Engineering topics

Crowley, T. J.

Publications and source records attributed to Crowley, T. J..

6 records

NASA NTRS2011

Climate Forcing Reconstructions for Use in PMIP Simulations of the Last Millennium (v1.0)

Simulations of climate over the Last Millennium (850-1850 CE) have been incorporated into the third phase of the Paleoclimate Modelling Intercomparison Project (PMIP3). The drivers of climate over this period are chiefly orbital, solar, volcanic, changes in land use/land cover and some variation in greenhouse gas levels. While some of these effects can be easily defined, the reconstructions of solar, volcanic and land use-related forcing are more uncertain. We describe here the approach taken in defining the scenarios used in PMIP3, document the forcing reconstructions and discuss likely implications.

volcanoes↗

NASA NTRS1986

Role of seasonality in the evolution of climate during the last 100 million years

A simple climate model has been used to calculate the effect of past changes in the land-sea distribution on the seasonal cycle of temperatures during the last 100 million years. Modeled summer temperature decreased over Greenland by more than 10 C and over Antarctica by 5 to 8 C. For the last 80 million years, this thermal response is comparable in magnitude to estimated atmospheric carbon dioxide effects. Analysis of paleontological data provides some support for the proposed hypothesis that large changes due to seasonality may have sometimes resulted in an ice-free state due to high summer temperatures rather than year-round warmth. Such 'cool' nonglacials may have prevailed for as much as one-third of the last 100 million years.

Crowley, T. J.↗

NASA NTRS1984

Modeling glacial climates

Mathematical climate modelling has matured as a discipline to the point that it is useful in paleoclimatology. As an example a new two dimensional energy balance model is described and applied to several problems of current interest. The model includes the seasonal cycle and the detailed land-sea geographical distribution. By examining the changes in the seasonal cycle when external perturbations are forced upon the climate system it is possible to construct hypotheses about the origin of midlatitude ice sheets and polar ice caps. In particular the model predicts a rather sudden potential for glaciation over large areas when the Earth's orbital elements are only slightly altered. Similarly, the drift of continents or the change of atmospheric carbon dioxide over geological time induces radical changes in continental ice cover. With the advance of computer technology and improved understanding of the individual components of the climate system, these ideas will be tested in far more realistic models in the near future.

North, G. R.↗

NASA NTRS1983

The geologic record of climatic change

Major results from paleoclimatic investigations are investigated, and background material is included. The time interval surveyed extends from the formation of the earth 4.6 billion years ago to the development of the instrumental record. Previously announced in STAR as N82-33946

Crowley, T. J.↗

NASA NTRS1982

The geologic record of climatic change

Major results from paleoclimatic investigations are investigated, and background material is included. The time interval surveyed extends from the formation of the Earth 4.6 billion years ago to the development of the instrumental record.

Crowley, T. J.↗

NASA NTRS1971

Individual variation in circadian rhythms of sleep, EEG, temperature, and activity among monkeys - Implications for regulatory mechanisms.

Investigation of circadian rhythms in a number of variables related to sleep, EEG, temperature, and motor activity in rhesus monkeys on an LD 12:12 schedule. Circadian rhythms were found to appear in each of 15 variables investigated. Statistical procedures assessed the variables for evidence of common regulation in these aspects of their circadian rhythms: acrophase (timing), amplitude (extent of change), and level (24-hr mean value). Patterns appearing in the data suggested that the circadian rhythms of certain variables are regulated in common. The circadian modulation of activity in the beta and sigma frequency bands of the EEG was correlated with statistical significance in acrophase, level, and amplitude. The delta frequency band appeared to be under circadian rhythm regulation distinct from that of the other bands. The circadian rhythm of REM stage sleep was like that of beta activity in level and amplitude. The data indicate that REM stage may share some common regulation of circadian timing with both stage 3-4 sleep and with temperature. Generally, however, the circadian rhythm of temperature appeared to bear little relation to the circadian rhythms of motor activity, EEG, or sleep.

Crowley, T. J.↗