CryoSat-2 SARIn模式二级产品在内陆水域的偏差分析

Bias Analysis of CryoSat-2 Level 2 Products in SARIn Mode over Inland Water

对比青藏高原及天山地区所有湖泊内CryoSat-2基线C版本二级产品(SIR_SIN_L2I)和ICESat测高结果发现,它们之间存在一个多达几十米的系统性偏差,这种偏差限制了多源测高数据的联合研究,必须加以消除。从一级数据出发,利用经典的重跟踪方法重新获得湖面高程,能很好地消除这个偏差。研究发现,当前的二级产品在生成过程中使用了错误的窗口延迟参数,从而导致该系统性偏差。因此,CryoSat-2的SARIn模式二级产品不能直接用于多源数据的联合分析,需要对一级数据重跟踪或直接在二级数据上加一个偏差改正。

We obtain lake elevations on the Tibetan plateau and Tianshan using CryoSat-2 baseline C level 2 products(SIR_SIN_L2 I) in SARIn mode and with ICESat level 2 products, finding a bias of tens of meters between them. The bias must be removed before joint analysis of multi-mission data. Using classic waveform retracking method, the new elevation measurements are obtained from CryoSat-2 L1 b products in SARIn mode. Results show that waveform retracking can remove the bias. We find that the bias is caused by a wrong window delay that is used during the production of the SARIn level 2 products. We conclude that current CryoSat-2 baseline C level 2 products in SARIn mode cannot be directly used in joint analysis of multi-mission data, and either waveform retracking or a bias correction should be added to level 2 products.