DOI: 10.5061/dryad.xksn02vrv
title: Supporting data for: A big chill: Examining an extremely sharp cold front from three perspectives

description: On 21–22 December 2022, an extremely strong cold front moved southward
 through the High Plains of the United States. The frontal passage
 was associated with rapid temperature decreases that rivaled or
 exceeded the largest that have been reported in the literature. In
 many locations in Wyoming and Colorado, the temperature dropped
 from above freezing to below zero Fahrenheit (below –17.8°C) in a
 few hours. High-resolution observations from an eddy
 covariance tower in Akron, Colorado revealed a 2-m air
 temperature drop of 13.8°C in 10 s and 15.4°C in 30 s, showing
 that this front effectively represented a discontinuity in temperature.
 Operational forecast models indicated the potential for a strong
 cold front up to 9 days in advance, but displayed considerable
 run-to-run variability and uncertainty in the timing of frontal passage.
 Forecasts from data-driven weather prediction models (trained
 using deep learning) were generally more accurate than those from
 physics-based models in terms of the timing and location of the front, but
 did not represent the extreme temperature gradients that
 occurred. Short-term operational model forecasts provided a
 detailed depiction of the front, but predicted the frontal passage to be
 slightly slower and weaker than was observed. A high-resolution
 numerical simulation reveals a frontal structure akin to a
 density current with a hydraulic head, consistent with past observations
 of intense cold fronts to the east of the Rocky Mountains. In
 total, this study provides climatological context and a detailed
 picture of forecast performance and physical processes for one of the
 sharpest cold fronts in U.S. records.
description: This dataset includes the information required to reproduce the
 model simulation presented in the manuscript. This includes the namelist
 and initial and lateral boundary conditions for the WRF model simulation.
 Time series output at each model timestep is also included for the
 locations shown in the manuscript. Also included are
 observations from the eddy covariance tower at the USDA research facility
 Akron, Colorado, provided by David Poss of USDA.
description: ## Supporting data for: A big chill: examining an extremely sharp cold
 front from three perspectives
 [https://doi.org/10.5061/dryad.xksn02vrv](https://doi.org/10.5061/dryad.xksn02vrv) ## Description of the data and file structure Included here are the files required to configure and reproduce the numerical simulation presented in this manuscript. (Full model output is not included owing to its large size.) The manuscript includes analysis of a simulation from the Weather Research and Forecasting model, version 4.3. The WRF model is available from the National Center for Atmospheric Research at: [https://www.mmm.ucar.edu/models/wrf](https://www.mmm.ucar.edu/models/wrf) Also included is a file with the observations from the Akron, Colorado eddy covariance tower presented in the manuscript. Additional parameters, such as the wind direction using meteorological convention, and air temperature derived from the sonic temperature, are included along with the standard parameters described in the LI-COR documentation. ### Files and variables #### File: STN01.d02.TS **Description:** WRF model time series output at the grid point nearest to the CoAgMET station in Stratton, Colorado. The specific latitude/longitude location of each of these time series is given in the first line the file. #### File: GLY04.d02.TS **Description:** WRF model time series output at the grid point nearest to the CoAgMET station in Greeley, Colorado. The specific latitude/longitude location of each of these time series is given in the first line the file. #### File: cys.d02.TS **Description:** WRF model time series output at the grid point nearest to the ASOS in Cheyenne, Wyoming. The specific latitude/longitude location of each of these time series is given in the first line the file. #### File: namelist.input **Description:** WRF model configuration file. #### File: wrfbdy\_d01 **Description:** lateral boundary conditions for the WRF model in the standard WRF netCDF format (domain 1). #### File: wrfinput\_d01 **Description:** initial conditions for the WRF model in the standard WRF netCDF format (domain 1). #### File: wrfinput\_d02 **Description:** initial conditions for the WRF model in the standard WRF netCDF format (domain 2). #### File: usda\_akron\_21dec22\_share.csv **Description:** Observations from the USDA eddy covariance tower located near Akron, Colorado.  ##### Variables * TIMESTAMP: time stamp * Temperature (C): temperature from the thermistor * Pressure (kPa): pressure * U (m/s): component of the wind, with positive being 2 degrees west of north * V (m/s): component of the wind with positive values 90 degrees counter-clockwise from the U component * W (m/s): vertical wind component * T (C): sonic temperature * wspd: wind speed (calculated) in m/s * wdir_corr: wind direction, corrected to meteorological convention where a wind from the north is zero degrees. * uuu_corr: u-component of the wind, where positive is pointed to the east * vvv_corr: v-component of the wind, where positive is pointed to the north * spfh: specific humidity (kg/kg) * Ta_sonic: air temperature from the sonic anemometer, calculated as Ta = Ts/(1+0.51q), where q is the specific humidity #### File: tslist **Description:** WRF "tslist" file, with a listing of the locations where time series are recorded at each model timestep, for the nearest model grid point. ## Code/software The format of the WRF time series (.TS) files is described at [https://github.com/wrf-model/WRF/blob/master/run/README.tslist.](https://github.com/wrf-model/WRF/blob/master/run/README.tslist) The specific latitude/longitude location of each of these time series is given in the first line of each file. The "tslist" configuration file that describes the latitude/longitude of each location (also described at the WRF model link above) is also included. These are plain text files that can be viewed or manipulated with any text editor, and can also be imported to tools like Excel using "from text" or using R or python/pandas "read.table" functions. WRF-formatted netCDF files can be viewed using tools like [ncview](https://cirrus.ucsd.edu/ncview/), or read and analyzed in [xarray](https://docs.xarray.dev/en/stable/index.html) for python. The WRF namelist.input file is a plain text file that can be viewed or manipulated with any text editor (*e.g.*, Linux `less` command, Nano, Vim, Text Editor). The format follows the [WRF model specifications.](https://www2.mmm.ucar.edu/wrf/users/wrf_users_guide/build/html/namelist_variables.html) usda_akron_21dec22_share.csv is a comma-separated text file that can be imported using tools like Excel, R, or the pandas package in python. A github repository that includes jupyter notebooks used to prepare many of the figures in this manuscript is at: [https://github.com/russ-schumacher/dec2022_coldfront/](https://github.com/russ-schumacher/dec2022_coldfront/). In particular, the notebook [wrf_hrrr_asos_tser_compare_loop.ipynb](https://github.com/russ-schumacher/dec2022_coldfront/blob/main/wrf_hrrr_asos_tser_compare_loop.ipynb) includes code for reading the WRF time series files, as well as output from the HRRR model and station observations, and plotting comparisons between them. The notebook [akron_ec_tser_pub.ipynb](https://github.com/russ-schumacher/dec2022_coldfront/blob/main/akron_ec_tser_pub.ipynb) includes code for reading and plotting the data from the Akron eddy covariance tower in the file usda_akron_21dec22_share.csv.