scholarly journals Estimating aerosol emission from SPEXone on the NASA PACE mission using an ensemble Kalman Smoother: Observing System Simulation Experiments (OSSEs)

2021 ◽  
Author(s):  
Athanasios Tsikerdekis ◽  
Nick A. J. Schutgens ◽  
Guangliang Fu ◽  
Otto P. Hasekamp
Keyword(s):  
Global Climate ◽  
System Simulation ◽  
Sea Salt ◽  
Simulation Experiments ◽  
Reanalysis Dataset ◽  
Kalman Smoother ◽  
Aerosol Emission ◽  
Emission Fluxes ◽  
Emission Estimation ◽  
Aerosol Emissions

Abstract. We present a top-down approach for aerosol emission estimation from SPEXone polarimetric retrievals related to the aerosol amount, size, and absorption using a fixed-lag ensemble Kalman smoother (LETKS) in combination with the ECHAM-HAM model. We assess the system by performing Observing System Simulation Experiments (OSSEs), in order to evaluate the ability of the future multi-angle polarimeter instrument, SPEXone, as well as a satellite with near perfect global coverage. In our OSSEs, the Nature Run (NAT) is a simulation by the global climate aerosol model ECHAM-HAM with altered aerosol emissions. The Control (CTL) and the data assimilation (DAS) experiments are composed of an ensemble of ECHAM-HAM simulations, where the default aerosol emissions are perturbed with factors taken from a Gaussian distribution. Synthetic observations, specifically Aerosol Optical Depth at 550 nm (AOD550), Angstrom Exponent from 550 nm to 865 nm (AE550-865) and Single Scattering Albedo at 550 nm (SSA550) are assimilated in order to estimate the aerosol emission fluxes of desert dust (DU), sea salt (SS), organic carbon (OC), black carbon (BC) and sulphate (SO4), along with the emission fluxes of two SO4 precursor gases (SO2, DMS). The synthetic observations are sampled from the NAT according to two satellite observing systems, with different spatial coverages. The first is the sensor SPEXone, a hyperspectral multi-angle polarimeter with a narrow swath (~100 km), that will be a part of the NASA PACE mission. The second is an idealized sensor that can retrieve observations over the whole globe even under cloudy conditions. The prior emission global relative Mean Absolute Error (MAE) before the assimilation ranges from 33 % to 117 %. Depending on the species, the assimilated observations sampled using the idealized sensor, reduce this error to equal to or lower than 5 %. Despite its limited coverage, the SPEXone sampling bares similar results, with somewhat larger errors for DU and SS (both having a MAE equal to 11 %). Further, experiments show that doubling the measurement error, increases the global relative MAE to 22 % for DU and SS. The emission estimation of the other species is not affected as much by these changes. In addition, the role of biased meteorology on emission estimation was quantified by using two different datasets (ERA-5 and ERA-interim) to nudge the U and V wind components of the model. The results reveal that when the wind of DAS uses a different reanalysis dataset than the NAT the estimated SS emissions are negatively affected the most, while the estimated emissions of DU, OC, BC and SO2 are negatively affected to a smaller extent. If the DAS uses dust or sea salt emission parametrisations that are very different from the NAT, posterior emissions can still be successfully estimated but this experiment revealed that the source location is important for the estimation of dust emissions. This work suggests that the upcoming SPEXone sensor will provide observations related to aerosol amount, size and absorption with sufficient coverage and accuracy, in order to estimate aerosol emissions.

Aerosol emission estimation using SPEXone observational capabilities and Observing System Simulation Experiments (OSSEs) 

2021 ◽  
Author(s):  
Athanasios Tsikerdekis ◽  
Nick Schutgens ◽  
Guangliang Fu ◽  
Otto Hasekamp
Keyword(s):  
System Simulation ◽  
Absolute Error ◽  
Single Scattering ◽  
Sea Salt ◽  
Simulation Experiments ◽  
Aerosol Emission ◽  
Spatial Coverage ◽  
Emission Fluxes ◽  
Emission Estimation ◽  
Aerosol Emissions

<p>A top-down approach for aerosol emission estimation from polarimetric retrievals of aerosol amount, size, and absorption is employed . The method uses a fixed-lag ensemble Kalman smoother (LETKF-Smoother) under the framework of Observing System Simulation Experiments (OSSEs), in order to evaluate the observational capabilities of a satellite with near perfect global coverage as well as of the future multi-angle polarimeter instrument, SPEXone. ECHAM-HAM is used for the nature runs (NATs), the control (CTL) and the data assimilation (DAS) experiments. The ensemble is composed by 32 simulations where the default aerosol emissions for all species are perturbed with factors taken from a Gaussian distribution. Synthetic observations, specifically Aerosol Optical Depth at 550nm (AOD<sub>550</sub>), Angstrom Exponent 550nm to 865nm (AE<sub>550-865</sub>) and Single Scattering Albedo at 550nm (SSA<sub>550</sub>) are assimilated in order to estimate the aerosol emission fluxes of desert dust (DU), sea salt (SS), organic carbon (OC), black carbon (BC) and sulphates (SO<sub>4</sub>), along with the emission fluxes of two SO<sub>4</sub> precursor gases (SO<sub>2</sub>, DMS). The synthetic observations are sampled from the NATs according to two satellite observing systems, with different spatial coverage capabilities. The first, is an idealized sensor that retrieves observations over the whole globe in 2days even under cloudy conditions, hence is named PERFECT. The second, is the sensor SPEXone, a hyperspectral multi-angle polarimeter with a narrow swath (100km), that will be a part of the NASA PACE mission. The assimilated observations sampled using the PERFECT sensor, estimate the emission of all aerosol species with a global relative Mean Absolute Error (MAE) equal or lower than 5% (except SO<sub>4</sub>). Despite its limited coverage, the SPEXone sampling bares similar results, although MAE is a bit larger for Dust and Sea Salt. Further, experiments show that doubling the measurement error on the assimilated observations, increases additionally the global relative MAE by less than 10%. In addition, the role of biased meteorology on emission estimation was quantified by using two different datasets (ERA5 and ERAi) to nudge the U and V wind components of the model. The results reveal that when the wind of NAT and DAS are nudged to different datasets the global relative MAE of SS grows by 24%, while the estimated emissions of DU, OC, BC and SO<sub>2</sub> are negatively affected to a smaller extent (~10%). The upcoming SPEXone sensor will provide observations related to aerosol amount size and absorption, with sufficient coverage and accuracy, in order to estimate aerosol emission accurately.</p>

scholarly journals The sensitivity of global climate to the episodicity of fire aerosol emissions

2013 ◽  
Vol 13 (9) ◽  
pp. 23691-23717
Author(s):  
S. K. Clark ◽  
D. S. Ward ◽  
N. M. Mahowald
Keyword(s):  
Direct Effect ◽  
Radiative Forcing ◽  
Global Climate ◽  
Sensitivity Study ◽  
Climate Impacts ◽  
Mixed Effect ◽  
Fire Emissions ◽  
Aerosol Emission ◽  
The Tropics ◽  
Aerosol Emissions

Abstract. One of the major ways in which forest and grass fires have an impact on global climate is through the release of aerosols. Most studies focusing on calculating the radiative forcing and other climate impacts of fire aerosols use monthly mean emissions derived from the Global Fire Emissions Database that captures only the seasonal cycle of fire aerosol emissions. Here we present the results of a sensitivity study that investigates the climate response to the episodicity of the fires, based on the standard approach which releases emissions every day, and contrasts that to the response when fires are represented as intense pulses of emissions that occur only over 1–2 days on a monthly, yearly, or five-yearly basis. Overall we find that in the modified cases with increased levels of episodicity, the all sky direct effect radiative forcing increases, the clear sky direct effect radiative forcing remains relatively constant, and the magnitude of the indirect effect radiative forcing decreases by about 1 W m−2 (from −1.6 to −0.6 W m−2). In the long term, we find that an increase in aerosol emission episodicity leads to an asymmetric change in indirect radiative forcing in the Northern Hemisphere compared to the Southern Hemisphere contributes to a slight shift in the annual average position of the intertropical convergence zone (ITCZ). This shift is found to have a mixed effect on the overall performance of the model at predicting precipitation rates in the tropics. Given these results we conclude that future studies that look to assess the present day global climate impacts of fire aerosols should consider the need to accurately represent fire episodicity.

scholarly journals Baltic Sea Spray Emissions: In Situ Eddy Covariance Fluxes vs. Simulated Tank Sea Spray

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 274
Author(s):  
Ernst Douglas Nilsson ◽  
Kim A. H. Hultin ◽  
Eva Monica Mårtensson ◽  
Piotr Markuszewski ◽  
Kai Rosman ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Size Distribution ◽  
Eddy Covariance ◽  
Sea Salt ◽  
Sea Spray ◽  
Layer Model ◽  
Mono Layer ◽  
Aerosol Emission ◽  
Emission Fluxes ◽  
The Baltic

We present the first ever evaluation of sea spray aerosol eddy covariance (EC) fluxes at near coastal conditions and with limited fetch, and the first over water with brackish water (on average 7 ppt). The measurements were made on the island of Garpen in the Baltic Sea (56°23′ N, 16°06′ E) in September 2005. We found that wind speed is a major factor that is driving an exponential increase in sea spray sea salt emissions, comparable to previous studies over waters with higher salinity. We were able to show that the inclusion of a thermodenuder in the EC system allowed for the parallel measurements of the dry unheated aerosol flux (representing both organic and sea salt sea spray emissions) and the heated (300 °C) non-volatile sea salt emissions. This study’s experimental approach also included measurements of the artificial sea spray formed in a tank in locally sampled water at the same location as the EC fluxes. We attempted to use the EC aerosol flux measurements to scale the tank measurements to aerosol emissions in order to derive a complete size distribution for the sea spray emission fluxes below the size range (0.3–2 µm dry diameter) of the optical particle counters (OPCs) in the EC system, covering in total 0.01 µm to 2 µm diameter. In the wind directions with long fetches (corresponding to conditions similar to open sea), we were able to distinguish between the aerosol emission fluxes of dry aerosol and heated non-volatile (sea salt only) in the smallest size bins of the OPC, and could therefore indirectly estimate the organic sea spray fraction. In agreement with several previous ambient and tank experiments deriving the size resolved chemical mass concentration of sea salt and water-insoluble organic sea spray, our EC fluxes showed that sea sprays were dominated by sea salt at sizes ≥1 µm diameter, and by organics at the smallest OPC sizes. Since we used direct measures of the sea spray emission fluxes, we confirmed previous suggestions that this size distribution of sea salt and organics is a signature of sea spray aerosols. We were able to show that two sea salt source parameterizations (Mårtensson et al. (2003) and Salter et al. (2015)) agreed fairly well with our observed heated EC aerosol emission fluxes, as long as their predicted emissions were modified for the actual salinity by shifting the particle diameters proportionally to the cubic rote of the salinity. If, in addition, we added organics to the parameterized sea spray following the mono-layer model by Ellison et al. (1999), the combined sea spray parameterizations for sea salt and organics fell reasonably close to the observed fluxes for diameters > 0.15 µm, while one of them overpredicted the sea spray emissions below this size. The organic mono-layer model by Ellison et al. appeared to be able to explain most of the differences we observed between the aerosol emission fluxes with and without the thermodenuder.

Downscaling of precipitation on a lake basin: evaluation of rule and decision tree induction algorithms

2012 ◽  
Vol 43 (3) ◽  
pp. 215-230 ◽  
Author(s):  
Manish Kumar Goyal ◽  
C. S. P. Ojha
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Lake Basin ◽  
Monthly Precipitation ◽  
M5 Model Tree ◽  
Reanalysis Dataset ◽  
Model Tree ◽  
Basin Scale ◽  
M5 Model

We investigate the performance of existing state-of-the-art rule induction and tree algorithms, namely Single Conjunctive Rule Learner, Decision Table, M5 Model Tree, Decision Stump and REPTree. Downscaling models are developed using these algorithms to obtain projections of mean monthly precipitation to lake-basin scale in an arid region in India. The effectiveness of these algorithms is evaluated through application to downscale the predictand for the Lake Pichola region in Rajasthan state in India, which is considered to be a climatically sensitive region. The predictor variables are extracted from (1) the National Centre for Environmental Prediction (NCEP) reanalysis dataset for the period 1948–2000 and (2) the simulations from the third-generation Canadian Coupled Global Climate Model (CGCM3) for emission scenarios A1B, A2, B1 and COMMIT for the period 2001–2100. M5 Model Tree algorithm was found to yield better performance among all other learning techniques explored in the present study. The precipitation is projected to increase in future for A2 and A1B scenarios, whereas it is least for B1 and COMMIT scenarios using predictors.

scholarly journals Dynamic Downscaling of the Impact of Climate Change on the Ocean Circulation in the Galápagos Archipelago

2013 ◽  
Vol 2013 ◽  
pp. 1-18 ◽  
Author(s):  
Yanyun Liu ◽  
Lian Xie ◽  
John M. Morrison ◽  
Daniel Kamykowski
Keyword(s):  
Climate Change ◽  
Ocean Circulation ◽  
Global Climate Change ◽  
Climate Model ◽  
Global Climate ◽  
Ocean Model ◽  
Reanalysis Dataset ◽  
Equatorial Undercurrent ◽  
Galapagos Archipelago ◽  
The Impact

The regional impact of global climate change on the ocean circulation around the Galápagos Archipelago is studied using the Hybrid Coordinate Ocean Model (HYCOM) configured for a four-level nested domain system. The modeling system is validated and calibrated using daily atmospheric forcing derived from the NCEP/NCAR reanalysis dataset from 1951 to 2007. The potential impact of future anthropogenic global warming (AGW) in the Galápagos region is examined using the calibrated HYCOM with forcing derived from the IPCC-AR4 climate model. Results show that although the oceanic variability in the entire Galápagos region is significantly affected by global climate change, the degree of such effects is inhomogeneous across the region. The upwelling region to the west of the Isabella Island shows relatively slower warming trends compared to the eastern Galápagos region. Diagnostic analysis suggests that the variability in the western Galápagos upwelling region is affected mainly by equatorial undercurrent (EUC) and Panama currents, while the central/east Galápagos is predominantly affected by both Peru and EUC currents. The inhomogeneous responses in different regions of the Galápagos Archipelago to future AGW can be explained by the incoherent changes of the various current systems in the Galápagos region as a result of global climate change.

The local and remote atmospheric impacts of Africa’s 21st century aerosol emission trajectory

2021 ◽  
Author(s):  
Chris Wells ◽  
Apostolos Voulgarakis
Keyword(s):  
Regional Climate ◽  
Emission Region ◽  
Anthropogenic Aerosol ◽  
Remote Locations ◽  
Aerosol Emission ◽  
Radiation Fluxes ◽  
The World ◽  
Aerosol Emissions ◽  
The Impact ◽  
Lower Biomass

<p>Aerosols are a major climate forcer, but their historical effect has the largest uncertainty of any forcing; their mechanisms and impacts are not well understood. Due to their short lifetime, aerosols have large impacts near their emission region, but they also have effects on the climate in remote locations. In recent years, studies have investigated the influences of regional aerosols on global and regional climate, and the mechanisms that lead to remote responses to their inhomogeneous forcing. Using the Shared Socioeconomic Pathway scenarios (SSPs), transient future experiments were performed in UKESM1, testing the effect of African emissions following the SSP3-RCP7.0 scenario as the rest of the world follows SSP1-RCP1.9, relative to a global SSP1-RCP1.9 control. SSP3 sees higher direct anthropogenic aerosol emissions, but lower biomass burning emissions, over Africa. Experiments were performed changing each of these sets of emissions, and both. A further set of experiments additionally accounted for changing future CO<sub>2</sub> concentrations, to investigate the impact of CO<sub>2</sub> on the responses to aerosol perturbations. Impacts on radiation fluxes, temperature, circulation and precipitation are investigated, both over the emission region (Africa), where microphysical effects dominate, and remotely, where dynamical influences become more relevant. </p>

scholarly journals Highly-controlled, reproducible measurements of aerosol emissions from African biomass combustion

2017 ◽  
Author(s):  
Sophie L. Haslett ◽  
J. Chris Thomas ◽  
William T. Morgan ◽  
Rory Hadden ◽  
Dantong Liu ◽  
...  
Keyword(s):  
Black Carbon ◽  
Thermal Environment ◽  
Organic Aerosol ◽  
Biomass Combustion ◽  
Particulate Emissions ◽  
Radiative Balance ◽  
Mass Spectral ◽  
Aerosol Emission ◽  
Flaming Combustion ◽  
Aerosol Emissions

Abstract. Particulate emissions from biomass burning can both alter the atmosphere's radiative balance and cause significant harm to human health. However, due to the large effect on emissions caused by even small alterations to the way in which a fuel burns, it is difficult to study particulate production of biomass combustion mechanistically and in a repeatable manner. In order to address this gap, in this study, small wood samples sourced from Côte D'Ivoire in West Africa were burned in a highly-controlled laboratory environment. The shape and mass of samples, available airflow and surrounding thermal environment were carefully regulated. Organic aerosol and refractory black carbon emissions were measured in real time using an Aerosol Mass Spectrometer and a Single Particle Soot Photometer, respectively. This methodology produced remarkably repeatable results, allowing aerosol emissions to be mapped directly onto different phases of combustion. Emissions from pyrolysis were visible as a distinct phase before flaming was established. After flaming combustion was initiated, a black-carbon-dominant flame was observed during which very little organic aerosol was produced, followed by a period that was dominated by organic-carbon-producing smouldering combustion, despite the presence of residual flaming. During pyrolysis and smouldering, the two phases producing organic aerosol, distinct mass spectral signatures that correspond to previously-reported variations in biofuel emissions measured in the atmosphere are found. Organic aerosol emission factors averaged over an entire combustion event were found to be representative of the time spent in the pyrolysis and smouldering phases, rather than reflecting a coupling between emissions and the mass loss of the sample. Further exploration of aerosol yields from similarly carefully controlled fires and a careful comparison with data from macroscopic fires and real-world emissions will help to deliver greater constraints on variability of particulate emissions in atmospheric systems.

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