First evidence for the detection of natural surface films by the QuikSCAT scatterometer

Lin, I. I.; Alpers, Werner; Liu, W. Timothy

doi:10.1029/2003gl017415

Cited by 10 publications

(9 citation statements)

References 9 publications

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“…As for oceanic rain, it is foreseen that one can build a slick climatology within different chosen regions. These climatologies could then be profitably compared with the regions of reduced backscatter observed in scatterometer data which have been associated with natural surface slicks by comparison with ocean color data [ Lin et al , 2003; Hashizume and Liu , 2004].…”

Section: Resultsmentioning

confidence: 99%

A satellite altimeter model for ocean slick detection

et al. 2006

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[1] About 5% of Ku-band altimeter ocean data are degraded by the occurrence of high radar return cross sections (s 0 ), usually called s 0 blooms. During blooms, which occur during no or low wind conditions, the mean altimeter waveform can significantly depart from the expected shape. In about 60% of the cases the waveforms are distorted to such an extent that either the range tracker loses lock or the off-nadir angle estimate becomes unrealistic. The analysis of high data rate altimeter waveforms during bloom events reveals the presence of V-shaped patterns similar to the ones observed during rain events. These patterns trace small-scale (i.e., smaller than the altimeter footprint) changes in surface backscatter. Such variations of surface roughness are commonly observed in SAR images under low wind conditions. On the basis of the experience gained through the analysis of high-resolution altimeter waveforms in the presence of rain cell, a model is developed to analyze the altimeter response to phenomena whose length scale is smaller than the altimeter footprint. The model is applied to simple patterns (linear slicks and circular patches) as well as to realistic surface s 0 estimated by SAR. It is also used to analyze bloom events in terms of surface slicks. The model results shows that the smallscale s 0 variations explain the behavior of altimeter waveforms in bloom events. The results also show that a good proportion of data during bloom events are still valid for estimating geophysical parameters as the Brown model remains valid. Use of highresolution altimeter waveforms may also offer an interesting mean to study marine slick occurrence rates and type.

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Section: Resultsmentioning

confidence: 99%

A satellite altimeter model for ocean slick detection

et al. 2006

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“…The relations between dW and log 10 (CHL) are almost linear, and that dW increases from ∼−1 m s −1 to ∼0.5 m s −1 as CHL increases from ∼0.1 mg m −3 to ∼3 mg m −3 . This ∼1.5 m s −1 reduction of scatterometer wind is quantitatively reasonable relative to the previous experimental studies although it is much smaller than the amplitude of dW observed from instantaneous comparison by Lin et al [2003]. For instance, Feindt 's [1985] laboratory wind wave tank experiments with X‐band (9.8 GHz) scatterometer [see also Alpers and Hühnerfuss , 1989, Figure 5] shows that artificial surface film causes ∼7 dB backscatter reduction at 7 m s −1 wind speed, which corresponds to ∼3 m s −1 wind speed underestimation.…”

Section: Resultsmentioning

confidence: 99%

“…There are also some airborne Ku‐band scatterometer experiment studies [e.g., Hühnerfuss et al , 1978; Singh et al , 1986; Gade et al , 1998]. There have been no observations of such effect on spacebased scatterometers in open ocean until the recent study by Lin et al [2003]. They showed that backscatter reduction on QuikSCAT occurred near the chlorophyll‐a‐rich area in the northern North Atlantic.…”

Section: Introductionmentioning

confidence: 99%

Systematic error of microwave scatterometer wind related to the basin‐scale plankton bloom

Hashizume

Liu

2004

Geophysical Research Letters

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[1] Chlorophyll-a concentration derived from satellite ocean color sensor are compared with coincident wind speed difference between microwave scatterometer QuikSCAT product and reanalysis product from the National Center for Environmental Prediction over global oceans. The objective is to explore if a natural surface film, which originates in biological productivity, causes the underestimation of surface wind in scatterometer measurement by damping the small capillary wave through the surface tension. The wind speed difference (Reanalysis wind -QuikSCAT wind) is found to correlate positively with chlorophyll-a over the biologically highly productive areas, especially from intra-seasonal to seasonal time scales, indicating the surface film effect. The wind speed difference increases from $À1 m s À1 to $0.5 m s À1 as chlorophyll-a increases from $0.1 mg m À3 to $3 mg m À3 , which is comparable with the results of previous laboratory experiments with artificial oil.

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“…), Chapron et al (2000) considered that the shape of the sea surface slope probability distribution function can partially explain such discrepancies. In particular, Lin et al (2003) have showed that anomalous backscatter regions observed by the Quick scatterometer (QuikSCAT) often correspond to such phenomena locations as recalled by Mitchum et al (2004). Anderson et al (2002) also pointed out the limitations they ran into as a result of the lack of absolute calibration of TOPEX 0 .…”

Section: Benefits Expected From the Absolute Calibration Of Altimementioning

confidence: 95%

Absolute Calibration of Jason-1 and Envisat Altimeter Ku-Band Radar Cross Sections from Cross Comparison with TRMM Precipitation Radar Measurements

Tran

Zanifé

Chapron

et al. 2005

Journal of Atmospheric and Oceanic Technology

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One year of collocated, rain-free nadir Ku-band backscatter cross-section measurements from the Tropical Rainfall Mapping Mission (TRMM) precipitation radar (PR) and both Jason-1 and Envisat RA-2 altimeter measurements have been compiled to compare these three sources of Ku-band radar cross section. With the exception of a ϩ1.46 dB relative offset between Jason-1 and PR measurements and a Ϫ1.40 dB offset between Envisat and PR ones, all three Ku-band measurements compare very well in terms of dependencies upon model wind speed estimates and significant wave height measurements. The altimeter radars and the rain radar thus provide consistent measurements, and observed biases can be rationalized as differences in the radar calibration. The precipitation radar, which also covers off-nadir measurements, has been absolutely calibrated using an active radar calibrator. Consequently, the observed relative offsets can be used to indirectly calibrate both Jason-1 and Envisat altimeter Ku-band radar cross sections in an absolute sense.

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First evidence for the detection of natural surface films by the QuikSCAT scatterometer

Cited by 10 publications

References 9 publications

A satellite altimeter model for ocean slick detection

A satellite altimeter model for ocean slick detection

Systematic error of microwave scatterometer wind related to the basin‐scale plankton bloom

Absolute Calibration of Jason-1 and Envisat Altimeter Ku-Band Radar Cross Sections from Cross Comparison with TRMM Precipitation Radar Measurements

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