Among all of the sources of tropical cyclone (TC) intensity forecast errors, the uncertainty of sea surface temperature (SST) has been shown to play a significant role. In the present study, we determine the SST forcing error that causes the largest simulation error of TC intensity during the entire simulation period by using the WRF model with time-dependent SST forcing. The SST forcing error is represented through the application of a nonlinear forcing singular vector (NFSV) structure. For the selected 12 TC cases, the NFSV-type SST forcing errors have a nearly coherent structure with positive (or negative) SST anomalies located along the track of TCs but are especially concentrated in a particular region. This particular region tends to occur during the specific period of the TCs life cycle when the TCs present relatively strong intensity, but are still intensifying just prior to the mature phase, especially within a TC state exhibiting a strong secondary circulation and very high inertial stability. The SST forcing errors located along the TC track during this time period are verified to have the strongest disturbing effect on TC intensity simulation. Physically, the strong inertial stability of TCs during this time period induces a strong response of the secondary circulation from diabatic heating errors induced by the SST forcing error. Consequently, this significantly influences the subsidence within the warm core in the eye region, which, in turn, leads to significant errors in TC intensity. This physical mechanism explains the formation of NSFV-type SST forcing errors. According to the sensitivity of the NFSV-type SST forcing errors, if one increases the density of SST observations along the TC track and assimilates them to the SST forcing field, the skill of TC intensity simulation generated by the WRF model could be greatly improved. However, this adjustment is most advantageous in improving simulation skill during the time period when TCs become strong but are still intensifying just prior to reaching full maturity. In light of this, the region along the TC track but in the time period of TC movement when the NFSV-type SST forcing errors occur may represent the sensitive area for targeting observation for SST forcing field associated with TC intensity simulation.

在热带气旋（TC）强度预报误差的所有来源中，海表温度（SST）的不确定性已显示出重要作用。在本研究中，我们通过使用具有随时间变化的SST强迫的WRF模型，确定在整个模拟期间导致TC强度最大模拟误差的SST强迫误差。通过应用非线性强迫奇异矢量（NFSV）结构来表示SST强迫误差。对于选定的12个TC案例，NFSV型SST强迫误差具有沿TC轨迹位于正（或负）SST异常的近乎连贯的结构，但尤其集中在特定区域。当TC呈现相对较强的强度时，该特定区域往往会在TC生命周期的特定时期内发生，但在成熟阶段之前仍会加剧，尤其是在TC状态下，该状态显示出强大的二次循环和非常高的惯性稳定性。验证了在此时间段内沿TC轨道定位的SST强迫误差对TC强度模拟的影响最大。从物理上讲，TCs在此期间的强大惯性稳定性引起了次级循环对SST强迫误差引起的绝热加热误差的强烈响应。因此，这严重影响了眼睛区域温暖核内的沉降，进而导致了TC强度的显着误差。这种物理机制解释了NSFV型SST强迫错误的形成。根据NFSV型SST强迫错误的敏感性，如果增加沿TC轨道的SST观测的密度并将其同化到SST强迫场，则WRF模型生成的TC强度模拟的技巧将大大提高。但是，这种调整在提高TC强度但在达到完全成熟之前仍在加剧的时间段内提高仿真技能方面最有利。鉴于此，当发生NFSV型SST强迫错误时，沿着TC轨迹但在TC运动的时间段内的区域可能代表敏感区域，用于与TC强度模拟相关的SST强迫场的目标观测。在TC变得强大但在达到完全成熟之前仍在不断增强的时间段内，此调整最有利于提高仿真技能。鉴于此，当发生NFSV型SST强迫错误时，沿着TC轨迹但在TC运动的时间段内的区域可能代表敏感区域，用于与TC强度模拟相关的SST强迫场的目标观测。在TC变得强大但在达到完全成熟之前仍在不断增强的时间段内，此调整最有利于提高仿真技能。鉴于此，当发生NFSV型SST强迫错误时，沿着TC轨迹但在TC运动的时间段内的区域可能代表敏感区域，用于与TC强度模拟相关的SST强迫场的目标观测。