利用最优插值法改正宽刈幅高度计对流层湿延迟

Wet Tropospheric Correction of Wide-swath Altimeter by Optimum Interpolation Method

    摘要
  • 摘要: 宽刈幅高度计仅在星下点携带微波辐射计，使得两侧刈幅内的对流层湿延迟只能采用水汽模型改正或采用星下点实测值替代，导致改正精度较低。提出了使用最优插值法融合星下点辐射计实测的对流层湿延迟改正值，提升两侧刈幅内的改正精度，并以SWOT(surface water and ocean topography)卫星宽刈幅高度计进行了验证。在刈幅内，采用ERA5(ECMWF reanalysis 5th generation)水汽数据计算湿延迟改正时，最优插值法融合改进后的残余湿延迟误差较采用星下点实测值替代方法减小约40%；采用辐射计实测湿延迟波数谱模拟计算湿延迟改正时，最优插值法融合改进后的残余湿延迟误差较采用星下点实测值替代方法在各纬度区域均减小达80%。在水汽变化剧烈的情况下，最优插值法的改进效果远优于星下点实测值替代的效果。

     

    Abstract:
      Objectives  Since there is only nadir radiometer onboard for the wide-swath altimetry, the wet tropospheric delay can only be corrected by models inside the cross-swath or substituted by the nadir radio-meter measured data, which lead to the lower accuracy.
      Methods  In order to improve the accuracy of wet tropospheric correction (WTC) inside the cross-swath, an optimum interpolation method to fuse the nadir radiometer WTC is proposed, and it is verified by taken the SWOT (surface water and ocean topography) wide-swath altimeter as example.
      Results  Inside the cross-swath, when the ERA5 (ECMWF reanalysis 5th generation) data are used, the residual of WTC after correction by optimum interpolation method can be reduced by 40% compared with the nadir radiometer WTC substituted. When the simulated WTCs from the spectrum of radiometer measured WTCs are used, the residual of WTC after correction by optimum interpolation method can be reduced by 80% in all latitude areas compared with the nadir radiometer WTC substituted.
      Conclusions  The optimum interpolation method has much better accuracy than the nadir radiometer WTC substituted in the case of high water vapor variability.

     

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