Simulated Dust Aerosol Lifecycle in the NASA GEOS-5 Atmospheric Transport Model and Sensitivity to Source and Sink Mechanisms

Understanding interactions of mineral dust aerosols with the Earth system remains a key uncertainty in assessing global climate change. A significant portion of this uncertainty arises due to an incomplete understanding of the source, transport, and loss processes that control the dust aerosol lifecycle. Global aerosol transport models compliment traditional observational platforms to serve as useful tools for exploring aerosol-Earth system interactions. However, global models are limited by scale, requiring parameterizations to represent the lifecycle of dust. Here, the simulated dust lifecycle is explored in versions 4 and 5 of the NASA Goddard Earth Observing System (GEOS-4/5) model. Different treatments of the mobilizing physics are first explored by considering two mobilization schemes in GEOS-4. Both schemes produced similar distributions of aerosol optical thickness (AOT) and extinction that become more comparable with observations downwind of the source region. Despite similarities in the optical comparisons, the schemes differ in mass loadings owing to differences in emitted particle size distributions, suggesting that emission scheme choice is significant for mass budgets and particle size distributions. The effect of spatial resolution on source processes was investigated in GEOS-5. Model spatial resolution had a significant impact on simulated dust distributions, as increased model spatial resolution resolves higher wind speeds used to parameterize dust emissions. Model spatial resolution had regional implications, as simulated dust distribution exhibited the greatest sensitivity over the Asian source region. The incorporation of sub-grid wind variability in a coarse resolution simulation led to improved agreement with observed AOT magnitude, but did not improve the timing of simulated dust events over the Asian source region.GEOS-5 was used to investigate the cause of an observed barrier to dust transport across Central America into the Pacific. The baseline simulation did not develop as strong of a barrier when compared to observations. Better agreement was obtained when the parameterization for wet removal was treated as other hydrophilic aerosols. Analysis of the dust transport dynamics and loss processes suggest that while both mechanisms play a role in defining the barrier, loss processes by wet removal are about twice as important as transport

Effects of Spatial Resolution on the Simulated Dust Aerosol Lifecycle: Implications for Dust Event Magnitude and Timing in the NASA GEOS-5 AGCM

The NASA GEOS-5 atmospheric transport model simulates global aerosol distributions with an online aerosol module. GEOS-5 may be run at various horizontal spatial resolutions depending on the research application. For example, long integration climate simulations are typically run at 2 deg or 1 deg grid spacing, whereas aerosol reanalysis and forecasting applications may be performed at O.5 deg or 0.25 deg resolutions. In this study, we assess the implications of varying spatial resolution on the simulated aerosol fields, with a particular focus on dust. Dust emissions in GEOS-5 are calculated with one of two parameterizations, one based on the Goddard Chemistry, Aerosol, Radiation, and Transport (GO CART) model and another based on the Dust Entrainment and Deposition (DEAD) model. Emission fluxes are parameterized in terms of the surface wind speed, either the 10-m (GO CART) or friction (DEAD) wind speed. We consider how surface wind speeds and thus the dust emission rates are a function of the model spatial resolution. We find that spatial resolution has a significant effect on the magnitude of dust emissions, as higher resolution versions of the model have typically higher surface wind speeds. Utilizing space-borne observations from MISR, MODIS, and CALIOP, we find that simulated Aerosol Optical Thickness (AOT) distributions respond differently to spatial resolution over the African and Asian source regions, highlighting the need to regional dust emission tuning. When compared to ground-based observations from AERONET, we found improved timing of dust events with as spatial resolution was increased. In an attempt to improve the representation of the dust aerosol lifecycle at coarse resolutions, we found that incorporating the effects of sub-grid wind variability in a course resolution simulation led to improved agreement with observed AOT magnitudes, but did not impact the timing of simulated dust events

170 Jaar parthogenese - Ter herinnering aan de ontdekking van pastor Dr. Johann Dzierzon

In 1835 deed Dzierzon de ontdekking dat een koninging met een lege zaadblaas alleen darreneitjes legt. Deze waarneming vormde 170 jaar geleden de basis voor Dzierzon's theorie van de parthogenese (= maagdelijke geboorte

The Fate of Saharan Dust Across the Atlantic and Implications for a Central American Dust Barrier

Saharan dust was observed over the Caribbean basin during the summer 2007 NASA Tropical Composition, Cloud, and Climate Coupling (TC4) field experiment. Airborne Cloud Physics Lidar (CPL) and satellite observations from MODIS suggest a barrier to dust transport across Central America into the eastern Pacific. We use the NASA GEOS-5 atmospheric transport model with online aerosol tracers to perform simulations of the TC4 time period in order to understand the nature of this barrier. Our simulations are driven by the Modem Era Retrospective-Analysis for Research and Applications (MERRA) meteorological analyses. We evaluate our baseline simulated dust distributions using MODIS and CALIOP satellite and ground-based AERONET sun photometer observations. GEOS-5 reproduces the observed location, magnitude, and timing of major dust events, but our baseline simulation does not develop as strong a barrier to dust transport across Central America as observations suggest. Analysis of the dust transport dynamics and lost processes suggest that while both mechanisms play a role in defining the dust transport barrier, loss processes by wet removal of dust are about twice as important as transport. Sensitivity analyses with our model showed that the dust barrier would not exist without convective scavenging over the Caribbean. The best agreement between our model and the observations was obtained when dust wet removal was parameterized to be more aggressive, treating the dust as we do hydrophilic aerosols

Diversity als Diskurs: Exklusion inklusive?! Bericht über eine internationale Konferenz vom 15.–17. Juli 2009 in Istanbul

"Es werden kontroverse Aspekte der EOI-Konferenz 2009 zum Thema 'Equality, Diversity and Inclusion in Times of Global Crisis' im Hinblick auf ihre Relevanz und Verortung in wissenschaftlichen Diskursen und ihre politische Bedeutung beleuchtet und reflektiert. Der Fokus liegt auf dominanten Lesarten des Diversity-Diskurses als 'business case', Vielfalt und Inklusion. Anhand von ausgewählten Konferenzdebatten problematisiert der Bericht Ausblendungen, Hierarchisierungen und gewaltvolle Zuschreibungsprozesse im Feld von Fortbildung und Lehre. Dabei wird gezeigt, wie in Kontexten, die explizit den Anspruch haben, zu inkludieren, Exklusionsmechanismen aufrechterhalten und reproduziert werden. Abschließend werden die Ansätze von Diversität und Intersektionalität hinsichtlich ihrer kritischen Potenziale für die Transformation von Machtarenen skizziert." (Autorenreferat)"Diversity as a discourse: exclusion included?! Report on an international conference in Istanbul from 15th–17th July 2009. The article highlights and reflects on controversial aspects of the EOI conference 2009, entitled 'Equality, Diversity and Inclusion in Times of Global Crisis', with regard to their relevance in academic and political discourses. It focuses on dominant readings of the diversity-discourse as a 'business-case', as diversity of strands and as inclusion. Using examples from discussions at the conference, the report problematizes marginalisations, hierarchies, and violent forms of attribution in the field of training and education. It will be shown how mechanisms of exclusion are reproduced and perpetuated in contexts that explicitly intend to be inclusive. In conclusion, the article outlines approaches of diversity and intersectionality regarding their critical potential for the transformation of formations of power." (author's abstract

Does a Theoretical Estimation of the Dust Size Distribution at Emission Suggest More Bioavailable Iron Deposition?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95443/1/grl28895.pd

Exploring Dust Impacts on Tropical Systems from the NASA HS-3 Field Campaign

One of the overall scientific goals of the NASA Hurricane and Severe Storm Sentinel (HS-3) field campaign is to better understand the role of the Saharan Air Layer (SAL) in tropical storm development. During the 2012 HS-3 deployment, the Cloud Physics Lidar (CPL) observed dust within SAL air in close proximity to a developing Nadine (September 11, 2012). Throughout the mission, the NASA GEOS-5 modeling system supported HS-3 by providing 0.25 degrees resolution 5-day global forecasts of aerosols, which were used to support mission planning. The aerosol module was radiatively interactive within the GEOS-5 model, but aerosols were not directly coupled to cloud and precipitation processes. In this study we revisit the aerosol forecasts with an updated version of the GEOS-5 model. For the duration of Hurricane Nadine, we run multiday climate simulations leading up to each respective Global Hawk flight with and without aerosol direct interaction. For each set of simulations, we compare simulated dust mass fluxes to identify differences in SAL entrainment related to the interaction between dust aerosols and the atmosphere. We find that the direct effects of dust induce a low level anticyclonic circulation that temporarily shields Nadine from the intrusion of dry air, leading to a more intense storm

CATS Single-Wavelength Data Products and Performance

CATS Single-Wavelength Data Products and Performanc