A Saturnian stratospheric seasonal climate model     

Robert D. Cess  John Caldwell 《Icarus》1979,38(3):349-357

Motivated by recent observational evidence that seasonal processes occur within Saturn's stratosphere, we have constructed a seasonal stratospheric climate model. This model predicts stratospheric temperatures, above the P = 0.1-atm level, as a function of time throughout the Saturnian year. Specific results are presented for South-polar and equatorial temperatures. The model predicts that substantial seasonal phase lags exist; maximum stratospheric temperatures at the South pole occur at the Southern Hemisphere's autumnal equinox. Brightness temperature observations at 17.8 μm, taken during 1977/1978, indicate that stratospheric temperatures are greater at the South pole than at the equator. The model is consistent with these observations, predicting enhanced South-polar temperatures, relative to the equator, from 1975 to 1983.  相似文献   

On the elastic-perfectly plastic bending of the lithosphere under generalized loading with application to the Kurd Trench     

D. C. McAdoo  J. G. Caldwell  D. L. Turcotte 《Geophysical Journal International》1978,54(1):11-26

Summary. The bending of the lithosphere as it approaches an oceanic trench is modelled using an elastic-perfectly plastic rheology. The rock within the elastic lithosphere is assumed to behave elastically until a yield stress is reached; for larger strains the stress is assumed to remain at the yield value (no strain hardening). The deflection of the lithosphere is obtained numerically for a range of applied moments, vertical forces and horizontal forces at the trench axis. The results of the analysis are compared with a series of topographic and gravity profiles across the Kuril Trench. In order to model the large observed curvatures of the lithosphere on the outer trench slope plasticity is required. The location of the region of high curvatures gives a value for the compressive axial load. One conclusion is that the lithosphere is under compression seaward of the Kuril Trench.  相似文献   

A field study on the acute effects of the dispersant Corexit 9527 on glucose uptake by marine microorganisms     

R.P. Griffiths  T.M. McNamara  B.A. Caldwell  R.Y. Morita 《Marine environmental research》1981,5(2):83-91

The effects of the dispersant Corexit 9527 and Corexit with crude oil on the rate of glucose uptake and mineralisation were studied in Arctic and Subarctic marine waters and sediments. Essentially all of the 149 water and 95 sediment samples tested displayed decreased glucose uptake rates in the presence of either 15 or 50 ppm Corexit. Depressed uptake rates were observed at concentrations as low as 1 ppm. The mean concentration at which Corexit depressed glucose uptake by 50% was 12 ppm. The effect of Corexit was more pronounced on pelagic than on benthic microbial populations.  相似文献   

The strength of the tropical inversion and its response to climate change in 18 CMIP5 models     

Xin Qu  Alex Hall  Stephen A. Klein  Peter M. Caldwell 《Climate Dynamics》2015,45(1-2):375-396

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Design and Evaluation of a Mesoscale Model Vadose Zone and Ground-Water System     

J. R. Lawrence  B. N. Zanyk  M. J. Hendry  G. M. Wolfaardt  R. D. Robarts  D. E. Caldwell 《Ground water》1993,31(3):446-455

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Responses of soil and water chemistry to mountain pine beetle induced tree mortality in Grand County,Colorado, USA     

David W. Clow  Charles Rhoades  Jennifer Briggs  Megan Caldwell  William M. Lewis 《Applied Geochemistry》2011

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On the spread of changes in marine low cloud cover in climate model simulations of the 21st century   总被引：2，自引：1，他引：1  

Xin Qu  Alex Hall  Stephen A. Klein  Peter M. Caldwell 《Climate Dynamics》2014,42(9-10):2603-2626

In 36 climate change simulations associated with phases 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5), changes in marine low cloud cover (LCC) exhibit a large spread, and may be either positive or negative. Here we develop a heuristic model to understand the source of the spread. The model’s premise is that simulated LCC changes can be interpreted as a linear combination of contributions from factors shaping the clouds’ large-scale environment. We focus primarily on two factors—the strength of the inversion capping the atmospheric boundary layer (measured by the estimated inversion strength, EIS) and sea surface temperature (SST). For a given global model, the respective contributions of EIS and SST are computed. This is done by multiplying (1) the current-climate’s sensitivity of LCC to EIS or SST variations, by (2) the climate-change signal in EIS or SST. The remaining LCC changes are then attributed to changes in greenhouse gas and aerosol concentrations, and other environmental factors. The heuristic model is remarkably skillful. Its SST term dominates, accounting for nearly two-thirds of the intermodel variance of LCC changes in CMIP3 models, and about half in CMIP5 models. Of the two factors governing the SST term (the SST increase and the sensitivity of LCC to SST perturbations), the SST sensitivity drives the spread in the SST term and hence the spread in the overall LCC changes. This sensitivity varies a great deal from model to model and is strongly linked to the types of cloud and boundary layer parameterizations used in the models. EIS and SST sensitivities are also estimated using observational cloud and meteorological data. The observed sensitivities are generally consistent with the majority of models as well as expectations from prior research. Based on the observed sensitivities and the relative magnitudes of simulated EIS and SST changes (which we argue are also physically reasonable), the heuristic model predicts LCC will decrease over the 21st-century. However, to place a strong constraint, for example on the magnitude of the LCC decrease, will require longer observational records and a careful assessment of other environmental factors producing LCC changes. Meanwhile, addressing biases in simulated EIS and SST sensitivities will clearly be an important step towards reducing intermodel spread in simulated LCC changes.  相似文献   

Assessing the potential of drone‐based thermal infrared imagery for quantifying river temperature heterogeneity     

Stephen J. Dugdale  Christa A. Kelleher  Iain A. Malcolm  Samuel Caldwell  David M. Hannah 《水文研究》2019,33(7):1152-1163

Climate change is altering river temperature regimes, modifying the dynamics of temperature‐sensitive fishes. The ability to map river temperature is therefore important for understanding the impacts of future warming. Thermal infrared (TIR) remote sensing has proven effective for river temperature mapping, but TIR surveys of rivers remain expensive. Recent drone‐based TIR systems present a potential solution to this problem. However, information regarding the utility of these miniaturised systems for surveying rivers is limited. Here, we present the results of several drone‐based TIR surveys conducted with a view to understanding their suitability for characterising river temperature heterogeneity. We find that drone‐based TIR data are able to clearly reveal the location and extent of discrete thermal inputs to rivers, but thermal imagery suffers from temperature drift‐induced bias, which prevents the extraction of accurate temperature data. Statistical analysis of the causes of this drift reveals that drone flight characteristics and environmental conditions at the time of acquisition explain ~66% of the variance in TIR sensor drift. These results shed important light on the factors influencing drone‐based TIR data quality and suggest that further technological development is required to enable the extraction of robust river temperature data. Nonetheless, this technology represents a promising approach for augmenting in situ sensor capabilities and improved quantification of advective inputs to rivers at intermediate spatial scales between point measurements and “conventional” airborne or satellite remote sensing.  相似文献   

Evaluation of a WRF dynamical downscaling simulation over California   总被引：3，自引：1，他引：2  

Peter Caldwell  Hung-Neng S. Chin  David C. Bader  Govindasamy Bala 《Climatic change》2009,95(3-4):499-521

This paper presents results from a 40 year Weather Research and Forecasting (WRF) based dynamical downscaling experiment performed at 12 km horizontal grid spacing, centered on the state of California, and forced by a 1° × 1.25° finite-volume current-climate Community Climate System Model ver. 3 (CCSM3) simulation. In-depth comparisons between modeled and observed regional-average precipitation, 2 m temperature, and snowpack are performed. The regional model reproduces the spatial distribution of precipitation quite well, but substantially overestimates rainfall along windward slopes. This is due to strong overprediction of precipitation intensity; precipitation frequency is actually underpredicted by the model. Moisture fluxes impinging on the coast seem to be well-represented over California, implying that precipitation bias is caused by processes internal to WRF. Positive-definite moisture advection and use of the Grell cumulus parameterization result in some decrease in precipitation bias, but other sources are needed to explain the full bias magnitude. Surface temperature is well simulated in all seasons except summer, when overly-dry soil moisture results in a several degree warm bias in both CCSM3 and WRF. Additionally, coastal temperatures appear to be too warm due to a coastal sea surface temperature bias inherited from CCSM3. Modeled snowfall/snowmelt agrees quite well with observations, but snow water equivalent is found to be much too low due to monthly reinitialization of all regional model fields from CCSM3 values.  相似文献   

Restored methane band images of Uranus and Neptune     

J.N. Heasley  Carl B. Pilcher  Robert R. Howell  John J. Caldwell 《Icarus》1984,57(3):432-442

Charge-coupled device images of Uranus and Neptune taken in the 8900-Å absorption band of methane are presented. The images have been digitally processed by means of nonlinear deconvolution techniques to partially remove the effects of atmospheric seeing. The restored Uranus images show strong limb brightening consistent with previous observations and theoretical models of the planet's atmosphere. The computer-processed images of Neptune show discreted cloud features similar to those reported previously by B. A. Smith, H. J. Reitsema and S. M. Larson (1979 Bull. Amer. Astron. Soc.11, 570). A time series of the restored Neptune images shows a continuous variation which may be due to the planet's rotation.  相似文献