Time scales of pattern evolution from cross-spectrum analysis of advanced very high resolution radiometer and coastal zone color scanner imagery Public Deposited

http://ir.library.oregonstate.edu/concern/defaults/wh246t71n

copyrighted by American Geophysical Union

Descriptions

Attribute NameValues
Creator
Abstract or Summary
  • We have selected square subareas (110 km on a side) from coastal zone color scanner (CZCS) and advanced very high resolution radiometer (AVHRR) images for 1981 in the California Current region off northern California for which we could identify sequences of cloud-free data over periods of days to weeks. We applied a two-dimensional fast Fourier transform to images after median filtering, (x, y) plane removal, and cosine tapering. We formed autospectra and coherence spectra as functions of a scalar wavenumber. Coherence estimates between pairs of images were plotted against time separation between images for several wide wavenumber bands to provide a temporal lagged coherence function. The temporal rate of loss of correlation (decorrelation time scale) in surface patterns provides a measure of the rate of pattern change or evolution as a function of spatial dimension. We found that patterns evolved (or lost correlation) approximately twice as rapidly in upwelling jets as in the "quieter" regions between jets. The rapid evolution of pigment patterns (lifetime of about 1 week or less for scales of 50-100 km) ought to hinder biomass transfer to zooplankton predators compared with phytoplankton patches that persist for longer times. We found no significant differences between the statistics of CZCS and AVHRR images (spectral shape or rate of decorrelation). In addition, in two of the three areas studied, the peak correlation between AVHRR and CZCS images from the same area occurred at zero lag, indicating that the patterns evolved simultaneously. In the third area, maximum coherence between thermal and pigment patterns occurred when pigment images lagged thermal images by 1-2 days, mirroring the expected lag of high pigment behind low temperatures (and high nutrients) in recently upwelled water. We conclude that in dynamic areas such as coastal upwelling systems, the phytoplankton cells (identified by pigment color patterns) behave largely as passive scalars at the mesoscale and that growth, death, and sinking of phytoplankton collectively play at most a marginal role in determining the spectral statistics of the pigment patterns.
Resource Type
Date Available
Date Issued
Citation
  • Denman, K. L., and Abbott, M. R. , 1994, Time scales of pattern evolution from cross - spectrum analysis of advanced very high resolution radiometer and coastal zone color scanner imagery, Jour. Geophys. Res., v. 99, p. 7433 - 7442.
Series
Rights Statement
Publisher
Language
Replaces
Additional Information
  • description.provenance : Approved for entry into archive by Mark Abbott(mark@coas.oregonstate.edu) on 2010-03-12T20:44:35Z (GMT) No. of bitstreams: 1 Denman_and_Abbott_JGR_1994.pdf: 1009482 bytes, checksum: 75a29bbefa8608d6d4d7e7493af6d2c7 (MD5)
  • description.provenance : Made available in DSpace on 2010-03-12T20:44:35Z (GMT). No. of bitstreams: 1 Denman_and_Abbott_JGR_1994.pdf: 1009482 bytes, checksum: 75a29bbefa8608d6d4d7e7493af6d2c7 (MD5) Previous issue date: 1994
  • description.provenance : Submitted by Mary Phan (mpscanner@gmail.com) on 2010-03-12T18:02:14Z No. of bitstreams: 1 Denman_and_Abbott_JGR_1994.pdf: 1009482 bytes, checksum: 75a29bbefa8608d6d4d7e7493af6d2c7 (MD5)

Relationships

In Administrative Set:
Last modified: 07/24/2017

Downloadable Content

Download PDF
Citations:

EndNote | Zotero | Mendeley

Items