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arXiv2008

Our climate fix must be big and quick

We need enough new carbon sinks to 1) cancel out any continuing use of fossil fuels, 2) overcome the delayed effect of earlier excesses, and then 3) lower atmospheric CO2 concentrations to the old maximum value of 280 ppm. We need to sink about 25 billion tonnes of carbon each year, half to counter current emissions and commitments, and half for drawing down the CO2 concentrations within a few decades. A very large carbon sink could be created by sinking sewage in offshore dead zones. Half of all people live close enough to a coast to personally contribute, making the sink size close to half the annual food production.

physics.ao-ph↗

arXiv2009

Impacts of Typhoons on the Kuroshio Large Meander: Observation Evidences

The formation of the Kuroshio large meander in summer 2004 was investigated by using the cruise data, Argo profiles data, and satellite remote sensing data. We validated the point that cyclonic eddy contributes to the large meander. Besides, the impacts of typhoons on Kuroshio meanders were studied. From 29 July to 4 August, the typhoons stirred the ocean and upwelled the deep water, which enhanced the existed cyclonic eddy, and immediately made a drastic meander of the Kuroshio. Moreover, the unexpected typhoons in June 2004 also contributed to the initial meander at Tokara Strait. The result suggests an alternative meander mechanism of Kuroshio path via typhoon-eddy-Kuroshio interactions. It is argued that typhoons accompanied with cyclonic eddies, might play crucial roles in meanders of the Kuroshio. This will provide a more comprehensive understanding of the dynamics of the west boundary flows like the Kuroshio and the Gulf Stream, and will be useful in eddy-resolution models.

physics.ao-ph↗

arXiv2008

Thermal emissions and climate change: Cooler options for future energy technology

Global warming arises from 'temperature forcing', a net imbalance between energy fluxes entering and leaving the climate system and arising within it. Humanity introduces temperature forcing through greenhouse gas emissions, agriculture, and thermal emissions from fuel burning. Up to now climate projections, neglecting thermal emissions, typically foresee maximum forcing around the year 2050, followed by a decline. In this paper we show that, if humanity's energy use grows at 1%/year, slower than in recent history, and if thermal emissions are not controlled through novel energy technology, temperature forcing will increase indefinitely unless combated by geoengineering. Alternatively, and more elegantly, humanity may use renewable sources such as wind, wave, tidal, ocean thermal, and solar energy that exploit energy flows already present in the climate system, or act as effective sinks for thermal energy.

physics.ao-ph↗

arXiv2008

Identification of Optimal Topography by Variational Data Assimilation

The use of data assimilation technique to identify optimal topography is discussed in frames of time-dependent motion governed by non-linear barotropic ocean model. Assimilation of artificially generated data allows to measure the influence of various error sources and to classify the impact of noise that is present in observational data and model parameters. The choice of assimilation window is discussed. Assimilating noisy data with longer windows provides higher accuracy of identified topography. The topography identified once by data assimilation can be successfully used for other model runs that start from other initial conditions and are situated in other parts of the model's attractor.

physics.ao-ph↗

arXiv2009

Routine monitoring and analysis of ocean swell fields using a spaceborne SAR

Satellite Synthetic Aperture Radar (SAR) observations can provide a global view of ocean swell fields when using a specific "wave mode" sampling. A methodology is presented to routinely derive integral properties of the longer wavelength (swell) portion of the wave spectrum from SAR Level 2 products, and both monitor and predict their evolution across ocean basins. SAR-derived estimates of swell height, and energy-weighted peak period and direction, are validated against buoy observations, and the peak directions are used to project the peak periods in one dimension along the corresponding great circle route, both forward and back in time, using the peak period group velocity. The resulting real time dataset of great circle-projected peak periods produces two-dimensional maps that can be used to monitor and predict the spatial extent, and temporal evolution, of individual ocean swell fields as they propagate from their source region to distant coastlines. The methodology is found to be consistent with the dispersive arrival of peak swell periods at a mid-ocean buoy. The simple great circle propagation method cannot project the swell heights in space like the peak periods, because energy evolution along a great circle is a function of the source storm characteristics and the unknown swell dissipation rate. A more general geometric optics model is thus proposed for the far field of the storms. This model is applied here to determine the attenuation over long distances. For one of the largest recorded storms, observations of 15 s period swells are consistent with a constant dissipation rate that corresponds to a 3300 km e-folding scale for the energy. In this case, swell dissipation is a significant term in the wave energy balance at global scales.

physics.ao-ph↗

arXiv2008

El Nino Southern Oscillation as Sporadic Oscillations between Metastable States

The main objective of this article is to establish a new mechanism of the El Nino Southern Oscillation (ENSO), as a self-organizing and self-excitation system, with two highly coupled processes. The first is the oscillation between the two metastable warm (El Nino phase) and cold events (La Nina phase), and the second is the spatiotemporal oscillation of the sea surface temperature (SST) field. The interplay between these two processes gives rises the climate variability associated with the ENSO, leads to both the random and deterministic features of the ENSO, and defines a new natural feedback mechanism, which drives the sporadic oscillation of the ENSO. The new mechanism is rigorously derived using a dynamic transition theory developed recently by the authors, which has also been successfully applied to a wide range of problems in nonlinear sciences.

physics.ao-ph↗

arXiv2009

Atmospheric O2 from astronomical data

Environmental research aimed at monitoring and predicting O2 depletion is still lacking or in need of improvement, in spite of many attempts to find a relation between atmospheric gas content and climate variability. The aim of the present project is to determine accurate historical sequences of the atmospheric O2 depletion by using the telluric lines present in stellar spectra. A better understanding of the role of oxygen in atmospheric thermal equilibrium may become possible if high-resolution spectroscopic observations are carried out for different airmasses, in different seasons, for different places, and if variations are monitored year by year. The astronomical spectroscopic technique involves mainly the investigation of the absorption features in high-resolution stellar spectra, but we are also considering whether accurate measures of the atmospheric O2 abundances can be obtained from medium and low resolution stellar spectra.

physics.ao-ph↗

arXiv2009

Some reports of snowfall from fog during the UK winter of 2008/09

Snowfall during anticyclonic, non-frontal, and foggy conditions is surprising. Because it is often not forecast, it can present a hazard to transport and modify the surface albedo. In this report, we present some observations of snowfall during conditions of freezing fog in the UK during the winter of 2008/09. [v2 includes typographical corrections]

physics.ao-ph↗

arXiv2009

Comments on the "Proof of the atmospheric greenhouse effect" by Arthur P. Smith, arXiv:0802.4324

In this paper it is shown that Smith (2008) used inappropriate and inconsistent formulations in averaging various quantities over the entire surface of the Earth considered as a sphere. Using two instances of averaging procedures as customarily applied in studies on turbulence, it is shown that Smith's formulations are highly awkward. Furthermore, Smith's discussion of the infrared absorption in the atmosphere is scrutinized and evaluated. It is shown that his attempt to refute the criticism of Gerlich and Tscheuschner (2007, 2009) on the so-called greenhouse effect is rather fruitless.

physics.ao-ph↗

arXiv2009

Stratospheric Albedo Modification by Aerosol Injection

This paper reviews and develops the proposal, widely discussed but not examined in detail, to use stratospheric aerosols to increase the Earth's albedo to Solar radiation in order to control climate change. The potential of this method has been demonstrated by the "natural experiments" of volcanic injection of sulfate aerosols into the stratosphere that led to subsequent observed global cooling. I consider several hygroscopic oxides as possible aerosol materials in addition to oxides of sulfur. Aerosol chemistry, dispersion and transport have been the subject of little study and are not understood, representing a significant scientific risk. Even the optimal altitude of injection and aerosol size distribution are poorly known. Past attention focused on guns and airplanes as means of lofting aerosols or their chemical precursors, but large sounding rockets are cheap, energetically efficient, can be designed to inject aerosols at any required altitude, and involve little technical risk. Sophisticated, mass-optimized "engineered" particles have been proposed as possible aerosols, but the formidable problems of their production in quantity, lofting and dispersion have not been addressed.

physics.soc-ph↗

arXiv2009

Lunar semimonthly signal in cloud amount

Based on NASA satellite infrared and visible range measurements, cloud amount ISCCP_D1 summer nighttime data, representing the tropospheric cloud activity at Central Russia are examined over 1994-2007, and the lunar signal in the cloud amount was extracted. The ISCCP_D1 database was used to confirm previous results of Pertsev, Dalin and Romejko (2007) on the large importance of lunar declination effect compared to the lunar phase effect. Since this database provides much more information than it was used in that previous investigation, it has become possible to separate the lunar phase effect and the lunar declination effect in cloudiness. The relative cloud amount tends to grow with a change of lunar phase from a quadrature to the New Moon or Full Moon and with increasing of the lunar declination by absolute value. The both effects are statistically significant, the second one is a little stronger.

physics.ao-ph↗

arXiv2009

Wind-wave stabilization by a foam layer between the atmosphere and the ocean

The study is motivated by recent findings of the decrease in the momentum transfer from strong winds to sea. The Kelvin-Helmholtz instability (KHI) of a three-fluid system of air, foam and water is examined within the range of intermediately short surface waves. The foam layer thickness necessary for effective separation of the atmosphere and the ocean is estimated. Due to high density contrasts in the three-fluid system, even a relatively thin foam layer between the atmosphere and the ocean can provide a significant stabilization of the water surface by the wavelength shift of the instability towards smaller scales. It is conjectured that such stabilization qualitatively explains the observed reduction of roughness and drag.

physics.ao-ph↗

arXiv2010

Minimal atmospheric finite-mode models preserving symmetry and generalized Hamiltonian structures

A typical problem with the conventional Galerkin approach for the construction of finite-mode models is to keep structural properties unaffected in the process of discretization. We present two examples of finite-mode approximations that in some respect preserve the geometric attributes inherited from their continuous models: a three-component model of the barotropic vorticity equation known as Lorenz' maximum simplification equations [Tellus, \textbf{12}, 243--254 (1960)] and a six-component model of the two-dimensional Rayleigh--Bénard convection problem. It is reviewed that the Lorenz--1960 model respects both the maximal set of admitted point symmetries and an extension of the noncanonical Hamiltonian form (Nambu form). In a similar fashion, it is proved that the famous Lorenz--1963 model violates the structural properties of the Saltzman equations and hence cannot be considered as the maximum simplification of the Rayleigh--Bénard convection problem. Using a six-component truncation, we show that it is again possible retaining both symmetries and the Nambu representation in the course of discretization. The conservative part of this six-component reduction is related to the Lagrange top equations. Dissipation is incorporated using a metric tensor.

physics.ao-ph↗

arXiv2010

Field theoretical approach to the description of the coherent structures in 2D fluids and plasmas

Evolving from turbulent states the 2D fluids and the plasmas reach states characterized by a high degree of order, consisting of few vortices. These asymptotic states represent a small subset in the space of functions and are characterised by properties that are difficult to identify in a direct approach. The field theoretical approach to the dynamics and to the asymptotic states of fluids and plasmas in 2D provides a considerable extension of the usual perspective. The present works discusses a series of consequences of the field theoretical approach, when it is applied to particular problems. The discussion is developed around known physical problems: the current density profiles in cylindrical plasma, the density pinch in tokamak and the concentration of vorticity.

physics.flu-dyn↗

arXiv2009

Nonlinear spin-up of a thermally stratified fluid in cylindrical geometries

This is an entry for the Gallery of Fluid Motion of the 62nd Annual Meeting of the APS-DFD (fluid dynamics videos). This video shows the three-dimensional time-dependent incremental spin-up of a thermally stratified fluid in a cylinder and in an annulus. The rigid bottom/side wall(s) are non-slip, and the upper surface is stress-free. All the surfaces are thermally insulated. The working fluid is water characterized by the kinematic viscosity $ν$ and thermal diffusivity $κ$. Initially, the fluid temperature varies linearly with height and is characterized by a constant buoyancy frequency $N$, which is proportional to the density gradient. The system undergoes an abrupt change in the rotation rate from its initial value $Ω_i $, when the fluid is in a solid-body rotation state, to the final value $Ω_f$. Our study reveals a feasibility for transition from an axisymmetric initial circulation to non-axisymmetric flow patterns at late spin-up times.

physics.flu-dyn↗

arXiv2010

Comparison of Bayesian Land Surface Temperature algorithm performance with Terra MODIS observations

An approach to land surface temperature (LST) estimation that relies upon Bayesian inference has been tested against multiband infrared radiometric imagery from the Terra MODIS instrument. Bayesian LST estimators are shown to reproduce standard MODIS product LST values starting from a parsimoniously chosen (hence, uninformative) range of prior band emissivity knowledge. Two estimation methods have been tested. The first is the iterative contraction mapping of joint expectation values for LST and surface emissivity described in a previous paper. In the second method, the Bayesian algorithm is reformulated as a Maximum \emph{A-Posteriori} (MAP) search for the maximum joint \emph{a-posteriori} probability for LST, given observed sensor aperture radiances and \emph{a-priori} probabilities for LST and emissivity. Two MODIS data granules each for daytime and nighttime were used for the comparison. The granules were chosen to be largely cloud-free, with limited vertical relief in those portions of the granules for which the sensor zenith angle $| ZA | < 30^{\circ}$. Level 1B radiances were used to obtain LST estimates for comparison with the Level 2 MODIS LST product. The Bayesian LST estimators accurately reproduce standard MODIS product LST values. In particular, the mean discrepancy for the MAP retrievals is $| < ΔT > | < 0.3 K$, and its standard deviation does not exceed $1 K$. The $\pm 68 %$ confidence intervals for individual LST estimates associated with assumed uncertainty in surface emissivity are of order $0.8 K$. The Appendix presents a proof of convergence of the iterative contraction mapping algorithm.

physics.data-an↗

arXiv2011

Investigation of particle and molecular extinction effects in remote sensing by ultraviolet DIAL in the lower atmosphere

This study presents theoretical investigation of the effects of particle and molecular extinction in horizontal remote sensing near the ground for several visibilities at UV wavelengths by neglecting the spatial inhomogeneity of aerosol in the atmosphere and taking into account the dependence of refracting on air temperature and pressure. Due to weak attenuation of oxygen and other gaseous atmospheric constituents in this region, we have only considered the effect of ozone in calculation. The results are important to estimate systematic errors in measuring gas concentration introduced by large wavelength separation in UV-DIAL. The total attenuation (km-1) at wavelengths is listed in the form of a table from 200 to 400 nm for several values of visibilities. It is found the aerosol attenuation in UV region varies quite smoothly with wavelength and therefore systematic error caused by aerosol scattering is negligible in remote sensing by UV-DIAL even with large wavelength separation. Moreover, it has been found that only aerosol extinction is dominant in lidar remote sensing in the lower atmosphere in UV region. In large altitude that aerosol concentration is lower; the molecular scattering is important especially for wavelengths larger than 310 nm.

physics.ao-ph↗

arXiv2010

Microburst windspeed potential assessment: progress and recent developments

Recent testing and validation have found that the GOES microburst products are effective in the assessment and short-term forecasting of downburst potential and associated wind gust magnitude. Two products, the GOES sounder Microburst Windspeed Potential Index and the multispectral GOES imager product have demonstrated capability in downburst potential assessment. Each microburst product consists of a set of predictor variables that generates output of expected microburst risk. This paper compares and contrasts the sounder and imager microburst products and outlines the advantages of each product in the nowcasting process. An updated assessment of the sounder MWPI and imager microburst products, case studies demonstrating effective operational use of the microburst products, and validation results for the 2009 convective season over United States Great Plains is presented.

physics.ao-ph↗