The Multiscale TROPIcal CatchmentS critical zone observatory M-TROPICS dataset II: Land use,hydrology and sediment production monitoring in Houay Pano,northern Lao PDR     

Laurie Boithias  Yves Auda  Stéphane Audry  Jean-Pierre Bricquet  Alounsavath Chanhphengxay  Vincent Chaplot  Anneke de Rouw  Thierry Henry des Tureaux  Sylvain Huon  Jean-Louis Janeau  Keooudone Latsachack  Yann Le Troquer  Guillaume Lestrelin  Jean-Luc Maeght  Pierre Marchand  Pierre Moreau  Andrew Noble  Anne Pando-Bahuon  Kongkeo Phachomphon  Khambai Phanthavong  Alain Pierret  Olivier Ribolzi  Jean Riotte  Henri Robain  Emma Rochelle-Newall  Saysongkham Sayavong  Oloth Sengtaheuanghoung  Norbert Silvera  Nivong Sipaseuth  Bounsamay Soulileuth  Xaysatith Souliyavongsa  Phapvilay Sounyaphong  Sengkeo Tasaketh  Chanthamousone Thammahacksa  Jean-Pierre Thiebaux  Christian Valentin  Olga Vigiak  Marion Viguier  Khampaseuth Xayyathip 《水文研究》2021,35(5):e14126

Mountain regions of the humid tropics are characterized by steep slopes and heavy rains. These regions are thus prone to both high surface runoff and soil erosion. In Southeast Asia, uplands are also subject to rapid land-use change, predominantly as a result of increased population pressure and market forces. Since 1998, the Houay Pano site, located in northern Lao PDR (19.85°N 102.17°E) within the Mekong basin, aims at assessing the long-term impact of the conversion of traditional slash-and-burn cultivation systems to commercial perennial monocultures such as teak tree plantations, on the catchment hydrological response and sediment yield. The instrumented site monitors hydro-meteorological and soil loss parameters at both microplot (1 m²) and small catchment (0.6 km²) scales. The monitored catchment is part of the network of critical zone observatories named Multiscale TROPIcal CatchmentS (M-TROPICS). The data shared by M-TROPICS in Houay Pano are (1) rainfall, (2) air temperature, air relative humidity, wind speed, and global radiation, (3) catchment land use, (4) stream water level, suspended particulate matter, bed particulate matter and stones, (5) soil surface features, and (6) soil surface runoff and soil detachment. The dataset has already been used to interpret suspended particulate matter and bed particulate matter sources and dynamics, to assess the impact of land-use change on catchment hydrology, soil erosion, and sediment yields, to understand bacteria fate and weed seed transport across the catchment, and to build catchment-scale models focused on hydrology and water quality issues. The dataset may be further used to, for example, assess the role of headwater catchments in large tropical river basin hydrology, support the interpretation of new variables measured in the catchment (e.g., contaminants other than faecal bacteria), and assess the relative impacts of both climate and land-use change on the catchment.  相似文献   

Temporal variation of the tropospheric cloud and haze in the jovian equatorial zone     

Patrick S. Lii  Michael H. Wong  Imke de Pater 《Icarus》2010,209(2):591-601

We analyze the temporal variation of the tropospheric cloud and haze in the jovian equatorial zone. In order to investigate the time evolution of the haze, we utilize a comprehensive set of archival WFPC2 images in the 953 and 893-nm wavelengths spanning over a decade of HST observations of Jupiter. We find that the latitude of the peak haze reflectivity experienced a southerly shift in between late-1998 and early-2001 (not to be confused with southerly bulk transport of haze particles themselves); before this shift, the latitude of peak reflectivity had remained relatively stable at +7° (planetographic latitude). We examine the average haze reflectivity at three equatorial latitudes (−5°, 0°, +5°) and find variability of amplitude ±20%. Equatorial clouds, which lie deeper than the haze, showed zonal mean variability with an amplitude of about 5% except during the global upheaval of 2006-2007 in which cloud reflectivity dropped up to 16% depending on latitude. An analysis of temporal correlation between zonally averaged cloud reflectivity and zonally averaged haze reflectivity indicates a time-lag of about 1200 days (with a lower limit of 800 days) between changes in cloud reflectivity and later changes in haze reflectivity, but limitations in the temporal coverage of even this extensive dataset make it impossible to rule out even longer time-lags.  相似文献   

In-flight calibration of the Cassini imaging science sub-system cameras     

Robert West  Benjamin Knowles  Sebastien Charnoz  Matthew Hedman  Alfred McEwen  Carolyn Porco  Henry Throop 《Planetary and Space Science》2010,58(11):1475-1488

We describe in-flight calibration of the Cassini Imaging Science Sub-system narrow- and wide-angle cameras using data from 2004 to 2009. We report on the photometric performance of the cameras including the use of polarization filters, point spread functions over a dynamic range greater than 10⁷, gain and loss of hot pixels, changes in flat fields, and an analysis of charge transfer efficiency. Hot pixel behavior is more complicated than can be understood by a process of activation by cosmic ray damage and deactivation by annealing. Point spread function (PSF) analysis revealed a ghost feature associated with the narrow-angle camera Green filter. More generally, the observed PSFs do not fall off with distance as rapidly as expected if diffraction were the primary contributor. Stray light produces significant signal far from the center of the PSF. Our photometric analysis made use of calibrated spectra from eighteen stars and the spectral shape of the satellite Enceladus. The analysis revealed a shutter offset that differed from pre-launch calibration. It affects the shortest exposures. Star photometry results are reproducible to a few percent in most filters. No degradation in charge transfer efficiency has been detected although uncertainties are large. The results of this work have been digitally archived and incorporated into our calibration software CISSCAL available online.  相似文献   

Analysis of climate policy targets under uncertainty   总被引：1，自引：1，他引：0  

Mort Webster  Andrei P. Sokolov  John M. Reilly  Chris E. Forest  Sergey Paltsev  Adam Schlosser  Chien Wang  David Kicklighter  Marcus Sarofim  Jerry Melillo  Ronald G. Prinn  Henry D. Jacoby 《Climatic change》2012,112(3-4):569-583

Although policymaking in response to the climate change threat is essentially a challenge of risk management, most studies of the relation of emissions targets to desired climate outcomes are either deterministic or subject to a limited representation of the underlying uncertainties. Monte Carlo simulation, applied to the MIT Integrated Global System Model (an integrated economic and earth system model of intermediate complexity), is used to analyze the uncertain outcomes that flow from a set of century-scale emissions paths developed originally for a study by the U.S. Climate Change Science Program. The resulting uncertainty in temperature change and other impacts under these targets is used to illustrate three insights not obtainable from deterministic analyses: that the reduction of extreme temperature changes under emissions constraints is greater than the reduction in the median reduction; that the incremental gain from tighter constraints is not linear and depends on the target to be avoided; and that comparing median results across models can greatly understate the uncertainty in any single model.  相似文献   

Multiproxy reconstructions of climate for three sites in the Canadian High Arctic using Cassiope tetragona     

Shelly A. Rayback  Gregory H. R. Henry  Andrea Lini 《Climatic change》2012,114(3-4):593-619

We developed calibration models and reconstructed climate for sites in the central and eastern Canadian High Arctic using dendroclimatological and stable isotope analysis techniques on the dwarf-shrub, Cassiope tetragona. Our results may suggest complex temporal and spatial patterns of climate change in the region over the past century. For sites on Bathurst and Devon Islands, we reconstructed fall mean and June–July mean temperature using multiple linear regression analysis that explained 54?% and 40?% of the variance, respectively. The predictor variables included annual growth, annual production of leaves, flower buds and annual δ13C values for the Bathurst Island model, and annual growth and δ13C values for the Devon Island model. Both models revealed warmer than average temperatures throughout the mid-20th century, followed by a cooling trend from the early 1960s and mid-1970s at the Devon and Bathurst Island sites, respectively. Temperatures remained cool until the early 1980s and then increased until 1998/1999 at both sites. Our models are supported by other paleoclimate proxies and the instrumental record from the Canadian Arctic. For sites on Axel Heiberg and Bathurst Islands, we developed models using multivariate regresssion for February and March total precipitation that explained 44?% and 42?% of the variance, respectively. The Axel Heiberg Island model included annual production of flowers and flower buds, as well as annual δ13C values as predictor variables, while the Bathurst Island model only included the annual production of flower buds as a predictor. Both models showed lower than average precipitation from the early to mid-1900s, followed by increasing precipitation from the late 1980s to 1998/1999. Our precipitation models, supported by instrumental and proxy data, suggest a trend of increasing late-winter/early spring precipitation in the late 20th century. The lack of a single detectable climate signal across the study sites suggests local climate, topography, genetic variation and/or ecological conditions may dictate, in part, site responses and result in a heterogeneous climatescape over space and time. Yet, like other arctic paleoclimate proxies, chronology error and temporal discrepancies may complicate our interpretations. However, comparisons with other arctic proxies and the meteorological record suggest our models have also registered a regional climate signal.  相似文献   

Carbon sequestration potential of parkland agroforestry in the Sahel   总被引：1，自引：0，他引：1  

Eike Luedeling  Henry Neufeldt 《Climatic change》2012,115(3-4):443-461

Establishing parkland agroforestry on currently treeless cropland in the West African Sahel may help mitigate climate change. To evaluate its potential, we used climatically suitable ranges for parklands for 19 climate scenarios, derived by ecological niche modeling, for estimating potential carbon stocks in parkland and treeless cropland. A biocarbon business model was used to evaluate profitability of hypothetical Terrestrial Carbon Projects (TCPs), across a range of farm sizes, farm numbers, carbon prices and benefit sharing mechanisms. Using climate analogues, we explored potential climate change trajectories for selected locations. If mature parklands covered their maximum range, carbon stocks in Sahelian productive land would be about 1,284?Tg, compared to 725?Tg in a treeless scenario. Due to slow increase rates of total system carbon by 0.4?Mg?C?ha^?1 a^?1, most TCPs at carbon prices that seem realistic today were not feasible, or required the participation of large numbers of farmers. For small farms, few TCP scenarios were feasible, and low Net Present Values for farmers made it unlikely that carbon payments would motivate many to participate in TCPs, unless additional benefits were provided. Climate analogue locations indicated an uncertain climate trajectory for the Sahel, but most scenarios projected increasing aridity and reduced suitability for parklands. The potentially severe impacts of climate change on Sahelian ecosystems and the uncertain profitability of TCPs make the Sahel highly risky for carbon investments. Given the likelihood of degrading environmental conditions, the search for appropriate adaptation strategies should take precedence over promoting mitigation activities.  相似文献   

Comment on “Transport of nonmethane hydrocarbons to Jupiter's troposphere by descent of smog particles” by Donald M. Hunten [Icarus 194 (2008) 616-622]     

Michael H. Wong 《Icarus》2009,199(1):231-235

The downward transport of nonmethane hydrocarbons, condensed onto solid photochemically produced particles termed “smust,” may indeed be an important process in the methane-rich atmospheres of Jupiter and Titan. However, evidence supporting this mechanism on Jupiter [Hunten, D.M., 2008. Icarus 194, 616-622] is considerably weakened by three new considerations: the ethane mixing ratio does not increase with depth or show a 1-bar minimum, atmospheric characteristics measured by the probe throughout its descent are representative of much higher altitudes in the “normal” jovian atmosphere, and transport models must consider the lower boundary condition imposed by deep thermochemical destruction of nonmethane hydrocarbons. Additionally, ethane was not the most abundant nonmethane hydrocarbon detected by the Galileo Probe Mass Spectrometer (GPMS) near 11 bar, reinforcing previously published findings that some (if not all) of the nonmethane hydrocarbons detected by the GPMS were of instrumental rather than atmospheric origin.  相似文献   

Stability of polar oscillations of non-rotating Newtonian superfluid stars     

K. S. Wong 《Monthly notices of the Royal Astronomical Society》2009,396(1):439-461

In this paper, we shall study the problem of stability of polar oscillations of a non-rotating Newtonian superfluid star. We find that the stability of the latter system is guaranteed by the positive definiteness of a matrix quantity. We also find conditions which characterize the occurrence of zero-frequency polar modes, which marks the onset of polar instability. We find that the negative definiteness of the mentioned matrix quantity implies instability of the system. We apply our results to show that the polar oscillations of a non-rotating Newtonian superfluid star in the zero-temperature approximation are marginally stable.  相似文献   

NOIRCAT – the Northern HIPASS Optical/IR Catalogue     

O. I. Wong  R. L. Webster  V. A. Kilborn  M. Waugh  L. Staveley-Smith 《Monthly notices of the Royal Astronomical Society》2009,399(4):2264-2278

We present the Northern HIPASS (H  i Parkes All-Sky Survey) Optical/Infrared Catalogue (NOIRCAT), an optical/near-infrared (NIR) counterpart to the Northern HIPASS Catalogue (NHICAT). Of the 1002 sources in NHICAT, 655 (66 per cent) have optical counterparts with matching optical velocities. A further 85 (8 per cent) sources have optical counterparts with matching velocities from previous radio emission-line surveys. We find a correlation between the gas and stellar content of the NOIRCAT sources. Our H  i -selected sample of isolated galaxies also presents a wider range in NIR colours than previous optically selected studies of regular, isolated galaxies. All H  i detections in optically unobscured fields could be matched with either a NASA/IPAC Extragalactic Database optical counterpart, or a galaxy visible in Second Palomar Observatory Sky Survey or Digitized Sky Survey images. However, as over 200 of these matched galaxies have no velocity information, further follow-up observations are needed to confirm the matches, and hence confirm or deny the existence of dark galaxies in this data set.  相似文献   

Crack Coalescence in Molded Gypsum and Carrara Marble: Part 1. Macroscopic Observations and Interpretation   总被引：8，自引：5，他引：3  

L. N. Y. Wong  H. H. Einstein 《Rock Mechanics and Rock Engineering》2009,42(3):475-511

Cracking and coalescence behavior has been studied experimentally with prismatic laboratory-molded gypsum and Carrara marble specimens containing two parallel pre-existing open flaws. This was done at both the macroscopic and the microscopic scales, and the results are presented in two separate papers. This paper (the first of two) summarizes the macroscopic experimental results and investigates the influence of the different flaw geometries and material, on the cracking processes. In the companion paper (also in this issue), most of the macroscopic deformation and cracking processes shown in this present paper will be related to the underlying microscopic changes. In the present study, a high speed video system was used, which allowed us to precisely observe the cracking mechanisms. Nine crack coalescence categories with different crack types and trajectories were identified. The flaw inclination angle (β), the ligament length (L), that is, intact rock length between the flaws, and the bridging angle (α), that is, the inclination of a line linking up the inner flaw tips, between two flaws, had different effects on the coalescence patterns. One of the pronounced differences observed between marble and gypsum during the compression loading test was the development of macroscopic white patches prior to the initiation of macroscopic cracks in marble, but not in gypsum. Comparing the cracking and coalescence behaviors in the two tested materials, tensile cracking generally occurred more often in marble than in gypsum for the same flaw pair geometries.

H. H. EinsteinEmail:

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