arXiv subjects

Robert S. Knox

Publications and source records attributed to Robert S. Knox.

5 recordsLinked to original sources

arXiv2009

Application of a dynamical two-box surface-atmosphere model to the Mount Pinatubo cooling event

We analyze the global temperature change due to the Mt. Pinatubo eruption using a simple two-layer model of the atmosphere and surface to obtain results consistent with satellite data. Through analytic and numerical analysis we find a principal characteristic response time of 5 to 8 months and a climate sensitivity of 0.17 to 0.20 C/(W/m^2), corresponding to a negative instantaneous feedback. Our solutions were fit to the data, reproducing the results of a one-box model, and providing somewhat more detailed information about the feedbacks related to surface layer temperature. The formalism for coupling of the surface layer to the thermocline is set up but not applied.

physics.geo-ph↗

arXiv2005

Climate Forcing by the Volcanic Eruption of Mount Pinatubo. Revised edition

We determine the volcano climate sensitivity and response time for the Mount Pinatubo eruption. This is achieved using observational measurements of the temperature anomalies of the lower troposphere and the aerosol optical density (AOD) in combination with a radiative forcing proxy for AOD. Using standard linear response theory we find sensitivity = 0.18 +- 0.04 K/(W/m2), which implies a negative feedback of -1.0 +- 0.4. The intrinsic response time is 5.8+-1.0 months. Both results are contrary to the conventional paradigm that includes long response times and positive feedback. In addition, we analyze the outgoing longwave radiation during the Pinatubo eruption and find that its time dependence follows the forcing much more closely than the temperature, and even has an amplitude equal to that of the AOD proxy. This finding is independent of the response time and feedback results.

physics.geo-ph↗

arXiv2004

Climate sensitivity of Earth to solar irradiance: update

This paper is a continuation of a study by Douglass and Clader. We extend the analysis through December 2003 using the latest updates of the observational temperature and solar irradiance data sets in addition to a new volcano proxy data set. We have re-determined the solar effect on the temperature from satellite measurements of the solar irradiance and the temperature of the lower troposphere the sensitivity to solar irradiance. This re-analysis calculates two newly recognized dynamic and non-radiative flux factors which must be applied to the observed sensitivity. The sensitivity is about twice that expected from a no-feedback Stefan-Boltzmann radiation balance model, which implies positive feedback. The sensitivity to volcano forcing is also determined. Preliminary results indicate that negative feedback is present in this case. Response times of fractions of a year are found for both solar and volcano forcing. We note that climate models generally assume relaxation times of 5 to 10 years and we comment on the consequences of this large disparity. We also have determined a linear trend in the data.

physics.geo-ph↗

arXiv2004

Temperature response of Earth to the annual solar irradiance cycle

We directly determine the sensitivity and time delay of Earth's surface temperature response to annual solar irradiance variations from 60 years of data. A two-layer energy balance model is developed to interpret the results. Explaining both the resulting low sensitivity and time delay of 1-2 months requires negative feedback.

astro-ph↗

arXiv2003

Development of an elementary climate model: two-layer cellular case

A qualitative understanding of the greenhouse effect has long been available through models based on globally- and time-averaged quantities. We examine here a simple 864-cell climatological model that emphasizes vertical radiative energy transport within each cell. It reproduces yearly average temperatures obtained earlier from one of these global models and predicts a locally distributed non-radiative flux when observed temperatures are employed as input data. Vertical and lateral transport of latent heat do not appear explicitly in this model. They are apparently handled well by one non-radiative flux variable, SNR, which shows a strong latitude dependence. Only the Sahara desert and Saudi Arabian regions appear to be complex. For those interested in climatology and construction of climate models, our model provides constraints upon specifying averaged non-radiative energy transport. The model is a useful simplification for learning about radiative energy transfer into and out of Earth?s atmosphere and for representing the results of more sophisticated models.

physics.ao-ph↗