1. Diurnal warming in the Arctic Ocean: Observations at CMS
Sonia Péré
Centre de Météorologie Spatiale, Météo-France, Lannion, France
SST variability meeting, Lannion 3 Nov. 2011

2. Outline Introduction : How to quantify DW in the Arctic ?
Reference: Previous « night » vs foundation SST?
Buoy observations (drifters)
Application to satellite data
Modelling
Conclusion
Arctic SST workshop, Exeter December 2013
SST variability meeting, Lannion 3 Nov. 2011

3. Buoys observations : drifters DW vs lst in arctic
What is DW ?
Buoys observations : drifters DW vs lst in arctic
DW = sst -ref_sst
Ref_sst= previous « night » SST
: the mean SST value
between 20 lst the day before
and 10 lst the same day
Previous night SST is DW contaminated
(most of the time)
Can we use foundation SST as a reference ?
DW latitude >66 with drifters
Arctic SST workshop, Exeter December 2013
SST variability meeting, Lannion 3 Nov. 2011

4. How to determine foundation SST ?
Time series  for drifter 62926: lat 70.6 lon 41
Threshold on wind speed?
Reference SST? 
Arctic SST workshop, Exeter December 2013
SST variability meeting, Lannion 3 Nov. 2011

5. How to determine foundation SST
Wind threshold ?
Residual DW after 21 lst
WIND
Which Wind value leads
to close the cycle ?
Wind above 5m/s
Summer 2012
Arctic SST workshop, Exeter December 2013
SST variability meeting, Lannion 3 Nov. 2011

6. How to determine foundation SST
We adopt a wind threshold > 7m/s and 10 day centered averages.
Arctic SST workshop, Exeter December 2013
SST variability meeting, Lannion 3 Nov. 2011

7. Satellite observations
Buoy 62926
Metop SST
Buoy 62926
Time serie from 16 to 19 of july
Arctic SST workshop, Exeter December 2013
SST variability meeting, Lannion 3 Nov. 2011

8. Previous night vs foundation SST
Wind > 7 m/s
+- 5 days
Dw =sst-Foundation sst 
Arctic SST workshop, Exeter December 2013
SST variability meeting, Lannion 3 Nov. 2011

9. Previous night vs foundation SST
Daily reference :
The previous « night » SST
Dw =SST-daily reference
Arctic SST workshop, Exeter December 2013
SST variability meeting, Lannion 3 Nov. 2011

10. Reference vs foundation SST
03/12/2018

11. Previous night vs foundation SST
03/12/2018

12. Relative number of clear sky cases with wind > 7ms-1
July 2012
Arctic SST workshop, Exeter December 2013
SST variability meeting, Lannion 3 Nov. 2011

13. Modelling : swr Buoy :62926 wind
Non solar fluxes
Arctic SST workshop, Exeter December 2013
SST variability meeting, Lannion 3 Nov. 2011

14. Modelling Wind =0 on 20120717 from 00h to 19h
Arctic SST workshop, Exeter December 2013
SST variability meeting, Lannion 3 Nov. 2011

15. Modelling Wind =0 on 20120717 from 00h to 19h + Non solar fluxes=0
Arctic SST workshop, Exeter December 2013
SST variability meeting, Lannion 3 Nov. 2011

16. Modelling Wind =0 on 20120717 from 00h to 19h + Non solar fluxes=0
+ surface salinity =0
Arctic SST workshop, Exeter December 2013
SST variability meeting, Lannion 3 Nov. 2011

17. Salinity assumption? Arctic SST workshop, Exeter 18-19 December 2013
SST variability meeting, Lannion 3 Nov. 2011

18. Conclusion
With drifter data, a « solar warming amplitude» over several days can be determined with SST foundation
With satellite data, the scarcity of wind >7m/s in clear sky does not permit to determine SST foundation (and solar warming events are difficult to quantify)
The use of daily reference permits to detect Diurnal Warming.
Localized amplitudes as large as 4 to 5 K are observed up to 80 North
It 's difficult to simulate such amplitudes unless we make extreme assumptions.
Further work :
 understand the origin of such large amplitudes
contribute to the Lake Vanern paper
Arctic SST workshop, Exeter December 2013
SST variability meeting, Lannion 3 Nov. 2011