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  • Journal article
    Ergun RE, Pathak N, Usanova ME, Qi Y, Vo T, Burch JL, Schwartz SJ, Torbert RB, Ahmadi N, Wilder FD, Chasipis A, Newman DL, Stawarz JE, Hesse M, Turner DL, Gershman Det al., 2022,

    Observation of Magnetic Reconnection in a Region of Strong Turbulence

    , ASTROPHYSICAL JOURNAL LETTERS, Vol: 935, ISSN: 2041-8205
  • Journal article
    Rasca AP, Farrell WM, Whittlesey PL, MacDowall RJ, Bale SD, Kasper JCet al., 2022,

    Magnetic Field Dropouts and Associated Plasma Wave Emission near the Electron Plasma Frequency at Switchback Boundaries as Observed by the Parker Solar Probe

    , ASTROPHYSICAL JOURNAL, Vol: 935, ISSN: 0004-637X
  • Journal article
    Telloni D, Zank GP, Sorriso-Valvo L, D'Amicis R, Panasenco O, Susino R, Bruno R, Perrone D, Adhikari L, Liang H, Nakanotani M, Zhao L, Hadid LZ, Sanchez-Cano B, Verscharen D, Velli M, Grimani C, Marino R, Carbone F, Mancuso S, Biondo R, Pagano P, Reale F, Bale SD, Kasper JC, Case AW, de Wit TD, Goetz K, Harvey PR, Korreck KE, Larson D, Livi R, MacDowall RJ, Malaspina DM, Pulupa M, Stevens ML, Whittlesey P, Romoli M, Andretta V, Da Deppo V, Fineschi S, Heinzel P, Moses JD, Naletto G, Nicolini G, Spadaro D, Stangalini M, Teriaca L, Capobianco G, Capuano GE, Casini C, Casti M, Chioetto P, Corso AJ, De Leo Y, Fabi M, Frassati F, Frassetto F, Giordano S, Guglielmino SL, Jerse G, Landini F, Liberatore A, Magli E, Massone G, Messerotti M, Pancrazzi M, Pelizzo MG, Romano P, Sasso C, Schuhle U, Slemer A, Straus T, Uslenghi M, Volpicelli CA, Zangrilli L, Zuppella P, Abbo L, Auchere F, Cuadrado RA, Berlicki A, Ciaravella A, Lamy P, Lanzafame A, Malvezzi M, Nicolosi P, Nistico G, Peter H, Solanki SK, Strachan L, Tsinganos K, Ventura R, Vial J-C, Woch J, Zimbardo Get al., 2022,

    Linking Small-scale Solar Wind Properties with Large-scale Coronal Source Regions through Joint Parker Solar Probe-Metis/Solar Orbiter Observations

    , ASTROPHYSICAL JOURNAL, Vol: 935, ISSN: 0004-637X
  • Journal article
    Zhao L-L, Zank GP, Adhikari L, Telloni D, Stevens M, Kasper JC, Bale SD, Raouafi NEet al., 2022,

    Turbulence and Waves in the Sub-Alfvenic Solar Wind Observed by the Parker Solar Probe during Encounter 10

    , ASTROPHYSICAL JOURNAL LETTERS, Vol: 934, ISSN: 2041-8205
  • Journal article
    Clear CP, Pickering JC, Nave G, Uylings P, Raassen Tet al., 2022,

    Wavelengths and energy levels of singly ionized nickel (Ni ii) measured using fourier transform spectroscopy

    , The Astrophysical Journal Supplement Series, Vol: 261, Pages: 35-35, ISSN: 0067-0049

    High-resolution spectra of singly ionized nickel (Ni ii) have been recorded using Fourier transform spectroscopy in the region 143–5555 nm (1800–70,000 cm−1) with continuous, nickel–helium hollow cathode discharge sources. An extensive analysis of identified Ni ii lines resulted in the confirmation and revision of 283 previously reported energy levels, from the ground state up to the 3d8(ML)6s subconfigurations. Typical energy-level uncertainties are a few thousandths of a cm−1, representing at least an order-of-magnitude reduction in uncertainty with respect to previous measurements. Twenty-five new energy levels have now been established and are reported here for the first time. Eigenvector compositions of the energy levels have been calculated using the orthogonal operator method. In total, 159 even and 149 odd energy levels and 1424 classified line wavelengths of Ni ii are reported and will enable more accurate and reliable analyses of Ni ii in astrophysical spectra.
  • Journal article
    Sulaiman A, Mauk B, Szalay J, Allegrini F, Clark G, Gladstone R, Kotsiaros, Kurth W, Bagenal F, Bonfond B, Connerney J, Ebert R, Elliott S, Gershman D, Hospodarsky G, Hue V, Lysak R, Masters A, Santolik, Saur J, Bolton Set al., 2022,

    Jupiter’s low-altitude auroral zones: Fields, particles, plasma waves, and density depletions

    , Journal of Geophysical Research: Space Physics, Vol: 127, ISSN: 2169-9380

    The Juno spacecraft's polar orbits have enabled direct sampling of Jupiter's low-altitude auroral field lines. While various data sets have identified unique features over Jupiter's main aurora, they are yet to be analyzed altogether to determine how they can be reconciled and fit into the bigger picture of Jupiter's auroral generation mechanisms. Jupiter's main aurora has been classified into distinct “zones”, based on repeatable signatures found in energetic electron and proton spectra. We combine fields, particles, and plasma wave data sets to analyze Zone-I and Zone-II, which are suggested to carry upward and downward field-aligned currents, respectively. We find Zone-I to have well-defined boundaries across all data sets. H+ and/or H3+ cyclotron waves are commonly observed in Zone-I in the presence of energetic upward H+ beams and downward energetic electron beams. Zone-II, on the other hand, does not have a clear poleward boundary with the polar cap, and its signatures are more sporadic. Large-amplitude solitary waves, which are reminiscent of those ubiquitous in Earth's downward current region, are a key feature of Zone-II. Alfvénic fluctuations are most prominent in the diffuse aurora and are repeatedly found to diminish in Zone-I and Zone-II, likely due to dissipation, at higher altitudes, to energize auroral electrons. Finally, we identify significant electron density depletions, by up to 2 orders of magnitude, in Zone-I, and discuss their important implications for the development of parallel potentials, Alfvénic dissipation, and radio wave generation.
  • Journal article
    Sioulas N, Huang Z, Velli M, Chhiber R, Cuesta ME, Shi C, Matthaeus WH, Bandyopadhyay R, Vlahos L, Bowen TA, Qudsi RA, Bale SD, Owen CJ, Louarn P, Fedorov A, Maksimovic M, Stevens ML, Case A, Kasper J, Larson D, Pulupa M, Livi Ret al., 2022,

    Magnetic Field Intermittency in the Solar Wind: Parker Solar Probe and SolO Observations Ranging from the Alfven Region up to 1 AU

    , ASTROPHYSICAL JOURNAL, Vol: 934, ISSN: 0004-637X
  • Journal article
    Brunmayr AS, Graven H, 2022,

    Comment on "Probability Distributions of Radiocarbon in Open Linear Compartmental Systems at Steady-State" by I. Chanca, S. Trumbore, K. Macario, and C. A. Sierra
  • Journal article
    Schwartz SJ, Goodrich KA, Wilson III LB, Turner DL, Trattner K, Kucharek H, Gingell I, Fuselier SA, Cohen IJ, Madanian H, Ergun RE, Gershman DJ, Strangeway RJet al., 2022,

    Energy partition at collisionless supercritical quasiperpendicular shocks
  • Journal article
    Graven H, Keeling R, Xu X, 2022,

    Radiocarbon dating: going back in time

    , NATURE, Vol: 607, Pages: 449-449, ISSN: 0028-0836
  • Journal article
    Kilpua EKJ, Good SW, Ala-Lahti M, Osmane A, Pal S, Soljento JE, Zhao LL, Bale Set al., 2022,

    Structure and fluctuations of a slow ICME sheath observed at 0.5 au by the Parker Solar Probe

    , ASTRONOMY & ASTROPHYSICS, Vol: 663, ISSN: 0004-6361
  • Journal article
    Fargette N, Lavraud B, Rouillard AP, Reville V, Bale SD, Kasper Jet al., 2022,

    The preferential orientation of magnetic switchbacks and its implications for solar magnetic flux transport

    , ASTRONOMY & ASTROPHYSICS, Vol: 663, ISSN: 0004-6361
  • Journal article
    McManus MD, Verniero J, Bale SD, Bowen TA, Larson DE, Kasper JC, Livi R, Matteini L, Rahmati A, Romeo O, Whittlesey P, Woolley Tet al., 2022,

    Density and Velocity Fluctuations of Alpha Particles in Magnetic Switchbacks

    , ASTROPHYSICAL JOURNAL, Vol: 933, ISSN: 0004-637X
  • Journal article
    Gangopadhyay A, Seshadri AK, Sparks NJ, Toumi Ret al., 2022,

    The role of wind-solar hybrid plants in mitigating renewable energy-droughts

    , Renewable Energy, Vol: 194, Pages: 926-937, ISSN: 0960-1481

    Increasing the share of weather-dependent renewables in the electricity grid is essential to deeply decarbonize the electricity system. Wind and solar “droughts” or low generation days can severely impact grid stability in a renewable-rich grid. This paper analyzes for the first time wind, solar, and hybrid energy-droughts in India using a stochastic weather generator. Available literature analyze the observational data that is of limited duration (30–40 years). Therefore, discussion of low-probability high-impact renewable energy-droughts that have long return periods (in the range of 30 years) is limited in the literature. The present study seeks to address this research gap by exploring the risk of wind, solar, and wind-solar powered energy-droughts based on simulated long time series (5000 years). It is found that the weather generator captures mean, seasonality, and correlation between wind speed and solar irradiance and is therefore used to estimate return periods of extreme wind and solar-droughts. Our analysis shows that wind-droughts are more intense than solar-droughts in India. We examine the role that wind-solar hybridization can play in offsetting low wind energy episodes. The benefits of hybridization are regionally dependent. In South India, hybrid plants have advantages over either wind or solar plants alone. In comparison, for Rajasthan, the benefits of hybridization are limited. When one of the regions (South India or Rajasthan) has a renewable drought, the other region has only a 10% probability of having a similar drought. Our findings highlight the need for having robust inter-regional grid connections to mitigate regional level renewable droughts.
  • Journal article
    Gryspeerdt E, McCoy DT, Crosbie E, Moore RH, Nott GJ, Painemal D, Small-Griswold J, Sorooshian A, Ziemba Let al., 2022,

    The impact of sampling strategy on the cloud droplet number concentration estimated from satellite data

    , Atmospheric Measurement Techniques, Vol: 15, Pages: 3875-3892, ISSN: 1867-1381

    Cloud droplet number concentration (Nd) is of central importance to observation-based estimates of aerosol indirect effects, being used to quantify both the cloud sensitivity to aerosol and the base state of the cloud. However, the derivation of Nd from satellite data depends on a number of assumptions about the cloud and the accuracy of the retrievals of the cloud properties from which it is derived, making it prone to systematic biases.A number of sampling strategies have been proposed to address these biases by selecting the most accurate Nd retrievals in the satellite data. This work compares the impact of these strategies on the accuracy of the satellite retrieved Nd, using a selection of in situ measurements. In stratocumulus regions, the MODIS Nd retrieval is able to achieve a high precision (r2 of 0.5–0.8). This is lower in other cloud regimes but can be increased by appropriate sampling choices. Although the Nd sampling can have significant effects on the Nd climatology, it produces only a 20 % variation in the implied radiative forcing from aerosol–cloud interactions, with the choice of aerosol proxy driving the overall uncertainty. The results are summarised into recommendations for using MODIS Nd products and appropriate sampling.
  • Journal article
    Trotta D, Pecora F, Settino A, Perrone D, Hietala H, Horbury T, Matthaeus W, Burgess D, Servidio S, Valentini Fet al., 2022,

    On the Transmission of Turbulent Structures across the Earth's Bow Shock

    , ASTROPHYSICAL JOURNAL, Vol: 933, ISSN: 0004-637X
  • Journal article
    Davies EE, Winslow RM, Scolini C, Forsyth RJ, Moestl C, Lugaz N, Galvin ABet al., 2022,

    Multi-spacecraft Observations of the Evolution of Interplanetary Coronal Mass Ejections between 0.3 and 2.2 au: Conjunctions with the Juno Spacecraft

    , ASTROPHYSICAL JOURNAL, Vol: 933, ISSN: 0004-637X
  • Journal article
    Smith AW, Forsyth C, Rae IJ, Garton TM, Jackman CM, Bakrania M, Shore RM, Richardson GS, Beggan CD, Heyns MJ, Eastwood JP, Thomson AWP, Johnson JMet al., 2022,

    On the considerations of using near real time data for space weather hazard forecasting

    , Space Weather, Vol: 20, ISSN: 1542-7390

    Space weather represents a severe threat to ground-based infrastructure, satellites and communications. Accurately forecasting when such threats are likely (e.g., when we may see large induced currents) will help to mitigate the societal and financial costs. In recent years computational models have been created that can forecast hazardous intervals, however they generally use post-processed “science” solar wind data from upstream of the Earth. In this work we investigate the quality and continuity of the data that are available in Near-Real-Time (NRT) from the Advanced Composition Explorer and Deep Space Climate Observatory (DSCOVR) spacecraft. In general, the data available in NRT corresponds well with post-processed data, however there are three main areas of concern: greater short-term variability in the NRT data, occasional anomalous values and frequent data gaps. Some space weather models are able to compensate for these issues if they are also present in the data used to fit (or train) the model, while others will require extra checks to be implemented in order to produce high quality forecasts. We find that the DSCOVR NRT data are generally more continuous, though they have been available for small fraction of a solar cycle and therefore DSCOVR has experienced a limited range of solar wind conditions. We find that short gaps are the most common, and are most frequently found in the plasma data. To maximize forecast availability we suggest the implementation of limited interpolation if possible, for example, for gaps of 5 min or less, which could increase the fraction of valid input data considerably.
  • Journal article
    Thaller SA, Andersson L, Schwartz SJ, Mazelle C, Fowler C, Goodrich K, Newman D, Halekas J, Pilinski MD, Pollard Met al., 2022,

    Bipolar Electric Field Pulses in the Martian Magnetosheath and Solar Wind; Their Implication and Impact Accessed by System Scale Size

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 127, ISSN: 2169-9380
  • Journal article
    Sroka S, Czaja A, Chakravorty S, 2022,

    Assessing the importance of mesoscale sea-surface temperature variations for surface turbulent cooling of the Kuroshio Extension in wintertime

    , QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Vol: 148, Pages: 2742-2754, ISSN: 0035-9009
  • Journal article
    Howes GG, Verniero JL, Larson DE, Bale SD, Kasper JC, Goetz K, Klein KG, Whittlesey PL, Livi R, Rahmati A, Chen CHK, Wilson LB, Alterman BL, Wicks RTet al., 2022,

    Revolutionizing Our Understanding of Particle Energization in Space Plasmas Using On-Board Wave-Particle Correlator Instrumentation

    , FRONTIERS IN ASTRONOMY AND SPACE SCIENCES, Vol: 9, ISSN: 2296-987X
  • Conference paper
    Glassmeier F, Hoffmann F, Feingold G, Gryspeerdt E, van Hooft A, Yamaguchi T, Johnson JS, Carslaw KSet al., 2022,

    Gaussian-process emulation for integrating data-driven aerosol-cloud physics from simulation, satellite, and ground-based data

    <jats:p>&amp;lt;p&amp;gt;Data-driven quantification and parameterization of cloud physics in general, and of aerosol-cloud interactions in particular, rely on input data from observations or detailed simulations. These data sources have complementary limitations in terms of their spatial and temporal coverage and resolution; simulation data has the advantage of readily providing causality but cannot represent the full process complexity. In order to base data-driven approaches on comprehensive information, we therefore need ways to integrate different data sources.&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;We discuss how the classical statistical technique of Gaussian-process emulation can be combined with specifically initialized ensembles of detailed cloud simulations (large-eddy simulations, LES) to provide a framework for evaluating data-driven descriptions of cloud characteristics and processes across different data sources. We specifically illustrate this approach for integrating LES and satellite data of aerosol-cloud interactions in subtropical stratocumulus cloud decks. We furthermore explore the extension of our framework to ground-based observations of Arctic mixed-phase clouds.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;lt;strong&amp;gt;References:&amp;lt;/strong&amp;gt;&amp;lt;/p&amp;gt;&amp;lt;ul&amp;gt;&amp;lt;li&amp;gt;Glassmeier, F., F. Hoffmann, J. S. Johnson, T. Yamaguchi, K. S. Carslaw and G. Feingold (2019): &amp;amp;#8220;An emulator approach to stratocumulus susceptibility&amp;amp;#8221;, Atmos. Chem. Phys., 19, 10191- 10203, doi: 10.5194/acp-19-10191-2019&amp;lt;/li&amp;gt;&amp;lt;li&amp;gt;Hoffmann, F., F. Glassmeier, T. Yamaguchi and G. Feingold (2020)
  • Journal article
    Good SW, Hatakka LM, Ala-Lahti M, Soljento JE, Osmane A, Kilpua EKJet al., 2022,

    Cross helicity of interplanetary coronal mass ejections at 1 au

    , MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 514, Pages: 2425-2433, ISSN: 0035-8711
  • Journal article
    Vasko IY, Mozer FS, Bale SD, Artemyev Aet al., 2022,

    Ion-Acoustic Waves in a Quasi-Perpendicular Earth's Bow Shock

    , GEOPHYSICAL RESEARCH LETTERS, Vol: 49, ISSN: 0094-8276
  • Journal article
    Ergun RE, Usanova ME, Turner DL, Stawarz Jet al., 2022,

    Bursty bulk flow turbulence as a source of energetic particles to the outer radiation belt

    , Geophysical Research Letters, Vol: 49, ISSN: 0094-8276

    We report observations of a Bursty Bulk Flow (BBF) penetrating close to the outer edge of the radiation belt. The turbulent BBF braking region is characterized by ion velocity fluctuations, magnetic field (B) variations, and intense electric fields (E). In this event, energetic (>100 keV) electron and ion fluxes are appreciably enhanced. Importantly, fluctuations in energetic electrons and ions suggest local energization. Using correlation distances and other observed characteristics of turbulent E, test-particle simulations support local energization by E that favors higher-energy electrons and leads to an enhanced energetic shoulder and tail in the electron distributions. The energetic shoulder and tail could be amplified to MeV energies by adiabatic transport into the radiation belt where |B| is higher. This analysis suggests that turbulence generated by BBFs can, in part, supply energetic particles to the outer radiation belt and that turbulence can be a significant contributor to particle acceleration.
  • Journal article
    Breul P, Ceppi P, Shepherd TG, 2022,

    Relationship between southern hemispheric jet variability and forced response: the role of the stratosphere

    , Weather and Climate Dynamics, Vol: 3, Pages: 645-658, ISSN: 2698-4016

    Climate models show a wide range of southern hemispheric jet responses to greenhouse gas forcing. One approach to constrain the future jet response is by utilising the fluctuation–dissipation theorem (FDT) which links the forced response to internal variability timescales, with the Southern Annular Mode (SAM) the most dominant mode of variability of the southern hemispheric jet. We show that interannual stratospheric variability approximately doubles the SAM timescale during austral summer in both re-analysis data and models from the Coupled Model Intercomparison Project, Phases 5 (CMIP5) and 6 (CMIP6). Using a simple barotropic model, we demonstrate how the enhanced SAM timescale subsequently leads to an overestimate of the forced jet response based on the FDT, and we introduce a method to correct for the stratospheric influence. This result helps to resolve a previously identified discrepancy between the seasonality of jet response and the internal variability timescale. However, even after accounting for this influence, the SAM timescale cannot explain inter-model differences in the forced jet shift across CMIP models during austral summer.
  • Journal article
    Wang S, Toumi R, 2022,

    An analytic model of the tropical cyclone outer size

    , npj Climate and Atmospheric Science, Vol: 5, ISSN: 2397-3722

    There are simple conceptual models of tropical cyclone intensification and potential intensity. However, such a framework has been lacking to describe the evolution of the outer circulation. An analytic growth model of the tropical cyclone outer size is derived from the angular momentum equation. The growth model fits a full-physics idealized tropical cyclone simulation. The lifecycle composite of the best-track outer size growth shows a strong super-linear nature, which supports an exponential growth as predicted by the growth model. The climatology of outer size growth measured by the radius of gale-force wind in the North Atlantic and Eastern Pacific during the period 2004–2017, can be understood in terms of four growth factors of the model: the initial size, the growth duration, the mean growth latitude, and the mean top-of-boundary-layer effective local inflow angle. All four variables are significantly different between the two basins. The observed lifetime maximum size follows a lognormal distribution, which is in line with the law of the proportionate effect of this exponential growth model. The growth model fits the observed outer size well in global basins. The time constant of the exponential size growth is approximately equal to the product of the Coriolis parameter and the mean effective inflow angle above the boundary layer. Further sensitivity experiments with the growth model suggest that the interannual variability of the global lifetime maximum size is largely driven by the variation of growth duration.
  • Journal article
    Jia H, Quaas J, Gryspeerdt E, Bohm C, Sourdeval Oet al., 2022,

    Addressing the difficulties in quantifying droplet number response to aerosol from satellite observations

    , Atmospheric Chemistry and Physics, Vol: 22, Pages: 7353-7372, ISSN: 1680-7316

    Aerosol–cloud interaction is the most uncertain component of the overall anthropogenic forcing of the climate, in which cloud droplet number concentration (Nd) sensitivity to aerosol (S) is a key term for the overall estimation. However, satellite-based estimates of S are especially challenging, mainly due to the difficulty in disentangling aerosol effects on Nd from possible confounders. By combining multiple satellite observations and reanalysis, this study investigates the impacts of (a) updraft, (b) precipitation, (c) retrieval errors, and (d) vertical co-location between aerosol and cloud on the assessment of S in the context of marine warm (liquid) clouds. Our analysis suggests that S increases remarkably with both cloud-base height and cloud geometric thickness (proxies for vertical velocity at cloud base), consistent with stronger aerosol–cloud interactions at larger updraft velocity for midlatitude and low-latitude clouds. In turn, introducing the confounding effect of aerosol–precipitation interaction can artificially amplify S by an estimated 21 %, highlighting the necessity of removing precipitating clouds from analyses of S. It is noted that the retrieval biases in aerosol and cloud appear to underestimate S, in which cloud fraction acts as a key modulator, making it practically difficult to balance the accuracies of aerosol–cloud retrievals at aggregate scales (e.g., 1 grid). Moreover, we show that using column-integrated sulfate mass concentration (SO4C) to approximate sulfate concentration at cloud base (SO4B) can result in a degradation of correlation with Nd, along with a nearly twofold enhancement of S, mostly attributed to the inability of SO4C to capture the full spatiotemporal variability of SO4B. These findings point to several potential ways forward to practically account for the major influential factors by means of satellite observations and reanalysis, aiming at optimal observational estimates of global radia
  • Journal article
    Archer M, Cottingham M, Hartinger M, Shi X, Coyle S, Hill E, Fox M, Masongsong Eet al., 2022,

    Listening to the magnetosphere: How best to make ULF waves audible

    , Frontiers in Astronomy and Space Sciences, Vol: 9, ISSN: 2296-987X

    Observations across the heliosphere typically rely on in situ spacecraft observations producing time-series data. While often this data is analysed visually, it lends itself more naturally to our sense of sound. The simplest method of converting oscillatory data into audible sound is audification—a one-to-one mapping of data samples to audio samples—which has the benefit that no information is lost, thus is a true representation of the original data. However, audification can make some magnetospheric ULF waves observations pass by too quickly for someone to realistically be able to listen to effectively. For this reason, we detail various existing audio time scale modification techniques developed for music, applying these to ULF wave observations by spacecraft and exploring how they affect the properties of the resulting audio. Through a public dialogue we arrive at recommendations for ULF wave researchers on rendering these waves audible and discuss the scientific and educational possibilities of these new methods.
  • Journal article
    Shaylor M, Brindley H, Sellar A, 2022,

    An evaluation of two decades of aerosol optical depth retrievals from MODIS over Australia

    , Remote Sensing, Vol: 14, Pages: 1-23, ISSN: 2072-4292

    We present an evaluation of Aerosol Optical Depth (AOD) retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) over Australia covering the period 2001–2020. We focus on retrievals from the Deep Blue (DB) and Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithms, showing how these compare to one another in time and space. We further employ speciated AOD estimates from Copernicus Atmospheric Monitoring Service (CAMS) reanalyses to help diagnose aerosol types and hence sources. Considering Australia as a whole, monthly mean AODs show similar temporal behaviour, with a well-defined seasonal peak in the Austral summer. However, excepting periods of intense biomass burning activity, MAIAC values are systematically higher than their DB counterparts by, on average, 50%. Decomposing into seasonal maps, the patterns of behaviour show distinct differences, with DB showing a larger dynamic range in AOD, with markedly higher AODs (ΔAOD∼0.1) in northern and southeastern regions during Austral winter and summer. This is counter-balanced by typically smaller DB values across the Australian interior. Site level comparisons with all available level 2 AOD data from Australian Aerosol Robotic Network (AERONET) sites operational during the study period show that MAIAC tends to marginally outperform DB in terms of correlation (RMAIAC = 0.71, RDB = 0.65) and root-mean-square error (RMSEMAIAC = 0.065, RMSEDB = 0.072). To probe this behaviour further, we classify the sites according to the predominant surface type within a 25 km radius. This analysis shows that MAIAC’s advantage is retained across all surface types for R and all but one for RMSE. For this surface type (Bare, comprising just 1.2% of Australia) the performance of both algorithms is relatively poor, (RMAIAC = 0.403, RDB = 0.332).

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