bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sensitivity Study of North Atlantic Summer Cyclone Activity in Dynamical Downscaled Simulations
Authors: Zhang Minghong , Perrie William , Long Zhenxia 
Published: July 2019

AbstractWe conduct a sensitivity study of the North Atlantic cyclone climate, with respect to the cumulus parameterization (CP) and planetary boundary layer (PBL) schemes, applied in the dynamical downscaling of HadGEM2‐ES simulations using Polar Weather Research and Forecasting. A set of seven sensitivity experiments is conducted for 1979–2004 using these CP and PBL schemes. CP schemes are Kain‐Fritsch (KF), Zhang‐McFarlane (ZM), and the modified Tiedtke (TZ). PBL schemes are the local Mellor‐Yamada‐Janjić (MYJ), Mellor‐Yamada‐Nakanishi‐Niino Level 2.5 (MYNN2) schemes, and nonlocal Yonsei University (YSU) scheme. In terms of cyclone intensities, our results show that the fine‐resolution Weather Research and Forecasting simulations capture higher intensities of summer cyclones than the HadGEM2‐ES results, in better agreement with the ERA‐Interim reanalysis, and exhibit a weak sensitivity to CP and PBL schemes. However, the frequency of summer cyclones is quite sensitive to CP and PBL schemes. Four KF experiments suggest comparable numbers of cyclone tracks as derived from ERA‐Interim reanalysis data, which is about 21% more than the ZM‐MYJ or TZ experiments and 11% more than HadGEM2‐ES results. Larger tropospheric potential vorticity and more cyclogenesis in the KF simulation than in TZ or ZM simulations are associated with different cyclone triggering functions and different vertical distributions of heating. We also find increased cyclone activities over the North Atlantic in the YSU or MYNN2 schemes compared to MYJ, but results also depend on the KF CP scheme. This can be attributed to stronger vertical mixing in YSU and MYNN schemes, resulting in smaller static stability and enhanced atmospheric moisture.
Impacts of Three Gorges Dam on Regional Circulation: A Numerical Simulation
Authors: Li Yan , Wu Liguang , Chen Xianyan , Zhou Weican 
Published: July 2019

AbstractThe Three Gorges Dam (TGD) is the largest hydropower project in the world. The resulting Three Gorges Reservoir (TGR) extends 660 km along the waterway of the Yangtze River in surrounded by complicated terrain. The dam and its impounded reservoir has triggered large‐scale land use and land cover change, which can potentially impact the environment and climate significantly. In this study, the impact of the TGD on regional‐scale circulation is explored through high‐resolution simulation using the weather research and forecast model. It is found that the construction of the TGD has little influence on the near‐surface temperature in the TGR region even when extreme hot weather occurs in the region. The numerical experiments performed in this study indicate that the construction of the TGD can alter the atmospheric circulation on the regional scale when the weak southeasterly wind in the lower troposphere prevails in the region. Due to the blocking effects of the TGD and the expanding water surface area of the TGR, the low‐level southeasterly flow is turned into northeasterly and southeasterly flows before reaching the dam, leading to an anomalous cyclone over 112–115°E, 33–34°N, and an anomalous anticyclone over 110–112°E, 28–29°N. It is also found that the anomalous cyclone can evidently enhance precipitation locally under some special atmospheric conditions. This study suggests that the impact of the TGD can be amplified due to the complicated terrain in the surrounding areas of the TGD.
Amplified Urban Heat Islands during Heat Wave Periods
Authors: Jiang Shaojing , Lee Xuhui , Wang Jiankai , Wang Kaicun 
Published: July 2019

AbstractHeat waves and urban heat islands (UHIs) may interact together, but the dependence of their interaction on background climate is unclear. Hourly meteorological observations in June to August from 2013 to 2015 collected in the megacities of Beijing (temperate semihumid monsoon climate), Shanghai (subtropical humid monsoon climate), and Guangzhou (marine subtropical monsoon climate) in China were used to study the interaction. At each megacity, eight rural stations and eight urban stations, respectively, were selected to study the UHI. Although under different background climates, UHIs in Beijing and Guangzhou shared a similar diurnal variability, that is, higher in the nighttime. However, the diurnal cycle is opposite for Shanghai if rural coastal stations were selected as rural reference stations. During heat wave periods, daytime (10:00–16:00) UHIs were intensified by 0.9 ± 0.13 (mean ± 1 standard deviation) °C in Shanghai, nighttime (22:00–4:00) UHIs were intensified by 0.9 ± 0.36 and 0.8 ± 0.20 °C in Beijing and Guangzhou, respectively. The surface solar radiation during the heat wave period was approximately 1.5 times to that under normal conditions in each city. The enhanced solar radiation during heat waves, which was absorbed by the urban canopy in the daytime and released at night, was closely related to nighttime UHIs in Beijing and Guangzhou and daytime UHIs in Shanghai. Additionally, changes in wind direction were observed in Shanghai under heat waves, that is, with more than 63% (wind direction) of the wind originating from neighboring hot cities in the southwest instead of the cool sea breeze from the southeast, which led to a significant increase in daytime UHIs during heat wave periods.
Variation of Radiation Belt Electron Flux During CME‐ and CIR‐Driven Geomagnetic Storms: Van Allen Probes Observations
Authors: Pandya Megha , Bhaskara Veenadhari , Ebihara Yusuke , Kanekal Shrikanth G. , Baker Daniel N. 
Published: July 2019

AbstractRelativistic electron flux responses in the inner magnetosphere are investigated for 28 magnetic storms driven by corotating interaction region (CIR) and 27 magnetic storms driven by coronal mass ejection (CME), using data from the Relativistic Electron‐Proton Telescope instrument on board Van Allen Probes from October 2012 to May 2017. In this present study we analyze the role of CIRs and CMEs in electron dynamics by sorting the electron fluxes in terms of averaged solar wind parameters, L‐values, and energies. The major outcomes from our study are the following: (i) At L = 3 and E = 3.4 MeV, for >70% cases the electron flux remains stable, while at L = 5, for ~82% cases it changes with the geomagnetic conditions. (ii) At L = 5, ~53% of the CIR storms and 30% of the CME storms show electron flux increase. (iii) At a given L‐value, the tendency for the electron flux variation diminishes with the increasing energies for both categories of storms. (iv) In case of CIR‐driven storms, the electron flux changes are associated with changes in Vsw and Sym‐H. (v) At L ~ 3, CME storms show increased electron flux, while at L ~ 5, CIR storms are responsible for the electron flux enhancements. (vi) During CME‐ and CIR‐driven storms, distinct electron flux variations are observed at L = 3 and L = 5.
Partial Melting of Mixed Sediment‐Peridotite Mantle Source and Its Implications
Authors: Zhang Yanfei , Wang Chao , Zhu Lüyun , Jin Zhenmin , Li Wei 
Published: July 2019

AbstractSubducted sediments play an important role in the transport of incompatible elements back into the Earth's mantle. In recent years, studies of volcanic rocks from Samoan (Jackson et al., 2007, https://doi.org/10.1038/nature06048), NE China (Wang, Chen, et al., 2017, https://doi.org/10.1016/j.epsl.2017.02.028), and Gaussberg, Antarctica (Murphy et al., 2002, https://doi.org/10.1093/petrology/43.6.981), have shown geochemical records of a sediment‐influenced mantle source from the deep Earth. However, experimental studies on the partial melting behavior of mixed sediment‐peridotite mantle beyond subarc depths are very rare. In this study, we conducted experiments to investigate the partial melting behavior of mixed sediment‐peridotite mantle at 4–15 GPa and 1200–1800 °C. The experimental solidi of mixed sediment‐peridotite and K‐feldspar‐peridotite systems (Mixes A and B) cross the hot mantle geotherm at depths of around the X discontinuity (seismic discontinuity, ~300‐km depth). The trace element compositions of the corresponding partial melts in Mix A showed similar characteristics to those of the Samoan basaltic lavas, potassic basalts from NE China, and Gaussberg lamproites. Therefore, the experimental results provide a possible explanation for the origin of some unusual mantle‐derived volcanic rocks that contain recycled sediment signatures and have very deep origins. At depths of ~300 km (X discontinuity), a mixed sediment‐peridotite source was heated by a hot‐upwelling mantle and produced enriched melt. The enriched melt may interact with the surrounding mantle before incorporated into the upwelling mantle plume and becoming involved in the origin of some volcanic rocks. The experiments also provide a possible link between the enriched‐mantle source in the deep mantle and the X discontinuity.
Impacts of Changjiang River Discharge and Kuroshio Intrusion on the Diatom and Dinoflagellate Blooms in the East China Sea
Authors: Zhou Zheng‐Xi , Yu Ren‐Cheng , Sun Chaojiao , Feng Ming , Zhou Ming‐Jiang 
Published: July 2019

AbstractThe coastal area adjacent to the Changjiang River estuary is a high‐risk region for harmful algal blooms. Both Changjiang River discharge and Kuroshio intrusion influence the hydrological conditions and nutrient composition in this area which could affect the onset of diatom and dinoflagellate blooms. However, current understandings on their roles in regulating different microalgal blooms are limited. In this study, changes in stratification, water masses, and the ratio of phosphorus to nitrogen were examined during the diatom and dinoflagellate blooms in 2005 using ship cruise data. The observations showed that both the diatom and dinoflagellate blooms occurred in the continental coastal water. By enhancing the pycnocline and phosphorus stress, the Changjiang diluted water plays an important role in affecting the diatom bloom. The dinoflagellate bloom is partly supported by the supply of phosphate transported by Kuroshio intrusion and upwelling. The results of this study will help elucidate the mechanisms of large‐scale harmful algal blooms in the coastal area adjacent to the Changjiang River estuary.
Initial Leader Properties During the Preliminary Breakdown Processes of Lightning Flashes and Their Associations With Initiation Positions
Authors: Zheng Dong , Shi Dongdong , Zhang Yang , Zhang Yijun , Lyu Weitao , Meng Qing 
Published: July 2019

AbstractThe properties of initial leaders (ILs) of 1,056 flashes in two thunderstorms in Guangzhou, China, are analyzed. The median values of IL properties are 11.1 ms for duration, 2.2 km for vertical distance, 2.7 km for 3‐D distance, 1.9 × 105 m/s for vertical displacement speed, 2.4 × 105 m/s for 3‐D displacement speed, 28° for angle between the IL's displacement direction and the vertical direction, 1.1 per ms for pulse rate, 179 m for vertical step length, and 224 m for 3‐D step length. All the IL properties follow lognormal distributions. Strong monotonic relationships of IL duration with speed and pulse rate and pulse rate with speed and step length are revealed. With increasing initiation altitude, IL duration and step length tend to increase, and IL speed and pulse rate tend to decrease. The ILs initiated at approximately the −20 °C isotherm are more vertically orientated on average than those initiated at lower or higher levels. The ILs initiated in the strong kinematic areas generally had a greater speed and pulse rate but smaller duration, distance, and step length relative to those initiated in the weak kinematic areas. The possible impacts of the charge distribution patterns and density on the IL properties in different types of thunderstorms or thunderstorm areas are discussed.
Global Modeling of Secondary Organic Aerosol With Organic Nucleation
Authors: Zhu Jialei , Penner Joyce E. 
Published: July 2019

AbstractOrganic nucleation has been identified as an important way to form secondary organic aerosol (SOA) and change the number concentration of aerosol and thus its climate effect. A global atmospheric chemistry model is developed to include a comprehensive organic nucleation scheme that includes heteromolecular nucleation of sulfuric acid and organics, neutral pure organic nucleation, and ion‐induced pure organic nucleation. Our model simulation shows reasonable agreement with the seasonal as well as spatial pattern of organic carbon concentration in America, while it fails to predict the seasonal pattern of organic carbon in Europe due to the lack of sharp increases in primary organic aerosol emissions in the winter. Including organic nucleation decreases the bias of the annual average particle number concentration at 54% of the available observation sites and increases the temporal correlation coefficients at 58% of the sites. Ion‐induced pure organic nucleation contributes the most to the total organic nucleation rate, which peaks around 400 hPa in the tropics. Heteromolecular nucleation of sulfuric acid and organics dominates the total organic nucleation rate in the summer and mostly occurs in the lower troposphere. The number concentration of particles formed from organic nucleation (newSOA) in the nucleation and Aitken modes is highest in the tropics, while accumulation mode newSOA is highest in the Northern Hemisphere due to growth as a result of the condensation of sulfate. Three sensitivity experiments suggest that more studies are needed to investigate the formation mechanism of newSOA, so that a more accurate simulation of the spatial and size distribution of newSOA can be developed.
Estimation of Soil Evaporation and Vegetation Transpiration Using Two Trapezoidal Models From MODIS Data
Authors: Jiang Yazhen , Tang Ronglin , Jiang Xiaoguang , Li Zhao‐Liang , Gao Caixia 
Published: July 2019

AbstractSoil evaporation (ETs) and vegetation transpiration (ETv) are essential in evaporative demand analyses and agricultural applications. This study estimated ETs and ETv using two trapezoidal models, that is, the conventional trapezoidal model and the end‐member‐based soil and vegetation energy partitioning (ESVEP) model, at three AmeriFlux tower sites. First, the land surface temperature of a Moderate Resolution Imaging Spectroradiometer (MODIS) pixel was decomposed into soil and vegetation temperatures (Ts and Tv, respectively) which involve important information related to ETs and ETv and were compared with corresponding temperatures from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). Then ETs and ETv were parameterized, and the total evapotranspiration (ET) was validated with the eddy covariance system measurements after energy imbalance corrections via the residual energy and Bowen ratio methods. The results showed that the ESVEP model partitioned Ts, with a root‐mean‐square error (RMSE) of 1.56–2.70 K (4.98–10.16%), and Tv, with an RMSE of 2.54–2.80 K (9.73–11.11%), indicating a higher accuracy than that from the conventional trapezoidal model, where the RMSE was 2.26–3.64 K (7.31–13.40%) for Ts separation and 2.82–4.62 K (9.80–15.49%) for Tv separation. For the ET estimation, the ESVEP model still performed better. The estimation RMSE was 49.8–58.4 W/m2 (22.8–27.2%) for the ESVEP model and 72.0–89.5 W/m2 (29.8–41.1%) for the conventional trapezoidal model, compared to the RE corrected measurements; the RMSE was 42.6–53.3 W/m2 (24.4–28.1%) for the ESVEP model and 57.5–78.1 W/m2 (32.3–37.9%) for the conventional trapezoidal model, compared to the Bowen ratio corrected measurements.
Observational Constraints on the Formation of Cl2 From the Reactive Uptake of ClNO2 on Aerosols in the Polluted Marine Boundary Layer
Authors: Haskins Jessica D. , Lee Ben H. , Lopez‐Hilifiker Felipe D. , Peng Qiaoyun , Jaeglé Lyatt , Reeves J. Michael , Schroder Jason C. , Campuzano‐Jost Pedro , Fibiger Dorothy , McDuffie Erin E. , Jiménez José L. , Brown Steven S. , Thornton Joel A. 
Published: July 2019

AbstractWe use observations from the 2015 Wintertime Investigation of Transport, Emissions, and Reactivity (WINTER) aircraft campaign to constrain the proposed mechanism of Cl2 production from ClNO2 reaction in acidic particles. To reproduce Cl2 concentrations observed during WINTER with a chemical box model that includes ClNO2 reactive uptake to form Cl2, the model required the ClNO2 reaction probability, γ (ClNO2), to range from 6 × 10−6 to 7 × 10−5, with a mean value of 2.3 × 10−5 (±1.8 × 10−5). These field‐determined γ (ClNO2) are more than an order of magnitude lower than those determined in previous laboratory experiments on acidic surfaces, even when calculated particle pH is ≤2. We hypothesize this is because thick salt films in the laboratory enhanced the reactive uptake ClNO2 compared to that which would occur in submicron aerosol particles. Using the reacto‐diffusive length‐scale framework, we show that the field and laboratory observations can be reconciled if the net aqueous‐phase reaction rate constant for ClNO2 (aq) + Cl‐(aq) in acidic particles is on the order of 104 s−1. We show that wet particle diameter and particulate chloride mass together explain 90% of the observed variance in the box model‐derived γ (ClNO2), implying that the availability of chloride and particle volume limit the efficiency of the reaction. Despite a much lower conversion of ClNO2 into Cl2, this mechanism can still be responsible for the nocturnal formation of 10–20 pptv of Cl2 in polluted regions, yielding an atmospherically relevant concentration of Cl atoms the following morning.
Modeling Dust in East Asia by CESM and Sources of Biases
Authors: Wu Mingxuan , Liu Xiaohong , Yang Kang , Luo Tao , Wang Zhien , Wu Chenglai , Zhang Kai , Yu Hongbin , Darmenov Anton 
Published: July 2019

AbstractEast Asian dust has a significant impact on regional and global climate. In this study, we evaluate the spatial distributions and temporal variations of dust extinction profiles and dust optical depth (DOD) over East Asia simulated from the Community Earth System Model (CESM) with satellite retrievals from Luo, Wang, Ferrare, et al. (2015, https://doi.org/10.1029/2002JD002775), Luo, Wang, Zhang, et al. (2015, https://doi.org/10.1002/2014GL062111) (L15), Yu et al. (2015, https://doi.org/10.1016/j.rse.2014.12.010) (Y15), and Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) level 3 products. Both L15 and Y15 are based on CALIPSO products but use different algorithms to separate dust from nondust aerosols. We find high model biases of dust extinction in the upper troposphere over the Taklamakan desert, Gobi desert, and Tibetan Plateau, especially in the summer (June‐July‐August). CESM with dust emission scheme of Kok, Mahowald, et al. (2014, https://doi.org/10.5194/acp‐14‐13023‐2014) and Kok, Albani, et al. (2014, https://doi.org/10.5194/acp‐14‐13043‐2014) has the best agreement with dust extinction profiles and DOD from L15 in the Taklamakan desert and Tibetan Plateau. CESM with the default dust emission scheme of Zender, Bian, and Newman (2003, https://doi.org/10.1029/2002JD002775) underpredicts DOD in the Tibetan Plateau compared with observations from L15 due to the underestimation of local dust emission. Large uncertainties exist in observations from L15, Y15, and CALIPSO level 3 products and have significant impacts on the model evaluation of dust spatial distributions. We also assess dust surface concentrations and 10‐m wind speed with meteorological records from weather stations in the Taklamakan and Gobi deserts during dust events. CESM underestimates dust surface concentrations at most weather stations due to the inability of CESM to capture strong surface wind events.
Predictability of Stratospheric Sudden Warmings in the Beijing Climate Center Forecast System with Statistical Error Corrections
Authors: Rao Jian , Ren Rongcai , Chen Haishan , Liu Xiangwen , Yu Yueyue , Hu Jinggao , Zhou Yang 
Published: July 2019

AbstractPrevious studies have reported that the predictive limit of stratospheric sudden warming (SSW) events in the Beijing Climate Center forecast system (BCC_CSM) is shorter than 2 weeks. This study continues to analyze the general characteristics of this model in forecasting SSWs and carries out a trial of error corrections. The ratio of the ensemble members that forecast the zonal wind reversal with a 5‐day delay allowed (hit ratio) is higher for SSW events with a small decrease in the zonal mean zonal winds (moderate SSWs) than for events with a large decrease in the zonal mean zonal winds (radical SSWs) in hindcasts initialized around 1 (D‐7) and 2 (D‐14) weeks in advance. The underestimated cumulative eddy heat flux associated with weak wave activities accounts for the weaker‐than‐observed deceleration of westerlies. The preexisting extratropical wave patterns are satisfactorily forecast in D‐14 for most (9/12) cases, and the wave phase bias is reasonably small for those cases. After the climatology bias is deducted from the hindcasts, an increase in the hit ratio can be identified for moderate SSW events as the evolutions of zonal winds are improved. Following the error correction by remapping the zonal wind probability distribution function in the forecast system to the reanalysis, the SSW hit ratios increase in the D‐7 (43% to 57%) and/or D‐14 (11% to 21%) initializations. Based on the composite result, this error correction method robustly improves the hit ratio not only for both radical SSWs and moderate SSWs but also for both polar vortex split SSWs and polar vortex displacement SSWs. The best error correction method might propel the prediction limit of SSW events to around 2 weeks.
Thermotectonic History of the Kluane Ranges and Evolution of the Eastern Denali Fault Zone in Southwestern Yukon, Canada
Authors: McDermott Robert G. , Ault Alexis K. , Caine Jonathan Saul , Thomson Stuart N. 
Published: July 2019

AbstractExhumation and landscape evolution along strike‐slip fault systems reflect tectonic processes that accommodate and partition deformation in orogenic settings. We present 17 new apatite (U‐Th)/He (He), zircon He, apatite fission‐track (FT), and zircon FT dates from the eastern Denali fault zone (EDFZ) that bounds the Kluane Ranges in Yukon, Canada. The dates elucidate patterns of deformation along the EDFZ. Mean apatite He, apatite FT, zircon He, and zircon FT sample dates range within ~26–4, ~110–12, ~94–28, and ~137–83 Ma, respectively. A new zircon U‐Pb date of 113.9 ± 1.7 Ma (2σ) complements existing geochronology and aids in interpretation of low‐temperature thermochronometry data patterns. Samples ≤2 km southwest of the EDFZ trace yield the youngest thermochronometry dates. Multimethod thermochronometry, zircon He date‐effective U patterns, and thermal history modeling reveal rapid cooling ~95–75 Ma, slow cooling ~75–30 Ma, and renewed rapid cooling ~30 Ma to present. The magnitude of net surface uplift constrained by published paleobotanical data, exhumation, and total surface uplift from ~30 Ma to present are ~1, ~2–6, and ~1–7 km, respectively. Exhumation is highest closest to the EDFZ trace but substantially lower than reported for the central Denali fault zone. We infer exhumation and elevation changes associated with ~95–75 Ma terrane accretion and EDFZ activity, relief degradation from ~75–30 Ma, and ~30 Ma to present exhumation and surface uplift as a response to flat‐slab subduction and transpressional deformation. Integrated results reveal new constraints on landscape evolution within the Kluane Ranges directly tied to the EDFZ during the last ~100 Myr.