Thanks Miguel, Have a nice weekend.
When I've regenerated the forecast using the corrected temperature and dewpoint values I'll post to the list. I too had thought about modifying the solar flux directly - this may be a plausible solution, like I said I'll give it some thought. Regarding the melting snow condition that we found in our case - I see why the model produced this based on the definition. What's puzzling me though is how the road temperatures got so high - they went from zero Celsius to about 17 Celsius in 4 hours, and the forecast was for snow to continue falling. Yes the air temperature forecast was 3-4 degC above freezing, but I don't think that can be the source of this heat. I am suspecting that the radiation fluxes are the problem, perhaps due to too much energy absorbed at the road surface (e.g. if the albedo is set too low in the model).....for now we are assuming that we need to pay attention to the cloud cover field to limit the amount of incoming direct solar radiation. Does the rate of increase of pavement temperature (17 C in 4 hours on a road which is at freezing point with snow falling) seem high to you ? Regards Iain -----Original Message----- From: Miguel Tremblay [mailto:[EMAIL PROTECTED] Sent: March 20, 2008 3:27 PM To: Iain Russell Cc: '[email protected]' Subject: Re: [Metro-developers] High pavement forecast temperature with melting snow road condition Hi Iain, Iain Russell wrote: > Thanks Miguel. > > 1. I won't be able to re-generate the roadcast until over the weekend; sorry > to be a burden, but do you have time to change the air temperature and > dewpoint temperatures so that they match the observed and then re-run the > model ? > > I don't have time either, I am going for the weekend. > 2. Yes I understand about site exposure, and yes we could adjust the cloud > cover values to control the amount of solar flux. Would prefer to have some > other parameter to control this other than cloud cover though..I'll think > about that... > > Starting from next version (3.2.0, release is schedule for this spring), you will be able to set directly the solar flux in W/m² in the atmospheric forecast file and use it directly instead of the cloud cover. The infrared flux would be created using the cloud cover and you could modify directly the solar flux. Does this sound like a possible solution? > 3. So the definition of the melting snow condition is when snow is falling on > a road that is already above freezing ? > > Yes. Have an happy Easter, Miguel _______________________________________________ METRo-developers mailing list [email protected] https://mail.gna.org/listinfo/metro-developers
