Showing papers by "Cooperative Institute for Research in the Atmosphere published in 1992"

Covariance of Biophysical Data With Digital Topographic and Land Use Maps Over the FIFE Site

Abstract: This paper discusses the biophysical stratification of the FIFE site, implementation of the stratification utilizing geographic information system methods, and validation of the stratification with respect to field measurements of biomass, Bowen ratio, soil moisture, and the greenness vegetation index (GVI) derived from TM satellite data. Maps of burning and topographic position were significantly associated with variation in GVI, biomass, and Bowen ratio. The stratified design did not significantly alter the estimated site-wide means for surface climate parameters but accounted for between 25 and 45 percent of the sample variance depending on the variable.

Feedback between a simple biosystem and the temperature of the Earth

Abstract: A detailed mathematical analysis is presented of the model of Daisyworld, proposed by Watson and Lovelock. The stationary solutions of a resulting quartic system of ODEs are examined and their local and global attractivity is proved. The model shows, in a suitable range of values of the albedo and of the diffusion of the temperature, a mitigation of the climate in response to luminosity perturbations. The feedback between the biological components and the Earth's climate can be so efficient that the temperature of the Earth will stay practically constant even under substantial variations of the solar luminosity.

A Delayed Biophysical System for the Earth's Climate

Abstract: We consider further the Differential Daisyworld model of Watson and Lovelock that we have analyzed in a previous paper (De Gregorio et al., 1992). In this work we introduce a delay in the birthrate of the species. We consider three different models: the constant time lag model and the strong and the weak delay models. In the weak delay case no value of the delay changes the asymptotic stability of the stationary solutions. In the constant time lag and in the strong delay models, however, there exists a critical value of the delay, above which periodic solutions appear. These periodic solutions are numerically found to be globally attracting even for large delay when the linear approximation analysis is no longer valid. For both models, very regular behavior is obtained if the percentage coverage of the fertile ground of the Earth is much less than 1. As the percentage of the fertile ground increases, however, chaotic behavior is possible.

Comparison of Column Water Vapor Measurements Using Downward-looking Near-Infrared and Infrared Imaging Systems and Upward-looking Microwave Radiometers

Abstract: Remote soundings of precipitable water vapor from three systems are compared with each other and with ground truth from radiosondes. Ancillary data from a mesoscale network of surface observing stations and from wind-profiling radars are also used in the analysis. The three remote-sounding techniques are: (a) a reflectance technique using spectral data collected by the Airborne Visible-Infrared Imaging Spectrometer; (b) an emission technique using Visible-Infrared Spin Scan Radiometer Atmospheric Sounder (VAS) data acquired from the NOAA's GOES; and (c) a microwave technique using data from a limited network of three ground-based dual-channel microwave radiometers. The data were taken over the Front Range of eastern Colorado on 22-23 March 1990. The generally small differences between the three types of remote-sounding measurements are consistent with the horizontal and temporal resolutions of the instruments. The microwave and optical reflectance measurements agreed to within 0.1 cm; comparisons of the microwave data with radiosondes were also either as good or explainable. The largest differences between the VAS and the microwave radiometer at Elbert were between 0.4 and 0.5 cm and appear to be due to variable terrain within the satellite footprint.

An analysis of the relationship between cloud anomalies and sea surface temperature anomalies in a global circulation model

Abstract: The relationship between the sea surface temperature anomalies (SSTAs) and the anomalies of the monthly mean cloud cover (including the high-level, low-level, and total cloud cover), the outgoing longwave radiation, and the reflected solar radiation was analyzed using a least absolute deviations regression at each grid point over the open ocean for a 6-yr period. The results indicate that cloud change in association with a local 1-C increase in SSTAs cannot be used to predict clouds in a potential future world where all the oceans are 1-C warmer than at present, because much of the observed cloud changes are due to circulation changes, which in turn are related not only to changes in SSTAs but to changes in SSTA gradients. However, because SSTAs are associated with changes in the local ocean-atmosphere moisture and heat fluxes as well as significant changes in circulation (such as ENSO), SSTAs can serve as a surrogate for many aspects of global climate change.

Influence of Mesoscale Circulations on Long-Range Transport in the Grand Canyon Area

Abstract: Using a climatological analysis scheme results are presented relating the relative contribution of long-range versus local pollution to visibility degradation in Grand Canyon National Park. Among the results, we demonstrate that the poorest visibility in the winter is generally associated with synoptic stagnation and/or transport of pollution from the northeast.

Impact of Local Sources During Stagnant Conditions in Shenandoah National Park

Abstract: Shenandoah National Park (SNP) is located in the eastern United States within the northern portion of the Blue Ridge mountains in Virginia. Large urban areas within a few hundred kilometers (i.e. Washington, D.C.) and large regional sources (i.e. industrial facilities in the Ohio River valley) commonly produce high levels of pollutants which influence visibility at SNP during all seasons of the year with the summertime being considered the worst from the standpoint of visibility degradation. Although some of the larger regional sources have been identified, little emphasis has been given to the influence of local sources within the region. These local sources could possibly contribute substantially to the amount of pollutants observed at SNP especially during stagnant conditions.

Comparison of satellite and ship observations for total cloud amount

Abstract: The data series of monthly clouldiness over global ocean from COADS was compared with that of from satellite Nimbus-7 during April 1979 to March 1985. The correspondence between them is good. Both the two methods of observation can provide useful information of the distribution of cloudiness and the two data sets can be mutually complementary.