There is high uncertainty in the direct radiative forcing of black carbon (BC), an aerosol that strongly absorbs solar radiation. The observation-constrained estimate, which is several times larger than the bottom-up estimate, is influenced by the spatial representativeness error due to the mesoscale inhomogeneity of the aerosol fields and the relatively low resolution of global chemistry-transport models. Here we evaluated the spatial representativeness error for two widely used observational networks (AErosol RObotic NETwork and Global Atmosphere Watch) by downscaling the geospatial grid in a global model of BC aerosol absorption optical depth to 0.1 degrees x0.1 degrees. Comparing the models at a spatial resolution of 2 degrees x2 degrees with BC aerosol absorption at AErosol RObotic NETwork sites (which are commonly located near emission hot spots) tends to cause a global spatial representativeness error of 30%, as a positive bias for the current top-down estimate of global BC direct radiative forcing. By contrast, the global spatial representativeness error will be 7% for the Global Atmosphere Watch network, because the sites are located in such a way that there are almost an equal number of sites with positive or negative representativeness error.

Bright high-redshift quasars (z > 6) hosting supermassive black holes (M-BH > 10(8)M circle dot) are expected to reside in massive host galaxies embedded within some of the earliest and most massive galaxy overdensities. We analyze 1.2 mm ALMA dust continuum maps of 35 bright quasars at 6 < z < 7 and search the primary beam for excess dust continuum emission from sources with L-IR greater than or similar to 10(12) L circle dot as evidence for early protoclusters. We compare the detection rates of continuum sources at >= 5 sigma significance in the fields surrounding the quasars (A(eff).= 4.3 arcmin(2)) with millimeter number counts in blank field surveys. We discover 15 mm sources in the fields excluding the quasars themselves, corresponding to an overdensity of delta(gal) = (N-gal -N-exp)/N-exp= -0.07 +/- 0.56, consistent with no detected overdensity of dusty galaxies within 140 physical kpc of the quasars. However, the apparent lack of continuum overdensity does not negate the hypothesis that quasars live in overdense environments, as evidenced by strong [C II] overdensities found on the same scales as similarly selected quasars. The small field of view of ALMA could miss a true overdensity if it exists on scales larger than 1 cMpc, if the quasar is not centered in the overdensity, or if quasar feedback plays a role close to the quasar, but it is most likely that the large line-of-sight volume probed by a continuum survey will wash out a true overdensity signal. We discuss the necessary factors in determining the bias with which dusty star-forming galaxies trace true dark matter overdensities in order to improve upon overdensity searches in the dust continuum.

We present a survey of the [C II] 158 mu m line and underlying far-infrared (FIR) dust continuum emission in a sample of 27 greater than or similar to 6 quasars using the Atacama Large Millimeter Array (ALMA) at similar to 1 '' resolution. The [C II] line was significantly detected (at > 5-sigma) in 23 sources (85%). We find typical line luminosities of L-[C (II]) = 10(9-10) L-circle dot, and an average line width of similar to 385 km s(-1). The [C II]-to-far-infrared luminosity ratios ([C II]/FIR) in our sources span one order of magnitude, highlighting a variety of conditions in the star-forming medium. Four quasar host galaxies are clearly resolved in their [C II] emission on a few kpc scales. Basic estimates of the dynamical masses of the host galaxies give masses between 2 x 10(10) and 2 x 10(11) M-circle dot, i.e., more than an order of magnitude below what is expected from local scaling relations, given the available limits on the masses of the central black holes (> 3 x 10(8) M-circle dot, assuming Eddington-limited accretion). In stacked ALMA [C II] spectra of individual sources in our sample, we find no evidence of a deviation from a single Gaussian profile. The quasar luminosity does not strongly correlate with either the [C II] luminosity or equivalent width. This survey (with typical on-source integration times of 8 minutes) showcases the unparalleled sensitivity of ALMA at millimeter wavelengths, and offers a unique reference sample for the study of the first massive galaxies in the universe.

We present Atacama Large Millimeter Array 1 mm observations of the rest-frame far-infrared (FIR) dust continuum in 27 quasars at redshifts 6.0 less than or similar to z < 6.7. We detect FIR emission at greater than or similar to 3 sigma in all quasar host galaxies with flux densities at similar to 1900 GHz in the rest-frame of 0.12 < S-rest,S- (1900) (GHz) < 5.9 mJy, with a median (mean) flux density of 0.88 mJy (1.59 mJy). The implied FIR luminosities range from L-FIR = (0.27-13) x 10(12) L-circle dot, with 74% of our quasar hosts having L-FIR > 10(12) L-circle dot The estimated dust masses are M-dust = 10(7)-10(9) M-circle dot. If the dust is heated only by star formation, then the star formation rates in the quasar host galaxies are between 50 and 2700 M-circle dot yr(-1). In the framework of the host galaxy-black hole coevolution model a correlation between ongoing black hole growth and star formation in the quasar host galaxy would be expected. However, combined with results from the literature to create a luminosity-limited quasar sample, we do not find a strong correlation between quasar UV luminosity (a proxy for ongoing black hole growth) and FIR luminosity (star formation in the host galaxy). The absence of such a correlation in our data does not necessarily rule out the coevolution model, and could be due to a variety of effects (including different timescales for black hole accretion and FIR emission).

We present Atacama Large Millimeter/submillimeter Array band 8 observations of the [O III] 88 mu m line and the underlying thermal infrared continuum emission in the z = 6.08 quasar CFHQS J2100-1715 and its dust-obscured starburst companion galaxy (projected distance: similar to 60 kpc). Each galaxy hosts dust-obscured star formation at rates >100 M-circle dot yr(-1), but only the quasar shows evidence for an accreting 10(9) M-circle dot black hole. Therefore we can compare the properties of the interstellar medium in distinct galactic environments in two physically associated objects, similar to 1 Gyr after the big bang. Bright [O III] 88 mu m emission from ionized gas is detected in both systems; the positions and linewidths are consistent with earlier [C II] measurements, indicating that both lines trace the same gravitational potential on galactic scales. The [O III] 88 mu m/far-infrared (FIR) luminosity ratios in both sources fall in the upper range observed in local luminous infrared galaxies of similar dust temperature, although the ratio of the quasar is smaller than in the companion. This suggests that gas ionization by the quasar (expected to lead to strong optical [0 III] 5008 angstrom emission) does not dominantly determine the quasar's FIR [O III] 88 mu m luminosity. Both the inferred number of photons needed for the creation of O++ and the typical line ratios can be accounted for without invoking extreme (top-heavy) stellar initial mass functions in the starbursts of both sources.

Precipitation is one of the most important factors determining the occurrence of extreme hydro-meteorological events and water resource availability. Precipitation in different grades has diverse ecological effects, and slight precipitation (SP, defined as 0.1-1.0 mm/day) is the minimal level among them. In this study, we investigated SP trends from 1961 to 2013, as well as the relationship between SP and advanced very high radiometric resolution (AVHRR) normalized difference vegetation index (NDVI) in China during growing season from 1981 to 2006. The distributions and trends of SP were analysed by calculating the daily precipitation data. The average annual slight precipitation amount (SPA) and the number of slight precipitation days (SPD), derived from 839 monitoring stations in China, show a decreasing trend over the last five decades, which is in agreement with total precipitation (TP) but in different rates. When the trend was analysed seasonally, SP in most stations decreases significantly in September-October-November (SON) and June-July-August (JJA), and the largest decrease is found in SON. About 49.5 and 68.7% of monitoring stations show a decreasing trend in SON, in both SPA and SPD, whereas the trend is less popular in March-April-May (MAM, SPA: 19.7%, SPD: 41.4%) and December-January-February (JJF, SPA: 25.6%, SPD: 43.1%). Moreover, our analysis indicates that the decrease of SP is mainly due to the decrease of SPD as the median amount of daily SP was unchanged over the past five decades (close to 0.3 mm/day). Based on 26-year (1981-2006) semi-monthly AVHRR NDVI data and the records of SP data, the relationship between AVHRR NDVI and SP was also investigated. In regions with lower (< 600 mm) TP, the correlation coefficients between NDVI and SP tend to be higher. These results highlight that SP has different effects than TP on vegetation growth. We also analysed time lag effects and concluded that the sensitivity of NDVI to SP for grass vegetation (the correlation coefficient is 0.327) is more noticeable than for trees (0.211) or shrubs (-0.058). The relationship between SP and NDVI also provides us new insights on the dependence of vegetation growth on meteorological factors.

We present kiloparsec-scale Atacama Large Millimeter/submillimeter Array (ALMA) and Hubble Space Telescope imaging of the quasar PJ308-21 at z = 6.2342, tracing dust, gas (via the [C II] 158 mu m line), and young stars. At a resolution of similar to 0 ''.3 (approximate to 1.7kpc), the system is resolved over >4 '' (>20 kpc). In particular, it features a main component, identified to be the quasar host galaxy, centered on the accreting supermassive black hole; and two other extended components are on the west and east side: one redshifted and the other blueshifted relative to the quasar. The [C II] emission of the entire system stretches over >1500 km s(-1) along the line of sight. All the components of the system are observed in dust, [C II], and rest-frame ultraviolet (UV) emission. The inferred [C II] luminosities [(0.9-4.6)x 10(9) L-circle dot]; dust luminosities [(0.15-2.6)x 10(12) L-circle dot]; rest-frame UV luminosities [(6.6-15) x 10(10) L-circle dot], their ratios, and the implied gas/dust masses; and star formation rates [11-290 M G yr(-1)] are typical of high-redshift star-forming galaxies. A toy model of a single satellite galaxy that is tidally stripped by the interaction with the quasar host galaxy can account for the observed velocity and spatial extent of the two extended components. An outflow interpretation of the unique features in PJ308-21 is not supported by the data. PJ308-21 is thus one of the earliest galaxy mergers imaged at cosmic dawn.

Traditionally, around 34-38% of China's population resides in places experiencing high water scarcity for at least one month a year. However, the risk of water scarcity may be further exacerbated by inter-regional electricity transmission, due to the mismatch between the electricity-receiving population living in water abundant areas and the water scarcity experienced in the electricity-exporting region. Using detailed thermal/hydro-power plants data and water scarcity index at the water basin scale, this study systematically quantified this additional water scarcity risk across China. The affected population, i.e. those living in basins under lower water scarcity but needing electricity generated in basins with higher water scarcity, was estimated to be 134 million, or 10% of the total population in China. Among this, over 60 million people were considered as highly affected population (i.e. people who live in no/low stress basins rely on electricity generated in severe/extreme scarcity basins), the majority of whom lived in Southern China. This leads to a 12% increase in water-stressed population if the proposed transmission projects were implemented. On the other hand, more people, i.e., 285 million, would benefit from the inter-regional electricity transmissions. They relied on the electricity generated from basins under lower water scarcity. It is found that intra-grid's thermal electricity transmission was less effective in mitigating the water scarcity than the hydroelectricity. It determined that the southern part of China faced worse environmental performance in coordinating its water endowment with the electricity generation because of its use of electricity from water stressed basins rather than from the water sufficient basins.

The heat extracted from the core by the overlying mantle across the core-mantle boundary controls the thermal evolution of the core. This in turn leads to the solidification of the inner core in association with the exsolution of light alloying elements into the liquid outer core. Although the temperature (T) at the inner core boundary (ICB) would be adjusted to account for the effects of the light elements, the melting T of Fe places an upper bound at the ICB and it is a vital point in the thermal profile of the core. Here, we determine the melting T of Fe in the multi-anvil press by characterizing the interface of Fe-W interaction. Our data place a tighter constraint on the melting curve of Fe between 8 and 21 GPa, that is directly applicable to small planetary bodies and serves as an anchor for melting curve of Fe at higher pressure.