El Niño continues the most important coupled ocean-atmosphere phenomenon to cause global climate variability on
seasonal to inter annual time scales. The first independent spatial mode which carried out by EOF analysis of tropical
and north Pacific sea surface temperature (SST) for the period of 1985-2009 in AVHRR dataset is found to be associated
with well-known regional climate phenomena: the El Niño. This paper addresses the need for a reliable El Niño index
that allows for the historical definition of El Niño events in the instrumental record back to 1985-2009 with a new
perspective. For quantitative purposes, possible definitions are explored that match the El Niño identified historically in
1985-2009, and it is suggested that an El Niño can be said to occur if difference of sea surface temperature (SST)
anomalies between the tropical and north Pacific exceeds 0.6 times standard deviation for 5 months or more. An
advantage of such a definition is that it combines the characteristics between tropical and north Pacific. Through seasonal
analysis of SST in El Niño event, we found that the El Niño events are almost beginning in boreal spring or perhaps
boreal summer and peak from November to February. It provides a more complete and flexible description of the El
Niño phenomenon than single area in tropical Pacific.
Mesoscale eddies are widely found in the ocean. They play important roles in heat transport, momentum transport,
ocean circulation and so on. The automatic detection of mesoscale eddies based on satellite remote sensing images is an
important research topic. Some image processing methods have been applied to identify mesoscale eddies such as Canny
operator, Hough transform and so forth, but the accuracy of detection was not very ideal. This paper described a new
algorithm based on watershed segmentation algorithm for automatic detection of mesoscale eddies from sea level
anomaly(SLA) image. Watershed segmentation algorithm has the disadvantage of over-segmentation. It is important to
select appropriate markers. In this study, markers were selected from the reconstructed SLA image, which were used to
modify the gradient image. Then two parameters, radius and amplitude of eddy, were used to filter the segmentation
results. The method was tested on the Northwest Pacific using TOPEX/Poseidon altimeter data. The results are
encouraging, showing that this algorithm is applicable for mesoscale eddies and has a good accuracy. This algorithm has
a good response to weak edges and extracted eddies have complete and continuous boundaries. The eddy boundaries
generally coincide with closed contours of SSH.
The physical forcing and biological response are highly variable over multi-time scales ranging from biennial to interdecadal in the tropical Pacific Ocean. Satellite provides a systematic view of the coupled biological-physical variability over large spatial scales. Based on the satellite observation data from 1985 to 2011, we analyzed the multi-timescale variabilities of the physical ocean parameters (sea surface temperature, sea level anomaly, wind, rainfall) and the biological ocean parameter (chlorophyll-a) as well as the linkages between them over the tropical Pacific Ocean. The goal of this study was to investigate the multi-timescale variability and spatial-temporal association patterns of the physical-biological paramters in the tropical Pacific Ocean of the year from 1985 to 2011.
The visualization in a single view of abnormal association patterns obtained from mining lengthy marine raster datasets presents a great challenge for traditional visualization techniques. On the basis of the representation model of marine abnormal association patterns, an interactive visualization framework is designed with three complementary components: three-dimensional pie charts, two-dimensional variation maps, and triple-layer mosaics; the details of their implementation steps are given. The combination of the three components allows users to request visualization of the association patterns from global to detailed scales. The three-dimensional pie chart component visualizes the locations where more marine environmental parameters are interrelated and shows the parameters that are involved. The two-dimensional variation map component gives the spatial distribution of interactions between each marine environmental parameter and other parameters. The triple-layer mosaics component displays the detailed association patterns at locations specified by the users. Finally, the effectiveness and the efficiency of the proposed visualization framework are demonstrated using a prototype system with three visualization interfaces based on ArcEngine 10.0, and the abnormal association patterns among marine environmental parameters in the Pacific Ocean are visualized.
Monthly precipitation data from 66 rain gauge stations in northern China are analyzed for the
period 1976–2011. Variations in droughts and wet spells are described using the standardized
precipitation index (SPI). Empirical orthogonal functions and a global wavelet spectral analysis
are applied to capture modes of spatio-temporal variability in droughts over northern China. Time
series of monthly sea surface temperatures (SST) and the Multivariate El Niño Southern
Oscillation Index (MEI) are presented, and cross wavelet and wavelet coherence transforms are
carried out to investigate possible mechanisms behind variations in droughts and wet spells. From
1976 onwards, the northern parts of northern China have experienced an increase in the frequency
of droughts, while the southern parts of northern China have experienced a decrease in the
frequency of droughts. The north–south variability of droughts and wet spells is characterized by
interannual timescales of 3.3 years and 7.0–11.0 years. The former timescale is closely related
with the MEI, while the latter is closely related with sea surface temperature anomalies (SSTA)
over the North Pacific. Most parts of northern China experienced an increase in the frequency of
droughts during the periods 1980–2000 and 2004–present, and a decrease in the frequency of
droughts during the period 2000–2004. The variability of drought in northern China peaks at
timescales of 16.0–32.0 and 3.5–4.0 years. The first of these timescales shows a significant
correlation with SSTA over the Indian Ocean. The eastern parts of northern China have
experienced a decrease in the frequency of droughts since 1976, while the western parts of
northern China have experienced an increase in the frequency of droughts. The east–west
variability of droughts and wet spells is characterized by interannual timescales of 3.3-8.0 years,
which are related with SSTA over the Indian Ocean warm pool.
Being short of evolution mechanisms, theories of spatio-temporal representation and modeling have great challenges to
describe and represent the continuity and gradual geographical entities, still less deeper information retrievals and
knowledge mining. The spatio-temporal dynamic semantics, which contains geographical entities, changes of entities
and evolution mechanisms, is presented. According to the intrinsic process characteristics of dynamic entities, a
hierarchical semantics structure and process object sequences included by level are given. This paper describes the
process relationships and behaviors, and formalizes them into evolution operators, which subdivide into the process
recurrence operators and recurrence ones. Based on the object-oriented technologies, the evolution operators are
integrated into process object sequences, and a process-oriented dual representation framework on process objects'
recurrence and recursion (DRF-PORR) is presented as well. And finally, as a case study, the typical oceanographic
phenomena are taken to carry out the case modeling.
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