Celebrating the Physics in Geophysics

As 2005, the International Year of Physics, comes to an end, two physicists working primarily in geophysical research reflect on how geophysics is not an applied physics. Although geophysics has certainly benefited from progress in physics and sometimes emulated the reductionist program of mainstream physics, it has also educated the physics community about some of the generic behaviors of strongly nonlinear systems. Dramatic examples are the insights we have gained into the ``emergent'' phenomena of chaos, cascading instabilities, turbulence, self-organization, fractal structure, power-law variability, anomalous scaling, threshold dynamics, creep, fracture, and so on. In all of these examples, relatively simple models have been able to explain the recurring features of apparently very complex signals and fields. It appears that the future of the intricate relation between physics and geophysics will be as exciting as its past has been characterized by a mutual fascination. Physics departments in our universities should capitalize on this trend to attract and retain young talent motivated to address problems that really matter for the future of the planet. A pressing topic with huge impact on populations and that is challenging enough for both physics and geophysics communities to work together like never before is the understanding and prediction of extreme events.Comment: 6 pages, final version to appear in EOS-AGU Transactions in November 200

Nature's statistical symmetries and asymmetries, a characterization by wavelets and an illustration with clouds

Wavelets are the mathematical equivalent of a microscope, a means of looking at more or less detail in data. By applying wavelet transforms to remote sensing data (satellite images, atmospheric profiles, etc.), we can discover symmetries in Nature's ways of changing in time and displaying a highly variable environment at any given time. These symmetries are not exact but statistical. The most intriguing one is 'scale-invariance' which describes how spatial statistics collected over a wide range of scales (using wavelets) follow simple power laws with respect to the scale parameter. The geometrical counterparts of statistical scale-invariance are the random fractals so often observed in Nature. This wavelet-based exploration of natural symmetry will be illustrated with clouds where asymmetries and broken symmetries are also uncovered Both symmetry and symmetry-breaking have deep physical meanings

Trends in Cancer Mortality in 15 Industrialized Countries, 1969-1986

Background: Assessing trends in cancer provides a means for gauging progress against the disease, estimating future demands for care and treatment, and suggesting clues about shifting causal factors that may account for the more recent changes. Purpose: This study was designed to evaluate trends in the major sites of cancer associated with high mortality rates in 15 industrialized countries. To highlight differences among regions, we grouped these countries into six geographic areas: United States, Eastern Europe, Western Europe, East Asia, Oceania, and Nordic countries. In addition, cancer mortality trends in these regions were compared with incidence patterns in the United States. Methods: Data provided by the World Health Organization were used to evaluate age-specific mortality trends from 1969 through 1986 for lung, breast, prostate, stomach, and colorectal cancers and for all other sites considered as a group. We also assembled and analyzed data from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute for the same sites and age groups from 1973 through 1986. Results: Over the period 1969 through 1986, recorded cancer mortality in persons aged 45 years and older in the six regions studied has increased for lung, breast, and prostate cancers in most age groups, while the decline in stomach cancer mortality is substantial. The increase in lung cancer deaths in men aged 45-54 years has slowed greatly or reversed in all areas except Eastern Europe and East Asia. Trends for intestinal cancer vary by age and region. For all other sites considered as a group, increases have occurred for persons older than 64 years in most regions. In Eastern Europe, there are disturbingly high rates and rapid increases for several of the major forms of cancer in persons aged 45-54 years. In general, trends for cancer incidence in the United States parallel those for mortality. For intestinal cancer, however, incidence has increased while mortality has declined. Conclusions: The trends we report cannot be explained solely by changes in cigarette smoking or aging. Other causes of changes in cancer incidence and mortality need to be determined. Implications: The increasing and decreasing trends in mortality from and incidence of cancer that we found are important for health care planning and may also suggest opportunities for research in cancer prevention. [J Natl Cancer Inst 84: 313-320, 1992

Multi-View Polarimetric Scattering Cloud Tomography and Retrieval of Droplet Size

Tomography aims to recover a three-dimensional (3D) density map of a medium or an object. In medical imaging, it is extensively used for diagnostics via X-ray computed tomography (CT). We define and derive a tomography of cloud droplet distributions via passive remote sensing. We use multi-view polarimetric images to fit a 3D polarized radiative transfer (RT) forward model. Our motivation is 3D volumetric probing of vertically-developed convectively-driven clouds that are ill-served by current methods in operational passive remote sensing. Current techniques are based on strictly 1D RT modeling and applied to a single cloudy pixel, where cloud geometry defaults to that of a plane-parallel slab. Incident unpolarized sunlight, once scattered by cloud-droplets, changes its polarization state according to droplet size. Therefore, polarimetric measurements in the rainbow and glory angular regions can be used to infer the droplet size distribution. This work defines and derives a framework for a full 3D tomography of cloud droplets for both their mass concentration in space and their distribution across a range of sizes. This 3D retrieval of key microphysical properties is made tractable by our novel approach that involves a restructuring and differentiation of an open-source polarized 3D RT code to accommodate a special two-step optimization technique. Physically-realistic synthetic clouds are used to demonstrate the methodology with rigorous uncertainty quantification