Thermal infrared dust optical depth and coarse-mode effective diameter retrieved from collocated MODIS and CALIOP observations

In this study, we developed a novel algorithm based on the collocated Moderate Resolution Imaging Spectroradiometer (MODIS) thermal infrared (TIR) observations and dust vertical profiles from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) to simultaneously retrieve dust aerosol optical depth at 10 &micro;m (DAOD10&mu;m) and the coarse-mode dust effective diameter (Deff) over global oceans. The accuracy of the Deff retrieval is assessed by comparing retrieved Deff with the in-situ measured dust particle size distributions (PSDs) from the AER-D, SAMUM-2 and SALTRACE field campaigns through case studies. The new DAOD10&mu;m retrievals were evaluated first through comparisons with the collocated DAOD10.6&mu;m retrieved from the combined Imaging Infrared Radiometer (IIR) and CALIOP observations from our previous study (Zheng et al. 2022). The pixel-to-pixel comparison of the two retrievals indicates a good agreement (R~0.7) and a significant reduction of (~50 %) retrieval uncertainties largely thanks to the better constraint on dust size. In a climatological comparison, the seasonal and regional (5&deg;&times;2&deg;) mean DAOD10um retrievals based on our combined MODIS and CALIOP method are in good agreement with the two independent Infrared Atmospheric Sounding Interferometer (IASI) products over three dust transport regions (i.e., North Atlantic (NA; R = 0.9), Indian Ocean (IO; R = 0.8) and North Pacific (NP; R = 0.7)). Using the new retrievals from 2013 to 2017, we performed a climatological analysis of coarse mode dust Deff over global oceans. We found that dust Deff over IO and NP are up to 20 % smaller than that over NA. Over NA in summer, we found a ~50 % reduction of the number of retrievals with Deff &gt; 5 &mu;m from 15&deg; W to 35&deg; W and a stable trend of Deff average at 4.4 &mu;m from 35&deg; W throughout the Caribbean Sea (90&deg; W). Over NP in spring, only ~5 % of retrieved pixels with Deff &gt; 5 &mu;m are found from 150&deg; E to 180&deg;, while the mean Deff remains stable at 4.0 &mu;m throughout eastern NP. To our best knowledge, this study is the first to retrieve both DAOD and coarse-mode dust particle size over global oceans for multiple years. This retrieval dataset provides insightful information for evaluating dust long-wave radiative effects and coarse mode dust particle size in models.</p

The aerosol-climate model ECHAM5-HAM

The aerosol-climate modelling system ECHAM5-HAM is introduced. It is based on a flexible microphysical approach and, as the number of externally imposed parameters is minimised, allows the application in a wide range of climate regimes. ECHAM5-HAM predicts the evolution of an ensemble of microphysically interacting internally- and externally-mixed aerosol populations as well as their size-distribution and composition. The size-distribution is represented by a superposition of log-normal modes. In the current setup, the major global aerosol compounds sulfate (SU), black carbon (BC), particulate organic matter (POM), sea salt (SS), and mineral dust (DU) are included. The simulated global annual mean aerosol burdens (lifetimes) for the year 2000 are for SU: 0.80 Tg(S) (3.9 days), for BC: 0.11 Tg (5.4 days), for POM: 0.99 Tg (5.4 days), for SS: 10.5 Tg (0.8 days), and for DU: 8.28 Tg (4.6 days). An extensive evaluation with in-situ and remote sensing measurements underscores that the model results are generally in good agreement with observations of the global aerosol system. The simulated global annual mean aerosol optical depth (AOD) is with 0.14 in excellent agreement with an estimate derived from AERONET measurements (0.14) and a composite derived from MODIS-MISR satellite retrievals (0.16). Regionally, the deviations are not negligible. However, the main patterns of AOD attributable to anthropogenic activity are reproduced

Prediction of the number of cloud droplets in the ECHAM GCM

In this paper a prognostic equation for the number of cloud droplets (CDNC) is introduced into the ECHAM general circulation model. The initial CDNC is based on the mechanistic model of Chuang and Penner [1995], providing a more realistical prediction of CDNC than the empirical method previously used. Cloud droplet nucleation is parameterized as a function of total aerosol number concentration, updraft velocity, and a shape parameter, which takes the aerosol composition and size distribution into account. The total number of aerosol particles is obtained as the sum of marine sulfate aerosols produced from dimethyl sulfide, hydrophylic organic and black carbon, submicron dust, and sea-salt aerosols. Anthropogenic sulfate aerosols only add mass to the preexisting aerosols but do not form new particles. The simulated annual mean liquid water path, column CDNC, and effective radius agree well with observations, as does the frequency distributions of column CDNC for clouds over oceans and the variations of cloud optical depth with effective radius

The evolution of the global aerosol system in a transient climate simulation from 1860 to 2100

The evolution of the global aerosol system from 1860 to 2100 is investigated through a transient atmosphere-ocean General Circulation Model climate simulation with interactively coupled atmospheric aerosol and oceanic biogeochemistry modules. The microphysical aerosol module HAM incorporates the major global aerosol cycles with prognostic treatment of their composition, size distribution, and mixing state. Based on an SRES A1B emission scenario, the global mean sulfate burden is projected to peak in 2020 while black carbon and particulate organic matter show a lagged peak around 2070. From present day to future conditions the anthropogenic aerosol burden shifts generally from the northern high-latitudes to the developing low-latitude source regions with impacts on regional climate. Atmospheric residence- and aging-times show significant alterations under varying climatic and pollution conditions. Concurrently, the aerosol mixing state changes with an increasing aerosol mass fraction residing in the internally mixed accumulation mode. The associated increase in black carbon causes a more than threefold increase of its co-single scattering albedo from 1860 to 2100. Mid-visible aerosol optical depth increases from pre-industrial times, predominantly from the aerosol fine fraction, peaks at 0.26 around the sulfate peak in 2020 and maintains a high level thereafter, due to the continuing increase in carbonaceous aerosols. The global mean anthropogenic top of the atmosphere clear-sky short-wave direct aerosol radiative perturbation intensifies to −1.1 W m^−2 around 2020 and weakens after 2050 to −0.6 W m^−2, owing to an increase in atmospheric absorption. The demonstrated modifications in the aerosol residence- and aging-times, the microphysical state, and radiative properties challenge simplistic approaches to estimate the aerosol radiative effects from emission projections

An AeroCom initial assessment – optical properties in aerosol component modules of global models

The AeroCom exercise diagnoses multi-component aerosol modules in global modeling. In an initial assessment simulated global distributions for mass and mid-visible aerosol optical thickness (aot) were compared among 20 different modules. Model diversity was also explored in the context of previous comparisons. For the component combined aot general agreement has improved for the annual global mean. At 0.11 to 0.14, simulated aot values are at the lower end of global averages suggested by remote sensing from ground (AERONET ca. 0.135) and space (satellite composite ca. 0.15). More detailed comparisons, however, reveal that larger differences in regional distribution and significant differences in compositional mixture remain. Of particular concern are large model diversities for contributions by dust and carbonaceous aerosol, because they lead to significant uncertainty in aerosol absorption (aab). Since aot and aab, both, influence the aerosol impact on the radiative energy-balance, the aerosol (direct) forcing uncertainty in modeling is larger than differences in aot might suggest. New diagnostic approaches are proposed to trace model differences in terms of aerosol processing and transport: These include the prescription of common input (e.g. amount, size and injection of aerosol component emissions) and the use of observational capabilities from ground (e.g. measurements networks) or space (e.g. correlations between aerosol and clouds)

Science Writers' Guide to Terra

This guide was produced for science writers and the media and provides research profiles, as well as extensive background and contact information for NASA’s Terra spacecraft. Terra’s launch marked a new era of comprehensive monitoring of the Earth's atmosphere, oceans and continents from a single space-based platform. Data from the five Terra instruments are creating continuous, long-term records of the state of the land, oceans and atmosphere. Together with data from other satellite systems launched by NASA and other countries, Terra will inaugurate a new self-consistent data record that will be gathered over the next 15 years. Educational levels: Informal education

MODIS: Moderate Resolution Imaging Spectrometer

This brochure describes the Moderate Resolution Imaging Spectrometer (MODIS) instrument on NASA's Terra satellite. The first NASA Earth Observing System (EOS) satellite, Terra, was launched on December 18, 1999, carrying five remote sensors. The most comprehensive EOS sensor is MODIS which offers a unique combination of features: it detects a wide spectral range of electromagnetic energy; it takes measurements at three spatial resolutions (levels of detail); it takes measurements all day, every day; and it has a wide field of view. This continual, comprehensive coverage allows MODIS to complete an electromagnetic picture of the globe every two days. Educational levels: Undergraduate lower division, Undergraduate upper division, Graduate or professional, Informal education

Cloud microphysics and aerosol indirect effects in the global climate model ECHAM5-HAM

The double-moment cloud microphysics scheme from ECHAM4 has been coupled to the size-resolved aerosol scheme ECHAM5-HAM. ECHAM5-HAM predicts the aerosol mass and number concentrations and the aerosol mixing state. This results in a much better agreement with observed vertical profiles of the black carbon and aerosol mass mixing ratios than with the previous version ECHAM4, where only the different aerosol mass mixing ratios were predicted. Also, the simulated liquid, ice and total water content and the cloud droplet and ice crystal number concentrations as a function of temperature in stratiform mixed-phase clouds between 0 and –35°C agree much better with aircraft observations in the ECHAM5 simulations. ECHAM5 performs better because more realistic aerosol concentrations are available for cloud droplet nucleation and because the Bergeron-Findeisen process is parameterized as being more efficient. The total anthropogenic aerosol effect includes the direct, semi-direct and indirect effects and is defined as the difference in the top-of-the-atmosphere net radiation between present-day and pre-industrial times. It amounts to –1.8 W m^−2 in ECHAM5, when a relative humidity dependent cloud cover scheme and present-day aerosol emissions representative for the year 2000 are used. It is larger when either a statistical cloud cover scheme or a different aerosol emission inventory are employed

Emission-Induced Nonlinearities in the Global Aerosol System: Results from the ECHAM5-HAM Aerosol-Climate Model

In a series of simulations with the global ECHAM5-HAM aerosol-climate model, the response to changes in anthropogenic emissions is analyzed. Traditionally, additivity is assumed in the assessment of the aerosol climate impact, as the underlying bulk aerosol models are largely constrained to linearity. The microphysical aerosol module HAM establishes degrees of freedom for nonlinear responses of the aerosol system. In this study’s results, aerosol column mass burdens respond nonlinearly to changes in anthropogenic emissions, manifested in alterations of the aerosol lifetimes. Specific emission changes induce modifications of aerosol cycles with unaltered emissions, indicating a microphysical coupling of the aerosol cycles. Anthropogenic carbonaceous emissions disproportionately contribute to the accumulation mode numbers close to the source regions. In contrast, anthropogenic sulfuric emissions less than proportionally contribute to the accumulation mode numbers close to the source regions and disproportionately contribute in remote regions. The additivity of the aerosol system is analyzed by comparing the changes from a simulation with emission changes for several compounds with the sum of changes of single simulations, in each of which one of the emission changes was introduced. Close to the anthropogenic source regions, deviations from additivity are found at up to 30% and 15% for the accumulation mode number burden and aerosol optical thickness, respectively. These results challenge the traditional approach of assessing the climate impact of aerosols separately for each component and demand for integrated assessments and emission strategies

Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics 1.0: A General Circulation Model for Simulating the Climates of Rocky Planets

Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) is a 3-Dimensional General Circulation Model (GCM) developed at the NASA Goddard Institute for Space Studies for the modeling of atmospheres of Solar System and exoplanetary terrestrial planets. Its parent model, known as ModelE2 (Schmidt et al. 2014), is used to simulate modern and 21st Century Earth and near-term paleo-Earth climates. ROCKE-3D is an ongoing effort to expand the capabilities of ModelE2 to handle a broader range of atmospheric conditions including higher and lower atmospheric pressures, more diverse chemistries and compositions, larger and smaller planet radii and gravity, different rotation rates (slowly rotating to more rapidly rotating than modern Earth, including synchronous rotation), diverse ocean and land distributions and topographies, and potential basic biosphere functions. The first aim of ROCKE-3D is to model planetary atmospheres on terrestrial worlds within the Solar System such as paleo-Earth, modern and paleo-Mars, paleo-Venus, and Saturn's moon Titan. By validating the model for a broad range of temperatures, pressures, and atmospheric constituents we can then expand its capabilities further to those exoplanetary rocky worlds that have been discovered in the past and those to be discovered in the future. We discuss the current and near-future capabilities of ROCKE-3D as a community model for studying planetary and exoplanetary atmospheres.Comment: Revisions since previous draft. Now submitted to Astrophysical Journal Supplement Serie