Isoline retrieval: An optimal sounding method for validation of advected contours

Peter Mills

doi:10.1016/j.cageo.2008.12.015

Home/Archive/arXiv

arXiv · 1202.5659

Isoline retrieval: An optimal sounding method for validation of advected contours

Peter Mills

View original source ↗Read source document ↗Export metadata ↓

Abstract

The study of chaotic mixing is important for its potential to improve our understanding of fluid systems. Contour advection simulations provide a good model of the phenomenon by tracking the evolution of one or more contours or isolines of a trace substance to a high level of precision. The most accurate method of validating an advected contour is to divide the tracer concentration into discrete ranges and perform a maximum likelihood classification, a method that we term, "isoline retrieval." Conditional probabilities generated as a result provide excellent error characterization. In this study, a water vapour isoline of 0.001 mass-mixing-ratio is advected over five days in the upper troposphere and compared with high-resolution AMSU (Advanced Microwave Sounding Unit) satellite retrievals. The goal is to find the same fine-scale, chaotic mixing in the isoline retrievals as seen in the advection simulations. Some of the filaments generated by the simulations show up in the conditional probabilities as areas of reduced probability. By rescaling the probabilities, the filaments may be revealed in the isoline retrievals proper with little effect on the overall accuracy. Limitations imposed by the specific context, i.e. water-vapour retrieved with AMSU in the upper troposphere, are discussed. Nonetheless, isoline retrieval is shown to be a highly effective technique for atmospheric sounding, showing good agreement with both ECMWF (European Centre for Medium-range Weather Forecasts) assimilation data and radiosonde measurements. Software for isoline retrieval can be found at: http://isoret.sourceforge.net

Explore related subjects

physics.ao-ph physics.data-an

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Peter Mills. 2012-02-25. Isoline retrieval: An optimal sounding method for validation of advected contours. https://doi.org/10.1016/j.cageo.2008.12.015

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Surface Stokes drift from compact drifting wave buoys

Surface Stokes drift depends strongly on the energy and directions of short waves, which are incompletely resolved by routine wave observations. We derive surface Stokes drift vectors from wave measurements collected by compact drifting buoys during three deployments in the North-East Atlantic and the Alboran Sea. The calculation uses vertical-acceleration spectra and first directional Fourier moments, which describe the mean wave direction and directional concentration at each frequency; it accounts for the Doppler shift caused by buoy motion relative to the water and adds a calibrated high-frequency tail above an intrinsic frequency of 0.7 Hz. Across 13,139 records, the median estimated speed is 0.081 m/s at a median wind speed of 6.8 m/s. Over the measured band of 0.04-1 Hz, accounting for wave directions reduces the magnitude by a median 39% relative to the unidirectional assumption. The median ratio of the parameterised tail magnitude above 0.7 Hz to the total estimated magnitude is 0.37. Comparisons with WAVEWATCH III and Copernicus Marine MFWAM show strong covariation and similar wind-dependent differences from the buoy-derived estimates. On the station-matched sample from the two Atlantic deployments, WAVEWATCH III directional spectra indicate that these differences within the compared band arise mainly from spectral levels rather than from net directional reduction. The observations provide constraints for model evaluation; the contribution of the unresolved short waves remains sensitive to the assumed spectral tail and its directional spreading.

physics.ao-ph↗

arXiv2026

Unreported large errors from two PAMGuard three-dimensional localizers of whale calls

Confidence intervals of location (CIL) of calling marine mammals, derived from time-differences-of-arrival (TDOA) between receivers, depend on errors of TDOAs, receiver location, clocks, sound speeds, and location method. When these errors are minuscule, simulations yield small errors of PAMGuard's 3D simplex localizer when click sounds of beaked and sperm whales originate in a 1000 x 1000 x 1000 $\mbox{m}^3$ region using five receivers having horizontal and vertical separations of 1000 m and 150 m respectively. Realistic uncertainties of sound speed up to $\pm 10$ m/s lead to errors up to $10^{14}$ m. With clocks maintained by atomic standards and common practice of correcting TDOA from synchronization measurements at the start and end of an experiment, errors of location are up to $10^{4}$ m. Errors up to $10^2$ and $10^3$ m are found when the receiver's locations are uncertain within 10 and 40 m respectively. Errors of PAMGuard's 3D hyperbolic localizer are almost independent of the above uncertainties, yielding errors of location up to about $10^4$ m even when simulated errors are minuscule. Causes of PAMGuard's 3D location errors are unknown. These algorithms are briefly compared to another method designed to yield a reliable CIL.

physics.ao-ph↗

arXiv2026

Tropospheric Ozone Formation Potential and Related Design Considerations for Radiative Coolers

Recently, radiative coolers have been widely explored for reducing cooling loads or lowering temperatures in buildings, and at urban scales as a heat-mitigation measure. However, the potential impacts of radiative cooler deployment on the chemical composition of the atmosphere remain largely unexplored. A defining feature of recently-designed radiative coolers is their high ultraviolet (UV) reflectance, which is required for sub-ambient cooling under strong sunlight. Yet, wide adoption of such UV-reflective radiative coolers could substantially increase the UV actinic flux in the atmosphere above. This, in turn, may affect tropospheric ozone concentrations, particularly in urban atmospheres with high NOx concentrations. Here, as a case study, we use a 0-dimensional photochemical box model, constrained by field measurements of meteorological conditions and chemical concentrations in the urban environment of Houston, Texas, to explore the potential impact of the widespread use of UV-reflective radiative coolers on ozone concentrations. Our calculations show that complete deployment of radiative coolers may increase tropospheric ozone levels by as much as 30% during specific meteorological conditions in Houston. Informed by the wavelength-dependent modelling results, we propose specific designs, namely pigmented radiative coolers with different UV reflectances, and UV-absorptive visible-reemitting fluorescent radiative coolers, that could minimize negative ozone formation while retaining appreciable cooling performance. Our results motivate further study on the effects of widespread deployment of radiative cooling designs like superwhite roof paints on air quality, and materials that simultaneously minimize adverse photochemical impact and maximize cooling performance.

physics.ao-ph↗