 inversion cases, derived from a single transport model (MIROC4-ACTM) but different sets of a priori (bottom-up) terrestrial biosphere and oceanic fluxes, as well as prior flux and observational data uncertainties (50 sites) to estimate CO2 fluxes for 84 regions over the period 2000–2020. The ensemble inversions provide a mean flux field that is consistent with the global CO2 growth rate, land and ocean sink partitioning of −2.9 ± 0.3 (±1σ uncertainty on mean) and −1.6 ± 0.2 PgC yr−1, respectively, for the period 2011–2020 (without riverine export correction), offsetting about 22–33 % and 16–18 % of global fossil-fuel CO2 emissions. Aggregated fluxes for 15 land regions compare reasonably well with the best estimations for (approx. 2000–2009) given by the REgional Carbon Cycle Assessment and Processes (RECCAP), and all regions appeared as a carbon sink over 2011–2020. Interannual variability and seasonal cycle in CO2 fluxes are more consistently derived for different prior fluxes when a greater degree of freedom is given to the inversion system (greater prior flux uncertainty). We have evaluated the inversion fluxes using independent aircraft and surface measurements not used in the inversions, which raises our confidence in the ensemble mean flux rather than an individual inversion. Differences between 5-year mean fluxes show promises and capability to track flux changes under ongoing and future CO2 emission mitigation policies.

scholarly journals Development of the global atmospheric chemistry general circulation model BCC-GEOS-Chem v1.0: model description and evaluation

2020 ◽  
Vol 13 (9) ◽  
pp. 3817-3838
Author(s):  
Xiao Lu ◽  
Lin Zhang ◽  
Tongwen Wu ◽  
Michael S. Long ◽  
Jun Wang ◽  
...  
Keyword(s):  
General Circulation Model ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
General Circulation ◽  
Climate Models ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Circulation Model ◽  
Satellite Observations ◽  
Model Description

Abstract. Chemistry plays an indispensable role in investigations of the atmosphere; however, many climate models either ignore or greatly simplify atmospheric chemistry, limiting both their accuracy and their scope. We present the development and evaluation of the online global atmospheric chemical model BCC-GEOS-Chem v1.0, coupling the GEOS-Chem chemical transport model (CTM) as an atmospheric chemistry component in the Beijing Climate Center atmospheric general circulation model (BCC-AGCM). The GEOS-Chem atmospheric chemistry component includes detailed tropospheric HOx–NOx–volatile organic compounds–ozone–bromine–aerosol chemistry and online dry and wet deposition schemes. We then demonstrate the new capabilities of BCC-GEOS-Chem v1.0 relative to the base BCC-AGCM model through a 3-year (2012–2014) simulation with anthropogenic emissions from the Community Emissions Data System (CEDS) used in the Coupled Model Intercomparison Project Phase 6 (CMIP6). The model captures well the spatial distributions and seasonal variations in tropospheric ozone, with seasonal mean biases of 0.4–2.2 ppbv at 700–400 hPa compared to satellite observations and within 10 ppbv at the surface to 500 hPa compared to global ozonesonde observations. The model has larger high-ozone biases over the tropics which we attribute to an overestimate of ozone chemical production. It underestimates ozone in the upper troposphere which is likely due either to the use of a simplified stratospheric ozone scheme or to biases in estimated stratosphere–troposphere exchange dynamics. The model diagnoses the global tropospheric ozone burden, OH concentration, and methane chemical lifetime to be 336 Tg, 1.16×106 molecule cm−3, and 8.3 years, respectively, which is consistent with recent multimodel assessments. The spatiotemporal distributions of NO2, CO, SO2, CH2O, and aerosol optical depth are generally in agreement with satellite observations. The development of BCC-GEOS-Chem v1.0 represents an important step for the development of fully coupled earth system models (ESMs) in China.

scholarly journals Stratospheric lifetime ratio of CFC-11 and CFC-12 from satellite and model climatologies

2014 ◽  
Vol 14 (22) ◽  
pp. 12479-12497 ◽  
Author(s):  
L. Hoffmann ◽  
C. M. Hoppe ◽  
R. Müller ◽  
G. S. Dutton ◽  
J. C. Gille ◽  
...  
Keyword(s):  
Global Warming ◽  
Atmospheric Chemistry ◽  
Climate Model ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Michelson Interferometer ◽  
Coupled Model ◽  
Model System ◽  
Satellite Observations ◽  
The Impact

Abstract. Chlorofluorocarbons (CFCs) play a key role in stratospheric ozone loss and are strong infrared absorbers that contribute to global warming. The stratospheric lifetimes of CFCs are a measure of their stratospheric loss rates that are needed to determine global warming and ozone depletion potentials. We applied the tracer–tracer correlation approach to zonal mean climatologies from satellite measurements and model data to assess the lifetimes of CFCl3 (CFC-11) and CF2Cl2 (CFC-12). We present estimates of the CFC-11/CFC-12 lifetime ratio and the absolute lifetime of CFC-12, based on a reference lifetime of 52 years for CFC-11. We analyzed climatologies from three satellite missions, the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS), the HIgh Resolution Dynamics Limb Sounder (HIRDLS), and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). We found a CFC-11/CFC-12 lifetime ratio of 0.47±0.08 and a CFC-12 lifetime of 112(96–133) years for ACE-FTS, a ratio of 0.46±0.07 and a lifetime of 113(97–134) years for HIRDLS, and a ratio of 0.46±0.08 and a lifetime of 114(98–136) years for MIPAS. The error-weighted, combined CFC-11/CFC-12 lifetime ratio is 0.46±0.04 and the CFC-12 lifetime estimate is 113(103–124) years. These results agree with the recent Stratosphere-troposphere Processes And their Role in Climate (SPARC) reassessment, which recommends lifetimes of 52(43–67) years and 102(88–122) years, respectively. Having smaller uncertainties than the results from other recent studies, our estimates can help to better constrain CFC-11 and CFC-12 lifetime recommendations in future scientific studies and assessments. Furthermore, the satellite observations were used to validate first simulation results from a new coupled model system, which integrates a Lagrangian chemistry transport model into a climate model. For the coupled model we found a CFC-11/CFC-12 lifetime ratio of 0.48±0.07 and a CFC-12 lifetime of 110(95–129) years, based on a 10-year perpetual run. Closely reproducing the satellite observations, the new model system will likely become a useful tool to assess the impact of advective transport, mixing, and photochemistry as well as climatological variability on the stratospheric lifetimes of long-lived tracers.

scholarly journals A pre-processor of trace gases and aerosols emission fields for regional and global atmospheric chemistry models

2010 ◽  
Vol 3 (2) ◽  
pp. 855-888 ◽  
Author(s):  
S. R. Freitas ◽  
K. M. Longo ◽  
M. F. Alonso ◽  
M. Pirre ◽  
V. Marecal ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Atmospheric Chemistry ◽  
Transport Model ◽  
Agricultural Waste ◽  
Trace Gases ◽  
Transport Models ◽  
Map Projections ◽  
Global Transport ◽  
Fortran 90 ◽  
The Way

Abstract. The pre-processor PREP-CHEM-SRC presented in the paper is a comprehensive tool aiming at preparing emissions fields of trace gases and aerosols for use in regional or global transport models. The emissions considered are urban/industrial, biogenic, biomass burning, volcanic, biofuel use and burning from agricultural waste sources from most recent databases or from satellite fire detections for biomass burning. A plumerise model is used to derive the height of smoke emissions from satellite fire products. The pre-processor provides emission fields interpolated onto the transport model grid. Several map projections can be chosen. The way to include these emissions in transport models is also detailed. The pre-processor is coded using Fortran 90 and C and is driven by a namelist allowing the user to choose the type of emissions and the database.

scholarly journals Atmospheric Chemistry Measurements at Whiteface Mountain, NY: Ozone and Reactive Trace Gases

2016 ◽  
Vol 16 (3) ◽  
pp. 873-884 ◽  
Author(s):  
Richard E. Brandt ◽  
James J. Schwab ◽  
Paul W. Casson ◽  
Utpal K. Roychowdhury ◽  
Douglas Wolfe ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Trace Gases ◽  
Whiteface Mountain ◽  
Reactive Trace Gases

scholarly journals Temporal characteristics of atmospheric ammonia and nitrogen dioxide over China based on emission data, satellite observations and atmospheric transport modeling since 1980

2017 ◽  
Vol 17 (15) ◽  
pp. 9365-9378 ◽  
Author(s):  
Lei Liu ◽  
Xiuying Zhang ◽  
Wen Xu ◽  
Xuejun Liu ◽  
Yi Li ◽  
...  
Keyword(s):  
Nitrogen Dioxide ◽  
Atmospheric Chemistry ◽  
Transport Model ◽  
Atmospheric Transport ◽  
Temporal Trends ◽  
Satellite Observations ◽  
Transport Modeling ◽  
Emission Data ◽  
Atmospheric Ammonia ◽  
Atmospheric Transport Modeling

Abstract. China is experiencing intense air pollution caused in large part by anthropogenic emissions of reactive nitrogen (Nr). Atmospheric ammonia (NH3) and nitrogen dioxide (NO2) are the most important precursors for Nr compounds (including N2O5, HNO3, HONO and particulate NO3− and NH4+) in the atmosphere. Understanding the changes in NH3 and NO2 has important implications for the regulation of anthropogenic Nr emissions and is a requirement for assessing the consequence of environmental impacts. We conducted the temporal trend analysis of atmospheric NH3 and NO2 on a national scale since 1980 based on emission data (during 1980–2010), satellite observation (for NH3 since 2008 and for NO2 since 2005) and atmospheric chemistry transport modeling (during 2008–2015).Based on the emission data, during 1980–2010, significant continuous increasing trends in both NH3 and NOx were observed in REAS (Regional Emission inventory in Asia, for NH3 0.17 and for NOx 0.16 kg N ha−1 yr−2) and EDGAR (Emissions Database for Global Atmospheric Research, for NH3 0.24 and for NOx 0.17 kg N ha−1 yr−2) over China. Based on the satellite data and atmospheric chemistry transport model (CTM) MOZART-4 (Model for Ozone and Related chemical Tracers, version 4), the NO2 columns over China increased significantly from 2005 to 2011 and then decreased significantly from 2011 to 2015; the satellite-retrieved NH3 columns from 2008 to 2014 increased at a rate of 2.37 % yr−1. The decrease in NO2 columns since 2011 may result from more stringent strategies taken to control NOx emissions during the 12th Five Year Plan, while no control policy has focused on NH3 emissions. Our findings provided an overall insight into the temporal trends of both NO2 and NH3 since 1980 based on emission data, satellite observations and atmospheric transport modeling. These findings can provide a scientific background for policy makers that are attempting to control atmospheric pollution in China. Moreover, the multiple datasets used in this study have implications for estimating long-term Nr deposition datasets to assess its impact on soil, forest, water and greenhouse balance.

scholarly journals New approach to evaluate satellite derived XCO<sub>2</sub> over oceans by integrating ship and aircraft observations

2020 ◽  
Author(s):  
Astrid Müller ◽  
Hiroshi Tanimoto ◽  
Takafumi Sugita ◽  
Toshinobu Machida ◽  
Shin-ichiro Nakaoka ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Atmospheric Chemistry ◽  
Transport Model ◽  
Satellite Observations ◽  
Reference Dataset ◽  
Model Calculations ◽  
New Approach ◽  
Mixing Ratios ◽  
In Situ Data

Abstract. Satellite observations provide spatially-resolved global estimates of column-averaged mixing ratios of CO2 (XCO2) over the Earth's surface. The accuracy of these datasets can be validated against reliable standards in some areas, but other areas remain inaccessible. To date, limited reference data over oceans hinders successful uncertainty quantification or bias correction efforts, and precludes reliable conclusions about changes in the carbon cycle in some regions. Here, we propose a new approach to analyze and evaluate seasonal, interannual and latitudinal variations of XCO2 over oceans by integrating cargo-ship (SOOP, Ship Of Opportunity) and commercial aircraft (CONTRAIL, Comprehensive Observation Network for Trace gases by Airliner) observations with the aid of state-of-the art atmospheric chemistry-transport model calculations. The consistency of the in situ based column-averaged CO2 dataset (in situ XCO2) with satellite estimates was analyzed over the Western Pacific between 2014 and 2017, and its utility as reference dataset evaluated. Our results demonstrate that the new dataset accurately captures seasonal and interannual variations of CO2. Retrievals of XCO2 over the ocean from GOSAT (Greenhouse gases observing satellite: NIES v02.75, National Institute for Environmental Studies; ACOS v7.3, Atmospheric CO2 Observation from Space) and OCO-2 (Orbiting Carbon Observatory, v9r) observations show a negative bias of about 1 parts per million (ppm) in northern midlatitudes, which was attributed to measurement uncertainties of the satellite observations. The NIES retrieval had higher consistency with in situ XCO2 at midlatitudes as compared to the other retrievals. At low latitudes, it shows many fewer valid data and high scatter, such that ACOS and OCO-2 appear to provide a better representation of the carbon cycle. At different times, the seasonal cycles of all three retrievals show positive phase shifts of one month relative to the in situ data. The study indicates that even if the retrievals complement each other, remaining uncertainties limit the accurate interpretation of spatiotemporal changes in CO2 fluxes. A continuous long-term XCO2 dataset with wide latitudinal coverage based on the new approach has a great potential as a robust reference dataset for XCO2 and can help to better understand changes in the carbon cycle in response to climate change using satellite observations.

Investigation of global atmospheric carbonyl sulphide between 2004 and 2018: an observational and modelling study

2020 ◽  
Author(s):  
Michael P. Cartwright ◽  
Jeremy J. Harrison ◽  
David P. Moore ◽  
John J. Remedios ◽  
Martyn P. Chipperfield ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Atmospheric Carbon Dioxide ◽  
Transport Model ◽  
Carbonyl Sulfide ◽  
Global Scale ◽  
Chemical Transport Model ◽  
Sources And Sinks ◽  
Continental Scale ◽  
Retrieval Scheme ◽  
The Relationship

&lt;p&gt;The challenge in quantifying the sources and sinks of atmospheric carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;) is that the CO&lt;sub&gt;2&lt;/sub&gt; taken up by plants during photosynthesis cannot be distinguished from the CO&lt;sub&gt;2&lt;/sub&gt; released by plants and micro-organisms during respiration. It has been shown that carbonyl sulfide (OCS), the sulphur-containing analogue of CO&lt;sub&gt;2&lt;/sub&gt;, can be used as a proxy for photosynthesis. The relationship between the vegetative flux of OCS and CO&lt;sub&gt;2&lt;/sub&gt; has been quantified for various species of plants and ecosystems, the results of which have been used in observing the relationship on a continental scale. The aim of this project is to both quantify the location and magnitude of the sources and sinks of atmospheric OCS, and to use these data to infer photosynthetic uptake of CO&lt;sub&gt;2&lt;/sub&gt; by vegetation on a global scale.&lt;/p&gt;&lt;p&gt;A tracer version of the 3-dimensional chemical transport model TOMCAT has been adapted to include eleven different sources and sinks of OCS, including direct and indirect oceanic emissions, vegetative uptake and stratospheric photolysis. The modelled OCS (TOMCAT-OCS) distribution between 2004 and 2018 has been co-located spatially and temporally to OCS profiles measured by the Atmospheric Chemistry Experiment (ACE-FTS) over the 5 &amp;#8211; 30 km altitude, showing generally good agreement. Furthermore, surface TOMCAT-OCS has been compared to OCS measurements made at twelve NOAA-ESRL sites, across both hemispheres, showing that the model captures the seasonal cycle at the surface.&lt;/p&gt;&lt;p&gt;There have been several calls in recent years for a new satellite product of atmospheric OCS, which this project aims to satisfy. Work is ongoing to retrieve OCS total columns from measurements taken by the Infrared Atmospheric Sounding Interferometer (IASI) instruments on-board the MetOp satellites. The University of Leicester IASI Retrieval Scheme (ULIRS) has been adapted to retrieve OCS columns globally. Various case studies for different geographic regions and time periods will be presented and compared to other satellite observations.&lt;/p&gt;

scholarly journals Simulating CO<sub>2</sub> profiles using NIES TM and comparison with HIAPER Pole-to-Pole Observations

2015 ◽  
Vol 15 (5) ◽  
pp. 6745-6770
Author(s):  
C. Song ◽  
S. Maksyutov ◽  
D. Belikov ◽  
H. Takagi ◽  
J. Shu
Keyword(s):  
Atmospheric Chemistry ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Chemical Constituents ◽  
Vertical Profiles ◽  
Vertical Coordinate ◽  
Diurnal Cycles ◽  
Terrain Following ◽  
Carbon Dioxide Co2 ◽  
Made In

Abstract. We present a study on validation of the National Institute for Environmental Studies Transport Model (NIES TM) by comparing to observed vertical profiles of atmospheric CO2. The model uses a hybrid sigma-isentropic (σ–θ) vertical coordinate that employs both terrain-following and isentropic parts switched smoothly in the stratosphere. The model transport is driven by reanalyzed meteorological fields and designed to simulate seasonal and diurnal cycles, synoptic variations, and spatial distributions of atmospheric chemical constituents in the troposphere. The model simulations were run for biosphere, fossil fuel, air–ocean exchange, biomass burning and inverse correction fluxes of carbon dioxide (CO2) by GOSAT Level 4 product. We compared the NIES TM simulated fluxes with data from the HIAPER Pole-to-Pole Observations (HIPPO) Merged 10 s Meteorology, Atmospheric Chemistry, and Aerosol Data, including HIPPO-1, HIPPO-2 and HIPPO-3 from 128.0° E to −84.0° W, and 87.0° N to −67.2° S. The simulation results were compared with CO2 observations made in January and November 2009, and March and April 2010. The analysis attests that the model is good enough to simulate vertical profiles with errors generally within 1–2 ppmv, except for the lower stratosphere in the Northern Hemisphere high latitudes.

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