Inferring multiscale structure in atmospheric turbulence using satellite-based synthetic aperture radar imagery

被引:33
作者
Mourad, PD
机构
[1] Applied Physics Laboratory, Coll. of Ocean and Fishery Sciences, University of Washington
[2] Applied Physics Laboratory, Coll. of Ocean and Fishery Sciences, University of Washington, Seattle, WA 98105
关键词
D O I
10.1029/96JC00920
中图分类号
P7 [海洋学];
学科分类号
0707 ;
摘要
This paper describes the multiscale structure in synthetic aperture radar (SAR) backscatter seen in an image of a cold-air outbreak as being due to the influence on the surface of the ocean of three scales of interacting atmospheric turbulence. A low-resolution (pixels have side lengths of 100 m) SAR image shows the first class of backscatter pattern to be broken lines of enhanced radar backscatter (sigma), of order 1 dB above the background, with an average cross-wind scale of 5 km and downwind lengths of many tens of kilometers. These are associated with quasi-two-dimensional roll vortices. The second class of radar backscatter pattern is two-dimensional backscatter regions whose linear aggregrations constitute the lines of backscatter. They are, on average, 1 km wide in the cross-wind direction and are 2.5 km long in the downwind direction. A higher-resolution image (pixels have side lengths of 12.5 m) of the same area, shows a third class of structure: smaller-scale regions of enhanced backscatter up to several hundred meters in length downwind and greater than 190 m across wind that are associated with 7-dB variations in sigma in the unaveraged image. The modulated, fine-scale backscatter structure compares favorably in both scale and effect to observations of the modulation of ''microfronts'' in the atmospheric surface layer by kilometer-scale ''inactive eddies,'' the latter being of uncertain origin. Therefore the hypothesis offered here is that the fine-scale SAR structure is caused by the influence of atmospheric microfronts on the ocean surface, while the two-dimensional, kilometer-scale backscatter features are the signature of inactive eddies linearly aggregated by or possibly intrinsic to the roll vortices.
引用
收藏
页码:18433 / 18449
页数:17
相关论文
共 37 条
[1]   ATMOSPHERIC BOUNDARY-LAYER ROLLS OBSERVED BY THE SYNTHETIC-APERTURE RADAR ABOARD THE ERS-1 SATELLITE [J].
ALPERS, W ;
BRUMMER, B .
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 1994, 99 (C6) :12613-12621
[2]  
ATLAS D, 1994, B AM METEOROL SOC, V75, P1183, DOI 10.1175/1520-0477(1994)075<1183:TEOCSF>2.0.CO
[3]  
2
[4]   QUASI-COHERENT STRUCTURES IN THE MARINE ATMOSPHERIC SURFACE-LAYER [J].
BOPPE, RS ;
NEU, WL .
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 1995, 100 (C10) :20635-20648
[5]  
BRUMMER B, 1985, BEITR PHYS ATMOS, V58, P237
[6]   A NUMERICAL STUDY OF THE TURBULENT EKMAN LAYER [J].
COLEMAN, GN ;
FERZIGER, JH ;
SPALART, PR .
JOURNAL OF FLUID MECHANICS, 1990, 213 :313-348
[7]   A NUMERICAL STUDY OF THE CONVECTIVE BOUNDARY-LAYER [J].
COLEMAN, GN ;
FERZIGER, JH ;
SPALART, PR .
BOUNDARY-LAYER METEOROLOGY, 1994, 70 (03) :247-272
[8]   ROLL VORTICES IN THE PLANETARY BOUNDARY-LAYER - A REVIEW [J].
ETLING, D ;
BROWN, RA .
BOUNDARY-LAYER METEOROLOGY, 1993, 65 (03) :215-248
[9]  
FREILICH MH, 1993, P 1 ERS 1 S SPAC SER, P79
[10]   STRUCTURE OF THE SURFACE WIND-FIELD FROM THE SEASAT SAR [J].
GERLING, TW .
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 1986, 91 (C2) :2308-2320