Global dust model intercomparison in AeroCom phase I

This study presents the results of a broad intercomparison of a total of 15 global aerosol models within the AeroCom project. Each model is compared to observations related to desert dust aerosols, their direct radiative effect, and their impact on the biogeochemical cycle, i.e., aerosol optical depth (AOD) and dust deposition. Additional comparisons to Angström exponent (AE), coarse mode AOD and dust surface concentrations are included to extend the assessment of model performance and to identify common biases present in models. These data comprise a benchmark dataset that is proposed for model inspection and future dust model development. There are large differences among the global models that simulate the dust cycle and its impact on climate. In general, models simulate the climatology of vertically integrated parameters (AOD and AE) within a factor of two whereas the total deposition and surface concentration are reproduced within a factor of 10. In addition, smaller mean normalized bias and root mean square errors are obtained for the climatology of AOD and AE than for total deposition and surface concentration. Characteristics of the datasets used and their uncertainties may influence these differences. Large uncertainties still exist with respect to the deposition fluxes in the southern oceans. Further measurements and model studies are necessary to assess the general model performance to reproduce dust deposition in ocean regions sensible to iron contributions. Models overestimate the wet deposition in regions dominated by dry deposition. They generally simulate more realistic surface concentration at stations downwind of the main sources than at remote ones. Most models simulate the gradient in AOD and AE between the different dusty regions. However the seasonality and magnitude of both variables is better simulated at African stations than Middle East ones. The models simulate the offshore transport of West Africa throughout the year but they overestimate the AOD and they transport too fine particles. The models also reproduce the dust transport across the Atlantic in the summer in terms of both AOD and AE but not so well in winter-spring nor the southward displacement of the dust cloud that is responsible of the dust transport into South America. Based on the dependency of AOD on aerosol burden and size distribution we use model bias with respect to AOD and AE to infer the bias of the dust emissions in Africa and the Middle East. According to this analysis we suggest that a range of possible emissions for North Africa is 400 to 2200 Tg yr-1 and in the Middle East 26 to 526 Tg yr-1

Tropical biomass burning smoke plume size, shape, reflectance, and age based on 2001–2009 MISR imagery of Borneo

Land clearing for crops, plantations and grazing results in anthropogenic burning of tropical forests and peatlands in Indonesia, where images of fire-generated aerosol plumes have been captured by the Multi-angle Imaging SpectroRadiometer (MISR) since 2001. Here we analyze the size, shape, optical properties, and age of distinct fire-generated plumes in Borneo from 2001–2009. The local MISR overpass at 10:30 a.m. misses the afternoon peak of Borneo fire emissions, and may preferentially sample longer plumes from persistent fires burning overnight. Typically the smoke flows with the prevailing southeasterly surface winds at 3–4 m s<sup>−1</sup>, and forms ovoid plumes whose mean length, height, and cross-plume width are 41 km, 708 m, and 27% of the plume length, respectively. 50% of these plumes have length between 24 and 50 km, height between 523 and 993 m and width between 18% and 30% of plume length. Length and cross-plume width are lognormally distributed, while height follows a normal distribution. Borneo smoke plume heights are similar to previously reported plume heights, yet Borneo plumes are on average nearly three times longer than previously studied plumes. This could be due to sampling or to more persistent fires and greater fuel loads in peatlands than in other tropical forests. Plume area (median 169 km<sup>2</sup>, with 25th and 75th percentiles at 99 km<sup>2</sup> and 304 km<sup>2</sup>, respectively) varies exponentially with length, though for most plumes a linear relation provides a good approximation. The MISR-estimated plume optical properties involve greater uncertainties than the geometric properties, and show patterns consistent with smoke aging. Optical depth increases by 15–25% in the down-plume direction, consistent with hygroscopic growth and nucleation overwhelming the effects of particle dispersion. Both particle single-scattering albedo and top-of-atmosphere reflectance peak about halfway down-plume, at values about 3% and 10% greater than at the origin, respectively. The initially oblong plumes become brighter and more circular with time, increasingly resembling smoke clouds. Wind speed does not explain a significant fraction of the variation in plume geometry. We provide a parameterization of plume shape that can help atmospheric models estimate the effects of plumes on weather, climate, and air quality. Plume age, the age of smoke furthest down-plume, is lognormally distributed with a median of 2.8 h (25th and 75th percentiles at 1.3 h and 4.0 h), different from the median ages reported in other studies. Intercomparison of our results with previous studies shows that the shape, height, optical depth, and lifetime characteristics reported for tropical biomass burning plumes on three continents are dissimilar and distinct from the same characteristics of non-tropical wildfire plumes

Do biomass burning aerosols intensify drought in equatorial Asia during El Niño?

During El Niño years, fires in tropical forests and peatlands in equatorial Asia create large regional smoke clouds. We characterized the sensitivity of these clouds to regional drought, and we investigated their effects on climate by using an atmospheric general circulation model. Satellite observations during 2000–2006 indicated that El Niño-induced regional drought led to increases in fire emissions and, consequently, increases in aerosol optical depths over Sumatra, Borneo and the surrounding ocean. Next, we used the Community Atmosphere Model (CAM) to investigate how climate responded to this forcing. We conducted two 30 year simulations in which monthly fire emissions were prescribed for either a high (El Niño, 1997) or low (La Niña, 2000) fire year using a satellite-derived time series of fire emissions. Our simulations included the direct and semi-direct effects of aerosols on the radiation budget within the model. We assessed the radiative and climate effects of anthropogenic fire by analyzing the differences between the high and low fire simulations. Fire aerosols reduced net shortwave radiation at the surface during August–October by 19.1±12.9 W m<sup>−2</sup> (10%) in a region that encompassed most of Sumatra and Borneo (90° E–120° E, 5° S–5° N). The reductions in net shortwave radiation cooled sea surface temperatures (SSTs) and land surface temperatures by 0.5±0.3 and 0.4±0.2 °C during these months. Tropospheric heating from black carbon (BC) absorption averaged 20.5±9.3 W m<sup>−2</sup> and was balanced by a reduction in latent heating. The combination of decreased SSTs and increased atmospheric heating reduced regional precipitation by 0.9±0.6 mm d<sup>−1</sup> (10%). The vulnerability of ecosystems to fire was enhanced because the decreases in precipitation exceeded those for evapotranspiration. Together, the satellite and modeling results imply a possible positive feedback loop in which anthropogenic burning in the region intensifies drought stress during El Niño

Time delays in quasi-periodic pulsations observed during the X2.2 solar flare on 2011 February 15

We report observations of quasi-periodic pulsations (QPPs) during the X2.2 flare of 2011 February 15, observed simultaneously in several wavebands. We focus on fluctuations on time scale 1-30 s and find different time lags between different wavebands. During the impulsive phase, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) channels in the range 25-100 keV lead all the other channels. They are followed by the Nobeyama RadioPolarimeters at 9 and 17 GHz and the Extreme Ultra-Violet (EUV) channels of the Euv SpectroPhotometer (ESP) onboard the Solar Dynamic Observatory (SDO). The Zirconium and Aluminum filter channels of the Large Yield Radiometer (LYRA) onboard the Project for On-Board Autonomy (PROBA2) satellite and the SXR channel of ESP follow. The largest lags occur in observations from the Geostationary Operational Environmental Satellite (GOES), where the channel at 1-8 {\AA} leads the 0.5-4 {\AA} channel by several seconds. The time lags between the first and last channels is up to 9 s. We identified at least two distinct time intervals during the flare impulsive phase, during which the QPPs were associated with two different sources in the Nobeyama RadioHeliograph at 17 GHz. The radio as well as the hard X-ray channels showed different lags during these two intervals. To our knowledge, this is the first time that time lags are reported between EUV and SXR fluctuations on these time scales. We discuss possible emission mechanisms and interpretations, including flare electron trapping

Safety Recommendations for Evaluation and Surgery of the Head and Neck During the COVID-19 Pandemic

Importance The rapidly expanding novel coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2, has challenged the medical community to an unprecedented degree. Physicians and health care workers are at added risk of exposure and infection during the course of patient care. Because of the rapid spread of this disease through respiratory droplets, health care workers who come in close contact with the upper aerodigestive tract during diagnostic and therapeutic procedures, such as otolaryngologists–head and neck surgeons, are particularly at risk. A set of safety recommendations was created based on a review of the literature and communications with physicians with firsthand knowledge of safety procedures during the COVID-19 pandemic. Observations A high number of health care workers were infected during the first phase of the pandemic in the city of Wuhan, China. Subsequently, by adopting strict safety precautions, other regions were able to achieve high levels of safety for health care workers without jeopardizing the care of patients. The most common procedures related to the examination and treatment of upper aerodigestive tract diseases were reviewed. Each category was reviewed based on the potential risk imposed to health care workers. Specific recommendations were made based on the literature, when available, or consensus best practices. Specific safety recommendations were made for performing tracheostomy in patients with COVID-19. Conclusions and Relevance Preserving a highly skilled health care workforce is a top priority for any community and health care system. Based on the experience of health care systems in Asia and Europe, by following strict safety guidelines, the risk of exposure and infection of health care workers could be greatly reduced while providing high levels of care. The provided recommendations, which may evolve over time, could be used as broad guidance for all health care workers who are involved in the care of patients with COVID-19

SWI/SNF regulates a transcriptional programme that induces senescence to prevent liver cancer

Oncogene-induced senescence (OIS) is a potent tumour suppressor mechanism. To identify senescence regulators relevant to cancer, we screened an shRNA library targeting genes deleted in hepatocellular carcinoma (HCC). Here, we describe how knockdown of the SWI/SNF component ARID1B prevents OIS and cooperates with RAS to induce liver tumours. ARID1B controls p16INK4a and p21CIP1a transcription but also regulates DNA damage, oxidative stress and p53 induction, suggesting that SWI/SNF uses additional mechanisms to regulate senescence. To systematically identify SWI/SNF targets regulating senescence, we carried out a focused shRNA screen. We discovered several new senescence regulators including ENTPD7, an enzyme that hydrolyses nucleotides. ENTPD7 affects oxidative stress, DNA damage and senescence. Importantly, expression of ENTPD7 or inhibition of nucleotide synthesis in ARID1B-depleted cells results in re-establishment of senescence. Our results identify novel mechanisms by which epigenetic regulators can affect tumor progression and suggest that pro-senescence therapies could be employed against SWI/SNF-mutated cancers

The SWAP EUV Imaging Telescope Part I: Instrument Overview and Pre-Flight Testing

The Sun Watcher with Active Pixels and Image Processing (SWAP) is an EUV solar telescope on board ESA's Project for Onboard Autonomy 2 (PROBA2) mission launched on 2 November 2009. SWAP has a spectral bandpass centered on 17.4 nm and provides images of the low solar corona over a 54x54 arcmin field-of-view with 3.2 arcsec pixels and an imaging cadence of about two minutes. SWAP is designed to monitor all space-weather-relevant events and features in the low solar corona. Given the limited resources of the PROBA2 microsatellite, the SWAP telescope is designed with various innovative technologies, including an off-axis optical design and a CMOS-APS detector. This article provides reference documentation for users of the SWAP image data.Comment: 26 pages, 9 figures, 1 movi

NASA Dataset Interoperability Recommendations for Earth Science

NASA ESDS (Earth Science Data and Information System) Dataset Interoperability Working Group has been developing recommendations since 2012 aimed at improving interoperability of EOS (Earth Observing System) datasets. The first set of recommendations were published in 2016 as ESDS RFC-028. The latest set of recommendations is currently undergoing review and will be available as ESDS RFC-036 soon.This talk will inform the ESIP (Earth Science Information Partners) community about the recommendations because their application is relevant to other data producers as well

Present‐day climate forcing and response from black carbon in snow,

[1] We apply our Snow, Ice, and Aerosol Radiative (SNICAR) model, coupled to a general circulation model with prognostic carbon aerosol transport, to improve understanding of climate forcing and response from black carbon (BC) in snow. Building on two previous studies, we account for interannually varying biomass burning BC emissions, snow aging, and aerosol scavenging by snow meltwater. We assess uncertainty in forcing estimates from these factors, as well as BC optical properties and snow cover fraction. BC emissions are the largest source of uncertainty, followed by snow aging. The rate of snow aging determines snowpack effective radius (r e ), which directly controls snow reflectance and the magnitude of albedo change caused by BC. For a reasonable r e range, reflectance reduction from BC varies threefold. Inefficient meltwater scavenging keeps hydrophobic impurities near the surface during melt and enhances forcing. Applying biomass burning BC emission inventories for a strong (1998) and weak Citation: Flanner, M. G., C. S. Zender, J. T. Randerson, and P. J. Rasch (2007), Present-day climate forcing and response from black carbon in snow