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Boulder City, CO, United States

Smith A.K.,NCAR
Space Science Reviews | Year: 2012

This survey of atmospheric regions is based on a presentation given at the Workshop on Coupling between Earth's Atmosphere and its Plasma Environment. The workshop was sponsored by the International Space Science Institute (ISSI) during September 2010. This survey begins with descriptions of aspects of the troposphere, stratosphere, and mesosphere that affect vertical coupling. Then the tropopause, stratopause, and mesopause are considered, with a discussion of how they inhibit or allow the transmission of atmospheric mass or perturbations. Two transition interfaces are emphasized: the tropopause, which separates the troposphere from the middle atmosphere, and the mesopause, which separates the middle atmosphere from the thermosphere. The survey of coupling processes looks at radiative processes, wave propagation, and mass exchange. Each topic includes one or more specific examples drawn from recent literature. © 2011 Springer Science+Business Media B.V.

One tool for studying uncertainties in simulations of future climate is to consider ensembles of general circulation models where parameterizations have been sampled within their physical range of plausibility. This study is about simulations from two such ensembles: a subset of the climateprediction.net ensemble using the Met Office Hadley Centre Atmosphere Model, version 3.0 and the new "CAMcube" ensemble using the Community Atmosphere Model, version 3.5. The study determines that the distribution of climate sensitivity in the two ensembles is very different: the climateprediction.net ensemble subset range is 1.7-9.9 K, while the CAMcube ensemble range is 2.2-3.2 K. On a regional level, however, both ensembles show a similarly diverse range in their mean climatology. Model radiative flux changes suggest that the major difference between the ranges of climate sensitivity in the two ensembles lies in their clear-sky longwave responses. Large clear-sky feedbacks present only in the climateprediction.net ensemble are found to be proportional to significant biases in upper-tropospheric water vapor concentrations, which are not observed in the CAMcube ensemble. Both ensembles have a similar range of shortwave cloud feedback, making it unlikely that they are causing the larger climate sensitivities in climateprediction.net. In both cases, increased negative shortwave cloud feedbacks at high latitudes are generally compensated by increased positive feedbacks at lower latitudes. © 2011 American Meteorological Society.

Hardoy J.,IIED AL | Romero Lankao P.,NCAR
Current Opinion in Environmental Sustainability | Year: 2011

Although urban areas in Latin America and the Caribbean (LAC) are not major GHG emitters, they play crucial, yet understudied roles in the climate change arena. They are not only growing sources of greenhouse gases, but (in common with urban settlements in other regions) are also hotspots of vulnerability to floods, heat waves, and other hazards that climate change is expected to aggravate. This paper reviews the existing literature on the climate linkages and the relevance of urban development in LAC. It briefly describes research on existing mitigation and adaptation responses. It then explores why it is important to include a pro-poor perspective in adaptation actions. Although LAC cities have been the sources of many initiatives, policies and actions aimed at mitigating emissions and adapting to climate change, these have focused mostly on mitigation. It has been difficult to promote adaptation at the local level without the necessary support from higher levels of government and the international community. This has left a gap in the support and funding of locally determined, locally driven and necessary adaptation that serves and works with those most at risk. The best opportunities to adapt to climate change are linked with actions that address the underlying causes of vulnerability and respond to more than one problem at a time. © 2011 Elsevier B.V.

Jones P.D.,University of East Anglia | Wigley T.M.L.,NCAR
Climatic Change | Year: 2010

In this essay we discuss the development of and estimation of uncertainties in the global surface temperature record. We briefly discuss the similarities in and differences between the records from the institutions that produce such series. We then consider the numerous issues that must be addressed to enable accurate estimates to be derived. We consider these in their order of importance with respect to the record: biases in the sea surface temperature data, exposure of land-based thermometers before about 1900, urbanization effects in some series, and, finally, the homogeneity of individual land-based records. © Springer Science+Business Media B.V. 2010.

Konopka P.,Julich Research Center | Pan L.L.,NCAR
Journal of Geophysical Research: Atmospheres | Year: 2012

We present a case study on the formation and structure of the Extratropical Transition Layer (ExTL) using in situ observations and a Lagrangian chemical transport model. The results show that the model with mixing parameterized from the large-scale flow deformations well reconstructs the observed asymmetric structure of the ExTL with a deeper transition layer on the cyclonic side of the jet stream. Information from the model and observations are integrated using tracer-tracer correlations between ozone (O3) and carbon monoxide (CO). Transport of chemical tracers from the stratospheric or tropospheric background to the ExTL through mixing is identified by the change of the CO-O3 correlation in the CO-O3 space. The ExTL formation process simulated by the model, therefore, provides a scenario to connect the mixed air parcels to the history of mixing. An estimate of timescales of ExTL formation is made using model experiments. The results show that the fastest formation of the ExTL occurs on the isentropic levels below the subtropical jet core, e.g. around 3 weeks for 310 K, whereas at 360 K level (jet core) the formation of the ExTL needs around 3 months. Overall, this result demonstrates the important role of mixing in transport of trace gases across the tropopause.© 2012. American Geophysical Union.

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