Search Results

You are looking at 1 - 4 of 4 items for

  • Author or Editor: Chien-Hsiung Yang x
  • Refine by Access: All Content x
Clear All Modify Search
Chien-Hsiung Yang

Abstract

The performances of various one-dimensional interpolation schemes are evaluated using mean square errors of the point-wise estimates of the function values and component-wise estimates of the power spectrum. The schemes of interpolation considered include Gandin's optimum interpolation, cubic spline, and two-point linear interpolations. The test function is a random analytic function defined in a closed domain with a prescribed power spectrum, satisfying the conditions of homogeneity and ergodicity.

The experiment is carried out under the circumstance of interpolation which includes a conservative simulation of the large-scale state of the atmosphere and reflects the levels of data acquisition and resolution as practiced currently in meteorology.

The results of the experiment suggest that under all practical circumstances the error of interpolation, which is defined to be the ratio of the sample variance of estimation errors to the sample variance of true values, may not be reduced too much below the value of 0.05. The study also shows that the cubic spline interpolation performs very much like Gandin's optimum interpolation.

Full access
Chien-Hsiung Yang

Abstract

No abstract available.

Full access
Chien-Hsiung Yang
and
Ralph Shapiro

Abstract

By subjecting functions of known spectral constitution to a conventional procedure of obtaining the spectral estimates, the combined effect of the observation system and the method of interpolation on the spectral estimates are statistically assessed. The results suggest that linear interpolation applied on currently available observations may produce spectral estimates that yield an overestimated value for the slope of the spectral profile in the range 10 ≲ k ≲ 20, where k is the hemisphere wavenumber.

Full access
Sultan Hameed
,
Henry H. Norwood
,
Michael Flanagan
,
Steven Feldstein
, and
Chien-hsiung Yang

Abstract

Several studies have documented the effect of the recent secular climate warming on the distributions and geographical ranges of birds. Here the authors report the strong impact of a recurring climatic pattern in the equatorial Pacific, the El Niño–Southern Oscillation (ENSO) cycle of warm (El Niño) and cold (La Niña) events, on spring migrants along the Far Eastern flyway in northeast Asia. In El Niño years, an unusually large number of birds that use the flyway are observed at Attu Island, westernmost of the Aleutian Islands, nearly 960 km away from the Asian coast. This study is based on a 20-yr dataset documenting the year-to-year variation of Asian birds arriving on Attu in the spring season and uses a three-phased analytical methodology to examine climate impacts on bird movements and populations.

The authors offer evidence that birds are displaced toward the Attu area in strong eastward-moving storms. They also present results from a reverse trajectory model that was used to simulate trajectories that a sample of Attu arrivals likely followed in reaching the island. In a statistical analysis, it is shown that 79% of the variation of the Asian birds is explained by a single climate variable: sea surface temperature in the eastern equatorial Pacific in the previous fall. It is the rise in sea surface temperature in this region, more than 8000 km from Attu, that characterizes the onset of an El Niño episode.

Examining those years for which there was a strong ENSO signal in the fall, it is found that the following May is characterized by anomalously strong westerly winds in the northwest Pacific, conditions that are appropriate for large Asian bird fallouts at Attu. Because of the time lag between the fall sea surface temperatures in the El Niño region and the spring Asian bird count at Attu, and the strong correlation between these two quantities, the number of Asian birds arriving at Attu in spring is predictable in the previous autumn. Such predictions are presented for several years.

Full access