Revisiting the Observed Correlation Between Weekly Averaged Indian Monsoon Precipitation and Arabian Sea Aerosol Optical Depth

Dust influences the Indian summer monsoon on seasonal timescales by perturbing atmospheric radiation. On weekly time scales, aerosol optical depth retrieved by satellite over the Arabian Seais correlated with Indian monsoon precipitation. This has been interpreted to show the effect of dust radiative heating on Indian rainfall on synoptic (few-day) time scales. However, this correlation is reproduced by Earth System Model simulations, where dust is present but its radiative effect is omitted. Analysis of daily variability suggests that the correlation results from the effect of precipitation on dust through the associated cyclonic circulation. Boundary layer winds that deliver moisture to India are responsible for dust outbreaks in source regions far upwind, including the Arabian Peninsula. This suggests that synoptic variations in monsoon precipitation over India enhance dust emission and transport to the Arabian Sea. The effect of dust radiative heating upon synoptic monsoon variations remains to be determined

Reproductive Performance of Crossbred Ewes Selected for Fall vs Spring Lambing Under Range or Farm Flock Management Systems (Progress Report)

This study was initiated to evaluate the results of selecting for fall lambing under two management systems, farm vs range

Intensification of North American Megadroughts through Surface and Dust Aerosol Forcing

Tree-ring-based reconstructions of the Palmer drought severity index (PDSI) indicate that, during the Medieval Climate Anomaly (MCA), the central plains of North America experienced recurrent periods of drought spanning decades or longer. These megadroughts had exceptional persistence compared to more recent events, but the causes remain uncertain. The authors conducted a suite of general circulation model experiments to test the impact of sea surface temperature (SST) and land surface forcing on the MCA megadroughts over the central plains. The land surface forcing is represented as a set of dune mobilization boundary conditions, derived from available geomorphological evidence and modeled as increased bare soil area and a dust aerosol source (32deg-44degN, 105deg-95degW). In the experiments, cold tropical Pacific SST forcing suppresses precipitation over the central plains but cannot reproduce the overall drying or persistence seen in the PDSI reconstruction. Droughts in the scenario with dust aerosols, however, are amplified and have significantly longer persistence than in other model experiments, more closely matching the reconstructed PDSI. This additional drying occurs because the dust increases the shortwave planetary albedo, reducing energy inputs to the surface and boundary layer. The energy deficit increases atmospheric stability, inhibiting convection and reducing cloud cover and precipitation over the central plains. Results from this study provide the first model-based evidence that dust aerosol forcing and land surface changes could have contributed to the intensity and persistence of the central plains megadroughts, although uncertainties remain in the formulation of the boundary conditions and the future importance of these feedbacks

Ariel - Volume 3 Number 6

Editors Richard J. Bonanno Robin A. Edwards Associate Editors Steven Ager Tom Williams Lay-out Editor Eugenia Miller Contributing Editors Paul Bialas Robert Breckenridge Lynne Porter David Jacoby Mike LeWitt Terry Burt Mark Pearlman Michael Leo Editors Emeritus Delvyn C. Case, Jr. Paul M. Fernhof

A micro-geoarchaeological view on stratigraphy and site formation processes in the Middle, Upper and Epi-Paleolithic layers of Sefunim Cave, Mt. Carmel, Israel

This paper presents a micro-geoarchaeological study carried out on the sedimentary sequence exposed at the entrance of Sefunim Cave, Israel, a sequence that spans from the Middle Paleolithic to the early Epipaleolithic periods. Using FTIR and micromorphological techniques, we investigated the stratigraphic sequence to reconstruct patterns of site use and archaeological formation processes. We identified formation processes that are common among Paleolithic caves sites in the Southern Levant, mainly the deposition of local terra rossa through colluvial sedimentation. Taphonomic disturbances of the deposits range from minimal to moderate, exhibited mainly by root and burrowing activity, but with no evidence for significant transport of archaeological materials. While the upper layers (II–III) are decalcified, the precipitation of secondary calcite results in increasing cementation of the sediments with depth in the lower layers (V–VII). We observed variation at the microscopic scale and identified an inverse correlation between human and carnivore activity throughout the layers. We observed human activity by the presence of micro-archaeological materials such as chert, bone, charcoal, rubified clay, burnt bone and shell, and wood ash. We observed carnivore activity by the presence of phosphatic grains and coprolite fragments as well as chewed and digested bones. We conclude that human activity at the site was characterized by episodes of varying intensity, based on the frequency of archaeological finds within the different layers. The alternating episodes of human and carnivore activity at Sefunim Cave may demonstrate the close-knit interactions and reciprocal relations that humans and carnivore shared at Paleolithic caves.publishedVersio

Future Climate Change under SSP Emission Scenarios with GISS-E2.1

Abstract This paper presents the response to anthropogenic forcing in the GISS-E2.1 climate models for the 21st century Shared Socioeconomic Pathways (SSPs) emission scenarios within the Coupled Model Intercomparison Project phase 6 (CMIP6). The experiments were performed using an updated and improved version of the NASA Goddard Institute for Space Studies (GISS) coupled general circulation model that includes two different versions for atmospheric composition: a non-interactive version (NINT) with prescribed composition and a tuned aerosol indirect effect (AIE) and the One-Moment Aerosol model (OMA) version with fully interactive aerosols which includes a parameterized first indirect aerosol effect on clouds. The effective climate sensitivities are 3.0ºC and 2.9ºC for the NINT and OMA models, respectively. Each atmospheric version is coupled to two different ocean general circulation models: the GISS ocean model (E2.1-G) and HYCOM (E2.1-H). We describe the global mean responses for all future scenarios and spatial patterns of change for surface air temperature and precipitation for four of the marker scenarios: SSP1-2.6, SSP2-4.5, SSP4-6.0, and SSP5-8.5. By 2100, global mean warming ranges from 1.5ºC to 5.2ºC relative to 1850-1880 mean temperature. Two high-mitigation scenarios SSP1-1.9 and SSP1-2.6 limit the surface warming to below 2°C by the end of the 21st century, except for the NINT E2.1-H model that simulates 2.2°C of surface warming. For the high emission scenario SSP5-8.5, the range is 4.6-5.2ºC at 2100. Due to about 15\% larger effective climate sensitivity (ECS) and stronger transient climate response (TCR) in both NINT and OMA CMIP6 models compared to CMIP5 versions, there is a stronger warming by 2100 in the SSP emission scenarios than in the comparable RCP scenarios in CMIP5. Changes in sea ice area are highly correlated to global mean surface air temperature anomalies and show steep declines in both hemispheres, with the largest sea ice area decreases occurring during September in the Northern Hemisphere in both E2.1-G (-1.21×106 km2/°C) and E2.1-H models (-0.94×106 km2/°C). Both coupled models project decreases in the Atlantic overturning stream function by 2100. The largest decrease of 56-65\% in the 21st century overturning stream function is produced in the warmest scenario SSP5-8.5 in the E2.1-G model, comparable to the reduction in the corresponding CMIP5 GISS-E2 RCP8.5 simulation. Both low-end scenarios SSP1-1.9 and SSP1-2.6 also simulate substantial reductions of the overturning (9-37\%) with slow recovery of about 10\% by the end of the 21st century (relative to the maximum decrease at the middle of the 21st century)Development of GISS-E2.1 was supported by the NASA Modeling, Analysis, and Prediction (MAP) Program. CMIP6 simulations with GISS-E2.1 were made possible by the NASA High-End Computing (HEC) Program through the NASA Center for Climate Simulation (NCCS) at Goddard Space Flight Center. We thank Ellen Salmon and the NCCS staff for hosting and providing convenient access to the model output. CMIP6 standard variables analyzed in this study are available through the Earth System Grid Federation and from https://portal.nccs.nasa.gov/datashare/giss_cmip6.Peer Reviewed"Article signat per 46 autors/es: Larissa S. Nazarenko, Nick Tausnev, Gary L. Russell, David Rind, Ron L. Miller, Gavin A. Schmidt, Susanne E. Bauer, Maxwell Kelley, Reto Ruedy, Andrew S. Ackerman, Igor Aleinov, Michael Bauer, Rainer Bleck, Vittorio Canuto, Grégory Cesana, Ye Cheng, Thomas L. Clune, Ben I. Cook, Carlos A. Cruz, Anthony D. Del Genio, Gregory S. Elsaesser, Greg Faluvegi, Nancy Y. Kiang, Daehyun Kim, Andrew A. Lacis, Anthony Leboissetier, Allegra N. LeGrande, Ken K. Lo, John Marshall, Elaine E. Matthews, Sonali McDermid, Keren Mezuman, Lee T. Murray, Valdar Oinas, Clara Orbe, Carlos Pérez García-Pando, Jan P. Perlwitz, Michael J. Puma, Anastasia Romanou, Drew T. Shindell, Shan Sun, Kostas Tsigaridis, George Tselioudis, Ensheng Weng, Jingbo Wu, Mao-Sung Yao "Postprint (author's final draft

Predicting the mineral composition of dust aerosols: Insights from elemental composition measured at the Izaña Observatory

Regional variations of dust mineral composition are fundamental to climate impacts but generally neglected in climate models. A challenge for models is that atlases of soil composition are derived from measurements following wet sieving, which destroys the aggregates potentially emitted from the soil. Aggregates are crucial to simulating the observed size distribution of emitted soil particles. We use an extension of brittle fragmentation theory in a global dust model to account for these aggregates. Our method reproduces the size-resolved dust concentration along with the approximately size-invariant fractional abundance of elements like Fe and Al in the decade-long aerosol record from the Izaña Observatory, off the coast of West Africa. By distinguishing between Fe in structural and free forms, we can attribute improved model behavior to aggregation of Fe and Al-rich clay particles. We also demonstrate the importance of size-resolved measurements along with elemental composition analysis to constrain models.This research was supported by the Department of Energy (DE-SC0006713), the NASA Modeling, Analysis and Prediction Program, and the Aerosol Global Atmospheric Watch program of Izaña Observatory, which has been funded by AEMET and several research projects of the Ministry of Economy and Competitiveness of Spain and the European Regional Development Fund (ERDF) including POLLINDUST (CGL2011-26259) and AEROATLAN (CGL2015-66229-P)

Galactic contamination in the QMAP experiment

We quantify the level of foreground contamination in the QMAP Cosmic Microwave Background (CMB) data with two objectives: (a) measuring the level to which the QMAP power spectrum measurements need to be corrected for foregrounds and (b) using this data set to further refine current foreground models. We cross-correlate the QMAP data with a variety of foreground templates. The 30 GHz Ka-band data is found to be significantly correlated with the Haslam 408 MHz and Reich and Reich 1420 MHz synchrotron maps, but not with the Diffuse Infrared Background Experiment (DIRBE) 240, 140 and 100 micron maps or the Wisconsin H-Alpha Mapper (WHAM) survey. The 40 GHz Q-band has no significant template correlations. We discuss the constraints that this places on synchrotron, free-free and dust emission. We also reanalyze the foreground-cleaned Ka-band data and find that the two band power measurements are lowered by 2.3% and 1.3%, respectively.Comment: 4 ApJL pages, including 4 figs. Color figures and data at http://www.hep.upenn.edu/~angelica/foreground.html#qmap or from [email protected]

Elastic Wave Transmission at an Abrupt Junction in a Thin Plate, with Application to Heat Transport and Vibrations in Mesoscopic Systems

The transmission coefficient for vibrational waves crossing an abrupt junction between two thin elastic plates of different widths is calculated. These calculations are relevant to ballistic phonon thermal transport at low temperatures in mesoscopic systems and the Q for vibrations in mesoscopic oscillators. Complete results are calculated in a simple scalar model of the elastic waves, and results for long wavelength modes are calculated using the full elasticity theory calculation. We suggest that thin plate elasticty theory provide a useful and tractable approximation to the full three dimensional geometry.Comment: 35 pages, including 12 figure