John Dykema's Publications

Anderson, J. G., D. K. Weisenstein, K. P. Bowman, C. R. Homeyer, J. B. Smith, D. M. Wilmouth, D. S. Sayres, J. E. Klobas, S. S. Leroy, J. A. Dykema, and S. C. Wofsy (2017), Stratospheric ozone over the United States in summer linked to observations of convection and temperature via chlorine and bromine catalysis, Proceedings of the National Academy of Sciences 114: E4905-E4913; doi: 10.1073/pnas.1619318114.

We present observations defining (i) the frequency and depth of convective penetration of water into the stratosphere over the United States in summer using the Next-Generation Radar system; (ii) the altitude-dependent distribution of inorganic chlorine established in the same coordinate system as the radar observations; (iii) the high resolution temperature structure in the stratosphere over the...

Smith, J. B., D. M. Wilmouth, K. M. Bedka, K. P. Bowman, C. R. Homeyer, J. A. Dykema, M. R. Sargent, C. Clapp, S. S. Leroy, D. S. Sayres, J. M. Dean-Day, T. P. Bui, and J. G. Anderson (2017), A case-study of convectively sourced water vapor observed in the overworld stratosphere over the United States, J. Geophys. Res. Atmos. 122, doi:10.1002/2017JD026831.

On 27 August 2013, during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys field mission, NASA's ER‐2 research aircraft encountered a region of enhanced water vapor, extending over a depth of approximately 2 km and a minimum areal extent of 20,000 km2 in the stratosphere (375 K to 415 K potential temperature), south of...

Huang, Y., S. Leroy, P.J. Gero, J. Dykema, and J.G. Anderson (2010), Separation of Longwave Climate Feedbacks from Spectral Observations, J. Geophys. Res., 115, D07104, doi:10.1029/2009JD012766, 2010.

We conduct a theoretical investigation into whether changes in the outgoing longwave radiation (OLR) spectrum can be used to constrain longwave greenhouse-gas forcing and climate feedbacks, with a focus on isolating and quantifying their contributions to the total OLR change in all-sky conditions. First, we numerically compute the spectral signals of CO2 forcing and feedbacks of temperature,...

Leroy, Stephen, James Anderson, John Dykema, Richard Goody, 2008: Testing Climate Models Using Thermal Infrared Spectra. J. Climate, 21, 1863–1875. doi: http://dx.doi.org/10.1175/2007JCLI2061.1 

An approach to test climate models with observations is presented. In this approach, it is possible to directly observe the longwave feedbacks of the climate system in time series of annual average outgoing longwave spectra. Tropospheric temperature, stratospheric temperature, water vapor, and carbon dioxide have clear and distinctive signatures in the infrared spectrum, and it is possible to...

Leroy, S.S., J.A. Dykema, and J.G. Anderson, “Scalar prediction in climate using data and model,” Submitted to J. Climate (2008).

Scalar detection in climate change research, having taken the form of optimal detection/linear multi-pattern regression, has been used in the recent past to detect multiple climate signals in the presence of natural inter- annual variability and associate those signals with specific causes. It has been applied to many climate observables to show high probabilities of human influence on climatic...

Gero P J, Dykema J A and Anderson J G 2008 A blackbody design for SI-traceable radiometry for earth observation J. Atmos. Ocean. Technol. 25 2046–54

Spaceborne measurements pinned to international standards are needed to monitor the earth’s climate,quantify human influence thereon, and test forecasts of future climate change. The International System ofUnits (SI, from the French for Système International d’Unités) provides ideal measurement standards forradiometry as they can be realized anywhere, at any time in the future. The challenge is...

Leroy, S., J. G. Anderson, J. Dykema, and R. Goody (2008), Testing climate models with thermal infrared spectra, J. Clim., 21, 1863–1875.

An approach to test climate models with observations is presented. In this approach, it is possible to directly observe the longwave feedbacks of the climate system in time series of annual average outgoing longwave spectra. Tropospheric temperature, stratospheric temperature, water vapor, and carbon dioxide have clear and distinctive signatures in the infrared spectrum, and it is possible to...

J. A Dykema and Anderson, J.G. (2006), A methodology for obtaining on-orbit SI-traceable spectral radiance measurements in the thermal infrared, Metrologia, 43, 287-293. doi:10.1088/0026-1394/43/3/011

A methodology to achieve spectral thermal radiance measurements fromspace with demonstrable on-orbit traceability to the International System ofUnits (SI) is described. This technique results in measurements of infraredspectral radiance R(υ )˜ , with spectral index υ˜ in cm−1, with a relativecombined uncertainty uc[R(υ )˜ ] of 0.0015 (k = 1) for the averagemid-infrared radiance emitted by the...

Leroy SS, Dykema JA, Anderson JG (2006) Climate benchmarkingusing GNSS occultation. In: Foelsche et al. (2006b) pp 287–301.doi:10.1007/3-540-34121-8_24

We put climate monitoring in a scientific context, which can be arrived at through a careful implementation of Bayesian inference. What we find is that a good climate monitoring tool must help address the physics of a climate model so as to make it better able to predict future climates. GNSS occultation is ideal because it offers sensitivity to improve the model physics which affects the...

Leroy, S. S., J. G. Anderson, and J. A. Dykema (2006), Testing climate models using GPS radio occultation: A sensitivity analysis,J. Geophys. Res.111, D17105, doi:10.1029/2005JD006145.

We survey the IPCC AR4 models' responses to SRES A1B forcing in order to evaluate a prediction of climate change common to all models and testable using GPS radio occultation data over the coming decades. Of the IPCC AR4 models that submitted runs of the SRES A1B forcing scenario, we select twelve because of the timeliness of their submission. Trends in the global average surface air temperature...