Interaction of Typhoon Shanshan (2006) with the Midlatitude Trough from both Adjoint-Derived Sensitivity Steering Vector and Potential Vorticity Perspectives

Abstract

Targeted observation is one of the most important research and forecasting issues for improving tropical cyclone predictability. A new parameter [i.e., the adjoint-derived sensitivity steering vector (ADSSV)] has been proposed and adopted as one of the targeted observing strategies in the Dropwindsonde Observations for Typhoon Surveillance near the Taiwan Region (DOTSTAR). The ADSSV identifies the sensitive areas at the observing time to the steering flow at the verifying time through the adjoint calculation. In this study, the ADSSV is calculated from the nonlinear forecast model of the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) Mesoscale Model (MM5) and its adjoint to interpret the dynamical processes in the interaction between Typhoon Shanshan (2006) and the midlatitude trough. The ADSSV results imply that high-sensitivity regions affecting the motion of Typhoon Shanshan are located at the edge of the subtropical high and the 500-hPa midlatitude trough over northern central China. These ADSSV signals are in very good agreement with the quantitative evaluation based on the potential vorticity (PV) diagnosis. The vertical structure of the ADSSV is also shown for more physical insights into the typhoon-trough interaction. The maximum ADSSV occurs at 800-500 hPa to the southeast of Shanshan (associated with the subtropical high), while distinct ADSSV signals are located upstream of the storm center at about 500-300 hPa (associated with the mid-to upper-tropospheric midlatitude trough). Overall, it is demonstrated that the ADSSV features can well capture the signal of the large-scale trough feature affecting the motion of Shanshan, which can also be well validated from the PV analysis.

Singular Vector Structure and Evolution of a Recurving Tropical Cyclone

“…Recently, adaptive observation strategies have begun to apply for tropical cyclone (TC) evolution for the purpose of adaptive observations of TCs (e.g., Peng andReynolds 2005, 2006;Kim andJung 2006, 2009;Majumdar et al 2006;Wu et al 2007Wu et al , 2009). The observational regions detected by adaptive (or targeted) observation strategies are called sensitive regions because the observations in those regions may have a large influence on enhancing weather forecasts.…”

Identifying a Barotropic Growth Mechanism in East Pacific Tropical Cyclogenesis Using Adjoint-Derived Sensitivity Gradients

“…Application of adjoint models to TC development has largely been restricted to sensitivity of TC steering Wu et al 2007Wu et al , 2009Chen et al 2009;Hoover and Morgan 2010); this is at least partially due to the constraints of linearity and simplified moisture physics that limit the applicability of adjoint models to tropical dynamics, though adjoint techniques have been applied to problems surrounding TC structure and genesis in more recent years as models have grown more sophisticated (Doyle et al 2012;Lang et al 2012).…”

Statistical distributions of singular vectors for tropical cyclones affecting Korea over a 10-year period

“…Adaptive (or targeted) observations have been applied to TCs to increase the accuracy of TC forecasts by decreasing the initial condition uncertainties Reynolds 2005, 2006;Jung 2006, 2009a, b;Kim et al 2011a;Jung et al 2012;Majumdar et al 2006;Wu et al 2007Wu et al , 2009aLang et al 2012). The observational regions detected by adaptive observation strategies are called sensitive regions because the observations in those regions may have a large influence on enhancing weather forecasts (Kim et al 2004a).…”