Celebrating 40 years of the International Geoscience Program of UNESCO     

Kamlesh Lulla  M. Duane Nellis  Brad Rundquist 《国际地球制图》2013,28(2)

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Timing and duration of hydrological transitions in Arctic polygonal ground from stable isotopes     

Nathan Alec Conroy  Brent David Newman  Jeffrey Martin Heikoop  George Bradford Perkins  Xiahong Feng  Cathy Jean Wilson  Stan Duane Wullschleger 《水文研究》2020,34(3):749-764

Land surface models and Earth system models that include Arctic landscapes must capture the abrupt hydrological transitions that occur during the annual thaw and deepening of the active layer. In this work, stable water isotopes (δ²H and δ¹⁸O) are used to appraise hydrologically significant transitions during annual landscape thaw at the Barrow Environmental Observatory (Utqiaġvik, Alaska). These hydrologically significant periods are then linked to annual shifts in the landscape energy balance, deduced from meteorological data and described by the microclimatic periods: Winter, Pre-Melt, Melt, Post-Melt, Summer, and Freeze-Up. The tight coupling of the microclimatic periods with the hydrological transitions supports the use of microclimatic periods as a means of linking polygonal surface water hydrology to meteorological datasets, which provides a mechanism for improving the representation of polygonal surface water hydrology in process-based models. Rayleigh process reconstruction of the isotopic changes revealed that 19% of winter precipitation was lost to sublimation prior to melting and that 23% of surface water was lost to evaporation during the first 10 days post-melt. This agrees with evaporation rates reported in a separate study using an eddy covariance flux tower located nearby. An additional 17% was lost to evaporation during the next 33 days. Stable water isotopes are also used to identify the dominant sources of surface water to various hydrogeomorphological features prevalent in polygonal terrain (a lake, a low centre polygon centre, troughs within the rims of low centre polygons, flat centre polygon troughs, a high centre polygon trough, and drainages). Hydrogeomorphologies that retained significant old water or acted as snow drifts are isotopically distinct during the Melt Period and therefore are easily distinguished. Biogeochemical changes related to the annual thaw are also reported and coupled to the hydrological transitions, which provides insight into the sources and sinks of these ions to and from the landscape.  相似文献   

Using joint probability distribution functions to evaluate simulations of precipitation,cloud fraction and insolation in the North America Regional Climate Change Assessment Program (NARCCAP)     

Huikyo Lee  Jinwon Kim  Duane E. Waliser  Paul C. Loikith  Chris A. Mattmann  Seth McGinnis 《Climate Dynamics》2015,45(1-2):309-323

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Innovations in Geospatial technologies: CubeSats for Earth Observations     

Kamlesh Lulla  M. Duane Nellis  Brad Rundquist 《国际地球制图》2013,28(8)

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Comment on absorbing regions in the atmosphere of Venus as measured by radio occultation     

Von R. Eshleman  Duane O. Muhleman  Philip D. Nicholson  Paul G. Steffes 《Icarus》1980,44(3):793-803

Two recent papers, one by A.J. Kliore, C. Elachi, I.R. Patel, and J.B. Cimeno, Icarus37, 51-2- 72, 1979, and one by B. Lipa and G.L. Tyler, Icarus39, 192–208, 1979, reach fundamentally different conclusions concerning microwave absorption in the atmosphere of Venus, even though they are based on the same Mariner 10 radio occultation data. The Lipa and Tyler results are in general agreement with earlier Mariner 5 measurements analyzed by G. Fjeldbo, A.J. Kliore, and V.R. Eshleman, Astron. J.76, 123–140, 1971. We find that in the Kliore et al. treatment: (1) the effects of measurements and analysis uncertainties in the derived values of absorption are underestimated; (2) an incorrect formula is used for computation of the refractive effects needed to determine the absorption; (3) detailed features of a derived profile of absorption would have been created in an optically thin region by known motions of the spacecraft antenna, if its axial direction were biased about 0.5° from the computed directions; and (4) this particular angular bias is consistent with other available information about an apparent residual difference between true and reconstructed antenna pointing directions. We conclude that: (1) there is no credible evidence for measurable microwave absorption in the atmosphere of Venus at heights greater than 55 km for any of the wavelengths that have been used in radio occultation experiments, even though Kliore et al. indicate that there are significant amounts up to at least 70 km for both Mariner 10 wavelengths (13 and 3.6 cm); (2) absorption in the region 35 to 50 km has been reasonably well determined from the two concordant Mariner 5 and 10 analyses, but only at one wavelength (13 cm); and (3) improved instrumentation and careful planning and analysis will be required for the radio occultation technique to realize its potential for the study of absorbing regions in the atmospheres of Venus and the major planets.  相似文献   

Effects of atmospheric river landfalls on the cold season precipitation in California   总被引：2，自引：0，他引：2  

Jinwon Kim  Duane E. Waliser  Paul J. Neiman  Bin Guan  Ju-Mee Ryoo  Gary A. Wick 《Climate Dynamics》2013,40(1-2):465-474

Effects of atmospheric river (AR) landfalls in the California coast on the cold-season precipitation in California are examined for the cold seasons of 10 water years (WYs) 2001–2010 using observed data and regional modeling in conjunction with AR-landfall inventory based on visual inspections of precipitable water vapor (PWV) from remote sensing and reanalysis. The PWV in the SSM/I and SSMIS retrievals and the ERA-Interim reanalysis shows 95 AR-landfall days in the California coast that are almost evenly split between the northern and southern coasts across 37.5N. The CPC/NCEP gridded daily precipitation analysis shows that 10–30% of the cold-season precipitation totals in California have occurred during these AR landfalls. The analysis also reveals that the percentage of precipitation and the precipitation intensity during AR landfalls in California are characterized by strong north-to-south gradient. This north–south contrast in the AR precipitation is reversed for the non-AR precipitation in the coastal range. The frequency of AR landfalls and the cold-season precipitation totals in the Sierra Nevada region are only marginally correlated. Instead, AR landfalls are closely related with the occurrence of heavy precipitation events. The freezing-level altitudes are systematically higher for AR wet days than non-AR wet days indicating warmer low-troposphere during AR storms. Cold season simulations for the 10 WYs 2001–2010 show that the Weather Research and Forecast (WRF) model can reasonably simulate important features in both the seasonal and AR precipitation totals. The daily pattern correlation coefficients between the simulated and ERA-Interim upper-air fields exceed 0.9 for most of the period. This suggests that the simulated temporal variations in the atmospheric circulation agree reasonably with the reanalysis over seasonal time scales, characteristics critical for reliable simulations of regional scale hydrologic cycle. The simulated seasonal and AR precipitation totals also agree reasonably with the CPC/NCEP precipitation analysis. The most notable model errors include the overestimation (underestimation) of the season-total and AR precipitation in the northern (southern) California region. The differences in the freezing-level altitudes during the AR- and non-AR wet days in the simulation agree with those from the ERA-Interim reanalysis. The freezing level altitudes are systematically overestimated in the simulations, suggesting warm biases in the low troposphere. Overall, WRF appears to perform reasonably in simulating the key features in the cold season precipitation related with AR landfalls, an important capability for assessing the impact of global climate variations and change on future hydrology in California.  相似文献   

Three-dimensional slope stability analysis of South Peak, Crowsnest Pass, Alberta, Canada   总被引：2，自引：2，他引：0  

Marc-Andr�� Brideau  Andrea Pedrazzini  Doug Stead  Corey Froese  Michel Jaboyedoff  David van Zeyl 《Landslides》2011,8(2):139-158

South Peak is a 7-Mm³ potentially unstable rock mass located adjacent to the 1903 Frank Slide on Turtle Mountain, Alberta. This paper presents three-dimensional numerical rock slope stability models and compares them with a previous conceptual slope instability model based on discontinuity surfaces identified using an airborne LiDAR digital elevation model (DEM). Rock mass conditions at South Peak are described using the Geological Strength Index and point load tests, whilst the mean discontinuity set orientations and characteristics are based on approximately 500 field measurements. A kinematic analysis was first conducted to evaluate probable simple discontinuity-controlled failure modes. The potential for wedge failure was further assessed by considering the orientation of wedge intersections over the airborne LiDAR DEM and through a limit equilibrium combination analysis. Block theory was used to evaluate the finiteness and removability of blocks in the rock mass. Finally, the complex interaction between discontinuity sets and the topography within South Peak was investigated through three-dimensional distinct element models using the code 3DEC. The influence of individual discontinuity sets, scale effects, friction angle and the persistence along the discontinuity surfaces on the slope stability conditions were all investigated using this code.  相似文献   

Geochemistry and modification of oilfield brines in surface pits in Northern Kuwait     

Abeer A. Alfarhan  Michael J. Duane 《Arabian Journal of Geosciences》2011,5(5):1055-1068

Oilfield brines (produced water) are produced as a waste product daily at the gathering centers (GCs) in Kuwait oilfields. The geochemical evolution of the water produced at the GC (fresh brine) to stagnant pit water (evaporate) has been investigated in the northern fields of Kuwait, and a model is presented showing time-dependent variations. Kuwait oilfield brines are globally similar to others in other large sedimentary basins (USA, Canada), but modifications have occurred due to seawater injection practices performed episodically during the oil extraction process. Brine water chemistry changes from generally average brine chemistry (based on cations and anions) to saturated mixture of seawater, oilfield brine, and anthropogenic chemical pollutants. The objective of this study was to harmonize the database of brine waters in terms of regional identity by comparison with oilfield brines elsewhere, identify water–rock interaction, and statistically treat daily recordings from the pits in order to identify injection peaks and troughs. Laboratory analysis of major and minor cations and anions from the Rawdatayn samples gave the following concentration ranges in parts per million (ppm): (Na⁺, 11,698–203,977), (Ca²⁺, 2,216–98,514), (Mg²⁺, 1,602–28,885), (K⁺, 1,528–16,573), (Sr²⁺, 70–502), (Ba²⁺, 0.01–18.04), (Fe²⁺, 0.01–8.93), (Li⁺, 0.09–6.48), (Si²⁺, 0.00–13.18), (B³⁺, 0.05–37.45), (SO ₄ ²⁺ , 330–3100). For the Sabriyah oilfield samples, the major and minor cations and anions concentration ranges in ppm are: (Na⁺, 9,807–274,947), (Ca²⁺, 2,555–77,992), (Mg²⁺, 1,415–28,183), (K⁺, 764–19,201), (Sr²⁺, 77.84–641), (Ba²⁺, 0.15–6.76), (Fe²⁺, 0.016–38.88), (Li⁺, 0.05–6.83), (Si²⁺, 0.0195–16.84), (B³⁺, 7.17–55.33), (SO ₄ ²⁺ , 44,812–135,264). The stable isotopic analysis of five samples indicates normal trends in oxygen and hydrogen isotopes that classify the waters as “connate” which follow an evaporation trend. Carbon isotopic signatures are normal for hydrocarbon fields and average out around GC15, δ¹⁸O‰?=?1.4, δD‰?=??10, δ¹³C‰?=??3.6; while for GC23, δ¹⁸O‰?=?2.3, δD‰?=??4, δ¹³C‰?=??2.5; for GC25, δ¹⁸O‰?=??2.0, δD‰?=??14, δ¹³C‰?=??4.6; for pit1, δ¹⁸O‰?=?2.3, δD‰?=??5, δ¹³C‰?=??18.3; and for pit 2, δ¹⁸O‰?=?2.5, δD‰?=??4, δ¹³C‰?=??17.8. Carbon isotope average values for all brine samples from the GCs is?=??56 which falls within normal hydrocarbon formation water category. Data spikes coincide with injection periods at the following times (A: May–Jun, 2006), (B: Sep–Oct, 2006), (C: Jan–Feb, 2007), (D: Mar, 2007), (E: May–Jun, 2007), (F: Feb, 2006), (G: Mar–Apr, 2006) and, subsequently the decay to “normal” brine occurs over a period of several weeks. The database was large enough to apply a principal component statistical analysis (PCA). PCA and geo-statistical techniques reveal several distinct population groups. The main chemical groups in the data are as follows: plateau, spike groups, and pit evaporation group. The spike periods correlate closely with seawater injection periods (Jan–Feb, Mar–Apr, May–Jun, and Sep–Oct). The pit chemistry reveals exceptionally high evaporation processes coinciding with summer peak temperature. PCA results show distinct groupings centered around the major elements reminiscent of other oilfields, but with the added evaporation trend strongly enhanced.  相似文献   

The MJO and global warming: a study in CCSM4     

Aneesh Subramanian  Markus Jochum  Arthur J. Miller  Richard Neale  Hyodae Seo  Duane Waliser  Raghu Murtugudde 《Climate Dynamics》2014,42(7-8):2019-2031

The change in Madden–Julian oscillation (MJO) amplitude and variance in response to anthropogenic climate change is assessed in the 1° nominal resolution community climate system model, version 4 (CCSM4), which has a reasonable representation of the MJO characteristics both dynamically and statistically. The twentieth century CCSM4 run is compared with the warmest twenty-first century projection (representative concentration pathway 8.5, or RCP8.5). The last 20 years of each simulation are compared in their MJO characteristics, including spatial variance distributions of winds, precipitation and outgoing longwave radiation, histograms of event amplitude, phase and duration, and composite maps of phases. The RCP8.5 run exhibits increased variance in intraseasonal precipitation, larger-amplitude MJO events, stronger MJO rainfall in the central and eastern tropical Pacific, and a greater frequency of MJO occurrence for phases corresponding to enhanced rainfall in the Indian Ocean sector. These features are consistent with the concept of an increased magnitude for the hydrological cycle under greenhouse warming conditions. Conversely, the number of active MJO days decreases and fewer weak MJO events occur in the future climate state. These results motivate further study of these changes since tropical rainfall variability plays such an important role in the region’s socio-economic well being.  相似文献   

NASA Landsat program accomplishments continue to make a difference     

Kamlesh Lulla  M. Duane Nellis  Brad Rundquist 《国际地球制图》2013,28(4)

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