Bug #430

Stratospheric nudging of CO and HNO3

Added by Jason Williams over 6 years ago. Updated over 6 years ago.

Target version:
Start date:
Due date:
% Done:


Estimated time:
6.00 h


The ratios of CO/O3 and HNO3/O3 from the ODIN climatologies are calculated offline and stored as 1x1 zonal means in input files e.g. ODIN_CO_O3_ratio_4levels.hdf

This file contains the actual ratio and the difference of the ratio between latitudinal bins (therefore negative values can exist). There is a bug in boundary.F90 where both parameters are read in, coarsened and scattered then applied during the nudging introducing two issues:

(i) potentially negative scaling values !! Thus loss of mass when nudged.
(ii) Too low scaling factors applied (i.e. scaling_rato*difference_in_scaling_ratio)

The arrays scale_co_o3 and scale_hno3_o3 have been removed from the code.

Testing is ongoing.

HNO3_nudging_terms.pdf (23.2 KB) Jason Williams, 01/28/2016 01:00 PM

CO_nudging_terms.pdf (22.4 KB) Jason Williams, 01/28/2016 01:00 PM


#1 Updated by Jason Williams over 6 years ago

  • Assignee set to Jason Williams

#2 Updated by Jason Williams over 6 years ago

For the CO/O3 ratio if the ODIN flag is FALSE it reads the UARS HNO3/O3 ratio !!

Looks like a copy and paste error from the HNO3 nudging above.

If no ODIN is available then stratospheric CO should be kept as is.

#3 Updated by Jason Williams over 6 years ago

A new relaxation technique is applied to smooth the transition between months for the ODIN climatologies. The monthly mean ratio of (HNO3/O3) and (CO/O3) is applied for each month between the 10-20th days. A linear smoothing transition is then applied between the 21st day and 9th day of the next month.

For HNO3 (Jan 1999) this change in the nudging term increases from -0.188 Tg N to 2.546 Tg N (new nudging) and for CO (Jan 1999) from -0.377 to 5.092 Tg CO month (new nudging).

A full analysis for 1999 to follow.

#4 Updated by Jason Williams over 6 years ago

The smoothing approach introduced removes the zigzag monthly nudging terms for HNO3 exhibited in the original UARS ratios (see attachment for year 2000). Similar for CO. This approach will be adopted for the O3 and CH4 nudging in the stratosphere to maintain a consistent approach across species.

#5 Updated by Jason Williams over 6 years ago

  • Status changed from New to Closed
  • % Done changed from 80 to 100

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