Adjoint Sensitivity and Finite-Time Normal Mode Disturbances during Blocking

Abstract The finite-time normal mode instability of four-dimensional space–time basic states has been studied for cases of block development over the Gulf of Alaska, over the North Atlantic, and over southern Greenland using a two-level tangent linear model. The authors find three generic types of finite-time normal modes, denoted as “recurring,” “traveling,” and “flip” modes. The dominant finite-time normal modes associated with block development have large-scale structures in the respective blocking regions; they tend to closely reflect the structures of the developing blocks. The time evolution in the tangent linear model of finite-time adjoint modes has been examined for each of the three cases of block development. These adjoint modes have faster than normal mode exponential growth. The initial structures of the dominant adjoint modes are characterized by small-scale baroclinic wave trains located primarily upstream of the blocking region. As the disturbances grow explosively, they increase their sca...

[1]  Philippe Courtier,et al.  Sensitivity of forecast errors to initial conditions , 1996 .

[2]  J. Whitaker,et al.  An Adjoint Sensitivity Study of Blocking in a Two-Layer Isentropic Model , 1993 .

[3]  E. Lorenz.  Barotropic Instability of Rossby Wave Motion , 1972 .

[4]  P. Webster,et al.  Alternative theories of atmospheric teleconnections and low-frequency fluctuations , 1988 .

[5]  M. Kimoto,et al.  Medium-Range Forecast Skill Variation and Blocking Transition. A Case Study , 1992 .

[6]  J. Pedlosky,et al.  Large-amplitude coherent anomalies in baroclinic zonal flows , 1995 .

[7]  R. Dole,et al.  Life cycles of persistent anomalies. II - The development of persistent negative height anomalies over the North Pacific Ocean , 1990 .

[8]  Lennart Bengtsson,et al.  Numerical prediction of atmospheric blocking—A case study , 1981 .

[9]  I. Orlanski,et al.  On the Dynamics of a Storm Track , 1993 .

[10]  A. Joly,et al.  The Stability of Time-Dependent Flows: An Application to Fronts in Developing Baroclinic Waves , 1991 .

[11]  T. Nathan,et al.  On radiating baroclinic instability of zonally varying flow , 1993 .

[12]  J. Frederiksen.  Instability of planetary waves and zonal flows in two‐layer models on a sphere , 1978 .

[13]  D. Cacuci.  Sensitivity theory for nonlinear systems. I. Nonlinear functional analysis approach , 1981 .

[14]  S. Colucci.  Explosive Cyclogenesis and Large-Scale Circulation Changes: Implications for Atmospheric Blocking , 1985 .

[15]  Franco Molteni,et al.  On the operational predictability of blocking , 1990 .

[16]  J. Frederiksen,et al.  North atlantic blocking during January 1979: Linear theory , 1990 .

[17]  M. C. Hall,et al.  Application of adjoint sensitivity theory to an atmospheric general circulation model , 1986 .

[18]  The Robustness of Barotropic Unstable Modes in a Zonally Varying Atmosphere , 1991 .

[19]  Ronald M. Errico,et al.  Sensitivity Analysis Using an Adjoint of the PSU-NCAR Mesoseale Model , 1992 .

[20]  J. Whitaker,et al.  Organization of Storm Tracks in Zonally Varying Flows , 1995 .

[21]  G. Branstator.  Analysis of General Circulation Model Sea-Surface Temperature Anomaly Simulations Using a Linear Model. Part II: Eigenanalysis , 1985 .

[22]  J. Tribbia,et al.  On the Problem of Prediction Beyond the Deterministic Range , 1993 .

[23]  J. Whitaker,et al.  Type B Cyclogenesis in a Zonally Varying Flow , 1992 .