Interloper bias in future large-scale structure surveys

Next-generation spectroscopic surveys will map the large-scale structure of the observable universe, using emission line galaxies as tracers. While each survey will map the sky with a specific emission line, interloping emission lines can masquerade as the survey's intended emission line at different redshifts. Interloping lines from galaxies that are not removed can contaminate the power spectrum measurement, mixing correlations from various redshifts and diluting the true signal. We assess the potential for power spectrum contamination, finding that an interloper fraction worse than 0.2% could bias power spectrum measurements for future surveys by more than 10% of statistical errors, while also biasing power spectrum inferences. We also construct a formalism for predicting cosmological parameter bias, demonstrating that a 0.15%-0.3% interloper fraction could bias the growth rate by more than 10% of the error, which can affect constraints on gravity upcoming surveys. We use the COSMOS Mock Catalog (CMC), with the emission lines re-scaled to better reproduce recent data, to predict potential interloper fractions for the Prime Focus Spectrograph (PFS) and the Wide-Field InfraRed Survey Telescope (WFIRST). We find that secondary line identification, or confirming galaxy redshifts by finding correlated emission lines, can remove interlopers for PFS. For WFIRST, we use the CMC to predict that the 0.2% target can be reached for the WFIRST H$\alpha$ survey, but sensitive optical and near-infrared photometry will be required. For the WFIRST [OIII] survey, the predicted interloper fractions reach several percent and their effects will have to be estimated and removed statistically (e.g. with deep training samples). (Abridged)Comment: Matches version accepted by PAS

Search for CII Emission on Cosmological Scales at Redshift Z~2.6

We present a search for CII emission over cosmological scales at high-redshifts. The CII line is a prime candidate to be a tracer of star formation over large-scale structure since it is one of the brightest emission lines from galaxies. Redshifted CII emission appears in the submillimeter regime, meaning it could potentially be present in the higher frequency intensity data from the Planck satellite used to measure the cosmic infrared background (CIB). We search for CII emission over redshifts z=2-3.2 in the Planck 545 GHz intensity map by cross-correlating the 3 highest frequency Planck maps with spectroscopic quasars and CMASS galaxies from the Sloan Digital Sky Survey III (SDSS-III), which we then use to jointly fit for CII intensity, CIB parameters, and thermal Sunyaev-Zeldovich (SZ) emission. We report a measurement of an anomalous emission $\mathrm{I_\nu}=6.6^{+5.0}_{-4.8}\times10^4$ Jy/sr at 95% confidence, which could be explained by CII emission, favoring collisional excitation models of CII emission that tend to be more optimistic than models based on CII luminosity scaling relations from local measurements; however, a comparison of Bayesian information criteria reveal that this model and the CIB & SZ only model are equally plausible. Thus, more sensitive measurements will be needed to confirm the existence of large-scale CII emission at high redshifts. Finally, we forecast that intensity maps from Planck cross-correlated with quasars from the Dark Energy Spectroscopic Instrument (DESI) would increase our sensitivity to CII emission by a factor of 5, while the proposed Primordial Inflation Explorer (PIXIE) could increase the sensitivity further.Comment: 15 pages, 11 figures, published in MNRA

Spatial and chemical patterns of PM2.5 - differences between a maritime and an inland country

The Fine Resolution Atmospheric Multi-pollutant Exchange model was used to calculate the mean annual concentration of PM2.5 at a resolution of 5 km × 5 km for the United Kingdom (UK) and Poland for the year 2007. The modelled average PM2.5 concentration is higher for Poland than the UK and amounts to 9.2 µg · m−3 and 5.6 µg · m−3, respectively. The highest concentrations concern London and coastal areas (due to the sea salt contribution) for the UK and urban agglomerations in the case of Poland. Maximum values occurring close to the UK coastline can reach 18 µg · m−3. The average contribution of natural particles amounts to 34 and 20% of total PM2.5 concentration, respectively for the UK and Poland. Among anthropogenic particles for both countries the highest contribution falls on secondary inorganic aerosols and the lowest contribution is for secondary organic aerosols

Human excreta as a stable and important source of atmospheric ammonia in the megacity of Shanghai

Although human excreta as a NH3 source has been recognized globally, this source has never been quantitatively determined in cities, hampering efforts to fully assess the causes of urban air pollution. In the present study, the exhausts of 15 ceiling ducts from collecting septic tanks in 13 buildings with 6 function types were selected to quantify NH3 emission rates in the megacity of Shanghai. As a comparison, the ambient NH3 concentrations across Shanghai were also measured at 13 atmospheric monitoring sites. The concentrations of NH3 in the ceiling ducts (2809 μg m-3) outweigh those of the open air (~10 μg m-3) by 2–3 orders of magnitude, and there is no significant difference between different seasons. δ15N values of NH3 emitted from two ceiling ducts are also seasonally consistent, suggesting that human excreta may be a stable source of NH3 in urban areas. The NH3 concentration levels were variable and dependent on the different building types and the level of human activity. NH3 emission rates of the six residential buildings (RBNH3) were in agreement with each other. Taking occupation time into account, we confined the range of the average NH3 emission factor for human excreta to be 2–4 times (with the best estimate of 3 times) of the averaged RBNH3 of 66.0±58.9 g NH3 capita-1 yr-1. With this emission factor, the population of ~21 million people living in the urban areas of Shanghai annually emitted approximately 1386 Mg NH3, which corresponds to over 11.4% of the total NH3 emissions in the Shanghai urban areas. The spatial distribution of NH3 emissions from human excreta based on population data was calculated for the city of Shanghai at a high-resolution (100×100 m). Our results demonstrate that human excreta should be included in official ammonia emission inventories

Comparison of spatial rainfall data calculated with a meteorological model and from interpolation of measurements - implications for FRAME modelled wet deposition

This work quantifies the differences between the two sources of spatial information of precipitation on FRAME modelled wet deposition of oxidised sulphur (SOx), nitrogen (NOy) and reduced nitrogen (NHx) for two years in an area of Poland. The model was run twice, first with precipitation dataset calculated with the WRF model (pWRF). The second run was based on interpolation of measured precipitation with kriging (pOK). SOx, NOy and NHx wet deposition calculated with pWRF precipitation gives lower country mean values if compared with pOK. The maximum values are higher for pWRF precipitation. Grid to grid correlation between pOK and pWRF modelled wet deposition is similar for both years, with the lowest values for NHx and the highest for SOx. The model-measurement agreement is better for the pOK FRAME run. The results show large uncertainties related with wet deposition modelling due to uncertainties in rainfall data

Modelling the contribution of SO2 and NOx emissions from international shipping to sulphur and oxidised nitrogen deposition in the United Kingdom

A statistical Lagrangian atmospheric transport model was used to generate annual maps of deposition of sulphur and nitrogen for the United Kingdom at a 5 x 5 km2 resolution for the year 2005 and to assess the contribution attributed to emissions of SO2 and NOx from international shipping. A future emissions scenario for the year 2020 was used to investigate changes in the relative contribution of shipping emissions. The results show that, if shipping emissions are assumed to increase at a rate of 2.5% per year, their relative contribution to total sulphur and oxidised nitrogen deposition are expected to increase from 15% and 12% respectively to 37% and 28% between 2005 and 2020. Enforcement of the International Maritime Organisation (IMO) agreement to reduce the sulphur content in marine fuel to 0.5% was estimated to result in a 30% reduction in total sulphur deposition to the UK for the year 2020 compared to a business as usual scenario, with the result that the relative contribution from shipping to sulphur deposition in the UK would be reduced to 9% of the tota

Application of WRF-Chem to forecasting PM10 concentration over Poland

The meteorological and chemical transport model WRF-Chem was implemented to forecast PM10 concentrations over Poland. WRF-Chem version 3.5 was configured with three one-way nested domains using the GFS meteorological data and the TNO MACC II emissions. The 48 hour forecasts were run for each day of the winter and summer period of 2014 and there is only a small decrease in model performance for winter with respect to forecast lead time. The model in general captures the variability in observed PM10 concentrations for most of the stations. However, for some locations and specific episodes, the model performance is poor and the results cannot yet be used by official authorities. We argue that a higher resolution sector-based emission data will be helpful for this analysis in connection with a focus on planetary boundary layer processes in WRF-Chem and their impact on the initial distribution of emissions on both time and space

Atmospheric nitrogen deposition in the Yangtze River basin: spatial pattern and source attribution

The Yangtze River basin is one of the world's hotspots for nitrogen (N) deposition and likely plays an important role in China's riverine N output. Here we constructed a basin-scale total dissolved inorganic N (DIN) deposition (bulk plus dry) pattern based on published data at 100 observational sites between 2000 and 2014, and assessed the relative contributions of different reactive N (Nr) emission sectors to total DIN deposition using the GEOS-Chem model. Our results show a significant spatial variation in total DIN deposition across the Yangtze River basin (33.2 kg N ha−1 yr−1 on average), with the highest fluxes occurring mainly in the central basin (e.g., Sichuan, Hubei and Hunan provinces, and Chongqing municipality). This indicates that controlling N deposition should build on mitigation strategies according to local conditions, namely, implementation of stricter control of Nr emissions in N deposition hotspots but moderate control in the areas with low N deposition levels. Total DIN deposition in approximately 82% of the basin area exceeded the critical load of N deposition for semi-natural ecosystems along the basin. On the basin scale, the dominant source of DIN deposition is fertilizer use (40%) relative to livestock (11%), industry (13%), power plant (9%), transportation (9%), and others (18%, which is the sum of contributions from human waste, residential activities, soil, lighting and biomass burning), suggesting that reducing NH3 emissions from improper fertilizer (including chemical and organic fertilizer) application should be a priority in curbing N deposition. This, together with distinct spatial variations in emission sector contributions to total DIN deposition also suggest that, in addition to fertilizer, major emission sectors in different regions of the basin should be considered when developing synergistic control measures

The effect of emission inventory on modelling of seasonal exposure metrics of particulate matter and ozone with the WRF-Chem model for Poland

In Poland, high concentrations of particulate matter (with a diameter smaller than 2.5 or 10 μm) exceeding the WHO threshold values are often measured in winter, while ozone (O"sub"3"/sub") concentrations are high in spring. In winter high PM2.5 and PM10 concentrations are linked to high residential combustion and road transport. The main objective of this study was to assess performance of the Weather Research and Forecasting model with Chemistry (WRF-Chem) model in reproducing observations for a period of 2017–2018 covering various meteorological conditions. We compare modelled and observed exposure metrics for PM2.5, PM10 and O"sub"3"/sub" for two sets of the WRF-Chem model runs: with coarse and fine resolution emission inventory (European Monitoring and Evaluation Programme (EMEP) and Chief Inspectorate of Environmental Protection (CIEP), respectively). CIEP run reduces the negative bias of PM2.5 and PM10 and improves the model performance for number of days with exceedance of WHO (World Health Organization) threshold for PM2.5 and PM10 24-h mean concentration. High resolution emission inventory for primary aerosols helps to better distinguish polluted urban areas from non-urban ones. There are no large differences for the model performance for O"sub"3"/sub" and secondary inorganic aerosols, and high-resolution emission inventory does not improve the results in terms of 8-h rolling mean concentrations of ozone. Document type: Articl