ENSIP: the El Niño simulation intercomparison project     

M. Latif  K. Sperber  J. Arblaster  P. Braconnot  D. Chen  A. Colman  U. Cubasch  C. Cooper  P. Delecluse  D. Dewitt  L. Fairhead  G. Flato  T. Hogan  M. Ji  M. Kimoto  A. Kitoh  T. Knutson  H. Le Treut  T. Li  S. Manabe  O. Marti  C. Mechoso  G. Meehl  S. Power  E. Roeckner  J. Sirven  L. Terray  A. Vintzileos  R. Voß  B. Wang  W. Washington  I. Yoshikawa  J. Yu  S. Zebiak 《Climate Dynamics》2001,18(3-4):255-276

An ensemble of twenty four coupled ocean-atmosphere models has been compared with respect to their performance in the tropical Pacific. The coupled models span a large portion of the parameter space and differ in many respects. The intercomparison includes TOGA (Tropical Ocean Global Atmosphere)-type models consisting of high-resolution tropical ocean models and coarse-resolution global atmosphere models, coarse-resolution global coupled models, and a few global coupled models with high resolution in the equatorial region in their ocean components. The performance of the annual mean state, the seasonal cycle and the interannual variability are investigated. The primary quantity analysed is sea surface temperature (SST). Additionally, the evolution of interannual heat content variations in the tropical Pacific and the relationship between the interannual SST variations in the equatorial Pacific to fluctuations in the strength of the Indian summer monsoon are investigated. The results can be summarised as follows: almost all models (even those employing flux corrections) still have problems in simulating the SST climatology, although some improvements are found relative to earlier intercomparison studies. Only a few of the coupled models simulate the El Niño/Southern Oscillation (ENSO) in terms of gross equatorial SST anomalies realistically. In particular, many models overestimate the variability in the western equatorial Pacific and underestimate the SST variability in the east. The evolution of interannual heat content variations is similar to that observed in almost all models. Finally, the majority of the models show a strong connection between ENSO and the strength of the Indian summer monsoon.  相似文献   

A world ocean model for greenhouse sensitivity studies: resolution intercomparison and the role of diagnostic forcing     

Warren M Washington  Gerald A Meehl  Lynda VerPlank  Thomas W Bettge 《Climate Dynamics》1994,9(7):321-344

We have developed an improved version of a world ocean model with the intention of coupling to an atmospheric model. This article documents the simulation capability of this 1° global ocean model, shows improvements over our earlier 5° version, and compares it to features simulated with a 0.5° model. These experiments use a model spin-up methodology whereby the ocean model can subsequently be coupled to an atmospheric model and used for order 100-year coupled model integrations. With present-day computers, 1° is a reasonable compromise in resolution that allows for century-long coupled experiments. The 1° ocean model is derived from a 0.5°-resolution model developed by A. Semtner (Naval Postgraduate School) and R. Chervin (National Center for Atmospheric Research) for studies of the global eddy-resolving world ocean circulation. The 0.5° bottom topography and continental outlines have been altered to be compatible with the 1° resolution, and the Arctic Ocean has been added. We describe the ocean simulation characteristics of the 1° version and compare the result of weakly constraining (three-year time scale) the three-dimensional temperature and salinity fields to the observations below the thermocline (710 m) with the model forced only at the top of the ocean by observed annual mean wind stress, temperature, and salinity. The 1° simulations indicate that major ocean circulation patterns are greatly improved compared to the 5° version and are qualitatively reproduced in comparison to the 0.5° version. Using the annual mean top forcing alone in a 100-year simulation with the 1° version preserves the general features of the major observed temperature and salinity structure with most climate drift occurring mainly beneath the thermocline in the first 50–75 years. Because the thermohaline circulation in the 1° version is relatively weak with annual mean forcing, we demonstrate the importance of the seasonal cycle by performing two sensitivity experiments. Results show a dramatic intensification of the meridional overturning circulation (order of magnitude) with perpetual winter surface temperature forcing in the North Atlantic and strong intensification (factor of three) with perpetual early winter temperatures in that region. These effects are felt throughout the Atlantic (particularly an intensified and northward-shifted Gulf Stream outflow). In the Pacific, the temperature gradient strengthens in the thermocline, thus helping counter the systematic error of a thermocline that is too diffuse.Partial support is provided by the Office of Health and Environmental Research of the US Department of Energy The National Center for Atmospheric Research is sponsored by the National Science Foundation  相似文献   

An analysis and model for Automatic Dependent Surveillance Broadcast (ADS-B) continuity     

Ali  Busyairah Syd  Ochieng  Washington Yotto  Zainudin  Rozaimah 《GPS Solutions》2017,21(4):1841-1854

GPS Solutions - The surveillance function of air traffic management is critical to aviation safety. It determines the identity of an aircraft, its state and intent to support air traffic...  相似文献   

Micro‐mechanical simulation of geotechnical problems using massively parallel computers     

David W. Washington  Jay N. Meegoda 《国际地质力学数值与分析法杂志》2003,27(14):1227-1234

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Parallel climate model (PCM) control and transient simulations     

W. M. Washington  J. W. Weatherly  G. A. Meehl  A. J. Semtner Jr.  T. W. Bettge  A. P. Craig  W. G. Strand Jr.  J. Arblaster  V. B. Wayland  R. James  Y. Zhang 《Climate Dynamics》2000,16(10-11):755-774

The Department of Energy (DOE) supported Parallel Climate Model (PCM) makes use of the NCAR Community Climate Model (CCM3) and Land Surface Model (LSM) for the atmospheric and land surface components, respectively, the DOE Los Alamos National Laboratory Parallel Ocean Program (POP) for the ocean component, and the Naval Postgraduate School sea-ice model. The PCM executes on several distributed and shared memory computer systems. The coupling method is similar to that used in the NCAR Climate System Model (CSM) in that a flux coupler ties the components together, with interpolations between the different grids of the component models. Flux adjustments are not used in the PCM. The ocean component has 2/3° average horizontal grid spacing with 32 vertical levels and a free surface that allows calculation of sea level changes. Near the equator, the grid spacing is approximately 1/2° in latitude to better capture the ocean equatorial dynamics. The North Pole is rotated over northern North America thus producing resolution smaller than 2/3° in the North Atlantic where the sinking part of the world conveyor circulation largely takes place. Because this ocean model component does not have a computational point at the North Pole, the Arctic Ocean circulation systems are more realistic and similar to the observed. The elastic viscous plastic sea ice model has a grid spacing of 27?km to represent small-scale features such as ice transport through the Canadian Archipelago and the East Greenland current region. Results from a 300?year present-day coupled climate control simulation are presented, as well as for a transient 1% per year compound CO₂ increase experiment which shows a global warming of 1.27?°C for a 10?year average at the doubling point of CO₂ and 2.89?°C at the quadrupling point. There is a gradual warming beyond the doubling and quadrupling points with CO₂ held constant. Globally averaged sea level rise at the time of CO₂ doubling is approximately 7?cm and at the time of quadrupling it is 23?cm. Some of the regional sea level changes are larger and reflect the adjustments in the temperature, salinity, internal ocean dynamics, surface heat flux, and wind stress on the ocean. A 0.5% per year CO₂ increase experiment also was performed showing a global warming of 1.5?°C around the time of CO₂ doubling and a similar warming pattern to the 1% CO₂ per year increase experiment. El Niño and La Niña events in the tropical Pacific show approximately the observed frequency distribution and amplitude, which leads to near observed levels of variability on interannual time scales.  相似文献   

General circulation model CO2 sensitivity experiments: Snow-sea ice albedo parameterizations and globally averaged surface air temperature     

Warren M. Washington  Gerald A. Meehl 《Climatic change》1986,8(3):231-241

Two experiments are performed with the NCAR Community Climate Model (CCM) coupled to a swamp ocean with annually averaged solar forcing. A swamp ocean model is one in which the ocean temperature is computed from a surface energy balance. Both experiments are run with present (1 × CO₂) and doubled (2 × CO₂) amounts of atmospheric carbon dioxide (CO₂). The first tests the sensitivity of the model to a snow and sea-ice-albedo formulation which facilitates relatively greater ice melt. The second assesses the model response when the basic state of the model in the control run is colder due to a 2% decrease in solar constant. Both are compared to a previous experiment with the same model using a different snow and sea-ice-albedo formulation and the present value of the solar constant. It is found that the globally averaged surface air temperature increase due to a doubling of CO₂ is highly dependent on (1) the type of snow-sea-ice-albedo formulation used such that the parameterization which better facilitates relatively greater ice melt exhibits a greater sensitivity to increased CO₂, and (2) the basic state of the control run such that the colder the basic state, the greater the warming due to increased CO₂.A portion of this study is supported by the U.S. Department of Energy as part of its Carbon Dioxide Research Program.The National Center for Atmospheric Research is sponsored by the National Science Foundation  相似文献   

Mid-Century Ensemble Regional Climate Change Scenarios for the Western United States   总被引：3，自引：0，他引：3  

L. Ruby Leung  Yun Qian  Xindi Bian  Warren M. Washington  Jongil Han  John O. Roads 《Climatic change》2004,62(1-3):75-113

To study the impacts of climate change on water resources in the western U.S., global climate simulations were produced using the National Center for Atmospheric Research/Department of Energy (NCAR/DOE) Parallel Climate Model (PCM). The Penn State/NCAR Mesoscale Model (MM5) was used to downscale the PCM control (20 years) and three future(2040–2060) climate simulations to yield ensemble regional climate simulations at 40 km spatial resolution for the western U.S. This paper describes the regional simulations and focuses on the hydroclimate conditions in the Columbia River Basin (CRB) and Sacramento-San Joaquin River (SSJ) Basin. Results based on global and regional simulations show that by mid-century, the average regional warming of 1 to 2.5 °C strongly affects snowpack in the western U.S. Along coastal mountains, reduction in annual snowpack was about70% as indicated by the regional simulations. Besides changes in mean temperature, precipitation, and snowpack, cold season extreme daily precipitation increased by 5 to 15 mm/day (15–20%) along theCascades and the Sierra. The warming resulted in increased rainfall at the expense of reduced snowfall, and reduced snow accumulation (or earlier snowmelt) during the cold season. In the CRB, these changes were accompanied by more frequent rain-on-snow events. Overall, they induced higher likelihood of wintertime flooding and reduced runoff and soil moisture in the summer. Changes in surface water and energy budgets in the CRB and SSJ basin were affected mainly by changes in surface temperature, which were statistically significant at the 0.95 confidence level. Changes in precipitation, while spatially incoherent, were not statistically significant except for the drying trend during summer. Because snow and runoff are highly sensitive tospatial distributions of temperature and precipitation, this study shows that (1) downscaling provides more realistic estimates of hydrologic impacts in mountainous regions such as the western U.S., and (2) despite relatively small changes in temperature and precipitation, changes in snowpack and runoff can be much larger on monthly to seasonal time scales because the effects of temperature and precipitation are integrated over time and space through various surface hydrological and land-atmosphere feedback processes. Although the results reported in this study were derived from an ensemble of regional climate simulations driven by a global climate model that displays low climate sensitivity compared with most other models, climate change was found to significantly affect water resources in the western U.S. by the mid twenty-first century.  相似文献   

Future Climate Change of the Subtropical North Atlantic: Implications for the Cloud Forests of Tenerife     

Frank N. Sperling  Richard Washington  Robert J. Whittaker 《Climatic change》2004,65(1-2):103-123

This paper is concerned with climate change in the region of the Canary Islands and the potential implications for the laurel forests of Tenerife. Frequent orographic cloud formation during the dry season is of vital importance to the altitudinal distribution of the laurel forests, because it maintains a semi-humid environment in the otherwise semi-arid climate of the Canary Islands. The distinctive environmental conditions in conjunction with the location of the Canary Islands on the Northern poleward edge of the Hadley Circulation make these ecosystems potentially highly sensitive to regional changes in climatic conditions. To explore this sensitivity, we first quantify observed trends in humidity and temperature across an altitudinal transect at the base of the Anaga peninsular, and second, analyse the results of three GCM experiments (CGCM1, ECHAM4 and CSIRO) to develop alternative climate change scenarios, and third, use these data to assess likely shifts in the elevational distribution of the laurel forest climate envelope. We report a significant increase in relative humidity and decreases in the diurnal temperature range on Tenerife at altitudes below the trade wind inversion within the last 30 years during the dry season, which suggests an increased occurrence of low-level clouds. There is also partial evidence for a drying trend across the trade wind inversion, which may be linked to an increased subsidence. Overall, the models suggest a downward shift of the area climatically suitable for laurel forests, which may be driven by changes in temperature and moisture supply in the region as well as by larger-scale changes in the atmospheric circulation. Our findings contrast with previously published findings for a tropical montane cloud region, which predict an upward shift of the cloud base. This suggests, following the assumptions inherent in the models applied, that the ecological consequences of climate change for cloud forests may be linked to their relative location in the Hadley Circulation.  相似文献   

Effects of a variety of Indian Ocean surface temperature anomaly patterns on the summer monsoon circulation: Experiments with the NCAR general circulation model     

Warren M. Washington  Robert M. Chervin  G. V. Rao 《Pure and Applied Geophysics》1977,115(5-6):1335-1356

The time mean response of the summer monsoon circulation, as simulated by the 2.5° latitude-longitude resolution, July version of the National Center for Atmospheric Research (NCAR) General Circulation Model (GCM), to a variety of Indian Ocean surface temperature anomaly patterns is examined. In separate experiments, prescribed changes in surface temperature are imposed in the Western Arabian Sea, the Eastern Arbian Sea or the Central Indian Ocean. The influence of these anomaly patterns on the simulated summer monsoon circulation is evaluated in terms of the geographical distribution of the prescribed change response for any field of interest. This response is defined as the grid point difference between a 30-day mean from a prescribed change experiment and the ensemble average of the 30-day means from the control population for which the same set of climatological ocean surface temperatures are used in each simulation. The statistical significance of such a prescribed change response is estimated by relating the normalized response (defined as the ratio of the prescribed change response to the standard deviation of 30-day means as estimated from the finite sample of control cases) to the classical Student'st-statistic. Using this methodology, the most prominent and statistically significant features of the model's response are increased vertical velocity and precipitation over warm anomalies and typically decreased vertical velocity and precipitation in some preferred region adjacent to the prescribed change region. In the case of cold anomalies, these changes are of opposite sign. However, none of the imposed anomaly patterns produces substantial or statistically significant precipitation changes over large areas of the Indian sub-continent. The only evidence of a major nonlocal effect is found in the experiment with a large positive anomaly (+3°C) in the Central Indian Ocean. In this instance, vertical velocity and precipitation are reduced over Malaysia and a large area of the Equatorial Western Pacific Ocean. Thus, while these anomaly experiments produce only a local response (for the most part), it is hoped, as one of the purposes of the planned Monsoon Experiment (MONEX), that the necessary data will be provided to produce detailed empirical evidence on the extent to which Indian Ocean surface temperature anomalies correlate with precipitation anomalies over the Indian subcontinent—a correlation which generally does not appear in these GCM results.The National Center for Atmospheric Research is sponsored by the National Science Foundation  相似文献   

Behavior and Fate of PFOA and PFOS in Sandy Aquifer Sediment     

Mark L. Ferrey  John T. Wilson  Cherri Adair  Chunming Su  Dennis D. Fine  Xuyang Liu  John W. Washington 《Ground Water Monitoring & Remediation》2012,32(4):63-71

Microcosms were constructed with sediment from beneath a landfill that received waste containing PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonate). The microcosms were amended with PFOA and PFOS, and sampled after 91, 210, 343, 463, 574, and 740 d of incubation. After 740 d, selected microcosms were extracted to determine the mass of PFOA and PFOS remaining. There was no evidence for degradation of PFOA or PFOS. Over time, the aqueous concentrations of PFOA and PFOS increased in the microcosms, indicating that PFOA and PFOS that had originally sorbed to the sediment was desorbing. At the beginning of the experiment, the adsorption coefficient, K_d, averaged 0.27 L/kg for PFOA and 1.2 L/kg for PFOS. After 740 d of incubation, sorption of PFOA was not detectable and the K_d of PFOS was undetectable in two microcosms and was 0.08 L/kg in a third microcosm. During incubation, the pH of the pore water in the microcosms increased from pH 7.2 to pH ranging from 8.1 to 8.8. The zeta potential of the sediment decreased with increasing pH. These observations suggest that the sorption of PFOA and PFOS at near neutral pH was controlled by the electrostatic sorption on ferric oxide minerals, and not by the sorption to organic carbon. Accurate predictions of PFOA and PFOS mobility in ground water should be based on empirical estimates of sorption using affected aquifer sediment.  相似文献