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1.
Daniel Lane Colin P.R. McCarter Murray Richardson Chris McConnell Tim Field Huaxia Yao George Arhonditsis Carl P.J. Mitchell 《水文研究》2020,34(3):598-614
The estimation of hydrologic transit times in a catchment provides insights into the integrated effects of water storage, mixing dynamics, and runoff generation processes. There has been limited effort to estimate transit times in southern boreal Precambrian Shield landscapes, which are characteristically heterogeneous with surface cover including till, thin soils, bedrock outcrops, and depressional wetland features that play contrasting hydrologic roles. This study presents approximately 3.5 years of precipitation and streamflow water isotope data and estimates mean transit times (MTTs) and the young water fraction (py) across six small catchments in the Muskoka-Haliburton region of south-central Ontario. The main objectives were to define a typical range of MTTs for headwater catchments in this region and to identify landscape variables that best explain differences in MTTs/py using airborne light detection and ranging and digital terrain analysis. Of the transit time distributions, the two parallel linear reservoir and gamma distributions best describe the hydrology of these catchments, particularly because of their ability to capture more extreme changes related to events such as snowmelt. The estimated MTTs, regardless of the modelling approach or distribution used, are positively associated with the percent wetland area and negatively with mean slope in the catchments. In this landscape, low-gradient features such as wetlands increase catchment scale water storage when antecedent conditions are dryer and decrease transit times when there is a moisture surplus, which plausibly explains the increases in MTTs and mean annual runoff from catchments with significant coverage of these landscape features. 相似文献
2.
Philip B. James 《Icarus》1985,64(2):249-264
The Martian CO2 cycle, which includes the seasonal condensation and subsequent sublimation of up to 30% of the planet's atmosphere, produces meridional winds due to the consequent mass flux of CO2. These winds currently display strong seasonal and hemispheric asymmetries due to the large asymmetries in the distribution of insolation on Mars. It is proposed that asymmetric meridional advection of water vapor on the planet due to these CO2 condensation winds is capable of explaining the observed dessication of Mars' south polar region at the current time. A simple model for water vapor transport is used to verify this hypothesis and to speculate on the effects of changes in orbital parameters on the seasonal water cycle. 相似文献
3.
Richard T. Jones Jim D. Marshall Stephen F. Crowley Alan Bedford Nigel Richardson Jan Bloemendal Frank Oldfield 《第四纪科学杂志》2002,17(4):329-340
A lacustrine carbonate sequence from Hawes Water, Lancashire, UK, has been studied using stable isotopic, lithological, pollen and mineral magnetic analysis. The data reveal four abrupt climatic oscillations in the Late‐glacial Interstadial leading up to the onset of the Loch Lomond Stadial. The data also point to climatic warming relatively early within the stadial, ca. 12 500 GRIP yr, prior to the onset of the Holocene. The oxygen isotope record is taken as a signature of climate forcing against which the response of the lake‐system can be monitored. By adopting this approach it is revealed that the response of the biological system to the rapid climatic oscillations is non‐linear and primarily a function of the antecedent conditions. A significant end‐Devensian isotopic excursion (A) is matched by only minor changes in the cold‐adapted floras and faunas. During the warmer interstadial, the response of the biological ecosystem (events B–D) is clearly influenced by thresholds: major changes in the catchment vegetation associated with relatively minor oscillations in the isotopic signature. The stratigraphical patterns reveal significant lag effects between the onset of climate deterioration and resulting changes in vegetation. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
4.
Studies of soil productivity must compensate for the effects of temporal trends in order to examine the pattern of crop yields along spatial gradients. An analysis of the published yield estimates for 30 soils in 233 counties, however, did not find consistent yield increases over the past three decades. On the contrary, the yield estimates for many soils were markedly uniform since 1972. The uniformity appears to have two causes: the acknowledged difficulty of making yield estimates in a time of increasing variability in soil and crop management, both within and between regions, and surveyors' awareness of data stored in a national soils data base. The effect is to cast doubt on soil productivity data reported in county soil surveys published between 1973 and 1988. 相似文献
5.
6.
The paper employs statistical hypothesis tests to explore the question of whether natural hazards (hail and tornadoes being considered here) are or are not intertemporally random. The answer to this question, at least for these two hazards, is surprising and has important policy implications: hazards appear to be more likely in year t if an event was experienced in year t?1: hence, apparent ‘Gambler's Fallacy’ behaviour on the part of farmers and others may indeed be rational. Should this result hold for a full range of climate-related hazard types. as we suspect, hundreds of millions of dollars of crop loss and other damages may be preventable (e.g., rotating to frost-resistant crops if past events suggest greater than usual likelihood of early or late frost). The degree of positive serial correlation is also seen to vary a great deal regionally, with individuals in some states being unable to benefit from knowledge of prior hazard occurrence. 相似文献
7.
Cooper John F. Christian Eric R. Richardson John D. Wang Chi 《Earth, Moon, and Planets》2003,92(1-4):261-277
Times for accumulation of chemically significant dosages on icy surfaces of Centaur, Kuiper Belt, and Oort Cloud objects from plasma and energetic ions depend on irradiation position within or outside the heliosphere. Principal irradiation components include solar wind plasma ions, pickup ions from solar UV ionization of interstellar neutral gas, energetic ions accelerated by solar and interplanetary shocks, including the putative solar wind termination shock, and galactic cosmic ray ions from the Local Interstellar Medium (LISM). We present model flux spectra derived from spacecraft data and models for eV to GeV protons at 40 AU, a termination shock position at 85 AU, and in the LISM. Times in years to accumulate dosages ~100 eV per molecule are computed from the spectra as functions of sensible surface depth less than one centimeter at unit density.The collisional resurfacing model of Luu and Jewitt is reconsidered in thecontext of depth-dependent dosage rates from plasma, suprathermal,and higher energy protons, and global exposure, by micrometeoroiddust grain impacts, of moderately irradiated red material below athin crust of heavily irradiated neutral material. This material should be more visible on dynamically `cold’ objects in the ~40 AU region. 相似文献
8.
The gray crystalline hematite at Meridiani Planum first discovered by the Mars Global Surveyor Thermal Emission Spectrometer (MGS-TES) instrument occurs as spherules that have been interpreted as concretions. Analysis of the TES and mini-TES spectra shows that no 390 cm−1 feature is present in the characteristic martian hematite spectrum. Here, we incorporate the mid-IR optical constants of hematite into a simple Fresnel reflectance model to understand the effect of emission angle and crystal morphology on the presence or absence of the 390 cm−1 feature in an IR hematite spectrum. Based on the results we offer two models for the internal structure of the martian hematite spherules. 相似文献
9.
Glenn M. Frye Jr. Philip P. Dunphy Edward L. Chupp Paul Evenson 《Solar physics》1988,118(1-2):321-346
10.
A sonic well log was obtained within the basement complex of the Walvis Ridge during Deep Sea Drilling Project Leg 74. The top of the basement complex is characterized by smooth acoustic reflectors. The rocks recovered within the basement complex consist of basalts with intercalated sediments. According to the log ~-50% of the upper 75 m of basement are igneous rocks and the other 50% sedimentary. Sonobuoy results indicate that the ratio of sediments to basalt increases with depth for an additional 225 m until a typical oceanic velocity structure is observed. Paleontological results suggest that the processes forming this upper 300 m of the basement complex was accomplished within a short time interval. 相似文献