The Experts below are selected from a list of 1305 Experts worldwide ranked by ideXlab platform
David P Stepaniak - One of the best experts on this subject based on the ideXlab platform.
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seamless poleward atmospheric energy transports and implications for the hadley circulation
Journal of Climate, 2003Co-Authors: Kevin E Trenberth, David P StepaniakAbstract:Abstract A detailed vertically integrated atmospheric heat and energy budget is presented along with estimated heat budgets at the surface and top-of-atmosphere for the subtropics. It is shown that the total energy transports are remarkably seamless in spite of greatly varying mechanisms. From the Tropics to about 31° latitude, the primary transport mechanisms are the Hadley and Walker overturning circulations. In the extratropics the energy transports are carried out by baroclinic eddies broadly organized into storm tracks and quasi-stationary waves that covary in a symbiotic way as the location and activity in storm tracks are determined by, and in turn help maintain through eddy transports, the quasi-stationary flow. In the upward branch of the Hadley cell, the predominant Diabatic Process is latent heating that results from convergence of moisture by the circulation itself. Hence large poleward transports of dry static energy are compensated by equatorward transports of latent energy, resulting in a m...
Kevin E Trenberth - One of the best experts on this subject based on the ideXlab platform.
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2003: Seamless poleward atmospheric energy transports and implications for the Hadley circulation
2016Co-Authors: Kevin E Trenberth, P. StepaniakAbstract:A detailed vertically integrated atmospheric heat and energy budget is presented along with estimated heat budgets at the surface and top-of-atmosphere for the subtropics. It is shown that the total energy transports are remarkably seamless in spite of greatly varying mechanisms. From the Tropics to about 318 latitude, the primary transport mechanisms are the Hadley and Walker overturning circulations. In the extratropics the energy transports are carried out by baroclinic eddies broadly organized into storm tracks and quasi-stationary waves that covary in a symbiotic way as the location and activity in storm tracks are determined by, and in turn help maintain through eddy transports, the quasi-stationary flow. In the upward branch of the Hadley cell, the predominant Diabatic Process is latent heating that results from convergence of moisture by the circulation itself. Hence large poleward transports of dry static energy are compensated by equatorward transports of latent energy, resulting in a modest poleward transport of moist static energy. The subsidence warming in the downward branch is compensated by cooling in the subtropics that mainly arises from energy transport to higher latitudes by transient baroclinic eddies that are stronger in the winter hemisphere. Effectively, the outgoing longwave radiation to space is distributed over middle and high latitudes and is not limited to the clear dry regions in the subtropics. Further, some of the radiative cooling in the subtropics is a consequence of the circulation. Hence the coolin
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seamless poleward atmospheric energy transports and implications for the hadley circulation
Journal of Climate, 2003Co-Authors: Kevin E Trenberth, David P StepaniakAbstract:Abstract A detailed vertically integrated atmospheric heat and energy budget is presented along with estimated heat budgets at the surface and top-of-atmosphere for the subtropics. It is shown that the total energy transports are remarkably seamless in spite of greatly varying mechanisms. From the Tropics to about 31° latitude, the primary transport mechanisms are the Hadley and Walker overturning circulations. In the extratropics the energy transports are carried out by baroclinic eddies broadly organized into storm tracks and quasi-stationary waves that covary in a symbiotic way as the location and activity in storm tracks are determined by, and in turn help maintain through eddy transports, the quasi-stationary flow. In the upward branch of the Hadley cell, the predominant Diabatic Process is latent heating that results from convergence of moisture by the circulation itself. Hence large poleward transports of dry static energy are compensated by equatorward transports of latent energy, resulting in a m...
Hamidreza Ramezani - One of the best experts on this subject based on the ideXlab platform.
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eigenstates transition without undergoing an aDiabatic Process
Physical Review Letters, 2019Co-Authors: Fatemeh Mostafavi, Luqi Yuan, Hamidreza RamezaniAbstract:: We introduce a class of non-Hermitian Hamiltonians that offers a dynamical approach to a shortcut to aDiabaticity (DASA). In particular, in our proposed 2×2 Hamiltonians, one eigenvalue is absolutely real and the other one is complex. This specific form of eigenvalues helps us to exponentially decay the population in an undesired eigenfunction or amplify the population in the desired state while keeping the probability amplitude in the other eigenfunction conserved. This provides us with a powerful method to have a Diabatic Process with the same outcome as its corresponding aDiabatic Process. In contrast to standard shortcuts to aDiabaticity, our Hamiltonians have a much simpler form with a lower thermodynamic cost. Furthermore, we show that DASA can be extended to higher dimensions using the parameters associated with our 2×2 Hamiltonians. Our proposed Hamiltonians not only have application in DASA but also can be used for tunable mode selection and filtering in acoustics, electronics, and optics.
Wang Zhaohua - One of the best experts on this subject based on the ideXlab platform.
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aDiabatic and Diabatic Process of sum frequency conversion
Optics Express, 2010Co-Authors: Ren Liqing, Li Yongfang, Li Baihong, Wang ZhaohuaAbstract:Based on the dressed state formalism, we obtain the aDiabatic criterion of the sum frequency conversion. We show that this constraint restricts the energy conversion between the two dressed fields, which are superpositions of the signal field and the sum frequency field. We also show that the evolution of the populations of the dressed fields, which in turn describes the conversion of light photons from the seed frequency to the sum frequency during propagation through the nonlinear crystal. Take the quasiphased matched (QPM) scheme as an example, we calculate the expected bandwidth of the frequency conversion Process, and its dependence on the length of the crystal. We demonstrate that the evolutionary patterns of the sum frequency field’s energy are similar to the Fresnel diffraction of a light field. We finally show that the expected bandwidth can be also deduced from the evolution of the aDiabaticity of the dressed fileds.
Fatemeh Mostafavi - One of the best experts on this subject based on the ideXlab platform.
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eigenstates transition without undergoing an aDiabatic Process
Physical Review Letters, 2019Co-Authors: Fatemeh Mostafavi, Luqi Yuan, Hamidreza RamezaniAbstract:: We introduce a class of non-Hermitian Hamiltonians that offers a dynamical approach to a shortcut to aDiabaticity (DASA). In particular, in our proposed 2×2 Hamiltonians, one eigenvalue is absolutely real and the other one is complex. This specific form of eigenvalues helps us to exponentially decay the population in an undesired eigenfunction or amplify the population in the desired state while keeping the probability amplitude in the other eigenfunction conserved. This provides us with a powerful method to have a Diabatic Process with the same outcome as its corresponding aDiabatic Process. In contrast to standard shortcuts to aDiabaticity, our Hamiltonians have a much simpler form with a lower thermodynamic cost. Furthermore, we show that DASA can be extended to higher dimensions using the parameters associated with our 2×2 Hamiltonians. Our proposed Hamiltonians not only have application in DASA but also can be used for tunable mode selection and filtering in acoustics, electronics, and optics.