Ozone and aerosol changes during the 1991-1992 airborne arctic stratospheric expedition

Stratospheric ozone and aerosol distributions were measured across the wintertime Arctic vortex from January to March 1992 with an airborne lidar system as part of the 1992 Airborne Arctic Stratospheric Expedition (AASE II). Aerosols from the Mount Pinatubo eruption were found outside and inside the vortex with distinctly different distributions that clearly identified the dynamics of the vortex. Changes in aerosols inside the vortex indicated advection of air from outside to inside the vortex below 16 kilometers. No polar stratospheric clouds were observed and no evidence was found for frozen volcanic aerosols inside the vortex. Between January and March, ozone depletion was observed inside the vortex from 14 to 20 kilometers with a maximum average loss of about 23 percent near 18 kilometers.     

The persistently variable "background" stratospheric aerosol layer and global climate change

Recent measurements demonstrate that the "background" stratospheric aerosol layer is persistently variable rather than constant, even in the absence of major volcanic eruptions. Several independent data sets show that stratospheric aerosols have increased in abundance since 2000. Near-global satellite aerosol data imply a negative radiative forcing due to stratospheric aerosol changes over this period of about -0.1 watt per square meter, reducing the recent global warming that would otherwise have occurred. Observations from earlier periods are limited but suggest an additional negative radiative forcing of about -0.1 watt per square meter from 1960 to 1990. Climate model projections neglecting these changes would continue to overestimate the radiative forcing and global warming in coming decades if these aerosols remain present at current values or increase.     

Global carbon sinks and their variability inferred from atmospheric O2 and delta13C

Recent time-series measurements of atmospheric O2 show that the land biosphere and world oceans annually sequestered 1.4 +/- 0.8 and 2.0 +/- 0.6 gigatons of carbon, respectively, between mid-1991 and mid-1997. The rapid storage of carbon by the land biosphere from 1991 to 1997 contrasts with the 1980s, when the land biosphere was approximately neutral. Comparison with measurements of delta13CO2 implies an isotopic flux of 89 +/- 21 gigatons of carbon per mil per year, in agreement with model- and inventory-based estimates of this flux. Both the delta13C and the O2 data show significant interannual variability in carbon storage over the period of record. The general agreement of the independent estimates from O2 and delta13C is a robust signal of variable carbon uptake by both the land biosphere and the oceans.     

Organic aerosol growth mechanisms and their climate-forcing implications

Surface- and volume-limited chemical reactions on and in atmospheric aerosol particles cause growth while changing organic composition by 13 to 24% per day. Many of these particles contain carbonaceous components from mineral dust and combustion emissions in Africa, Asia, and North America and reveal reaction rates that are three times slower than those typically used in climate models. These slower rates for converting from volatile or hydrophobic to condensed and hygroscopic organic compounds increase carbonaceous particle burdens in climate models by 70%, producing organic aerosol climate forcings of as much as -0.8 watt per square meter cooling and +0.3 watt per square meter warming.     

Venus: implications from microwave spectroscopy of the atmospheric content of water vapor

From comparison of theoretical and observed microwave brightness temperatures of Venus at 1.35 centimeters, the center of a water-vapor line, we obtain an upper limit of 0.8 percent for the water-vapor mixing ratio in the lower atmosphere. This limit is consistent with the amount of water vapor detected by Venera 4, the existence of aqueous ice clouds, and a greenhouse effect caused by water vapor and carbon dioxide. The computed spectra suggest that a sensitive procedure for detection of water vapor is examination of the wavelength region between I and 1.4 centimeters.     

Superplumes from the core-mantle boundary to the lithosphere: implications for heat flux

Three-dimensional modeling of upper-mantle anelastic structure reveals that thermal upwellings associated with the two superplumes, imaged by seismic elastic tomography at the base of the mantle, persist through the upper-mantle transition zone and are deflected horizontally beneath the lithosphere. This explains the unique transverse shear wave isotropy in the central Pacific. We infer that the two superplumes may play a major and stable role in supplying heat and horizontal flow to the low-viscosity asthenospheric channel, lubricating plate motions and feeding hot spots. We suggest that more heat may be carried through the core-mantle boundary than is accounted for by hot spot fluxes alone.     

Carbon monoxide on jupiter and implications for atmospheric convection

A study of the equilibrium and disequilibrium thermochemistry of the recently discovered carbon monoxide on Jupiter suggests that the presence of this gas in the visible atmosphere is a direct result of very rapid upward mixing from levels in the deep atmosphere where the temperature is about 1100 degrees K and where carbon monoxide is thermodynamically much more stable. As a consequence the observed carbon monoxide mixing ratio is a sensitive function of the vertical eddy mixing coefficient. We infer a value for this latter coefficient which is about three to four orders of magnitude greater than that in the earth's troposphere. This result directly supports existing structural and dynamical theories implying very rapid convection in the deep Jovian atmosphere, driven by an internal heat source.     

Vapor pressures of solid hydrates of nitric Acid: implications for polar stratospheric clouds

Thermodynamic data are presented for hydrates of nitric acid: HNO(3).H(2)O, HNO(3).2H(2)O, HNO(3).3H(2)O, and a higher hydrate. Laboratory data indicate that nucleation and persistence of metastable HNO(3).2H(2)O may be favored in polar stratospheric clouds over the slightly more stable HNO(3).3H(2)O. Atmospheric observations indicate that some polar stratospheric clouds may be composed of HNO(3).2H(2)O and HNO(3).3H(2)O. Vapor transfer from HNO(3).2H(2)O to HNO(3).3H(2)O could be a key step in the sedimentation of HNO(3), which plays an important role in the depletion of polar ozone.     

A new laboratory source of ozone and its potential atmospheric implications

Although 248-nanometer radiation falls 0.12 electron volt short of the energy needed to dissociate O(2) large densities of ozone (O(3)) can be produced from unfocused 248-nanometer KrF excimer laser irradiation of pure O(2). The process is initiated in some undefined manner, possibly through weak two-photon O(2) dissociation, which results in a small amount of O(3) being generated. As soon as any O(3) is present, it strongly absorbs the 248-nanometer radiation and dissociates to vibrationally excited ground state O(2) (among other products), with a quantum yield of 0.1 to 0.15. During the laser pulse, a portion of these molecules absorb a photon and dissociate, which results in the production of three oxygen atoms for one O(3) molecule destroyed. Recombination then converts these atoms to O(3), and thus O(3) production in the system is autocatalytic. A deficiency exists in current models of O(3) photochemistry in the upper stratosphere and mesosphere, in that more O(3) iS found than can be explained. A detailed analysis of the system as it applies to the upper atmosphere is not yet possible, but with reasonable assumptions about O(2) vibrational distributions resulting from O(3) photodissociation and about relaxation rates of vibrationally excited O(2) a case can be made for the importance of incuding this mechanism in the models.     

模拟大气镉沉降量对空心菜种子发芽的影响

大气镉沉降严重威胁蔬菜安全生产,揭示其对种子发芽的影响能够为相关防控政策的制定提供依据。本研究以南京市场6个主流空心菜品种（白骨大叶、白骨柳叶、柳叶、双机竹叶、特选泰国和正宗三叉）为研究对象,设置3个大气镉沉降梯度（3.0、9.0、18.0 mg·m^-2）进行了7 d种子发芽实验。结果表明：大气镉沉降量使白骨大叶和双机竹叶的发芽峰值日提早1 d,分别显著降低白骨大叶的发芽势和白骨大叶、白骨柳叶、特选泰国空心菜种子的根长及后两者的根长活力指数,而显著提高柳叶的发芽势、发芽指数、根长和鲜质量两种活力指数及双机竹叶的活力指数。相关性分析发现,大气镉沉降量与白骨柳叶种子的根长活力指数显著负相关,与柳叶种子的根长活力指数呈显著正相关,与白骨大叶和双机竹叶种子的烂根率呈显著负相关。白骨柳叶和柳叶种子的发芽受大气镉沉降量的影响较大,主要是种子根发育受到大气镉沉降量的影响,且适量的大气镉沉降可以缓解白骨大叶和双机竹叶种子的烂根状况;特选泰国和正宗三叉品种的发芽情况受大气镉沉降量的影响不明显。     

Nightglow in the upper atmosphere of Mars and implications for atmospheric transport

We detected light emissions in the nightside martian atmosphere with the SPICAM (spectroscopy for the investigation of the characteristics of the atmosphere of Mars) ultraviolet (UV) spectrometer on board the Mars Express. The UV spectrum of this nightglow is composed of hydrogen Lyman alpha emission (121.6 nanometers) and the gamma and delta bands of nitric oxide (NO) (190 to 270 nanometers) produced when N and O atoms combine to produce the NO molecule. N and O atoms are produced by extreme UV photodissociation of O2, CO2, and N2 in the dayside upper atmosphere and transported to the night side. The NO emission is brightest in the winter south polar night because of continuous downward transport of air in this region at night during winter and because of freezing at ground level.     

Trace elements and radioactivity in lunar rocks: implications for meteorite infall, solar-wind flux, and formation conditions of moon

Lunar soil and type C breccias are enriched 3-to 100-fold in Ir, Au, Zn, Cd, Ag, Br, Bi, and Tl, relative to type A, B rocks. Smaller enrichments were found for Co, Cu, Ga, Pd, Rb, and Cs. The solar wind at present intensity can account for only 3 percent of this enrichment; an upper limit to the average proton flux during the last 4.5 x 109 years thus is 8 x 10(9) cm(-2) yr(-1). The remaining enrichment seems to be due to a 1.5 to 2 percent admixture of carbonaceous-chondritelike material, corresponding to an average influx rate of meteoritic and cometary matter of 2.9 x 10(-9) g cm(-2) yr(-1) at Tranquility Base. This is about one-quarter the terrestrial rate. Type A, B rocks are depleted 10-to 100-fold in Ag, Au, Zn, Cd, In, Tl, and Bi, relative to terrestrial basalts. This suggests loss by high-temperature volatilization, before or after accretion of the moon. Positron activities due mainly to (22)Na and (26)Al range from 90 to 220 beta(+) min(-1) kg(-1) in five small rocks or fragments (9 to 29 g). The higher activities presumably indicate surface locations. Th and U contents generally agree with those found by the preliminary examination team.     

A microphysical connection among biomass burning, cumulus clouds, and stratospheric moisture

A likely causal chain is established here that connects humidity in the stratosphere, relative humidity near the tropical tropopause, ice crystal size in towering cumulus clouds, and aerosols associated with tropical biomass burning. The connections are revealed in satellite-observed fluctuations of each quantity on monthly to yearly time scales. More aerosols lead to smaller ice crystals and more water vapor entering the stratosphere. The connections are consistent with physical reasoning, probably hold on longer time scales, and may help to explain why stratospheric water vapor appears to have been increasing for the past five decades.     

Simulations of atmospheric variability induced by sea surface temperatures and implications for global warming

An atmospheric general circulation model was forced with observed interannual changes in the global sea surface temperatures (SSTs) for the period 1982 to 1993. The simulated seasonal surface air temperature patterns over land areas closely resemble the observed. Over most of the globe, the patterns also resemble those associated with EI Ni?o events and are also reproduced in simulations with weak warm tropical SSTs near the date line. An exception is northern Asia, where the mechanisms for the observed warming are unclear. The results suggest that enhanced air-sea interactions resulting from recent, more persistent warm oceanic conditions in the tropics contributed to the observed global warming trend during this period.     

Nocturnality in dinosaurs inferred from scleral ring and orbit morphology

Variation in daily activity patterns facilitates temporal partitioning of habitat and resources among species. Knowledge of temporal niche partitioning in paleobiological systems has been limited by the difficulty of obtaining reliable information about activity patterns from fossils. On the basis of an analysis of scleral ring and orbit morphology in 33 archosaurs, including dinosaurs and pterosaurs, we show that the eyes of Mesozoic archosaurs were adapted to all major types of diel activity (that is, nocturnal, diurnal, and cathemeral) and provide concrete evidence of temporal niche partitioning in the Mesozoic. Similar to extant amniotes, flyers were predominantly diurnal; terrestrial predators, at least partially, nocturnal; and large herbivores, cathemeral. These similarities suggest that ecology drives the evolution of diel activity patterns.     

Neuron function inferred from behavioral and electrophysiological extimates of refractory period

The refrcactory period of neurons mediating an electrically elicited behavior (self-stimulation) was estimated by varying the intrapair pulse separation in a stimulating train made up of pulse pairs and measuring the intensity of the elicited behavior. Two neuronal systems with different refractory periods were indicated. Single-unit recording in acute preparations stimulated through self-stimulation electrodes revealed primarily two classes of units. Each class gave refractory period estimates characteristic of one of the behaviorally indicated systems. The experiments illustrate a technique for establishing functional relations between single units in the brain and gross behavior.     

Worldwide human relationships inferred from genome-wide patterns of variation

Human genetic diversity is shaped by both demographic and biological factors and has fundamental implications for understanding the genetic basis of diseases. We studied 938 unrelated individuals from 51 populations of the Human Genome Diversity Panel at 650,000 common single-nucleotide polymorphism loci. Individual ancestry and population substructure were detectable with very high resolution. The relationship between haplotype heterozygosity and geography was consistent with the hypothesis of a serial founder effect with a single origin in sub-Saharan Africa. In addition, we observed a pattern of ancestral allele frequency distributions that reflects variation in population dynamics among geographic regions. This data set allows the most comprehensive characterization to date of human genetic variation.     

Reduction of stratospheric ozone by nitrogen oxide catalysts from supersonic transport exhaust

Although a great deal of attention has been given to the role of water vapor from supersonic transport (SST) exhaust in the stratosphere, oxides of nitrogen from SST exhaust pose a much greater threat to the ozone shield than does an increase in water. The projected increase in stratospheric oxides of nitrogen could reduce the ozone shield by about a factor of 2, thus permitting the harsh radiation below 300 nanometers to permeate the lower atmosphere.     

Heat flux and precipitation estimates from oceanographic observations

Surface meteorological observations and salinity and temperature profiles were made in the intertropical convergence zone during July 1972. Over an 18-hour period, estimates of the heat budget in the top layer of the ocean and estimates of the total heat flux made by using aerodynamic parameterization equations balance within 10 percent. The salinity budget provides a precipitation estimate. Due to the stable stratification established by the salinity dilution in the wave-mixed layer by rain, the total heat flux to the atmosphere is being extracted from this shallow layer. As a result, large sea surface temperature drops occur regionally and may be capable of inhibiting atmospheric convection.     

Viscosity of oceanic asthenosphere inferred from remote triggering of earthquakes

A sequence of large interplate earthquakes from 1952 to 1965 along the Aleutian arc and Kurile-Kamchatka trench released accumulated stresses along nearly the entire northern portion of the Pacific Plate boundary. The postseismic stress evolution across the northern Pacific and Arctic basins, calculated from a viscoelastic coupling model with an asthenospheric viscosity of 5 x 10(17) pascal seconds, is consistent with triggering of oceanic intraplate earthquakes, temporal patterns in seismicity at remote plate boundaries, and space-based geodetic measurements of anomalous velocity over an area 7000 by 7000 kilometers square during the 30-year period after the sequence.