Observations of Lake-Breeze Events During the Toronto 2015 Pan-American Games

Enhanced meteorological observations were made during the 2015 Pan and Parapan American Games in Toronto in order to measure the vertical and horizontal structure of lake-breeze events. Two scanning Doppler lidars (one fixed and one mobile), a C-band radar, and a network including 53 surface meteorological stations (mesonet) provided pressure, temperature, humidity, and wind speed and direction measurements over Lake Ontario and urban areas. These observations captured the full evolution (prior, during, and after) of 27 lake-breeze events (73% of observation days) in order to characterize the convective and dynamic processes driving lake breezes at the local scale and mesoscale. The dominant signal of a passing lake-breeze front (LBF) was an increase in dew-point temperature of \(2.3 \pm 0.3 \,^{\circ }\hbox {C}\), coinciding with a \(180^{\circ }\) shift in wind direction and a decrease in air temperature of \(2.1 \pm 0.2 \,^{\circ }\hbox {C}\). Doppler lidar observations over the lake detected lake breezes 1 hour (on average) before detection by radar and mesonet. On days with the synoptic flow in the offshore direction, the lidars observed wedge-shaped LBFs with shallow depths, which inhibited the radar’s ability to detect the lake breeze. The LBF’s ground speed and inland penetration distance were found to be well-correlated (\(r = 0.78\)), with larger inland penetration distances occurring on days with non-opposing (non-offshore) synoptic flow. The observed enhanced vertical motion \(({>} 1\hbox { m s}^{-1})\) at the LBF, observed by the lidar on 54% of lake-breeze days, was greater (at times \({>} 2.5\hbox { m s}^{-1}\)) than that observed in previous studies and longer-lasting over the lake than over land. The weaker and less pronounced lake-breeze structure over land is illustrated in two case studies highlighting the lifetime of the lake-breeze circulation and the impact of propagation distance on lake-breeze intensity.     

Distributions of Downwelling Radiance at 10 and 20 μm in the High Arctic

In the Arctic, most of the infrared (IR) energy emitted by the surface escapes to space in two atmospheric windows centred at 10 and 20?μm. As the Arctic warms and its water vapour burden increases, the 20?μm cooling-to-space window, in particular, is expected to become increasingly opaque (or “closed”), trapping more IR radiation, with implications for the Arctic’s radiative energy balance. Since 2006, the Canadian Network for the Detection of Atmospheric Change has measured downwelling IR radiation with Atmospheric Emitted Radiance Interferometers at the Polar Environment Atmospheric Research Laboratory at Eureka, Canada, providing measurements of the 10 and 20?μm windows in the High Arctic. In this work, measurements of the distribution of downwelling 10 and 20?µm brightness temperatures at Eureka are separated based on cloud cover, providing a comparison to an existing 10?µm climatology from the Southern Great Plains. The downwelling radiance at both 10 and 20?μm exhibits strong seasonal variability as a result of changes in cloud cover, temperature, and water vapour. Given the 20?µm window’s limited transparency, its ability to allow surface IR radiation to escape to space is found to be highly sensitive to changes in atmospheric water vapour and temperature. When separated by season, brightness temperatures in the 20?µm window are independent of cloud optical thickness in the summer, indicating that this window is opaque in the summer. This may have long-term consequences, particularly as warmer temperatures and increased water vapour “close” the 20?μm window for a prolonged period each year.     

Thermochemical parameters of minerals from oxygen-buffered hydrothermal equilibrium data: Method,application to annite and almandine

Reversed univariant hydrothermal phase-equilibrium reactions, in which a redox reaction occurs and is controlled by oxygen buffers, can be used to extract thermochemical data on minerals. The dominant gaseous species present, even for relatively oxidizing buffers such as the QFM buffer, are H₂O and H₂; the main problem is to calculate the chemical potentials of these components in a binary mixture. The mixing of these two species in the gas phase was assumed by Eugster and Wones (1962) to be ideal; this assumption allows calculation of the chemical potentials of the two components in a binary gas mixture, using data in the literature. A simple-mixture model of nonideal mixing, such as that proposed by Shaw (1967), can also be combined with the equations of state for oxygen buffers to permit derivation of the chemical potentials of the two components. The two mixing models yield closely comparable results for the more oxidizing buffers such as the QFM buffer. For reducing buffers such as IQF, the nonideal-mixing correction can be significant and the Shaw model is better.The procedure of calculation of mineralogical thermochemical data, in reactions where hydrogen and H₂O simultaneously appear, is applied to the experimental data on annite, given by Wones et al. (1971), and on almandine, given by Hsu (1968). For annite the results are: Standard entropy of formation from the elements, S _f ⁰ (298, 1)=–283.35±2.2 gb/gf, S ⁰ (298, 1) =+92.5 gb/gf. G _f ⁰ (298, 1)=–1148.2±6 kcal, and H _f ⁰ (298, 1)=–1232.7±7 kcal. For almandine, the calculation takes into account the mutual solution of FeAl₂O₄ (Hc) in magnetite and of Fe₃O₄ (Mt) in hercynite and the temperature dependence of this solid solution, as given by Turnock and Eugster (1962); the calculations assume a regular-solution model for this binary spinel system. The standard entropy of formation of almandine, S _f,A ⁰ (298, 1) is –272.33±3 gb/gf. The third law entropy, S ⁰ (298, 1) is +68.3±3 gb/gf, a value much less than the oxide-sum estimate but the deviation is nearly the same as that of grossularite, referring to a comparable set of oxide standard states. The Gibbs free energy G _f,A ⁰ (298, 1) is –1192.36±4 kcal, and the enthalpy H _f,A ⁰ (298, 1) is –1273.56±5 kcal.Publication authorized by the Director, U. S. Geological Survey.     

Structural origin of Lake Singkarak in central Sumatra

Since long it has been accepted that Lake Singkarak in Central Sumatra is nothing else but a remnant of a gigantic volcano — the Singkarak volcano — which once blew off its top to form a lake. Van Bemmelen, though not referring to Singkarak lake especially, explained the numerous depressions in Sumatra as the combined result of volcanic and tectonic activities, a phenomenon he called volcano-tectonic process which caused the formation of the socalled volcano-tectonic depressions. A short visit to the lake area in the months of February and March (1970) convinced the author that Lake Singkarak is neither a volcanic ruin nor a volcano-tectonic depression in the sense of van Bemmelen. Faulting evidences, morphology and the position of the Singkarak trough plus the distribution of volcanic products north and south of the lake led to the conclusion that the Singkarak trough is a depression making part of the 1650 km graben zone which stretches from Sumatra’s northern tip untill the Semangko valley in the SE. Field evidences suggest that the lake results from a damming process by volcanic material produced by the Marapi-Singgalang-Tandikat volcanoes in the north and by the products from the Talang volcano in the south.     

Statistical properties of MHD fluctuations associated with high-speed streams from Helios-2 observations

A variance analysis of Helios-2 magnetic data has been used to derive several statistical properties of MHD fluctuations associated with the trailing edge of a given stream observed in different solar rotations. Such properties are derived both as a function of distance from the Sun and as a function of the frequency range included in the sample. The most noticeable result is that the radial gradients of various parameters, such as anisotropy and normalized power of the fluctuations, depend from frequency range. In particular the variation with distance of the normalized power does not correspond, for periods 1 hr, to what is expected from WKB propagation effects.Istituto di Fisica, Università di Roma, Rome, Italy.Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, Md 20771, U.S.A.     

A statistical study of MHD discontinuities in the inner solar system: Helios 1 and 2

A statistical study is made of the magnetic field directional discontinuities observed in early 1976 onboard Helios 1 and 2. Strong day-to-day variations of occurrence rates are found on either tangential (TD) or rotational (RD) discontinuities. No large variation (if any) is found versus either heliocentric distance or heliographic latitude. This contradicts previous findings obtained by the same technique on Pioneer 8 data in 1968–69; however, reasons are given to expect different results, under different solar conditions. The most interesting results come from the study of the morphology of discontinuities: first of all, the orientation of TD's and RD's normals (identified by a minimum variance technique) are strongly organized by the average magnetic field, following their progressive directional change when approaching the Sun. The inclination (θ _n ) and azimuthal (? _n ) distributions are gaussian and strongly peaked along the field lines for RD's; as regards TD's the normals are perpendicular to the average field and follow its progressive variation; the θ _n distribution is isotropic in solid angle, which is interpreted as evidence of crossing of flux tubes on the order of one/hour. Implications of this interpretation in contrast with a turbulent approach are also discussed.     

佳木斯地块东缘南双鸭山组碎屑锆石年代学及其大地构造意义

正佳木斯地块位于我国黑龙江省东部,大地构造上处于华北和西伯利亚两大古板块所夹持的中亚构造带最东端,东邻西太平洋大陆边缘中生代增生杂岩带。该地块以广泛出露有麻粒岩相高级变质表壳岩系,东缘发育晚古生代大陆边缘沉积层系和早中生代海相沉积地层为特征。早期的研究普遍认为,东北地区以佳木斯地块等为代表的诸变质构造单元是卷入到东亚晚古生代地槽褶皱带或古亚洲