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<div><span></span>Dear Sir/madam,</div><div>We have noticed that the ECCO4 product uses the Ocean Bottom Pressure (OBP) data from <span style="line-height: 1.5; background-color: transparent;">1992.1.1 to 2017.12.31. However, the GRACE satellite was launched in 2002. We are wondering how the grided OBP data before 2002 were obtained? Could you please list some references which validate or examine these data? Also, what is the difference between the grided OBP data from ECCO website (1992~2017) and those from NASA JPL website (starting in 2002 only)? If we are interested in the OBP data in the South China Sea region, can we use the one downloaded from ECCO4 between </span><span style="line-height: 1.5; background-color: transparent;">1992.1.1 and 2017.12.31, or, better use the segment after 2002?</span></div><div><span style="line-height: 1.5; background-color: transparent;">Your help is much appreciated.</span></div><div><span style="line-height: 1.5; background-color: transparent;">Best regards,</span></div><div><span style="line-height: 1.5; background-color: transparent;">Yaohua Zhu</span></div>
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<div><span><div style="MARGIN: 10px; FONT-FAMILY: verdana; FONT-SIZE: 10pt"><div>yhzhu@fio.org.cn</div></div></span></div>
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