Wave Steepness retrieved from scattermeter Data
Jie Guo1, Yijun He2
1 Yantai Institute of Coastal Zone Research,Chinese Academy of Sciences, BOX 264003
17 Chunhui Road, Laishan District, Yantai. E-mail:guo_jie8@sina.com
2
Institute of Oceanology and Key Laboratory of Ocean Circulation and Waves, Chinese
Academy of Science,Qingdao . BOX 266071, 7 Nanhai Road, Qingdao, Shandong.
1. Introduction
Wave Steepness of sea wave feature is an important wave characteristics about
voyage and Engineering of Port Construction and so on. As it is difficulty to obtain
from lack of frutis of resrarch on theory of wavelength dispersal and directly observed
of wavelength.
The wave steepness of single wave is definition as
S H
L
, H-wave height, L-wave
length, S- wave steepness.
In practice, the wavelength is usually estimated by period with the help of Dispersion
Relations in deep water of bilinear water wave theory. It is S t  2H / gT 2 , g is the
acceleration of gravity, subscript t denotes estimate wavesteepness by period. Based
on these distributions the definitions of characteristic steepness, including mean
steepness and sea state steepness a re studied. The mean steepness is definition as
means of single wavesteepness (S) under a definite oceanic. The sea state steepness is
2
S H  2H 1 / gT e ,
3
H1
is the significant wave height. Te is the mean step to zero
3
period. There are many scholars who had done a many work about wavesteepness,
thought they have different viewpoint. Here, we will introduce the sea state steepness
retrieved by scatterometer data.
During we retrieved wave parameter by scatterometer data, we found that we can
retrieved wavesteepness just as wind speed. In the following sections, our
methodology, results,and conclusions to retrieve wavesteepness from ERS-1/2
scatterometer data and Quickscat data are present.
2. Methods and results
ERS-1/2 scatterometer data and Quickscate data with NDBC buoy data are used to
research the relation between wave steepness and RCS, respectively. We find that
Their relationship looks like that between RCS and wind. We can retrieved the wave
steepness from ERS-1/2 scatterometer data and Quickscate data using neural network
algorithm.
The comparison of 2H 1 / gT 2 between buoys and retrieval from ERS-1/2
3
scatterometer data are shown. The bias, average absolute error and root mean square
of the 2H 1 / gT 2 retrievals with these measured by buoy are-0.0002, 0.005, 0.006,
3
respectively.
The comparison of 2H 1 / gT 2 between buoy and retrieval from Quickscate data
3
（the data from high-velocity of wind） 46  , 54  are shown. The bias, average
absolute error and root mean square of the 2H 1 / gT 2 retrievals with these
3
measured by buoy are 0.002, 0.006, 0.007； 0.001, 0.006 and 0.007, respectively.
3. Conclusions
A wave steepness retrieval model are established using scatterometer data and
NDBC buoy wave data. The results show that it is not affected from the oceanic
condition and band of scatterometer.