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# System prepended metadata

title: Conversion from counts to SWE for CRNS

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# Conversion from counts to SWE for CRNS 


**Summary discussion with Darin and parameter problems for counts to SWE conversion:**

Darins 3 options: 
1. **Go with published values**
Use parameters from Gugerli et al. 2019 (and some other papers use them as well):
1.144E+02
1.411E+01
3.133E-01
8.268E-02
1.117E+00

Scale N0 from Plaine Morte to HEF: 
Plaine Morte:  **N0=4143 @ P0=739 mb**
Scaled for HEF: **N0=4146*1.455=6032 cph**
Darins explanation of the scaling: 
--> *You can scale Plaine Morte to your glacier using https://crnslab.org/util/intensity.php (my calculator). This gives the counting rate relative to high latitude and sea level. So you do it for it each site independently and then find the factor relative to each other. I am happy to provide more guidance on this.*

(I don't quite understand it yet so I asked him to explain it a bit more already)

**Conclusion:** using 6032cph (or 1005c/10min) and 703hPa as base pressure the result is way better! 
![](https://hackmd.io/_uploads/SJ8P4wGro.png)


2. **Use the measured N0**
Measure N0 when it is snow free 
--> we have 2 periods of snow free N0: 12 days at the beginning and about 1 month 
In the 1 month perios at the end you can see a drop after the peak maybe due the sensor melting into the ice? 

station fell over: 20.07.2022 probably from SD measurement

![](https://hackmd.io/_uploads/r1BI_Dfrs.png)

Using **N0=895 c/10min and 703hPa** the CRNS_SWE is not matching the field measurements nicely 

![](https://hackmd.io/_uploads/rkBBFPMHj.png)

Comment from Darin on this method: *Furthermore theory and practice might not converge just yet (such that a best fit N0 may not be the real N0 and vice versa), so this might not work with the parameters given.*

3. **Fit N0 to the field data**
Use the parameters from Gugerli et al. and fit the curve to the field data to find N0 
--> would dislike to do that as it should be possible to use the mesaurement I think


**Open Questions**
- Is the way we use N0 and P0 right? Because Darin said: *Another thing to mention is that N0 is only defined for a given P0. And P0 is sort of arbitrary--which is fine so long as you consistently use the same P0 (i.e. reference all counts to the same baseline pressure). So if N0 = 5366 cph has a P0 implied in it. And Rebeccas also has a P0 implied in it. If the two P0s are not the same then the N0 will not be comparable. I don't know if this is the problem but we should check to make sure.*
--> for now I think I have been mixing both so using N0 scaled from Rebecca and P0 from our site is that right? (already asked Darin)
--> Checking this first as Darin suggested before moving on we should check that we are not making a mistake here 

- Are these for sure the 'best' parameters we have? Or ask other way around: why are we adapting N0 (which should be measureable) and not the parameters in the conversion function? 

- Interestingly Darin asked Rebecca about if she used a measured N0 or a theorectical one. She said on both sites (Plaine Morte and Findelen), they applied the measured N0. On Plaine Morte this worked really well and the CRNS_SWE matched their field measurements quite good. On Fidelen although they tried the measured N0 was off by about 15% from the theoretical one. This is approximalty the same difference we see now on Hintereisferner. Is there a relation? 
Idea by Lindsey: Can it have something to do with the fact that HEF and Findelen are valley glaciers and have high topography around. In comparison Plaine Morte is rather flat.

- Do the neutron counts have some kind of daily cycle --> doesnt seem so dirunal cycle over the whole season only shows variation in 10counts during the day 