Update README.md

README.md

@@ -27,6 +27,7 @@ era52arl will also convert the ensemble data.
 
 # Possible Issues
 
+### friction velocity
 Users may not want to use friction velocity, HYSPLIT code USTR, grib short name zust.
 This quantity is usually used in the default setting KBLS=1 to calculate stability (see https://ready.arl.noaa.gov/hysplitusersguide/S625.htm).
 
@@ -42,6 +43,13 @@ edit the era52arl.cfg file which is input into the era52arl program and remove t
 
 * edit the get_era5_cds.py so that USTR is not downloaded.
 
+### latent heat flux (LTHF)
+
+HYSPLIT convention is that upward heat flux is positive. ERA5 uses the opposite convention.
+
+Make sure that a conversion factor of -1 is used in the era52arl.cfg file. 
+
+
 # installing cdsapi
 https://cds.climate.copernicus.eu/api-how-to
 You will need to create an account with Copernicus Data Service to receive an api key.