The data2arl/era42arl utility, README, and corresponding example namelist/config file were immensely helpful in selecting and mapping the requisite variables, as was the “Meterology/Help/ARL Data Format” section of the HYSPLIT User’s guide and the ECMWF ERA5 data documentation web page <https://confluence.ecmwf.int/display/CK ... umentation>. However, I encountered a few issues and have a few questions regarding the era52arl.cfg input and overall variable mapping.
- ERA5 provides the total cloud cover (tcc/TCLD) as a fraction, while HYSPLIT expects it to be input as a percentage. The unit conversion factor should be 100 instead of 1.
- The latent heat flux ARL variable should be “LHTF” instead of “'LTHF'”.
- Upon comparing the (converted) GFSQ and ERA5 values for sensible and latent heat fluxes (SHTF, LHTF), it appears that GFSQ and ERA use different sign conventions (the ERA5 documentation states that “the ECMWF convention for vertical fluxes is positive downwards”). To address this, the unit conversion factors for SHTF and LHTF should be negative. There appears to be HYSPLIT logic that flips the sign if the model is labeled as “ETA” or “EDAS”, but not “ERA5”.
- Is there available documentation for the GFS output variables? The web pages <https://www.nco.ncep.noaa.gov/pmb/produ ... f000.shtml>, <https://www.nco.ncep.noaa.gov/pmb/produ ... f003.shtml>, and <https://www.nco.ncep.noaa.gov/pmb/docs/ ... e4-1.shtml> summarize the grib contents, but a reference that provides more context would help resolve the vertical-flux sign convention issue.
- The terrain height and surface roughness are provided to HYSPLIT via ASCII files in the bdyfiles directory. Do the variables in the met file take precedence over the variables in the ASCII file?
- The file metinp.f, which contains the HYSPLIT subroutine which reads in the meteorological data, does not read in surface specific humidity or surface dew point temperature variables (SPH2 or DP2M) – it only reads in surface relative humidity (RH2M). By contrast both relative humidity and specific humidity are read for the atmosphere-level variables. Is this a possible oversight? Since GFSQ provides SPH2 and ERA5 DP2M, it would seem that the surface humidity values are not used for either met dataset.
- The arl-224 technical document describes how the surface momentum fluxes are used to calculate the friction velocity (and then the boundary layer stability). Is it true then that if the met data provides the friction velocity (which both the GFSQ and ERA5 datasets do), the surface momentum fluxes are not necessary for HYSPLIT calculations (ERA5 provides turbulent surface stresses but not surface momentum fluxes).
- Just a comment, the era52arl code matches variables in the grib files using both the shortname and the “indicatorOfParameter” parameters. The “indicatorOfParameter” value is different from the “paramId” value (listed on the main ERA5 documentation page) for some parameters (particularly for the friction velocity, zust) .
Code: Select all
&SETUP numatm = 6 atmgrb = 'z' , 't' , 'u' , 'v' , 'w' , 'r' , atmcat = 129 , 130, 131, 132, 135, 157, atmnum = 129 , 130, 131, 132, 135, 157, atmcnv = 1.01972E-01, 1.0 , 1.0 , 1.0, 0.01, 1.0 , atmarl = 'HGTS' , 'TEMP', 'UWND' , 'VWND', 'WWND', 'RELH' , numsfc = 15 sfcgrb = '2t' , '10v' , '10u' , 'tcc' , 'sp' , '2d' , 'blh' , 'cape', 'z' , 'tp' , 'sshf' , 'ssrd' , 'slhf' , 'zust', 'fsr' , sfccat = 167 , 166, 165 , 164 , 134 , 168 , 159 , 59 , 129 , 228 , 146 , 169 , 147 , 3 , 244 , sfcnum = 167 , 166, 165 , 164 , 134 , 168 , 159 , 59 , 129 , 228 , 146 , 169 , 147 , 3 , 244 , sfccnv = 1.0 , 1.0 , 1.0 , 100.0 , 0.01 , 1.0 , 1.0 , 1.0 , 1.01972E-01, 1.0 , -2.77778E-04, +2.77778E-04, -2.77778E-04, 1.0 , 1.0 , sfcarl = 'T02M' , 'V10M', 'U10M' , 'TCLD', 'PRSS', 'DP2M' , 'PBLH', 'CAPE', 'SHGT' , 'TPP1', 'SHTF' , 'DSWF' , 'LHTF' , 'USTR', 'RGHS', numlev = 37 plev = 1000, 975, 950, 925, 900, 875, 850, 825, 800, 775, 750, 700, 650, 600, 550, 500, 450, 400, 350, 300, 250, 225, 200, 175, 150, 125, 100, 70, 50, 30, 20, 10, 7, 5, 3, 2, 1, /