Journal of Tropical Oceanography >
Variation assimilation using satellite data of sea surface temperature and altimeter
Received date: 2009-08-18
Revised date: 2010-04-07
Online published: 2011-07-20
A new method for assimilating altimeter and sea surface temperature (SST) data was developed for the second gen- eration Global Ocean Data Assimilation System of the Beijing Climate Center. The method allows the altimeter and SST data to be assimilated under one dynamic constraint based on the three-dimensional variation (3DVAR). In the cost function, the background was temperature and salinity from the model. The analytical variables were temperature and salinity. The sea sur- face high and SST were from the observations. The formula of steric high was introduced in the observation term. Because the steric high formula only constrained the integral of temperature and salinity in a water column from sea level to 1000 m, it will be unprincipled for the adjustment about the temperature and salinity analytics in the calculation of iteration absenting being short of accurate describing of vertical error covariance. Unfortunately we could not obtain the accurate covariance. To resolve this problem, the authors put the SST observation into the sea surface high observation term, making one part of the steric high be determined by the SST. So at least in the upper ocean, the adjustment of temperature and salinity is constrained by the SST according to appropriately chosen vertical relationship for them, which was already shown to be possible in many methods for SST assimilation. This new method was applied in the BCC_GODAS2.0. Five years (1993?2002) of assimilation experiment was performed to test this method, with the assimilation of AVHRR SST and TOPEX/Poseidon altimeter data. The experiment showed this method was successful. The root-mean-square errors for monthly temperature and salinity were reduced 0.67℃and 0.2 psu, respectively compared with the results without the assimilation. All the results were evaluated with independent observations or reanalysis data, such as TAO, OISST and SODA data. The improvement was significant, particularly in the mixed layer.
XIAO Xian-jun,HE Na ,ZHANG Zu-qiang,LIU Huai-ming,WANG Dong-xiao . Variation assimilation using satellite data of sea surface temperature and altimeter[J]. Journal of Tropical Oceanography, 2011 , 30(3) : 1 -8 . DOI: 10.11978/j.issn.1009-5470.2011.03.001
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