Information on ETA Model Diagnostics and SUNYPAK

Calculations displayed on the
ETA Diagnostics page are performed using a locally developed package known as SUNYPAK. SUNYPAK performs a number of calculations using GEMPAK grid files as input and output.

Figures show the eastern half of the US since this is the area of local interest, and topography is not currently included in the calculations (so they may not be as useful over the western US).

The first figure is a four-panel plot of model omega (vertical velocity in pressure coordinates), total Q vectors and adiabatic QG omega, along-isentrope Q vectors (Qs) and QG omega diagnosed from Qs, and across-isentrope Q vectors (Qn) and QG omega diagnosed from Qn at 850 mb. See Keyser et al. (1992).

The second figure is the same as the first except for 500 mb.

The third figure shows a four-panel plot of total ageostrophic wind, the portion of the ageostrophic wind associated with the boundary conditions (called the harmonic part), the rotational portion, and the divergent portion at 850 mb. See Loughe et al. (1995).

The fourth figure is the same as the third at 300 mb. Note the harmonic potion of the ageostrophic wind at this level can be quite large because the rightmost boundary on the ETA grids we receive is too close to the diagnostic domain.

The fifth figure shows potential temperature, pressure and winds on the dynamic tropopause, taken as the 1.5 PVU surface. Also shown are 1000 mb potential temperature and its horizontal gradient (shaded) and winds, along with the 500 mb model omega.

The software used to generate these diagnostics is freely available for noncommercial educational and research purposes.

Click here to download the software

Keyser, D., B. D. Schmidt, and D. G. Duffy, 1992: Quasigeostrophic vertical motions diagnosed from along- and cross-isentrope components of the Q vector. Mon. Wea. Rev., 120, 731-741.

Loughe, A., C.-C. Lai, and D. Keyser, 1995: A technique for diagnosing three-dimensional ageostrophic circulations in baroclinic disturbances on limited-area domains. Mon. Wea. Rev, 123, 1476-1504.

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