bluuebunny/crossref_metadata_2025 huggingface dataset:
Middle-Atmosphere Mountain Waves and Drag Near the Drake Passage: Observations, mini-MIP, and an OSSE
Authors: Kruse Christopher , Alexander Joan , Hoffmann Lars , Polichtchouk Inna , van Niekerk Annelize , Plougonven Riwal , Wrioght Corwin , Bacmeister Julio , Ern Manfred , Sato Kaoru , Shibuya Ryosuke , Meyer Catrin , Stein Olaf , Holt Laura , Šácha Petr , Gisinger Sonja
Published: March 2020

Orographic gravity wave (OGW) drag is one of the fundamental physics parametrizations employed in every global numerical model across timescales from weather to climate. These parameterizations have significant influences, both direct and indirect, on the atmosphere’s general circulation from the troposphere at least through the mesosphere. Despite their significant influence, observational constraints on these parameterizations are still largely lacking.

Presented here is a team project jointly supported by SPARC and the International Space Science Institute with the overall objective of providing new quantitative constraints for OGW drag parameterizations. Specific objectives are to evaluate methods that quantify vertical fluxes of horizontal momentum (MF) from satellite observations via an observing system simulation experiment (OSSE), a validation of WRF, UKMO, ECMWF, and ICON models against satellite and balloon observations, and an inter-comparison of OGW properties (e.g. MF and drag) within these models. Evaluation of satellite-based estimates of MF and model validation/inter-comparison will help to better quantify actual MF in the stratosphere, providing the best stratospheric MF and drag estimates for parameterizations to reproduce to date.

Two unique aspects of the project are that all models involved are deep, extending up to 1 Pa. The motivations for doing so was to include entire instrument weighting functions for AIRS observations, allowing direct, quantitative comparison between AIRS (and other satellite-borne) observations and the models. The second is the effort to perform an OSSE within the simulations, allowing comparison between MF from satellite-based methods within the models to the true MF in the models.

Preliminary results show that higher-res models (dx = 3 km) compare well and produce significantly more MF than lower-res global models, but the higher-res models still underrepresent OGW amplitudes. Mesospheric tides in analyses used to force the models significantly modulate resolved GWs and their drags.
Development of Ensemble-based Assimilation System for Aerosol Forecasting and Reanalysis at NOAA
Authors: Pagowski Mariusz , Martin Cory , Huang Bo , Kleist Daryl , Kondragunta Shobha
Published: March 2020

In 2016 NOAA chose the FV3 (Finite Volume) dynamical core as a basis for its future global modeling system. For aerosol modeling this dynamical core was supplemented with GFS (Global Forecast System) physics and coupled through an interface with GOCART (Goddard Global Ozone Chemistry Aerosol Radiation and Transport) parameterization. The assimilation methodology relies on a hybrid variational-ensemble approach within the newly developed model-agnostic JEDI (Joint Effort for Data assimilation Integration) framework. Observations include 550 nm AOD retrievals from VIIRS (Visible Infrared Imaging Radiometer Suite) instruments on polar-orbiting  SNPP and NOAA-20 satellites. The system is under development and early its results are compared with NASA'a MERRA-2 and ECMWF's CAMSiRA reanalyses.  

 
Future trends in oxygen minimum zone volume are sensitive to model representation of iron
Authors: Yao Wanxuan , Kvale Karin , Landolfi Angela , Koeve Wolfgang , Achterberg Eric , Oschlies Andreas
Published: March 2020

Increasing the complexity of the representation of iron in an earth system model can lead to significant differences in surface ocean nutrient pathways in a pre-industrial climate. These differences persist even after automated calibration forces the models to achieve similar fit to the same observational data. We explore the impact of these nutrient pathway differences in the context of climate change by forcing the models (one without iron, one with a seasonally-cyclic iron mask, and one with a fully dynamic iron module) with the RCP8.5 business-as-usual atmospheric CO2 concentration scenario from years 1800 until 2100. We find that while the global oxygen inventory drops across all models over this period, different trends in the oxygen minimum zone (OMZ) volume arise. Models with iron represented simulate decreases between 60 and 80 percent in OMZ volume, while the model without iron simulates an OMZ volume increase of 10 percent. The difference is attributed to the role of iron limitation in regulating the low latitude primary production response to warming and stratification. We further quantify the corresponding denitrification trends and impact on ocean nitrate inventory. This study illustrates that model structural uncertainty further challenges predictions under a changing climate, and highlights the strong role of iron in regulating nutrient cycling and ocean deoxygenation.
Ambient noise field and temporal changes on ambient noise auto/cross-correlogram at the sea bottom inferred from ocean-bottom seismic and pressure arrays
Authors: Ito Yoshihiro , Uemura Miyuu , Webb Spahr C. , Mochizuki Kimihiro , Henrys Stuart
Published: March 2020

The interactions of wind with the ocean surface, ocean wave with acoustic wave, acoustic wave with seismic wave below the sea bottom, and the interplay among them drive important energy flows from the atmosphere to the lithosphere. Uncertainty remains regarding the origin of wind-related noise in the ocean and its coupling to seismic noise below the sea floor. Seismic interferometry is a powerful tool that uses microseisms, or ambient noise within solid earth, to monitor temporal seismic velocity change by referring to the auto/cross-correlation as a Green’s function at the sites, and its temporal change. The most important assumption when detecting seismic velocity changes with seismic interferometry is that mutually uncorrelated noise sources are distributed randomly in space and time without any temporal changes in their density and intensity in a fully diffuse wave field. An effect of temporal variation on the ambit noise field to the retrieval of Green’s function is, however, not fully understood, nor is how reliable temporal changes in interferogram noise are, especially when accompanied by large earthquakes and slow slip events. Here, we show relationships among the temporal changes of sea surface wave, acoustic wave, and seismic wave fields, which are observed in ocean bottom pressure gauges and seismometer arrays installed in New Zealand. The temporal variation in the power spectrum obtained from continuous ocean bottom seismometer and pressure records near 200 mHz correlates with the temporal variation in wind speed above the sites, particularly during wind turbulence of more than 5 m/s. The temporal fluctuation in the ocean bottom pressure caused by the ocean surface wave field correlates to that of a microseism near 200 mHz. The temporal variations in the power spectrum from both continuous ocean bottom pressures and microseisms in the 200–800 mHz range show a positive correlation. After calculating the auto/cross-correlation functions (ACF/CCF) from ambient noise in a 200–800 mHz pass band every 6 h, the temporal variation in the correlation between the ACF/CCFs is investigated every 6 h. The temporal variation in the ACF/CCFs correlates with the time derivative of the temporal changes in the power spectrum amplitude of both the bottom pressure and the microseism rather than the temporal changes in the amplitude of the power spectrum. This suggests that the temporal change that occurs in the seismic interferogram owing to ambient noise, is mostly controlled by the temporal change in the ocean wave field undergoing fluctuations by the atmospheric turbulence over the sea surface. The temporal variations in the noise field in space and time may break the assumption on seismic interferometry, and eventually make the apparent temporal change in interferogram noise.
Spatio-temporal variations on the vertical deformation rate of the NW Anatolian Block: Luminescence chronology of the Sakarya River terraces
Authors: Erturac M. Korhan , Şahiner Eren , Sağlam Selçuk Azad , Gürbüz Alper , Okur Hilal , Zabcı Cengiz , Meriç Niyazi , Özeren Sinan , Sunal Gürsel
Published: March 2020

The study area (40-40.45°N and 30-32.15° E) exhibits a high topography (1200-1800 m elevation) and bounded by the Galatean Massif at east, Pontide Mountain Range to the north, the Central Anatolian Plateau to the south and the Marmara Sea to the west. The region is actively been deformed and dissected by the active branches of the dextral strike slip North Anatolian Fault Zone (NAFZ) and the Sakarya River (SR) system. We have investigated the depositional terraces formed along the main course and the major tributaries of the SR to reveal the dynamics of the terrace formation by climate, sea level changes and also to quantify the variations in rate of vertical deformation within the current geodynamics of the NW Anatolian Block. The geometry of the main river (1) and its tributaries (4) allow us to determine the spatio-temporal variations in four vertical (100 km) and three along fault sections (200 km) since the last ~150 ka.

Up to date, we have mapped 23 distinct evenly scattered multi-step terrace staircases along the main river course and its 6 major tributaries. Mapping is aided with high precision rtk-GPS profiling and SfM photogrammetry using UAV. The dating is carried by luminescence geochronology (OSL and p-IRIR) to constrain the timing of the formation and also abandonment of each depositional terrace step.

The results show that the focus region is under control of vertical deformation at a rate of 0.6-0.7 mm/year regardless from the distance to the main strand of the NAFZ. There is also evidence that this rate has been decelerated from ~1.0-1.1 mm/year since the last 100 ka. The distinct variations in the calculated uplift rates along the profiles reveal apperant southwards tilting in between the active branches of the NAFZ and also within the block.

This study is funded by TUBITAK 117Y426 project grant. 
Sediment residence time variations in an Alpine river system inferred by uranium activity ratio.
Authors: Thollon Maude , Dosseto Anthony , Toucanne Samuel , Bayon Germain
Published: March 2020

The sediment residence time represents the time elapsed since the formation of the sediment in soils until its deposition. In order to better constrain timescales of sedimentary processes (erosion, transport, and deposition), it is important to understand to what extent sediment residence time is controlled by geomorphological parameters (e.g. elevation, curvature, slope). Uranium isotopes have been used to infer the time elapsed since the formation of fine detrital grains (<63 µm) by physical and chemical weathering (i.e. comminution age).

In this study, uranium isotopes were measured in fluvial sediments (<63 µm) sampled at different locations in a catchment (Var, France) to determine the variation of uranium activity ratio (234U/238U) along the river profile. The absence of fluvial plain implies that the sediment residence time mainly represents the storage time on hillslopes, as sediment transport is expected to be very rapid in this mountainous sedimentary system. 

The catchment was divided into 27 sub-catchments to investigate the variability of the geomorphological parameters that have been extracted from spatial analysis. Additionally, sediment residence time was estimated based on soil thickness prediction data combined with denudation rate information to compare this predicted residence time to the one calculated with (234U/238U).

The correlation between (234U/238U) and the estimated sediment residence time confirms that (234U/238U) can be modelled to infer sediment residence time. Furthermore, the correlations between the slope, the elevation and (234U/238U) highlight the geomorphological controls on the sediment residence time. The use of (234U/238U) in sedimentary archives will help to determine past geomorphological variations and re-construct past links between catchment erosion and climate change.
Complexity measures and variability of the seismicity monitored whithin the Mexican flat slab before the main shock occurred on 19 September 2017
Authors: Ramírez-Rojas Alejandro , Flores-Márquez Elsa Leticia
Published: March 2020

Several subduction zones exists in Earth, which have a more or less known dynamic, however each of them has its particularities, as in the case of the Mexican subduction zone, where the flat slab is of special interest. The present flat-slab area is located along the central part of the Cocos-North America plate boundary that the convergence rate between Cocos and North America. The Cocos plate is a remnant of the large Farallon plate, which began to split into smaller plates since 28 Myr ago approximately, when the East Pacific Rise began to interact with the North American Plate. Within such flat slab could be trigger large and destructives earthquakes like the main shock occurred close to Mexico City on September 19, 2017. In this work, we analyze, under the natural time domain, the seismicity registered within the Mexican flat slab since 1995 until the main shock occurred on September 19, 2017. We analyzed the fluctuations of order parameter for seismicity in order to provide some complex measures defined on natural time. Our analysis reveals a possible precursor measure switching on a few weeks before the main shock.  Also we have observed that in the flat slab region the number of earthquakes recorded is lesser than those observed along the total south Pacific Mexican coast.
Historical (1700-2012) global multi-model estimates of the fire emissions from the Fire Modeling Intercomparison Project (FireMIP)
Authors: Li Fang ,   FireMIP
Published: March 2020

Fire emissions are a critical component of carbon and nutrient cycles and strongly affect climate and air quality. Dynamic global vegetation models (DGVMs) with interactive fire modeling provide important estimates for long-term and large-scale changes in fire emissions. Here we present the first multi-model estimates of global gridded historical fire emissions for 1700-2012, including carbon and 33 species of trace gases and aerosols. The dataset is based on simulations of nine DGVMs with different state-of-the-art global fire models that participated in the Fire Modeling Intercomparison Project (FireMIP), using the same and standardized protocols and forcing data, and the most up-to-date fire emission factor table based on field and laboratory studies in various land cover types. We evaluate the simulations of present-day fire emissions by comparing them with satellite-based products. The evaluation results show that most DGVMs simulate present-day global fire emission totals within the range of satellite-based products. They can capture the high emissions over the tropical savannas and low emissions over the arid and sparsely vegetated regions, and the main features of seasonality. However, most models fail to simulate the interannual variability, partly due to a lack of modeling peat fires and tropical deforestation fires. Before the 1850s, all models show only a weak trend in global fire emissions, which is consistent with the multi-source merged historical reconstructions used as input data for CMIP6. On the other hand, the trends are quite different among DGVMs for the 20th century, with some models showing an increase and others a decrease in fire emissions, mainly as a result of the discrepancy in their simulated responses to human population density change and land use and land cover change (LULCC). Our study provides an important dataset for further development of regional and global multi-source merged historical reconstructions, analyses of the historical changes in fire emissions and their uncertainties, and quantification of the role of fire emissions in the Earth system. It also highlights the importance of accurately modeling the responses of fire emissions to LULCC and population density change in reducing uncertainties in historical reconstructions of fire emissions and providing more reliable future projections.
Simulating the Reiner Gamma Swirl and Magnetic Anomaly: The Impact of the Solar Wind Alpha Population
Authors: Deca Jan , Hemingway Douglas J. , Divin Andrey , Lue Charles , Poppe Andrew R. , Garrick-Bethell Ian , Lembège Bertrand , Horányi Mihály
Published: March 2020

The Reiner Gamma swirl is one of the most prominent albedo features on the lunar surface. Its modest spatial scales and structure allows fully kinetic modelling. The region therefore presents a prime location to investigate the lunar albedo patterns and their co-location with magnetic anomalies. The precise relationship between the impinging plasma and the swirl, and in particular, how these interactions vary over the course of a lunar day, remains an open issue.

Here we use the fully kinetic particle-in-cell code,  iPIC3D, coupled with a magnetic field model based on Kaguya and Lunar Prospector observations, and simulate the interaction with the Reiner Gamma anomaly for all plasma regimes the region is exposed to along a typical orbit, including different solar wind incidence angles and the Moon's crossing through the terrestrial magnetosphere. We focus on the impact of the solar wind alpha population and construct energy and velocity distributions in key locations surrounding the interaction region of the anomaly.

The energy flux profile provides a better match to the albedo pattern only when integrating over the full lunar orbit. Including He2+ as a self-consistent plasma species improves the brightness ratios between the inner and outer bright lobes, the dark lanes, and the mare background. However, substantial differences between the observed albedo pattern and the predicted flux remain.  For example, the bright outer lobes are substantially brighter than predicted and the central portion of the anomaly is darker than predicted. This is likely due to an incomplete model of the near-surface field structure.

Solar wind standoff can explain the large-scale correlation between the Reiner Gamma swirl and the co-located magnetic anomaly. In particular, the outer bright lobes emerge in the simulated weathering pattern only when integrating over the entire lunar orbit, although they are much weaker than observed. Both the proton and helium energy flux to the surface need to be taken into account to best reproduce the swirl pattern. A complete understanding of the solar wind interaction with lunar magnetic anomalies and swirl formation could be vastly improved by low altitude measurements of the magnetic field and solar wind.
Drought Patterns over the Amazon River Basin (1993-2019) as Interpreted by the Climate-driven Total Water Storage Change Fields
Authors: Li Fupeng , Wang Zhengtao , Chao Nengfang , Liang Wei , Tian Kunjun , Gao Yu
Published: March 2020

The Gravity Recovery and Climate Experiment (GRACE) mission, since 2002, has measured total water storage change (TWSC) and interpreted drought patterns in an unparalleled way. Nevertheless, there are still few sources could be used to understand drought patterns prior to the GRACE era. Here we derived multi-decadal climate-driven TWSC grids and used them to interpret drought patterns (1993-2019) over the Amazon basin. The correlations of climate-driven TWSC as compared to GRACE, GRACE Follow-on, and Swarm TWSC are 0.95, 0.92, and 0.77 in Amazon at grid scale (0.5° resolution). The drought patterns assessed by the climate-driven TWSC are consistent to those interpreted by the Palmer Drought Severity Index and GRACE TWSC. We also found that the 1998 and 2016 drought events in Amazon, both induced by the strong El Niño events, show similar drought patterns. This study provides a new perspective for interpreting long-term drought patterns prior to the GRACE period.
A Feasibility Investigation for Developing Artificial Beachrocks: A Potential Measure for Coastal Protection in Southeast Yogyakarta Coast, Indonesia
Authors: Daryono Lutfian Rusdi , Nakashima Kazunori , Kawasaki Satoru , Suzuki Koichi , Titisari Anastasia Dewi , Barianto Didit Hadi , Suyanto Imam , Rahmadi Arief
Published: March 2020

Erosion prone sandy beaches are frequently covered by cement and mortar to preserve the coastal zone, but the conventional approach has an adverse impact on the environment, altering the coastal landscape and processes unfavorably. The term “beachrock” refers to cemented coastal sediments through a long-term formation of CaCO3 cement, and which is an important feature in many tropical coastlines as it appears to have a substantial anchoring effect against wave effects and erodibility. Therefore, the objective of this study is to evaluate the feasibility in progressing the formation of artificial beachrocks using natural materials (e.g., microbes, sand, shell, pieces of coral, and seaweed etc.) within a short-term, and to introduce the method as a novel candidate for coastal protection. In this study, both resistivity survey and multi analysis seismic wave (MASW) survey along the same lines were performed at first to elucidate the subsurface structure of existing beachrocks in the Southeast Yogyakarta coastal area (Indonesia), followed by the laboratory analysis, which is aimed understand the basics in the formation mechanism. Peloidal micrite cement, the cement comprised of aragonite needles, micritized granules and the cover of micritic were observed in natural beachrocks. Mimicking the mechanism, an attempt has been undertaken to develop artificial beachrocks in the laboratory via microbial induced carbonate precipitation (MICP). Finally, the physical and mechanical properties were well compared between the artificially formed beachrocks and natural beachrocks collected from the survey lines. The results suggest that the artificial deposits treated for 14 days under optimum conditions, achieved a peak unconfined compressive strength of around 6 MPa similar to that of weak-consolidated natural beachrock. The comparison further reveals that the variables such as porosity, Vp, Vs, and strength are primarily rely on the precipitated morphology of the crystals.
Probability and deterministic amount of precipitation on the multi-model ensemble
Authors: Kim Juwon , Kong Hae-Jin , Shin Hyuncheol
Published: March 2020

Multi-model ensemble using statistical post-processing is one of the methods to provide the impact of uncertainties of the Numerical Weather Prediction (NWP) models, with low cost and better accuracy for extreme weather forecasts. Extreme weather events such as heat/cold waves, windstorms, and heavy rainfall result in severe damage in human life and properties. However, the performance of the NWP models, particularly, heavy rain forecast is still low due to the intermittent and non-Gaussian properties. The light rain tends to be overestimated and the strong rain tends to be underestimated averagely on the NWP models. Thus the multi-model ensemble using statistical post-processing is activated to correct the discrepancies between the observation and the model intensity of precipitation.
The aim of this study is to provide the improvement of precipitation forecasts in probabilistic and deterministic aspects using a multi-model ensemble method with more weights on the less error and without any bias correction. Six types of models, namely, Local Data assimilation and Prediction System (LDPS), Local ENsemble System (LENS), Global Data assimilation and Prediction System (GDPS), Ensemble Prediction System-Global (EPSG) of Korea Meteorological Administration (KMA), the single and ensemble models of European Centre for Medium-Range Weather Forecasts (ECMWF), are used to blend. The preliminary results of the multi-model ensemble show similar results to the ECMWF ensemble mean in deterministic for 3-hourly accumulated precipitation over the East Asia and the middle of the performance among individual models in probabilistic over the South Korea. More details of the methodology, results, and improvements will be discussed in the presentation.
Regional modelling of aerosol interaction with deep convection and the effect on new particle formation over Amazonia
Authors: Wang Xuemei , Grosvenor Daniel , Gordon Hamish , Andreae Meinrat O. , Carslaw Ken
Published: March 2020

It has been estimated that over 50% of the present-day global low-level cloud condensation nuclei (CCN) are formed from new particle formation (NPF), and that this process has a substantial effect on the radiative properties of shallow clouds (Gordon et al. 2017). In contrast, we have a very limited understanding of how NPF affects deep convective clouds. Deep clouds could interact strongly with NPF because they extend into the high free troposphere where most new particles are formed, and they are responsible for most of the vertical transport of the nucleating vapours. Andreae et al. (2018) hypothesised from ACRIDICON-CHUVA campaign that organic gas molecules are transported by deep convection to the upper troposphere where they are oxidised and produce new particles, which are then be entrained into the boundary layer and grow to CCN-relevent sizes.

Here we study the interaction of deep convection and NPF using the United Kingdom Chemistry and Aerosols (UKCA) model coupled with the Cloud-AeroSol Interacting Microphyics (CASIM) embedded in the regional configuration of UK Met Office Hadley Centre Global Environment Model (HadGEM3). We simulate several days over a 1000 km region of the Amazon at 4 km resolution. We then compare the regional model, which resolves cloud up- and downdrafts, with the global model with parameterised convection and low resolution.

Our simulations highlight three findings. Firstly, solely using a binary H2SO4-H2O nucleation mechanism strongly underestimates total aerosol concentrations compared to observations by a factor of 1.5-8 below 3 km over the Amazon. This points to the potential role of an additional nucleation mechanism, most likely involving biogenic compounds that occurs throughout more of the free troposphere. Secondly, deep convection transports insoluble gases such as DMS and monoterpenes vertically but not SO2 or H2SO4. The time scale for DMS oxidation (~ 1 day) is much longer than for monoterpene (1-2 hours), which points to the importance of simulating biogenic nucleation over the Amazon in a cloud-resolving model, while lower-resolution global models may adequately capture DMS effects on H2SO4 nucleation. Finally, we also examine the Andreae et al (2018) hypothesis of aerosol supply to the boundary layer by quantifying cloud-free and cloudy up- and downdraft transport. The transport of newly formed aerosols into the boundary layer is 8 times greater in cloud-free regions than in the clouds, but these transport processes are of similar magnitude for large aerosols.
A Rarely Witnessed Summertime Upwelling Event northwest off the Hainan Island
Authors: Pan Ai-Jun , Kuang Fang-fang , Li Kai , Dong Xu
Published: March 2020

A field survey revealed a rare realization of upwelling event in the northwestern Hainan Island (UNWHI) on July 24, 2015. Model experiments suggest that the UNWHI is not locally generated, but can be treated as northward extension of the upwelling southwest off Hainan Island (USWHI) under favorable wind conditions. Therefore, presence of the USWHI is vital for the UNWHI occurrence. Tidal mixing is testified to be the primary driving force for the USWHI, whilst southerly winds plays an essential role in the induction of the UNWHI. Moreover, it is demonstrated that the UNWHI is not a stable, but intermittent coastal upwelling system. Shallow basin of the Beibu Gulf makes the interior circulation vulnerable to local monsoon changes. Given the favorable southerly winds, a cyclonic gyre northwest off Hainan Island will be induced and which, leads to northward coastal current and consequently, the UNWHI is to be formed due to the northward transport of the USWHI. Conversely, the UNWHI vanishes during northerly winds period, because the basin-scale anticyclonic gyre results in a southward current west off the Hainan Island and which, acts to push the upwelled water of the USWHI offshore and away from the northwestern Hainan Island. In addition, our diagnostics indicates that contributions from surface heat fluxes to the UNWHI occurrence is negligible. Besides, it also reminds us that application of a high-frequency, much closer to reality wind field is necessary for the coastal upwelling simulation. 
Analysis on the damage, vulnerability and correlation with temperature caused by heat waves in Jeju province(Korea), and Heatwave Impact Based Forecast and Warning Service(HIBFWS)
Authors: Kim Sanghyun
Published: March 2020

In Korea, severe heat waves are frequent in summer, and the number of people who affected by them increases year by year. This study analyzes the correlation between excess mortality and the daily maximum temperature(Tmax) in August for the last decade(2009-2018). In addition, it analyzes Tmax when the patients by heat illness occur. The analysis shows a positive correlation(R=0.524, P=0.02) between the number of excess mortality and Tmax. In terms of patients by heat waves, the patients occur variously from 26℃ to 39℃, and the maximum number of patients appears in 34~35℃. In case of the duration of Tmax ≥ 33℃, the number of patients shows a peak at entrance of the period, and it drops after the 4th day and no patients showing after the 9th day. But, in case of Tmax < 33℃, the heat illness in the 4th day occurs more than any other days, and it decreases slowly. In addition, it seems that it is not enough for the public to recognize accurately and respond risks appropriately with current temperature forecasts, so the Korea Meteorological Administration provides HIBFWS which includes countermeasures along with regional risk levels for the heatwave. Also, it analyzes socio-economic-environmental vulnerability for production of the information in Jeju province.
ISMIP6 Antarctica: a multi-model ensemble of the Antarctic ice sheet evolution over the 21st century
Authors: Seroussi Helene , Goelzer Heiko , Morlighem Mathieu ,   ISMIP6 Team
Published: March 2020

Ice flow models of the Antarctic ice sheet are commonly used to simulate its future evolution in response to differ- ent climate scenarios and inform on the mass loss that would contribute to future sea level rise. However, there is currently no consensus on estimated the future mass balance of the ice sheet, primarily because of differences in the representation of physical processes and the forcings employed. This study presents results from 18 simulations from 15 international groups focusing on the evolution of the Antarctic ice sheet during the period 2015-2100, forced with different scenarios from the Coupled Model Intercomparison Project Phase 5 (CMIP5) representative of the spread in climate model results. The contribution of the Antarctic ice sheet in response to increased warming during this period varies between -7.8 and 30.0 cm of Sea Level Equivalent (SLE). The evolution of the West Antarctic Ice Sheet varies widely among models, with an overall mass loss up to 21.0 cm SLE in response to changes in oceanic conditions. East Antarctica mass change varies between -6.5 and 16.5 cm SLE, with a significant increase in surface mass balance outweighing the increased ice discharge under most RCP 8.5 scenario forcings. The inclusion of ice shelf collapse, here assumed to be caused by large amounts of liquid water ponding at the surface of ice shelves, yields an additional mass loss of 8 mm compared to simulations without ice shelf collapse. The largest sources of uncertainty come from the ocean-induced melt rates, the calibration of these melt rates based on oceanic conditions taken outside of ice shelf cavities and the ice sheet dynamic response to these oceanic changes. Results under RCP 2.6 scenario based on two CMIP5 AOGCMs show an overall mass loss of 10 mm SLE compared to simulations done under present-day conditions, with limited mass gain in East Antarctica.
Could the cloud cover in future climate models be improved by incorporating the role of sea spray in surface heat fluxes?
Authors: Song Yajuan , Qiao Fangli , Shu Qi , Liu Jiping , Bao Ying , Wei Meng , Zhao Biao , Song Zhenya
Published: March 2020

Accurate cloud cover and radiative effect simulation remains a long-standing challenge for global climate models (GCMs). The Southern Ocean (SO) cloud cover is substantially underestimated by most GCMs. Therefore, too much shortwave radiation is absorbed by oceans, which causes an overly warm sea surface temperature (SST) bias over the SO. For the first time, sea spray effects on latent and sensible heat fluxes are considered in a climate model. The most notable sea spray impacts on heat fluxes occur over the SO, with anomalous latent heat fluxes up to -7.74 W m-2. Enhanced latent heat release lead to SST cooling. In addition, more clouds are formed over the SO to reflect excessive downward shortwave radiation, especially low-level clouds at 1.51% increments. Our results provide a feasible solution to mitigate the lack of low-level clouds and overly warm SST biases over the SO in GCMs.
Mapping Local Climate Zone in China’s Major Cities
Authors: Ma Qian , Wang Yongwei , Miao Shiguang
Published: March 2020

Progress in urban climate science is severely hindered by the lacuna of globally consistent and coherent information that describes aspects of the form and function of urban morphology at a detailed spatial resolution. The World Urban Database and Access Portal Tools (WUDAPT) project is proposed to solve the above problems, which has adopted the Local Climate Zone (LCZ) scheme as a basic and consistent description of form and function of cities at neighborhood scale. This study aims to develop a LCZ classification map and establish the urban morphology database for climate research and urban planning in China’s major cities. A simple workflow provided by WUDAPT project has been applied to perform this task.

The results from the quality assessments show that the LCZ maps of 63 cities in China are generally of good quality, i.e. 69–92% overall accuracy (OA). In particular, the acceptable accuracy (77-93%) is much higher when considering weights that take the morphological and climatic similarity of certain classes into account. The building height data from surveying of these cities, including of Beijing, shanghai, Changsha, Chongqing, Fuzhou, Qingdao, Lanzhou, Harbin and Lhasa，were used for testing, and a moderate accuracy (at building height) was of 51-68%. Most of buildings heights of LCZ types are in line with the surveying data, except for Compact high-rise (LCZ 1) and Open high-rise (LCZ 4), which is about 20.5±4.7 m, and has slightly lower than the LCZ standard value (>25 m). This is due to insufficient underlying input information on building height, and a general tendency to confuse these two classes with Compact mid-rise (LCZ 2) and Open mid-rise (LCZ 5).

Construction area is a very important type of underlying surface in developing countries like China. For example, in Beijing, Guangzhou and Chongqing, this type accounts for 21%, 9% and 9%, mainly distributed in suburban areas. This is an important urban underlying surface in China, but this underlying surface type has not been defined by Stewart and Oke. A follow-up study will try to define the underlying surface of construction area in LCZ classification system.
Evolution of Organized Shallow Convection
Authors: Schulz Hauke , Eastman Ryan , Stevens Bjorn
Published: March 2020

Uncertainty in the response of clouds to warming is the leading source of uncertainty in projections of future warming. To a large fraction the frequently occurring shallow cumulus clouds in the trade wind region contribute to this uncertainty. In symbiosis with thin clouds of stratiform extent they often create various cloud patterns.

We introduce a neural network that is able to detect the mesoscale organization from GOES16 and MODIS satellite imagery in order to put eight years of ground-based measurements of the Barbados Cloud Observatory into the context of mesoscale organization. With this combination of long-term ground-based measurements from the trade-wind region and satellite image classifications, we overcome the common resolution limitations of satellite derived cloud products of shallow cumuli and are able to present the characteristics of shallow convection depending on the mesoscale organization with great detail.

By using back-trajectories and EUREC4A field campaign data, we show that differences in the atmospheric environment are not only present at the time of pronounced mesoscale organization, but are already distinguishable days ahead in LTS, wind speed and SST.
Applying the ICA method to extract the potential signals in GNSS timeseries
Authors: Tan Weijie , Chen Junping , Qu Weijing
Published: March 2020

Spatial filtering is an effective way to identify and reduce the so-called common mode error (CME) from the regional GPS networks measurements, which could improve GPS positioning accuracy and precision for detection of subtle crustal deformation signals. In this work, we decompose GPS coordinate time series into a set of temporally varying modes with the widely used principal component analysis (PCA) on minizine the misfit calculated using a L2 norm(x2). The results show that the decomposed components from PCA are not statically independent to each other. It is difficult to reveal the original geophysical mechanisms for the related signals only on the PCA results. To work around the problems, we reanalysis the output from PCA to recovery and separate the original signals from mixed observations with the independent component analysis (ICA). Here, we firstly apply the PCA methods on the GPS position time series in Sichuan_Yunnan region of China to evaluate the ability in discerning and charactering different source of crust deformation in the space and time domains. Using the PCA decomposed first 6 PCs, we find that the spatially and temporally correlated CME can be decomposed into two independent components by ICA, the second IC shows obvious variations in the beginning of each year, the same characters are also seen in the atmosphere press variations. Then we compare the two timeseries and demonstrated that atmosphere high frequency pressure mass loading is one of the main contributors to the CME.
The impact of vertical resolution on tropical cyclone simulation
Authors: Huang Wei , Liu Mengjuan , Zhang Xu , Bao Jian-wen
Published: March 2020

It is well known that horizontal resolution has a great deal of impact on tropical cyclone simulations using numerical weather prediction models.  It is relatively less discussed in the literature how vertical resolution affects the solution convergence of tropical cyclone simulations.  In this study, the resolved kinetic energy spectrum, the Richardson number probability density function and resolved flow features are used as metrics to examine the behavior of solution convergence in tropical cyclone simulations using the Weather and Forecast Model (WRF).  It is found that for convective-scale simulations of a real tropical cyclone case with 3-km horizontal resolution, the model solution does not converge until a vertically stretched vertical resolution approaches 200 layers or more.  The results from this study confirm the results from a few previous studies that the subgrid turbulent mixing, particularly, the vertical mixing, plays a significant role in the behavior of model solution convergence with respect to vertical resolution.  They also provide a basis for the vertical grid configuration selection for the operational tropical cyclone model of Shanghai Meteorological Service.
Secondary Organic Aerosol Formation of Ambient Intermediate Volatility Organic Compounds: Implication from Gasoline Vehicles
Authors: Tang Rongzhi , Lu Quanyang , Zhu Wenfei , Song Kai , Fan Hanyun , Tan Rui , Liu Kefan , Yu Ying , Shen Ruizhe , Wang Hui , Chen Shiyi , Robinson Allen L. , Guo Song
Published: March 2020

Intermediate volatility organic compounds (IVOCs) have been proposed to be great contributors to SOA formation. In this study, we performed comprehensive measurement of ambient IVOCs and calculated their SOA production at an urban site Peking University Urban Atmospheric Environment Monitoring Stations (PKUERS). Results showed that the campaign-average concentration IVOCs was 62.5 ± 45.2 μg·m-3 (average ± standard deviation), which is comparable to the emission of VOCs. Only ~10% of the IVOCs could be speciated, with most of the IVOCs existing as unresolved complex mixture (UCM). Back trajectory analysis showed that clusters from near south has the highest IVOC concentration, suggesting the importance to control the IVOC emissions from the polluted regions of China. Using the OH exposure estimated by o-xylene to benzene and m/p-xylene to benzene, the estimated daily average SOA concentration was 5.8 ±3.4 μg·m-3, in which IVOCs contributed 15 times that of single-ring aromatics. The estimated vehicular-SOA could be 1.04 ± 0.7 μg·m-3. Considering its high SOA formation potential, this study highlights the importance to study the IVOC emissions in China.
Observing Interplanetary Scintillation with Dual-Antenna Interference
Authors: Liu Donghao
Published: March 2020

It is an important method to study solar wind speed through observation of Interplanetary Scintillation (IPS). There are two big antenna with multi- frequency channels simultaneous observing interplanetary scintillation in Miyun Observatories NAOC. The aperture of the antenna is 40 meters and 50 meters respectively. There are two dual-frequency channels available in these systems: 327/611 MHz and 2300/8400 MHz. We will carriy out a comparison of these method using the normalized cross-spectrum and dual- frequency IPS measurement to observing the solar wind speed. Dual-Antenna Interference system have better sensitivity and time resolution. It can observe more weak radio sources one by one around the Sun. We can obtain more solar wind information on the Solar-Terrestrial distribution. 
Impact of large-scale future floods on the railway system
Authors: Wang Weiping , Yang Saini , Sun Huijun , Wu Jianjun , Gao Jianxi
Published: March 2020

Increasing flood risk was caused by expanding climate change. The floods directly or indirectly disrupt the railway system and arise a significant negative impact on our social-economic system. This study developed an integrated approach to explore the impact of large-scale future floods on railway system. Firstly, A three layered traffic flow simulation model was constructed to study propagation and amplification effects of component failure after the event of flooding in the system. Secondly, future runoff scenarios were produced by using five global climate models and three different representative concentration pathways. The future floods was simulated by using CaMa-Flood model after inputting future runoff scenarios. Furthermore, we imposing simulated future floods into traffic simulation system and develop two measurements to evaluate the impact of floods on the railway system as the perspective of the entire system. Here we explore the impact of floods on the real-world highway network of China. The results illustrate that: (i) Unprecedented uncertainty. The damage of the flood to the railway system is not linearly and positively correlated with representative concentration pathway and the year within different global climate models; Floods in different years have different impacts in connections among regions; (ii) Unacceptable damage. 59.76 % of railway segments inundated and 98.61461% of large cities could not be reached by extreme floods. These results have critical policy implications for the transport sector in reference to railway location and design, railway network optimization and protection and can be also easily adapted to analyze other spatial damages for valuable protection suggestions.
Remote Sources of Surface Temperature Cold Bias over the Tibetan Plateau: Role of Tropical SST Climatological Bias
Authors: Wu Yuting , Hu Xiaoming , Wang Ziqian , Li Zhenning , Yang Song
Published: March 2020

The surface temperature cold bias over the Tibetan Plateau (TP) is a long-lasting problem in both reanalysis data and climate models. While previous studies have mainly focused on local processes for this bias, the TP surface temperature is also closely related to tropical SST in both observations and Coupled Model Inter-comparison Project (CMIP5) models. This study investigates the role of tropical SST climatological bias in the TP surface temperature cold bias, and analysis of CMIP5 models suggests that the surface temperature cold bias over the TP is more obvious (about 4 K) in winter, with an east-west distribution pattern, than in summer (about 1 K), with a south-north distribution pattern. Considering that the tropical SST bias in CMIP5 models may be an important source of the TP surface temperature cold bias, a series of model experiments were conducted by the NCAR CAM4 to test the hypothesis. Model experiment results show that the tropical SST bias can reproduce cold bias over the TP, with 2 K in winter and about 0.5 K in summer. The mechanisms for TP surface temperature cold bias are different in winter and summer. In winter, tropical SST bias influences the TP surface temperature mainly by anomalous snow cover, while anomalous precipitation and clouds are more important for the temperature bias in summer.
Layered anisotropy beneath the Japan Sea and NE China from inversion of surface wave dispersion using rj-MCMC method
Authors: Zhao Yanzhe , Guo Zhen , Fan Xingli , Wang Yanbin
Published: March 2020

The surface wave dispersion data with azimuthal anisotropy can be used to invert for the wavespeed azimuthal anisotropy, which provides essential dynamic information about depth-varying deformation of the Earth’s interior. In this study, we adopt an rj-MCMC (reversible jump Markov Chain Monte Carlo) technique to invert for crustal and upper mantle shear velocity and azimuthal anisotropy beneath the Japan Sea using Rayleigh wave azimuthally anisotropic phase velocity measurements from Fan et al. (2019). The rj-MCMC implements trans-dimensional sampling in the whole model space and derives the distribution for each model parameter (shear wave velocity and anisotropy parameters) directly from data. Without the prejudiced parameterization for model, the result can be more credible, from which some more reliable estimates for shear wave velocity and azimuthal anisotropy as well as their uncertainties can be acquired. Our preliminary results, together with shear wave splitting observations, show a layered anisotropy beneath the Japan Sea and NE China, suggesting the complicated mantle flow that is controlled by the subduction of the Pacific plate and the large-scale upwelling beneath the Changbaishan volcano.
China’s emission control strategies have suppressed unfavorable influences of climate on wintertime PM2.5 concentrations in Beijing since 2002
Authors: Gao Meng , Lin Kaili , Zhang Shiqing , Yung Ken kin lam
Published: March 2020

Severe wintertime PM2.5 pollution in Beijing has been receiving increasing worldwide attention, yet the decadal variations remain relatively unexplored. Combining field measurements and model simulations, we quantified the relative influences of anthropogenic emissions and meteorological conditions on PM2.5 concentrations in Beijing overwinters of 2002-2016. Between the winters of 2011 and 2016, stringent emission control measures resulted in a 21% decrease in mean mass concentrations of PM2.5 in Beijing, with 7 fewer haze days per winter on average. Given the overestimation of PM2.5 by model, the effectiveness of stringent emission control measures might have been slightly overstated. With fixed emissions, meteorological conditions over the study period would have led to an increase of haze in Beijing, but the strict emission control measures have suppressed the unfavorable influences of recent climate. The unfavorable meteorological conditions are attributed to the weakening of the East Asia Winter Monsoon associated particularly with an increase in pressure associated with the Aleutian low.