Understanding Regional Map Projections and Plotting Using WRF-ARW
Explore different map projections such as Lambert, Polar, Mercator, and Lat-lon in the context of WRF-ARW model. Learn about specifying grid spacing, map factors, and pole location adjustments. Discover how to create plots using Python with wrf-python for regional domains.
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Presentation Transcript
Geogrid assignment answers and discussion ATM 419/563 Spring 2019 Fovell 1
Results Specified resolution = 48 km Projection Map factor min Map factor max Grid spacing largest Grid spacing smallest Lambert #1 1.0 1.02673 48.0 46.6 Lambert #2 0.965648 1.00756 49.5 47.5 Polar 0.931069 1.10986 51.6 43.2 Mercator 0.802691 1.3075 60.0 36.7
Lat-lon projection WRF-ARW also permits a lat-lon (cylindrical equidistant) projection that can be used for regional (e.g., non-global) domains. It s a little trickier to use. Modifications for namelist.wps map_proj = lat-lon dx, dy need to be specified in degrees instead of kilometers degrees ~ kilometers/111.11 Need to move computational (as opposed to real) pole location (pole_lat) to minimize map distortion. For N Hemisphere: pole_lat = 90.0-ref_lat The standard longitude is antipodal to its usual value to orient the map the way you expect stand_lon = -1*ref_lon
Lat-lon with pole_lat=41.4 Mapfac_m: min 1.0 max 1.02439 (very competitive with Lambert)
Plots using python Using wrf-python
