High Glacier Q Low Snow Q

[Vishal Singh]

Dear Terink,

I have three queries:

1. How can I reduce glacier melt Q (which is coming around 50% and that is not possible in my case bcz the total glacier area is only 17%)

2. Snow melt Q is coming lower (which is coming around 10% and that should come around 80% in my case) and how can i increase it?

3. How can I prepare glacier fraction maps without using pre=processor?

Parameter details:

DDFCI = 6.0

DDFDb = 6.5

DDFsnow = 6.0

Tcric = 4 d cen

SnowFrac = 0.9

GlacFrac = 0.5

Apartly, my baseflow is coming around 35% of the total flow and 

Sim Q is getting highly overestimated than Obs Q

Kindly send me your suggestions.

Thank you very much.

Regards,

Vishal

[WilcoTerink]

Hi,

First of all, what version of the SPHY model are you using: https://sphy.readthedocs.io/en/latest/releases.html ? This defines for some part how certain parameters need to be set.

Looking at the list of parameters you have provided above I can see that you have set both SnowFrac and GlacFrac as a single parameter value? SnowFrac is not a parameter that you can set in the configuration file, so I am not sure why you have put it there being 0.9 (i.e. the model calculates the snowfrac for each time-step). Setting GlacFrac here as a single value, rather than providing a glacfrac.map, means that in this case each cell in your model is covered for 50% with glaciers; i.e. your model domain consists for 50% of glacier area. That might also explain why your glacier runoff is too high? Another way you can decrease glacier melt is by decreasing the DDFCI and DDFDB.

If snow melt is too low then that might be the result of a too low Tcrit value. If Tcrit is too low, then the chance of precipitation falling as rain instead of snow becomes higher. However, looking at your Tcrit value of 4 it seems this value is actually on the higher end, so I expect your climate forcing fields are incorrect. Likely your temperature is too high, causing too much glacier melt (in combination with the high glacier fraction) and too much precipitation falling as rain instead of snow.

How you can create the glacfrac.map is described under the link below:

https://sphy.readthedocs.io/en/latest/building.html#older-releases