Atmos 5110/6110: QG Height Tendency and Omega Diagnosis

Objectives:

The QG tendency equation is one means to diagnose the movement of troughs and ridges. The QG omega equation, in traditional and Q-vector forms, is a means with which to diagnose vertical motion. The purpose of this excercise is to examine how these tools can be used to examine the dynamics of the upper-level flow evolution and to diagnose large-scale vertical motion in gridded numerical model forecasts. Please complete this lab using powerpoint after importing the images.

Problem 1: Evaluating 500 mb Height Tendency

  • In this problem, we examine the evolution of the upper-level flow in the GFS model forecast initialized at 1200 UTC 8 November 2005. From observed and forecast maps of 500 mb geopotential height and geostrophic absolute vorticity valid at 1200 UTC Nov 8, 0000 UTC Nov 9, and 1200 UTC Nov 9 2005, indicate areas of cyclonic and anticyclonic vorticity advection and where 500 mb heightsshould fall and rise.
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  • From observed and forecast maps of 700 mb geopotential height and temperatureat 1200 UTC Nov 8, 0000 UTC Nov 9, and 1200 UTC Nov 9 2005, and 300 mb geopotential height and temperature at 1200 UTC Nov 8, 0000 UTC Nov 9, and 1200 UTC Nov 9 2005, indicate areas of cold and warm air advection and areas where 500 mb heights should fall and rise due to differential temperature advection.
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  • Identify areas in which both vorticity advection and differential temperature advection contribute to 500 mb height falls and rises. Identify areas where these two terms oppose one another.
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  • Using the direct model height tendencies for 2005110812-2005110900 and 2005110900-2005110912 discuss how the height tendency deduced from the model fields using QG agrees with the observed tendencies.
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Problem 2: Diagnosis of Vertical Motion Using the Traditional QG Omega Equation

  • In this problem, we compare the vertical motion diagnosed using the traditional QG Omega Equation with the simulated vertical motion (which is based on the continuity equation) from the GFS model forecast initialized at 1200 UTC 8 November 2005. From 24 h and 48 h forecast maps of 500 mb geopotential height and absolute vorticity indicate areas of cyclonic and anticyclonic vorticity advection and where areas of ascent and descent are likely.
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  • In order to indicate regions of ascent and descent, you have made an important assumption about the vertical distribution of vorticity advection. Explain what it is.
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  • From 24 h and 48 h forecast maps of 700 mb geopotential height and temperature, indicate areas of warme and cold advection and identify where ascent and descent are likely.
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  • In what areas do the two terms of the QG omega equation both contribute to vertical motion of the same sign? In what areas do the two terms oppose one another?
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  • In this problem, we compare the vertical motion diagnosed using the traditional QG Omega Equation with the simulated vertical motion (which is based on the continuity equation) from the GFS model forecast initialized at 1200 UTC 8 November 2005. From 24 h and 48 h forecast maps of 500 mb geopotential height and absolute vorticity indicate areas of cyclonic and anticyclonic vorticity advection and where areas of ascent and descent are likely.
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