Convective instability in the martian middle atmosphere     

N.G. Heavens  M.I. Richardson  W.G. Lawson  D.J. McCleese  A. Kleinböhl  W.A. Abdou 《Icarus》2010,208(2):574-589

Dry convective instabilities in Mars’s middle atmosphere are detected and mapped using temperature retrievals from Mars Climate Sounder observations spanning 1.5 martian years. The instabilities are moderately frequent in the winter extratropics. The frequency and strength of middle atmospheric convective instability in the northern extratropics is significantly higher in MY 28 than in MY 29. This may have coupled with changes to the northern hemisphere mid-latitude and tropical middle atmospheric temperatures and contributed to the development of the 2007 global dust storm. We interpret these instabilities to be the result of gravity waves saturating within regions of low stability created by the thermal tides. Gravity wave saturation in the winter extratropics has been proposed to provide the momentum lacking in general circulation models to produce the strong dynamically-maintained temperature maximum at 1-2 Pa over the winter pole, so these observations could be a partial control on modeling experiments.  相似文献   

Spectral Irradiance and Phytoplankton Community Composition in a Blackwater-Dominated Estuary,Winyah Bay,South Carolina,USA     

Evelyn Lawrenz  James L. Pinckney  Melissa L. Ranhofer  Hugh L. MacIntyre  Tammi L. Richardson 《Estuaries and Coasts》2010,33(5):1186-1201

We investigated spatial and temporal relationships between spectral irradiance and phytoplankton community composition in the blackwater-influenced estuary Winyah Bay, South Carolina. Upstream, high concentrations of chromophoric dissolved organic matter (CDOM) absorbed blue wavelengths, resulting in a predominantly red light field. Green light prevailed downstream near the lower-CDOM coastal ocean, and phytoplankton community composition was distinct from upstream and mid-estuarine communities. Diatoms were abundant throughout the estuary in January, August, and October, cryptophytes dominated in July, and chlorophytes were abundant in December 2006. Only diatoms and chlorophytes showed significant covariation with the spectral attenuation coefficient (k(λ)): Chlorophytes showed positive relationships with k(442) (blue light) while diatoms were negatively correlated with k(442) and k(490) (violet to blue). Phytoplankton community composition in Winyah Bay appears to be driven by strong horizontal flow rather than gradients in spectral irradiance, but results indicate that water color is likely to play a greater role in blackwater-influenced estuaries with longer residence times.  相似文献   

Spline models of contemporary, 2030, 2060 and 2090 climates for Mexico and their use in understanding climate-change impacts on the vegetation     

Cuauhtémoc Sáenz-Romero  Gerald E. Rehfeldt  Nicholas L. Crookston  Pierre Duval  Rémi St-Amant  Jean Beaulieu  Bryce A. Richardson 《Climatic change》2010,102(3-4):595-623

Spatial climate models were developed for México and its periphery (southern USA, Cuba, Belize and Guatemala) for monthly normals (1961–1990) of average, maximum and minimum temperature and precipitation using thin plate smoothing splines of ANUSPLIN software on ca. 3,800 observations. The fit of the model was generally good: the signal was considerably less than one-half of the number of observations, and reasonable standard errors for the surfaces would be less than 1°C for temperature and 10–15% for precipitation. Monthly normals were updated for three time periods according to three General Circulation Models and three emission scenarios. On average, mean annual temperature would increase 1.5°C by year 2030, 2.3°C by year 2060 and 3.7°C by year 2090; annual precipitation would decrease ?6.7% by year 2030, ?9.0% by year 2060 and ?18.2% by year 2090. By converting monthly means into a series of variables relevant to biology (e. g., degree-days > 5°C, aridity index), the models are directly suited for inferring plant–climate relationships and, therefore, in assessing impact of and developing programs for accommodating global warming. Programs are outlined for (a) assisting migration of four commercially important species of pine distributed in altitudinal sequence in Michoacán State (b) developing conservation programs in the floristically diverse Tehuacán Valley, and (c) perpetuating Pinus chiapensis, a threatened endemic. Climate surfaces, point or gridded climatic estimates and maps are available at http://forest.moscowfsl.wsu.edu/climate/.  相似文献   

Adjustment of conditions with parameters and error analysis     

J. L. Stearn  H. Richardson 《Journal of Geodesy》1962,36(2):117-135

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Opening of the Red Sea with two poles of rotation — Reply     

E.S. Richardson  C.G.A. Harrison 《Earth and Planetary Science Letters》1976,33(1):173-175

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Agents of low temperature ocean crust alteration     

Hubert Staudigel  Karlis Muehlenbachs  Stephen H. Richardson  Stanley R. Hart 《Contributions to Mineralogy and Petrology》1981,77(2):150-157

¹⁸O and⁸⁷Sr/⁸⁶Sr isotopic data from smectites, calcites, and whole rocks, together with published isotopic age determinations, alkali element concentration data and petrographic observations suggest a sequential model of ocean floor alteration. The early stage lasts about 3 m.y. and is characterized by palagonite and smectite formation, and solutions with a large basaltic component, increasing with temperature which varies from 15° to 80° C at DSDP site 418A. Most carbonates are depositedafter this stage from solutions with a negligible basaltic Sr component and temperatures of 15° to 40° C. Water of seawater Sr and O isotopic composition is shown to percolate to at least 500 m into the basaltic basement. No evidence was found for continuing exchange of strontium or oxygen after 3 m.y.Lamont-Doherty Geological Observatory Contribution number 3199  相似文献   

The solubility of fluorite in hydrothermal solutions,an experimental study     

Catherine K. Richardson  H.D. Holland 《Geochimica et cosmochimica acta》1979,43(8):1313-1325

The solubility of fluorite in NaCl solutions increases with increasing temperature at all ionic strengths up to about 100°C. Above this temperature, the solubility passes through a maximum and possibly a minimum with increasing temperature at NaCl concentrations of 1.0M or less, and increases continuously with increasing temperature at NaCl concentrations above 1.0M. At any given temperature, the solubility of fluorite increases with increasing salt concentration in NaCl, KCl and CaCl₂ solutions. The solubility follows Debye-Hückel theory for KCl solutions. In NaCl and CaCl₂ solutions, the solubility of fluorite increases more rapidly than predicted by Debye-Hückel theory: the excess solubility is due to the presence of NaF^c, CaF⁺, and possibly of Na₂F⁺. The solubility of fluorite in NaCl-CaCl₂ and in NaCl-CaCl₂-MgCl₂ solutions is controlled by the common ion effect and by the presence of NaF^c, CaF⁺, and MgF⁺. The solubility of fluorite in NaCl-HCl solutions increases rapidly with increasing initial HCl concentration; the large solubility increase is due to the presence of HF^c. It seems likely that complexes other than those identified in this study rarely play a major role in fluoride transport and fluorite deposition at temperatures below 300°C.  相似文献   

Fluorite deposition in hydrothermal systems   总被引：1，自引：0，他引：1  

Catherine K. Richardson  H.D. Holland 《Geochimica et cosmochimica acta》1979,43(8):1327-1335

During the formation of fluorite deposits fluorite is precipitated either as a consequence of changes in temperature and pressure along the flow path of hydrothermal solutions or due to fluid mixing, or as the result of the interaction of hydrothermal solutions with wall rocks.A decrease in temperature in the flow direction is the most appealing, though still unproven, mechanism of fluorite deposition in Mississippi Valley fluorite deposits.Mixing can produce solutions which are either undersaturated or supersaturated with respect to fluorite. The most important parameters are the temperature, the salinity, and the calcium and fluoride concentration of the fluids prior to mixing.A variety of wall rock reactions can lead to fluorite precipitation. Among these reactions which increase the pH of initially rather acid (pH ≤ 3) hydrothermal solutions are apt to be particularly important.  相似文献   

Concentrations of polybrominated diphenyl ethers (PBDEs) in Pearl River Delta sediments   总被引：1，自引：0，他引：1  

Zheng GJ  Martin M  Richardson BJ  Yu H  Liu Y  Zhou C  Li J  Hu G  Lam MH  Lam PK 《Marine pollution bulletin》2004,49(5-6):520-524

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Confronted by Insurmountable Opportunities: Geography in Society at the AAG's Centennial*   总被引：1，自引：0，他引：1  

Douglas Richardson  Patricia Solis 《The Professional geographer》2004,56(1):4-11

Geographers at the AAG's centennial are challenged with exceptional opportunities to create a more central place for geography in society and in the university. Realizing these opportunities requires identifying and leveraging key emerging trends in the formation and uses of geographic knowledge. Better integration of geography's profound technological innovations with its core traditions also is necessary to strengthen the discipline's research capacity, and to more effectively engage with and contribute to the needs of society. Trends toward multidisciplinary research and integrative science, and the heightened need for geographic understanding in today's world, hold further promise for advancing the discipline while sustaining its historic strengths and diversity.  相似文献