Huang Si-Xun

Review of the study of nonlinear atmospheric dynamics in China (1999–2002)

Researches on nonlinear atmospheric dynamics in China (1999–2002) are briefly surveyed. This review includes the major achievements in the following branches of nonlinear dynamics: nonlinear stability theory, nonlinear blocking dynamics, 3D spiral structure in the atmosphere, traveling wave solution of the nonlinear evolution equation, numerical predictability in a chaotic system, and global analysis of climate dynamics. Some applications of nonlinear methods such as hierarchy structure of climate and scaling invariance, the spatial-temporal series predictive method, the nonlinear inverse problem, and a new difference scheme with multi-time levels are also introduced.

Nonlinear Atmospheric and Climate Dynamics in China (2003--2006): A Review

Recent advances in the study of nonlinear atmospheric and climate dynamics in China (2003–2006) are briefly reviewed. Major achievements in the following eight areas are covered: nonlinear error dynamics and predictability; nonlinear analysis of observational data; eddy-forced envelope Rossby soliton theory; sensitivity and stability of the ocean’s thermohaline circulation; nonlinear wave dynamics; nonlinear analysis on fluctuations in the atmospheric boundary layer; the basic structures of atmospheric motions; some applications of variational methods.

An application of the adjoint method to a statistical-dynamical tropical-cyclone prediction model (SD-90) II: Real tropical cyclone cases

In the first paper in this series, a variational data assimilation of ideal tropical cyclone (TC) tracks was performed for the statistical-dynamical prediction model SD-90 by the adjoint method, and a prediction of TC tracks was made with good accuracy for tracks containing no sharp turns. In the present paper, the cases of real TC tracks are studied. Due to the complexity of TC motion, attention is paid to the diagnostic research of TC motion. First, five TC tracks are studied. Using the data of each entire TC track, by the adjoint method, five TC tracks are fitted well, and the forces acting on the TCs are retrieved. For a given TC, the distribution of the resultant of the retrieved force and Coriolis force well matches the corresponding TC track, i.e., when a TC turns, the resultant of the retrieved force and Coriolis force acts as a centripetal force, which means that the TC indeed moves like a particle; in particular, for TC 9911, the clockwise looping motion is also fitted well. And the distribution of the resultant appears to be periodic in some cases. Then, the present method is carried out for a portion of the track data for TC 9804, which indicates that when the amount of data for a TC track is sufficient, the algorithm is stable. And finally, the same algorithm is implemented for TCs with a double-eyewall structure, namely Bilis (2000) and Winnie (1997), and the results prove the applicability of the algorithm to TCs with complicated mesoscale structures if the TC track data are obtained every three hours.

Inversion and III-Posed Problem Solutions in Atmospheric Remote Sensing

With the swift advances in earth observation, satellite remote sensing and application of atmospheric radiation theory have been developed in the past decades, atmospheric sensing inversion with its algorithms is getting more and more importance. It is known that since a remote sensing equation falls into an integral equation of the first kind, thus leading to the fact that it is ill-posed and particularly the solution is unsteady, tremendous difficulties arise from the retrieval. This paper will present a simple review on the inversion techniques with some necessary remarks, before introducing the successful efforts with respect to such equations and the encouraging solutions achieved in recent decades by researchers of the world.

A new research on sea surface wind direction retrieval of synthetic aperture radar image

A new method to retrieve sea surface wind direction using synthetic aperture radar image is presented. Some pretreatment steps such as suppressing noise, down sampling and dividing into several sub-images are presented first. The method of two-dimensional numerical differentiation based on Tikhonov regularization is introduced to compute the gradient direction in the sub-image intensity of every point. The distance weighted objective function is used to compute the overall gradient direction in the sub-images. The retrieved wind direction is orthogonal to the overall gradient. When adding 10% of random errors, numerical simulations show that the result of numerical differentiation is better than that from the Sobel operator which is based on the finite difference method: the former error is 0.7293 °, and the latter error is 13.5069 °. Finally, an experiment based on real SAR data shows that the wind direction deviates from the overall direction determined by the method of Sobel operator, and the direction determined by the method of numerical differentiation is consistent well with the overall wind direction. Comparing the ship board wind direction and the corresponding location wind direction retrieved from the synthetic aperture radar sub-images with the two methods, the average result error of Sobel operator method is 9.0331°, while that of numerical differentiation method is 1.1148°. This new method is an effective and high accurate method to retrieve the sea surface wind direction of synthetic aperture radar image.

Study on Atmospheric Travelling Wave Solutions and Review of Its Present Developments

The scientific achievements of travelling waves in a barotropic atmosphere are introduced, including i) the existence conditions of periodic solutions (wavetrain solutions) and solitary wave solutions (pulse solutions), together with the solution finding methods and a series of related problems, ii) seeking solutions of monotonous wave (wave front) and of nonmonotonous travelling wave (oscillatory wave) by using phase plane shooting technique and iii) progress in the study of travelling wave solution at home and abroad. The investigation of travelling wave solutions in recent years has been found in mathematics, physics, chemistry, biology and other sciences. Over the past decade the problem has been the subject of much interest and become an important area of research. So it is no doubt of great significance to investigate the travelling wave solutions and thereby explain phenomena of weather.