bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of aerosols on regional climate in southern and northern China during strong/weak East Asian summer monsoon years
Authors: Li Shu , Wang Tijian , Solmon Fabien , Zhuang Bingliang , Wu Hao , Xie Min , Han Yong , Wang Xuemei 
Published: April 2016

AbstractIn this work, we mainly simulate the effects of aerosols on regional climate in southern China (SC) and northern China (NC) and compare the differences of aerosol climatic effects in strong/weak summer monsoon years with a modified regional climate model RegCM4. The results show that the total climatic effects of aerosols cause the decline of averaged air temperature and precipitation of SC and NC in summer. In NC, the strength of temperature drop in strong summer monsoon years is higher than that in weak summer monsoon years, indicating the possible impact from the different changes of radiation, circulation, and precipitation. The decrease of precipitation is more significant in NC in weak summer monsoon years, while it is stronger in SC in strong summer monsoon years due to the difference of aerosol distribution as well as the effects on circulation and cloud microphysics processes. Besides, aerosol effects also cause a decrease of zonal wind at 850 hPa in SC and an increase in NC. The cooling center is more northerly and stronger in strong monsoon year, while it is more southerly and weaker in weak summer monsoon years, which results in the differences of vertical circulation anomaly and meridional wind anomaly at 850 hPa. In weak summer monsoon years, meridional wind at 850 hPa is increased in NC, while it is found to be decreased in SC. In strong summer monsoon years, meridional winds at 850 hPa in both NC and SC are weakened. However, the decrease in SC is much more distinct and clear.
Using in situ airborne measurements to evaluate three cloud phase products derived from CALIPSO
Authors: Cesana G. , Chepfer H. , Winker D. , Getzewich B. , Cai X. , Jourdan O. , Mioche G. , Okamoto H. , Hagihara Y. , Noel V. , Reverdy M. 
Published: April 2016

AbstractWe compare the cloud detection and cloud phase determination of three independent climatologies based on Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) to airborne in situ measurements. Our analysis of the cloud detection shows that the differences between the satellite and in situ measurements mainly arise from three factors. First, averaging CALIPSO Level l data along track before cloud detection increases the estimate of high‐ and low‐level cloud fractions. Second, the vertical averaging of Level 1 data before cloud detection tends to artificially increase the cloud vertical extent. Third, the differences in classification of fully attenuated pixels among the CALIPSO climatologies lead to differences in the low‐level Arctic cloud fractions. In another section, we compare the cloudy pixels detected by colocated in situ and satellite observations to study the cloud phase determination. At midlatitudes, retrievals of homogeneous high ice clouds by CALIPSO data sets are very robust (more than 94.6% of agreement with in situ). In the Arctic, where the cloud phase vertical variability is larger within a 480 m pixel, all climatologies show disagreements with the in situ measurements and CALIPSO‐General Circulation Models‐Oriented Cloud Product (GOCCP) report significant undefined‐phase clouds, which likely correspond to mixed‐phase clouds. In all CALIPSO products, the phase determination is dominated by the cloud top phase. Finally, we use global statistics to demonstrate that main differences between the CALIPSO cloud phase products stem from the cloud detection (horizontal averaging, fully attenuated pixels) rather than the cloud phase determination procedures.
A modeling study of the response of Asian summertime climate to the largest geologic forcings of the past 50 Ma
Authors: Roe Gerard H. , Ding Qinghua , Battisti David S. , Molnar Peter , Clark Marin K. , Garzione Carmala N. 
Published: April 2016

AbstractThe modern Asian summer monsoon is known to be affected by the modern continental geometry, orography, atmospheric composition, interglacial climate state, and orbital configuration. All of these factors, however, have undergone substantial changes since the Indian and Asian continents collided 50 million years ago. Within the framework of one general circulation model we evaluate the relative importance of each of these factors for the spatial patterns of summertime climate fields and precipitation‐weighted 18O. We find that the continental‐scale structure of the monsoon circulation remains robust, but there are important impacts on local environmental conditions. The largest differences in climate are associated with changes in orbital configuration and topography because of how those factors influence local gradients in the summer climate variables. Finally, model calculations are consistent with the modern understanding of monsoon dynamics in which the strength of the circulation and the distribution of rainfall are tightly coupled to the spatial patterns of low‐level moist static energy and upper tropospheric temperature.
High‐resolution atmospheric inversion of urban CO2 emissions during the dormant season of the Indianapolis Flux Experiment (INFLUX)
Authors: Lauvaux Thomas , Miles Natasha L. , Deng Aijun , Richardson Scott J. , Cambaliza Maria O. , Davis Kenneth J. , Gaudet Brian , Gurney Kevin R. , Huang Jianhua , O'Keefe Darragh , Song Yang , Karion Anna , Oda Tomohiro , Patarasuk Risa , Razlivanov Igor , Sarmiento Daniel , Shepson Paul , Sweeney Colm , Turnbull Jocelyn , Wu Kai 
Published: April 2016

AbstractBased on a uniquely dense network of surface towers measuring continuously the atmospheric concentrations of greenhouse gases (GHGs), we developed the first comprehensive monitoring systems of CO2 emissions at high resolution over the city of Indianapolis. The urban inversion evaluated over the 2012–2013 dormant season showed a statistically significant increase of about 20% (from 4.5 to 5.7 MtC ± 0.23 MtC) compared to the Hestia CO2 emission estimate, a state‐of‐the‐art building‐level emission product. Spatial structures in prior emission errors, mostly undetermined, appeared to affect the spatial pattern in the inverse solution and the total carbon budget over the entire area by up to 15%, while the inverse solution remains fairly insensitive to the CO2 boundary inflow and to the different prior emissions (i.e., ODIAC). Preceding the surface emission optimization, we improved the atmospheric simulations using a meteorological data assimilation system also informing our Bayesian inversion system through updated observations error variances. Finally, we estimated the uncertainties associated with undetermined parameters using an ensemble of inversions. The total CO2 emissions based on the ensemble mean and quartiles (5.26–5.91 MtC) were statistically different compared to the prior total emissions (4.1 to 4.5 MtC). Considering the relatively small sensitivity to the different parameters, we conclude that atmospheric inversions are potentially able to constrain the carbon budget of the city, assuming sufficient data to measure the inflow of GHG over the city, but additional information on prior emission error structures are required to determine the spatial structures of urban emissions at high resolution.
Airborne characterization of subsaturated aerosol hygroscopicity and dry refractive index from the surface to 6.5 km during the SEAC4RS campaign
Authors: Shingler Taylor , Crosbie Ewan , Ortega Amber , Shiraiwa Manabu , Zuend Andreas , Beyersdorf Andreas , Ziemba Luke , Anderson Bruce , Thornhill Lee , Perring Anne E. , Schwarz Joshua P. , Campazano‐Jost Pedro , Day Douglas A. , Jimenez Jose L. , Hair Johnathan W. , Mikoviny Tomas , Wisthaler Armin , Sorooshian Armin 
Published: April 2016

AbstractIn situ aerosol particle measurements were conducted during 21 NASA DC‐8 flights in the Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys field campaign over the United States, Canada, Pacific Ocean, and Gulf of Mexico. For the first time, this study reports rapid, size‐resolved hygroscopic growth and real refractive index (RI at 532 nm) data between the surface and upper troposphere in a variety of air masses including wildfires, agricultural fires, biogenic, marine, and urban outflow. The Differential Aerosol Sizing and Hygroscopicity Spectrometer Probe (DASH‐SP) quantified size‐resolved diameter growth factors (GF = Dp,wet/Dp,dry) that are used to infer the hygroscopicity parameter κ. Thermokinetic simulations were conducted to estimate the impact of partial particle volatilization within the DASH‐SP across a range of sampling conditions. Analyses of GF and RI data as a function of air mass origin, dry size, and altitude are reported, in addition to κ values for the inorganic and organic fractions of aerosol. Average RI values are found to be fairly constant (1.52–1.54) for all air mass categories. An algorithm is used to compare size‐resolved DASH‐SP GF with bulk scattering f(RH = 80%) data obtained from a pair of nephelometers, and the results show that the two can only be reconciled if GF is assumed to decrease with increasing dry size above 400 nm (i.e., beyond the upper bound of DASH‐SP measurements). Individual case studies illustrate variations of hygroscopicity as a function of dry size, environmental conditions, altitude, and composition.
Status of high‐latitude precipitation estimates from observations and reanalyses
Authors: Behrangi Ali , Christensen Matthew , Richardson Mark , Lebsock Matthew , Stephens Graeme , Huffman George J. , Bolvin David , Adler Robert F. , Gardner Alex , Lambrigtsen Bjorn , Fetzer Eric 
Published: April 2016

AbstractAn intercomparison of high‐latitude precipitation characteristics from observation‐based and reanalysis products is performed. In particular, the precipitation products from CloudSat provide an independent assessment to other widely used products, these being the observationally based Global Precipitation Climatology Project (GPCP), Global Precipitation Climatology Centre, and Climate Prediction Center Merged Analysis of Precipitation (CMAP) products and the ERA‐Interim, Modern‐Era Retrospective Analysis for Research and Applications (MERRA), and National Centers for Environmental Prediction‐Department of Energy Reanalysis 2 (NCEP‐DOE R2) reanalyses. Seasonal and annual total precipitation in both hemispheres poleward of 55° latitude are considered in all products, and CloudSat is used to assess intensity and frequency of precipitation occurrence by phase, defined as rain, snow, or mixed phase. Furthermore, an independent estimate of snow accumulation during the cold season was calculated from the Gravity Recovery and Climate Experiment. The intercomparison is performed for the 2007–2010 period when CloudSat was fully operational. It is found that ERA‐Interim and MERRA are broadly similar, agreeing more closely with CloudSat over oceans. ERA‐Interim also agrees well with CloudSat estimates of snowfall over Antarctica where total snowfall from GPCP and CloudSat is almost identical. A number of disagreements on regional or seasonal scales are identified: CMAP reports much lower ocean precipitation relative to other products, NCEP‐DOE R2 reports much higher summer precipitation over Northern Hemisphere land, GPCP reports much higher snowfall over Eurasia, and CloudSat overestimates precipitation over Greenland, likely due to mischaracterization of rain and mixed‐phase precipitation. These outliers are likely unrealistic for these specific regions and time periods. These estimates from observations and reanalyses provide useful insights for diagnostic assessment of precipitation products in high latitudes, quantifying the current uncertainties, improving the products, and establishing a benchmark for assessment of climate models.
New gridded daily climatology of Finland: Permutation‐based uncertainty estimates and temporal trends in climate
Authors: Aalto Juha , Pirinen Pentti , Jylhä Kirsti 
Published: April 2016

AbstractLong‐term time series of key climate variables with a relevant spatiotemporal resolution are essential for environmental science. Moreover, such spatially continuous data, based on weather observations, are commonly used in, e.g., downscaling and bias correcting of climate model simulations. Here we conducted a comprehensive spatial interpolation scheme where seven climate variables (daily mean, maximum, and minimum surface air temperatures, daily precipitation sum, relative humidity, sea level air pressure, and snow depth) were interpolated over Finland at the spatial resolution of 10 × 10 km2. More precisely, (1) we produced daily gridded time series (FMI_ClimGrid) of the variables covering the period of 1961–2010, with a special focus on evaluation and permutation‐based uncertainty estimates, and (2) we investigated temporal trends in the climate variables based on the gridded data. National climate station observations were supplemented by records from the surrounding countries, and kriging interpolation was applied to account for topography and water bodies. For daily precipitation sum and snow depth, a two‐stage interpolation with a binary classifier was deployed for an accurate delineation of areas with no precipitation or snow. A robust cross‐validation indicated a good agreement between the observed and interpolated values especially for the temperature variables and air pressure, although the effect of seasons was evident. Permutation‐based analysis suggested increased uncertainty toward northern areas, thus identifying regions with suboptimal station density. Finally, several variables had a statistically significant trend indicating a clear but locally varying signal of climate change during the last five decades.
Exploring the metabolic potential of microbial communities in ultra‐basic, reducing springs at The Cedars, CA, USA: Experimental evidence of microbial methanogenesis and heterotrophic acetogenesis
Authors: Kohl Lukas , Cumming Emily , Cox Alison , Rietze Amanda , Morrissey Liam , Lang Susan Q. , Richter Andreas , Suzuki Shino , Nealson Kenneth H. , Morrill Penny L. 
Published: April 2016

AbstractPresent‐day serpentinization generates groundwaters with conditions (pH > 11, Eh < −550 mV) favorable for the microbial and abiotic production of organic compounds from inorganic precursors. Elevated concentrations of methane, C2‐C6 alkanes, acetate, and formate have been detected at these sites, but the microbial or abiotic origin of these compounds remains unclear. While geochemical data indicate that methane at most sites of present‐day serpentinization is abiogenic, the stable carbon, hydrogen, and clumped isotope data as well as the hydrocarbon gas composition from The Cedars, CA, USA, are consistent with a microbial origin for methane. However, there is no direct evidence of methanogenesis at this site of serpentinization. We report on laboratory experiments in which the microbial communities in fluids and sediments from The Cedars were incubated with 13C labeled substrates. Increasing methane concentrations and the incorporation of 13C into methane in live experiments, but not in killed controls, demonstrated that methanogens converted methanol, formate, acetate (methyl group), and bicarbonate to methane. The apparent fractionation between methane and potential substrates (α13CCH4‐CO2(g) = 1.059 to 1.105, α13CCH4‐acetate = 1.042 to 1.119) indicated that methanogenesis was dominated by the carbonate reduction pathway. Increasing concentrations of volatile organic acid anions indicated microbial acetogenesis. α13CCO2(g)‐acetate values (0.999 to 1.000), however, were inconsistent with autotrophic acetogenesis, thus suggesting that acetate was produced through fermentation. This is the first study to show direct evidence of microbial methanogenesis and acetogenesis by the native microbial community at a site of present‐day serpentinization.
Comparing TID simulations using 3‐D ray tracing and mirror reflection
Authors: Huang X. , Reinisch B. W. , Sales G. S. , Paznukhov V. V. , Galkin I. A. 
Published: April 2016

AbstractMeasuring the time variations of Doppler frequencies and angles of arrival (AoA) of ionospherically reflected HF waves has been proposed as a means of detecting the occurrence of traveling ionospheric disturbances (TIDs). Simulations are made using ray tracing through the International Reference Ionosphere (IRI) electron density model in an effort to reproduce measured signatures. The TID is represented by a wavelike perturbation of the 3‐D electron density traveling horizontally in the ionosphere with an amplitude that varies sinusoidally with time. By judiciously selecting the TID parameters the ray tracing simulation reproduces the observed Doppler frequencies and AoAs. Ray tracing in a 3‐D realistic ionosphere is, however, excessively time consuming considering the involved homing procedures. It is shown that a carefully selected reflecting corrugated mirror can reproduce the time variations of the AoA and Doppler frequency. The results from the ray tracing through the IRI model ionosphere and the mirror model reflections are compared to assess the applicability of the mirror‐reflection model.
SDR implementation of the receiver of adaptive communication system
Authors: Skarzynski Jacek , Darmetko Marcin , Kozlowski Sebastian , Kurek Krzysztof 
Published: April 2016

AbstractThe paper presents software implementation of a receiver forming a part of an adaptive communication system. The system is intended for communication with a satellite placed in a low Earth orbit (LEO). The ability of adaptation is believed to increase the total amount of data transmitted from the satellite to the ground station. Depending on the signal‐to‐noise ratio (SNR) of the received signal, adaptive transmission is realized using different transmission modes, i.e., different modulation schemes (BPSK, QPSK, 8‐PSK, and 16‐APSK) and different convolutional code rates (1/2, 2/3, 3/4, 5/6, and 7/8). The receiver consists of a software‐defined radio (SDR) module (National Instruments USRP‐2920) and a multithread reception software running on Windows operating system. In order to increase the speed of signal processing, the software takes advantage of single instruction multiple data instructions supported by x86 processor architecture.
Contribution of recycled moisture to precipitation in oases of arid central Asia: A stable isotope approach
Authors: Wang Shengjie , Zhang Mingjun , Che Yanjun , Chen Fenli , Qiang Fang 
Published: April 2016

AbstractTerrestrial moisture contributed by surface evaporation and transpiration, also known as recycled moisture, plays an important role in hydrological processes especially across arid central Asia. The stable hydrogen and oxygen isotopes can be used for water budget analysis to calculate the contribution of recycled moisture to precipitation between two locations along the moisture flow. Based on a three‐component isotopic mixing model, the moisture recycling in oasis stations of arid central Asia during summer months is assessed. At large oases of Urumqi, the proportional contribution of recycled moisture to local precipitation is approximately 16.2%, and the mean proportions of surface evaporation and transpiration are 5.9% ± 1.5% and 10.3% ± 2.2%, respectively. At small oases like Shihezi and Caijiahu the contribution of recycled moisture is less than 5%, and the proportion of surface evaporation is much less than that of transpiration. The vegetative cover in arid central Asia is generally sparse, but the evapotranspiration contribution to precipitation cannot be ignored at the widely distributed oases. The oasis effect shows great variability depending on locations and water availability for evapotranspiration.
Subinertial canyon resonance
Authors: Clarke Allan J. , Van Gorder Stephen 
Published: April 2016

AbstractNear the bottom of a narrow canyon currents that oscillate back and forth along the bottom slope hx in a stratified ocean of buoyancy frequency N do so with a natural internal gravitational frequency Nhx. From May 2012 to May 2013 Acoustic Doppler Current Profiler measurements were made at 715 m depth in the deep narrow part of the DeSoto Canyon south of Pensacola, Florida, in water with 2π/Nhx ≈ 2.5 days. Above the canyon the flow follows the large‐scale isobaths, but beneath the canyon rim the current oscillates along the canyon axis with 2‐3 day periodicity, and is much stronger than and uncorrelated with the overlying flow. A simple theoretical model explains the resonant response. Published observations from the Hudson and Gully canyons suggest that the strong subinertial current oscillations observed in these canyons occur close to the relevant local frequency Nhx, consistent with the proposed simple model physics.
The mass balance of earthquakes and earthquake sequences
Authors: Marc O. , Hovius N. , Meunier P. 
Published: April 2016

AbstractLarge, compressional earthquakes cause surface uplift as well as widespread mass wasting. Knowledge of their trade‐off is fragmentary. Combining a seismologically consistent model of earthquake‐triggered landsliding and an analytical solution of coseismic surface displacement, we assess how the mass balance of single earthquakes and earthquake sequences depends on fault size and other geophysical parameters. We find that intermediate size earthquakes (Mw 6–7.3) may cause more erosion than uplift, controlled primarily by seismic source depth and landscape steepness, and less so by fault dip and rake. Such earthquakes can limit topographic growth, but our model indicates that both smaller and larger earthquakes (Mw < 6, Mw > 7.3) systematically cause mountain building. Earthquake sequences with a Gutenberg‐Richter distribution have a greater tendency to lead to predominant erosion, than repeating earthquakes of the same magnitude, unless a fault can produce earthquakes with Mw > 8 or more.
Stratospheric ozone chemistry feedbacks are not critical for the determination of climate sensitivity in CESM1(WACCM)
Authors: Marsh Daniel R. , Lamarque Jean‐François , Conley Andrew J. , Polvani Lorenzo M. 
Published: April 2016

AbstractThe Community Earth System Model‐Whole Atmosphere Community Climate Model (CESM1‐WACCM) is used to assess the importance of including chemistry feedbacks in determining the equilibrium climate sensitivity (ECS). Two 4×CO2 model experiments were conducted: one with interactive chemistry and one with chemical constituents other than CO2 held fixed at their preindustrial values. The ECS determined from these two experiments agrees to within 0.01 K. Similarly, the net feedback parameter agrees to within 0.01 W m−2 K−1. This agreement occurs in spite of large changes in stratospheric ozone found in the simulation with interactive chemistry: a 30% decrease in the tropical lower stratosphere and a 40% increase in the upper stratosphere, broadly consistent with other published estimates. Off‐line radiative transfer calculations show that ozone changes alone account for the difference in radiative forcing. We conclude that at least for determining global climate sensitivity metrics, the exclusion of chemistry feedbacks is not a critical source of error in CESM.