Chongjian Liu

The relation between the atmospheric entropy flow field and local rainfall is examined in terms of the theory of dissipative structures. In this paper, the entropy balance equation in a form suitable for describing the entropy budget of the Earth’s atmosphere is derived starting from the Gibbs relation, and, as examples, the entropy flows of the two severe weather events associated with the development of an extratropical cyclone and a tropical storm are calculated, respectively. The results show that negative entropy flow (NEF) has a significant effect on the precipitation intensity and scope with an apparent matching of the NEF’s pattern with the rainfall distribution revealed and, that the diagnosis of NEF is able to provide a good indicator for precipitation forecasting.

Studies of the Hurricane Evolution Based on Modern Thermodynamics | InTechOpen, Published on: 2011-04-19. Authors: Chongjian Liu, Ying Liu, Zhexian Luo, et

The concept of entropy and its relevant principles, mainly the principle of maximum entropy production (MEP), the effect of negative entropy flow (NEF) on the organization of atmospheric systems and the principle of the Second Law of thermodynamics, as well as their applications to atmospheric sciences, are reviewed. Some formulations of sub-grid processes such as diffusion parameterization schemes in computational geophysical fluid dynamics that can be improved based on full-irreversibility are also discussed, although they have not yet been systematically subjected to scrutiny from the perspective of the entropy budgets. A comparative investigation shows that the principle of MEP applies to the entropy production of macroscopic fluxes and determines the most probable state, that is, a system may choose a development meta-stable trajectory with a smaller production since entropy production behavior involves many specific dynamical and thermodynamic processes in the atmosphere and the extremal principles only provide a general insight into the overall configuration of the atmosphere. In contrast to the principle of MEP, the analysis of NEF is able to provide a new insight into the mechanism responsible for the evolution of a weather system as well as a new approach to predicting its track and intensity trend.

The universal principle that an open system can be driven to a state far from equilibrium, or organized, by strong negative entropy flow from its surroundings has been validated in numerous fields from physics and chemistry to the life science. In this paper, entropy flows for a severe storm are calculated via the entropy flow formula using the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis data. The results show that the intensification of negative (positive) entropy flow entering into the storm preceded the strengthening (weakening) of its intensity, implying that entropy flow analysis can be used as a potential tool in forecasting changes in the intensity of a storm.

The problem of tropical cyclogenesis in a triple‐scale coexisting system which includes a subtropical high ridge, a preexisting cyclonic circulation with the initial maximum tangential wind V_bmax of 5 m s⁻¹, and single‐, double‐, or four‐cluster anomalies is examined in this paper, using a shallow water primitive equation (SWPE) model. This work validates the recent results concerning the upscale cascade mechanism suggested for tropical cyclogenesis in the double‐scale coexisting system containing the basic state vortex and anomalies, and it is shown that, for the double‐cluster anomaly, the mean azimuthal maximum tangential wind of the final vortex is increased and the radius of the maximum tangential wind (RMW) is contracted in the case of 1.388 ≥ K_ut ≥ 0.0 in which K_ut = ∣u_smax∣/V_bmax with u_smax being the maximum of the easterlies south of the initial subtropical ridge, which demonstrates an amplification of the vortex within this range of parameter. For the single‐cluster anomaly of large amplitude the anomaly will become a master vortex, and for the four‐cluster one the spin‐up of the initial basic state vortex will be decreased. Compared with the case of still environmental currents, introducing the subtropical ridge will have the following impact on axisymmetrization in horizontal shearing currents: (1) The interaction of a single‐cluster anomaly with the basic state vortex will occur in the environmental currents with cyclonic vorticity when the anomaly is located initially in the SW/SE quadrant of the basic state vortex; the interaction between the anomaly and the basic state vortex makes the spin‐up double that in the case of still environmental currents. (2) Although axisymmetrization of vortex configuration may occur, it is mainly limited to the inner region of the vortex with a distinct new nonaxisymmetry in its outer region, and there exist a series of cells of smaller scales in the northeastern quadrant of the outer region. (3) The total kinetic energy for the inner region of the vortex in the mean increases but fluctuates with time, unlike the still environmental currents case in which it increases monotonically.

This paper is aimed at investigating the interaction between a tropical storm (TS) and its adjacent mesoscale convective vortices (MCVs) using a barotropic primitive equation model. The results show that the interaction may result in vortex self‐organization. Compared with the case without MCVs, the quasi‐final state vortex becomes stronger with the increased kinetic energy and lower value of height at the vortex centre owing to the extra vorticity supplied by the MCVs. The intensity of the initial TS controls the complexity of the self‐organization process and determines whether the vorticity of MCVs is either fully or partially absorbed. The quasi‐final state vortex will either keep the intensity the initial TS has or decay dependently on the intensity or number of the MCVs, exhibiting the complexity of the characteristics of the organized quasi‐final state vortex.

The complexity of major vortex motion in a system where four scales are coexisting (a subtropical high ridge, the major vortex, meso‐ and small‐scale vortices) is examined numerically using a barotropic primitive equation model. The microenvironment of a major vortex consists of a group of small‐scale vortices in which varying values for the total number N of initial small‐scale vortices (N = 2, 3, 4, and 5, respectively) creates a diverse range of microenvironments. Three kinds of major vortex motion are observed: (i) the initial major vortex decays away with no new major vortex formation; (ii) a weak new major vortex forms while the major vortex decays; and (iii) a new major vortex occurs, via self‐organization, with its intensity and scale similar to those in the initial stages of the original major vortex, and this vortex continues to shift westwards after the old major vortex decays.

A proper description of the dissipation in a forcing‐dissipative system, such as the atmosphere, is very important when the system is discretized. Atmospheric dissipation is generally treated as diffusion in numerical weather prediction (NWP) models. The commonly used fourth‐order diffusion scheme (linear and nonlinear) generates spurious upgradient mass or heat transport, which violates the entropy constraint posed by non‐equilibrium thermodynamics. The second law of thermodynamics is used in this paper to re‐construct the diffusion scheme to ensure downgradient transport. The new physics‐based scheme is applied to the Penn State/NCAR non‐hydrostatic mesoscale model. A hurricane case simulation demonstrates that the new scheme improves the model accuracy in predicting the strength of the hurricane.