bluuebunny/crossref_metadata_2025_split huggingface dataset:
Particle dynamics of the Changjiang Estuary and adjacent coastal region determined by natural particle‐reactive radionuclides (7Be, 210Pb, and 234Th)
Authors: Huang Dekun , Du Jinzhou , Moore Willard S. , Zhang Jing 
Published: April 2013

AbstractThe timescale of transport processes in estuarine and coastal regions can be evaluated using natural radionuclides with different half‐lives. The distribution patterns of 7Be, 210Pb, and 234Th in the water column from April to July 2008 were used to calculate the removal and residence times in the Changjiang Estuary. The results showed that the maximum particulate activities of 7Be, 210Pb, and 234Th were observed approximately 150 km downstream (the turbidity maximum zone) of the freshwater end‐number. The mean distribution coefficients (Kd, cm3 g−1) of the high suspended particulate matter (SPM) group are higher than those of the lower‐SPM group for 7Be and 210Pb; for 234Th, the reverse is true. Based on a material balance in two‐dimensional models of 7Be, 210Pb, and 234Th in the Changjiang River mouth, the removal times of these nuclides were approximately 0.66–12, 1.6–21, and 1.2–5.4 days, respectively. The residence times increased toward the seaward side. In the coastal region, the removal times of 7Be, 210Pb, and 234Th calculated by material balance in one‐dimensional models were approximately 1.1–26, 1.2–27, and 0.70–23 days, respectively. Moreover, an enhanced resuspension process not only controlled the partitioning of 7Be, 210Pb, and 234Th between the particulate and dissolved phases, but also, this process may play a dominant role in controlling the dynamic behavior of SPM in the water column compared with the advection input/output fluxes of the SPM in the river mouth areas. The removal and the resuspension fluxes were comparable in the estuary. Meanwhile, old composition (whose deposition into the seabed for a long time is enough for 7Be to decay completely) occupied only a small part in the resuspended sediment during resuspension process.
The role of the solar irradiance variability in the evolution of the middle atmosphere during 2004–2009
Authors: Shapiro A. V. , Rozanov E. V. , Shapiro A. I. , Egorova T. A. , Harder J. , Weber M. , Smith A. K. , Schmutz W. , Peter T. 
Published: April 2013

AbstractRecent measurements by the Spectral Irradiance Monitor (SIM) and the Solar Stellar Irradiance Comparison Experiment (SOLSTICE) onboard the Solar Radiation and Climate Experiment satellite have revealed the spectral solar irradiance (SSI) changes in the ultraviolet between 2004 and 2009 to be several times higher than it was shown by all previous SSI measurements and reconstructions. In this paper, we simulate the O3, OH, and temperature responses to solar irradiance variability using four different SSI data sets trying to define which one gives the best agreement between the simulated and observed responses. First, we apply the 1‐D radiative‐convective model with interactive photochemistry to determine the regions of the atmosphere where the O3, OH, and temperature are most sensitive to the spectrum discrepancies between the different SSI data sets. As the comparison with observations can be only made taking into account dynamics and all known forcings of the atmosphere, we then apply the 3‐D chemistry‐climate model SOCOL to simulate the atmosphere evolution from May 2004 to February 2009. We compare the modeled OH, O3, and temperature changes with atmospheric data measured by several space instruments. Overall, the comparison shows that the atmospheric changes simulated with the 3‐D SOCOL model driven by the SIM and SOLSTICE SSI are closest to the atmospheric measurements.
Diurnal ozone variations in the stratosphere revealed in observations from the Superconducting Submillimeter‐Wave Limb‐Emission Sounder (SMILES) on board the International Space Station (ISS)
Authors: Sakazaki Takatoshi , Fujiwara Masatomo , Mitsuda Chihiro , Imai Koji , Manago Naohiro , Naito Yoko , Nakamura Tetsu , Akiyoshi Hideharu , Kinnison Douglas , Sano Takuki , Suzuki Makoto , Shiotani Masato 
Published: April 2013

AbstractConsiderable uncertainties remain in the global pattern of diurnal variation in stratospheric ozone, particularly lower to middle stratospheric ozone, which is the principal contributor to total column ozone. The Superconducting Submillimeter‐Wave Limb‐Emission Sounder (SMILES) attached to the Japanese Experiment Module (JEM) on board the International Space Station (ISS) was developed to gather high‐quality global measurements of stratospheric ozone at various local times, with the aid of superconducting mixers cooled to 4K by a compact mechanical cooler. Using the SMILES dataset, as well as data from nudged chemistry‐climate models (MIROC3.2‐CTM and SD‐WACCM), we show that the SMILES observational data have revealed the global pattern of diurnal ozone variations throughout the stratosphere. We also found that these variations can be explained by both photochemistry and dynamics. The peak‐to‐peak difference in the stratospheric ozone mixing ratio (total column ozone) reached 8% (1%) over the course of a day. This variation needs to be considered when merging ozone data from different satellite measurements and even from measurements made using one specific instrument at different local times.
Constrained dynamical downscaling for assessment of climate impacts
Authors: Harkey M. , Holloway T. 
Published: April 2013

AbstractTo assess climate change impacts on hydrology, conservation biology, and air quality, impact studies typically require future climate data with spatial resolution high enough to resolve urban‐rural gradients, complex topography, and sub‐synoptic atmospheric phenomena. We present here an approach to dynamical downscaling using analysis nudging, where the entire domain is constrained to coarser‐resolution parent data. Here meteorology from the North American Regional Reanalysis and the North American Regional Climate Change Assessment Program data archive are used as parent data and downscaled with the Advanced Research version of the Weather Research and Forecasting model to a 12 km × 12 km horizontal resolution over the Eastern U.S. Our results show when analysis nudging is applied to all variables at all levels, mean fractional errors relative to parent data are less than 2% for maximum 2 m temperatures, less than 15% for minimum 2 m temperatures, and less than 18% for10 m wind speeds. However, the skill of representing fields that are not nudged, such as boundary layer height and precipitation, is less clear. Our results indicate that though nudging can be a useful tool for consistent, comparable studies of downscaling climate for regional and local impacts, which variables are nudged and at what levels should be carefully considered based on the climate impact(s) of study.
Climatology of aerosol optical properties at ACRF sites in the tropical warm pool region
Authors: Yin Bangsheng , Min Qilong 
Published: April 2013

AbstractThe long‐term multifilter rotating shadowband radiometer measurements at three Atmospheric Radiation Measurements Climate Research Facility sites of Darwin, Nauru, and Manus have been processed to develop the climatology of aerosols in the tropical warm pool region at the interannual, seasonal, and diurnal temporal scales. Due to their unique geolocations and associated large‐scale circulation patterns, aerosols at the Nauru site exhibit background oceanic characteristics (strongly correlated with the sea surface wind), aerosols at the Darwin site show strong influences by biomass‐burning aerosols, particularly in the dry season, and aerosols at the Manus site have climatologic characteristics in between the Darwin and Nauru sites. There are no obvious trends of aerosol loading for past decades at all three sites. El Niño/Southern Oscillation has its impacts on aerosol optical depth, as well as particle size and composition, at all three sites. Madden‐Julian Oscillation modulates aerosol optical depth at the Manus and Nauru sites along the equator but has no apparent impact at the Darwin site. The annual or seasonal variation of aerosols is closely linked with Indo‐Australian monsoons, exhibiting wet and dry season differences. The aerosol loading is significant lower with relatively larger particles in the wet season than in the dry season. There are significant diurnal cycles in both aerosol optical depth and Angstrom exponent at the Darwin site: low values of aerosol optical depth and Angstrom exponent in the midday and the two peaks in the early morning and late afternoon. There are noticeable changes between the dry and wet seasons. The amplitude of diurnal variation during La Niña periods is greater than that during El Niño periods. However, there are no significant diurnal variations of aerosol loading at the Manus and Nauru sites.
Thermodynamic structure and evolution of the atmospheric mixed layer over the western North Pacific during the summer monsoon onset
Authors: Geng Biao , Yoneyama Kunio , Shirooka Ryuichi 
Published: April 2013

AbstractThis study examined the thermodynamic structure of the atmospheric mixed layer and its evolution in different periods during the onset of the western North Pacific summer monsoon by using data observed on board the research vessel Mirai at 12°N and 135°E during 6–24 June 2008. The overall mean depth of the mixed layer was 482 m, and the mixed layer tended to shrink after the monsoon onset. The mixed layer was relatively warm and moist during the early onset period. However, the mixed layer became very cool and dry during the latter onset period, when intense and sustained rainfall was observed. The surface buoyancy flux, environmental subsidence over the mixed layer, and upward motion at cloud base intensified after the monsoon onset. All of these factors were negatively correlated with the depth of the mixed layer, which implies that the upward motion at cloud base and compensating environmental subsidence act to suppress the growth of the mixed layer driven by buoyancy forcing and to shrink the mixed layer after the monsoon onset. A significant positive correlation existed between the surface buoyancy flux and the upward motion at cloud base after the monsoon onset. Such positive feedback between the sea surface and cumulus clouds facilitates the formation of the warmer and moister mixed layer during the early onset period, thereby benefiting the further development of the monsoon onset.
Impacts of ENSO on autumn rainfall over Yellow River loop valley in observation: Possible mechanism and stability
Authors: Li Chun , Zeng Gang 
Published: April 2013

AbstractThe Yellow River loop valley (YRLV) is one of major agricultural production zones in many Chinese dynasties. Predicting rainfall variability in the YRLV is important for the society and the economy. This study demonstrates impacts of El Niño–Southern Oscillation (ENSO) on autumn rainfall in the YRLV based on statistical analyses of instrumental rainfall in China and reanalyzed SST and atmospheric data. Results indicate that the autumn rainfall anomaly in the YRLV may be partially controlled by the ENSO‐like sea surface temperature (SST) pattern. The YRLV rainfall is below normal (above normal) in the El Niño (La Niña) developing years. This impact is mediated by an atmospheric response to the ENSO‐like SST anomaly forcing via a westward Rossby wave. Furthermore, Niño3.4 index may be used as a factor for autumn rainfall in the YRLV region with a lead of 4–5 months. However, the relationship between the autumn YRLV rainfall and ENSO does not persist and has gone through decadal weakening since the end of 1980s via a decadal response of atmospheric circulation to ENSO. The decadal change of the relationship between the autumn YRLV rainfall and ENSO may be modulated by climate decadal shifts.
Observed trends in the global jet stream characteristics during the second half of the 20th century
Authors: Pena‐Ortiz Cristina , Gallego David , Ribera Pedro , Ordonez Paulina , Alvarez‐Castro Maria Del Carmen 
Published: April 2013

AbstractIn this paper, we propose a new method based on the detection of jet cores with the aim to describe the climatological features of the jet streams and to estimate their trends in latitude, altitude, and velocity in the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) and 20th Century reanalysis data sets. Due to the fact that the detection method uses a single grid point to define the position of jet cores, our results reveal a greater latitudinal definition allowing a more accurate picture of the split flow configurations and double jet structures. To the best of our knowledge, these results provide the first multiseasonal and global trend analysis of jet streams based on a daily‐resolution 3‐D detection algorithm. Trends have been analyzed over 1958–2008 and during the post‐satellite period, 1979–2008. We found that, in general, trends in jet velocities and latitudes have been faster for the Southern Hemisphere jets and especially for the southern polar front jet which has experienced the fastest velocity increase and poleward shift over 1979–2008 during the austral summer and autumn. Results presented here show an acceleration and a poleward shift of the northern and southern winter subtropical jets over 1979–2008 that occur at a faster rate and over larger zonally extended regions during this latter period than during 1958–2008.
Eastern U.S. summer streamflow during extreme phases of the North Atlantic oscillation
Authors: Coleman Jill S. M. , Budikova Dagmar 
Published: April 2013

AbstractNumerous studies have suggested streamflow discharge in the conterminous U.S. has been increasing, particularly in the east starting in the latter half of the 20th century. Northern Hemisphere (NH) hydroclimatic variability has been connected to shifts in large‐scale atmospheric teleconnection patterns. This study ascertained the spatial and temporal influences of the extreme phases of the North Atlantic Oscillation (NAO) on interannual streamflow variability across the eastern U.S. during the summer season. We also assessed the presence of any delayed streamflow responses to NAO configurations during previous spring (March‐April‐May) and winter (December‐January‐February) seasons across the study area. Methods of inquiry included the use of various statistical and compositing analyses applied to records of mean daily summer streamflow obtained from the Hydro‐Climatic Data Network between 1950 and 2010. Results of this study suggest that summer streamflow across eastern U.S. may be related to and thus potentially predicted from the NAO up to three seasons in advance, information of significant hydrologic consequences for the area. Depending upon the season and geographic location, the relationships may be both linear and nonlinear in nature and may be masked by the presence of temporal trends in the index. Summer streamflow across the eastern U.S., in general, displays greatest response to the negative phase of the NAO during the previous winter and the concurrent summer seasons. Geographically, the greatest potential for predictability exists across the Northeast where cohesive responses to NAO exist in all three seasons, winter, spring, and summer.
Evaluation of black carbon semi‒direct radiative effect in a climate model
Authors: Li Jiangnan , von Salzen Knut , Peng Yiran , Zhang Hua , Liang Xin‒Zhong 
Published: April 2013

AbstractThe semi‒direct effect of black carbon (BC) is studied by using a newly proposed optical property parameterization for cloud droplets with BC inclusions. Based on Atmospheric Model Intercomparison Project‒type climate model simulations, it is found that the cloud amount can be either enhanced or reduced when BC is included in clouds. The decrease of the global annual mean total cloud amount is only about 0.023%. The 3‒D cloud fraction distribution, however, shows larger changes which vary with latitude. A correlation between the changes of the cloud fraction and the vertical velocity is found. The cloud water path is mainly affected by low clouds and so the impact of BC on the cloud water path is particularly strong. It is shown that the BC above clouds tends to stabilize the atmosphere and enhance the cloud amount in the boundary layer. This can be used to explain the relationship between aerosol optical depth and cloud amount according to satellite data. For BC in clouds and above, the global annual mean enhancement of solar absorption is about 0.049 W m−2 and 0.57 W m−2, respectively. The BC semi‒direct radiative forcing is estimated by subtracting the BC direct forcing from the BC total radiative forcing. The global annual mean of BC direct forcing and semi‒direct forcing at the top of the atmosphere are 0.264 W m−2 and 0.213 W m−2, respectively.
On the potential high acid deposition in northeastern China
Authors: Cao Junji , Tie Xuexi , Dabberdt Walter F. , Jie Tang , Zhao Zhuzi , An Zhisheng , Shen Zhenxing , Feng Yinchang 
Published: April 2013

AbstractThere is an acid deposition conundrum in China: contrary to conventional wisdom, extremely high ambient sulfate concentrations in northeastern China are not always accompanied by correspondingly high acidities. To investigate this discrepancy, data from two independent sets of in situ field measurements were analyzed along with Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) satellite observations and Model for Ozone and Related chemical Tracers (MOZART) chemical transport model calculations. The field measurements included soluble aerosol ion concentrations and pH and particulate data from 11 cities, as well as pH measurement data from 74 sites in China. This study explores the basis for and the impacts of the large discrepancy in northeastern China between the major acidity precursors (SO2 and NOx) and measured acidity levels as indicated by pH values. There are extremely high SO2 emissions and ambient concentrations in northeastern China, while the corresponding acidity is unusually low (high pH) in this region. This is inconsistent with the usual situation where high‐acidity precursor pollutants result in low pH (high acidity) values and acid rain conditions. In other regions, such as southern China and the United States, high SO2 concentrations are typically well correlated with high acidities. Using measured soluble particle measurements (including both positively and negatively charged ions), it is seen that there are high values of alkaline ions in northeastern China that play an important role in neutralizing acidity in this region. This result strongly suggests that the high alkaline concentrations, especially Ca2+, increase warm season pH values by about 0.5 in northern China, partially explaining the inconsistency between sulfate concentrations and acidity. This has a very important implication for acid rain mitigation—especially in northeastern China. However, there are additional issues pertaining to the precursor‐acidity relationship that need further investigation. Why is it that the reduction in acidity due to the alkaline ions is only significant in summer? During winter, the measured alkaline ions play a much smaller role in explaining the discrepancy. The measured alkaline ions in this study were mostly obtained from particles in the PM2.5 range. However, the size of calcium particles is typically much larger—extending well beyond 2.5 µm—and so a significant amount of calcium may be underestimated by PM2.5 measurements alone. The under‐sampling of calcium particles is further exacerbated in that the sampling protocol excluded particle (and soluble ion and pH) measurements during dust storms. This all leads to the need for an improved understanding of pollutant‐ion‐particulate interactions in China, and their role in explaining the counter‐intuitive conclusion that dust mitigation strategies in China could have the unintended consequence of exacerbating acid rain conditions.
Future changes in summertime precipitation amounts associated with topography in the Japanese islands
Authors: Tsunematsu Nobumitsu , Dairaku Koji , Hirano Junpei 
Published: April 2013

AbstractThis study investigates future changes in summertime precipitation amounts over the Japanese islands and their relations to the topographical heights by analyzing data from 20 km resolution regional climate model downscalings of MIROC3.2(hires) 20C3M and Special Report on Emission Scenarios A1B scenario data for the periods of 1981–2000 and 2081–2100. Results of the analyses indicate that future increases in June‐July‐August mean daily precipitation amounts are noticeable in the west and south sides (windward sides) of the mountainous regions, especially in western Japan where heavy rainfall is frequently observed in the recent climate. The large precipitation increases are likely to occur not only in high altitude areas but also at low altitudes where many urban areas are located. In such areas, the occurrence frequencies of precipitation amounts greater than 100 mm d−1 would also increase under the future climate scenario (A1B). One of the main causes of these precipitation changes appears to be the intensification of southwesterly moist air flows in the lower troposphere, which is likely to be associated with future increases in the north‐south atmospheric pressure gradient, especially at latitudes south of 35°N. The intensified southwesterly moist air flows that impinge on the western and southern slopes of the mountains can generate stronger upslope flows and well‐developed clouds, leading to increased precipitation. In contrast, future precipitation changes in the lee sides of the mountainous regions would be comparatively small. These results indicate that future precipitation changes strongly depend on the topography and prevailing wind direction.
Impact of sea surface temperature trend on late summer Asian rainfall in the twentieth century
Authors: Bian Qiying , Lu Riyu 
Published: April 2013

AbstractThe impact of the global sea surface temperature (SST) warming trend, which is the leading mode of SST variability, on late summer Asian rainfall is analyzed based on the simulations of five atmospheric general circulation models, which are performed by the U. S. Climate Variability and Predictability Drought Working Group. Our evaluations of the model outputs indicate that these models roughly capture the main features of climatological rainfall and circulations over Asia and the western North Pacific (WNP), but they simulate a too strong monsoon trough and a too northward shifted in the subtropical anticyclone in the WNP and fail to reproduce the rain belt over East Asia. It is found that all of the models simulate an intensified WNP subtropical high (WNPSH) in late summer, an enhanced precipitation in the tropical Indian Ocean and the maritime continent, and a suppressed precipitation in the South Asian monsoon region, the South China Sea, and the Philippine Sea, when the models are forced with the SST trend, which is characterized by a significant increase in the Indian Ocean and western Pacific. All these changes are suggested to be dynamically coherent. The warmer SST trend in the Indian Ocean and western Pacific may suppress precipitation over the Philippine Sea and thus result in a lower tropospheric anticyclonic circulation over the subtropical WNP. The warmer SSTs in the Indian Ocean may also be responsible for the anomalous easterlies and resultant less rainfall over the South Asian monsoon region. The precipitation changes forced by the SST trend are similar in the maritime continent but show an apparent difference over East Asia, in comparison with the observed rainfall trend over lands. The possible reasons for this difference are discussed.