Case 3: Deep convection, squall line
Part I: Idealized 2-D squall line
Please create a model domain that is 600 points in the horizontal and 81 points in the vertical with grid spacing of 1000 and 250 m in horizontal and vertical dimensions respectively. This will result in a model domain that is 600 km wide by 20 km high. The model timestep should be no more than 5 seconds and integrated for 8 hours. If possible, we advise using a Rayleigh dampening layer at model top with damping coefficient (inverse damping timescale) of 0.003 s−1 within the model's top 5 km to damp spurious waves in the stratosphere. The upper and lower boundaries are free-slip with zero vertical velocity and lateral boundary conditions are open. Surface fluxes should be zero, and radiative transfer and Coriolis effect should be neglected for this experiment. Horizontal and vertical turbulent diffusion may be decided by each researcher, and we will utilize a 1.5 order TKE scheme (Skamarock et al. 2007).
The model is initialized with the environmental temperature, moisture, and wind profiles used by Weisman and Klemp (1982; 1984) and others, and are broadly typical of the environment of mid-latitude squall lines. The initial convective available potential energy (CAPE) is 2200 J kg−1. The horizontal wind profile has a shear of 0.0048 s−1 in the lowest 2.5 km and zero shear above. The mean wind above 2.5 km is zero, which helps to keep the squall line near the center of the domain. Convection is initially triggered by adding a thermal with maximum perturbation in potential temperature of 3 K centered at a height of 1.5 km and varying as the cosine squared to the 0 K perturbation at its edge. The thermal has a horizontal radius of 4 km and a vertical radius of 1.5 km.
We request specific graphics be prepared for the workshop to facilitate comparisons among all participants. Please bring these graphics at minimum, but you are welcome to bring additional plots of model output that you find illustrative. Please return to this section later for the requested graphics list because we are still developing the material (last updated 29 Jan 2008).
Part II: Case study: 12-13 Jun 2002 from IHOP experiment
During the day of 12 June 2002, a surface low pressure system slowly developed in northwestern Oklahoma. A weak surface cold front extended southward through the pandhandle of Texas and into eastern New Mexico. To the north, along the Kansas and Oklahoma border, an east-west oriented outflow boundary created by convection the previous night remained mostly stationary throughout the day. Farther to the north, a surface trough extended northward through Kansas and into Nebraska. During the day, a dry line developed ahead of the surface cold front, just to the east and south of the surface low pressure. Conditions aloft included nearly zonal flow in the central U.S. with an upper-level low pressure center located on the Canada/North Dakota border.
- Map of region and observational assets
- Loop of regional radar images
- Loop of high-resolution visible satellite images
- Loop of U.S. visible satellite images
- Loop of U.S. infrared satellite images
- Loop of U.S. water vapor satellite images
More details and additions coming soon (last updated 31 Jan 2008).
References
Markowski, P., C. Hannon, and E. Rasmussen, 2006: Observations of convective initiation "failure" from the 12 June 2002 IHOP deployment. Mon. Wea. Rev., 134, 375–405.
Weckworth, T. M., H. V. Murphey, C. Flamant, J. Goldstein, and C. R. Pettet, 2008: An observational study of convective initiation on 12 June 2002 during IHOP_2002. Mon. Wea. Rev., xxx, mmm–nnn.
| Time | Surface obs | Rawinsonde obs | Gridded analyses |
|---|---|---|---|
| 0000 UTC 12 Jun |
METARs (raw) METARs (decoded) |
Rawinsondes (raw) Rawinsondes (decoded) |
NARR data (GRIB) |
| 0300 UTC 12 Jun |
METARs (raw) METARs (decoded) |
Rawinsondes (none) | NARR data (GRIB) |
| 0600 UTC 12 Jun |
METARs (raw) METARs (decoded) |
Rawinsondes (none) | NARR data (GRIB) |
| 0900 UTC 12 Jun |
METARs (raw) METARs (decoded) |
Rawinsondes (none) | NARR data (GRIB) |
| 1200 UTC 12 Jun |
METARs (raw) METARs (decoded) |
Rawinsondes (raw) Rawinsondes (decoded) |
NARR data (GRIB) Eta40 data (GRIB) RUC-b data (GRIB) RUC-p data (GRIB) RUC-s data (GRIB) |
| 1500 UTC 12 Jun |
METARs (raw) METARs (decoded) |
Rawinsondes (raw) Rawinsondes (decoded) |
NARR data (GRIB) Eta40 data (GRIB) RUC-b data (GRIB) RUC-p data (GRIB) RUC-s data (GRIB) |
| 1800 UTC 12 Jun |
METARs (raw) METARs (decoded) |
Rawinsondes (raw) Rawinsondes (decoded) |
NARR data (GRIB) Eta40 data (GRIB) RUC-b data (GRIB) RUC-p data (GRIB) RUC-s data (GRIB) |
| 2100 UTC 12 Jun |
METARs (raw) METARs (decoded) |
Rawinsondes (raw) Rawinsondes (decoded) |
NARR data (GRIB) Eta40 data (GRIB) RUC-b data (GRIB) RUC-p data (GRIB) RUC-s data (GRIB) |
| 0000 UTC 13 Jun |
METARs (raw) METARs (decoded) |
Rawinsondes (raw) Rawinsondes (decoded) |
NARR data (GRIB) Eta40 data (GRIB) RUC-b data (GRIB) RUC-p data (GRIB) RUC-s data (GRIB) |
| 0300 UTC 13 Jun |
METARs (raw) METARs (decoded) |
Rawinsondes (none) |
NARR data (GRIB) Eta40 data (GRIB) RUC-b data (GRIB) RUC-p data (GRIB) RUC-s data (GRIB) |
| 0600 UTC 13 Jun |
METARs (raw) METARs (decoded) |
Rawinsondes (none) |
NARR data (GRIB) Eta40 data (GRIB) RUC-b data (GRIB) RUC-p data (GRIB) RUC-s data (GRIB) |
| 0900 UTC 13 Jun |
METARs (raw) METARs (decoded) |
Rawinsondes (none) |
NARR data (GRIB) Eta40 data (GRIB) RUC-b data (GRIB) RUC-p data (GRIB) RUC-s data (GRIB) |
| 1200 UTC 13 Jun |
METARs (raw) METARs (decoded) |
Rawinsondes (raw) Rawinsondes (decoded) |
NARR data (GRIB) Eta40 data (GRIB) RUC-b data (GRIB) RUC-p data (GRIB) RUC-s data (GRIB) |
NARR = NCEP/NCAR North American Regional Reanalysis archive data.
Eta40 refers to the NCEP Eta model interpolated to a 40-km spaced grid (grid#211). RUC-b refers to the NCEP Rapid Update
Cycle model data on 'hybrid-b' vertical coordinate, RUC-p refers to the interpolated pressure-level data, and
RUC-S refers to the surface variables only GRIB files.
Questions regarding any data available in the table above should be directed to
Greg Thompson.