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23rd Annual CESM Workshop, 2018National Center for Atmospheric Research
qiang.sun@uconn.edu
Improving the representation of estuarine processes in CESM
Qiang Sun①, Michael M. Whitney①, Frank O. Bryan②and Yu-heng Tseng③
① UCONN, Department of Marine Sciences② NCAR, Oceanography Section③ NTU, Institute of Oceanography
Improving the representation of estuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
CESM workshop - 2018 qiang.sun@uconn.edu Slide 2 of 14
Overview
Introduction
Development of Estuary Box Model (EBM) and results
Implementation of EBM in POP2 and results
Current work: Tracking riverine freshwater globally
Summary
Improving the representation of estuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
CESM workshop - 2018 qiang.sun@uconn.edu Slide 3 of 14
The role of river in global hydrological cycle
Improving the representation of estuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
qiang.sun@uconn.edu Slide 4 of 14
6
-6
1
-1
CESM workshop - 2018
Sea surface salinity bias: model (CESM) – climatology (WOA13)
Improving the representation ofestuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
CESM workshop - 2018 qiang.sun@uconn.edu Slide 5 of 14
River runoff treatment in standard CESM• Applied as extra precipitation at sea surface.• Spreading around river mouth (300KM radius).• Discharge into ocean with ZERO salinity.• Using global reference salinity for VSF formula.
Improving river runoff by:• Remapping runoff as point source.• Introducing in the estuary mixing.• Local salinity for VSF formula.
(Tseng et al, Ocean Modelling, 2016)
Improving the representation ofestuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
CESM workshop - 2018 qiang.sun@uconn.edu Slide 6 of 14
Estuarine mixing in nature• Salty sea water
intrusions along bottom.
• Non-ZERO outflow at shallow depth.
• Mixing depends on both of runoff and tides.
http://www.ldeo.columbia.edu/~orton/salt_intrusion.html
Columbia River high discharge season
Columbia River low discharge season
River mouth
32PSU
5 PSU
32PSU
15 PSU
Improving the representation ofestuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
qiang.sun@uconn.edu Slide 7 of 14CESM workshop - 2018
Estuary Box Model (EBM): Two layer box
QR[QU]
H h
[SU]
[QL] SL
Landmodel
Ocean model
(Sun et al, Ocean Modelling, 2017)High Low
Salinity (Sun et al, Ocean Modelling, 2017)
Estuary Box Model (EBM): Control equationsContinuity:
Potential energy (PE) balance:
Salinity balance:
Improving the representation ofestuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
qiang.sun@uconn.edu Slide 8 of 14CESM workshop - 2018
Estuary Box Model (EBM): Algebraic solutions
Estuary Box Model (EBM): Parameters and forcing2 Mixing parameters: ; 3 dimensional parameters:
with
3 Forcing terms: QR , Qt and SL
Improving the representation ofestuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
qiang.sun@uconn.edu Slide 9 of 14CESM workshop - 2018
EBM outflow salinity vs. observations
EBM volume fluxes vs. ROMS
EBM compared with observations and ROMS in Columbia River
RMSE=1.7PSU, R2=70%
RMSE=513m3/s, R2=89%
(Sun et al, Ocean Modelling, 2017)
Improving the representation ofestuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
qiang.sun@uconn.edu Slide 10 of 14CESM workshop - 2018
Estuary Box Model (EBM) global parameterization specification
Hudson
Chang Jiang
Chesapeake
Mississippi
STR
ATIF
ICAT
ION
RIVER DISCHARGE
*Geyer (2010)Sun et al, Ocean Modelling, 2017
Puget Sound
Estuary stratification-circulation diagram
Improving the representation ofestuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
qiang.sun@uconn.edu Slide 11 of 14CESM workshop - 2018
Result (G-case): SSS difference with EBM – control casePSU
(Sun et al, Ocean Modelling, 2017)
31st to 60th year averaged sea surface salinity differenceimproved runoff – control run without improvement
Improving the representation ofestuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
qiang.sun@uconn.edu Slide 12 of 14CESM workshop - 2018
Result (G-case): global assessment with salinity skill scores
Coastal ocean bands mask
Upper 150m ocean integrated salinity SS, with or without high latitude ocean.
Sun et al, JAMES, 2018 (in review)
Improving the representation ofestuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
qiang.sun@uconn.edu Slide 13 of 14CESM workshop - 2018
Future work: global riverine freshwater pathway and influences
Improving the representation ofestuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
qiang.sun@uconn.edu Slide 14 of 14CESM workshop - 2018
Summary The Estuary Box Model is a physically based parameterization of
unresolved estuarine mixing processes in the CESM.
The offline tests of EBM show very good agreement with direct observations of outflow salinity and high-resolution simulations of exchange flow volume fluxes.
A reduced set of parameters allows the parameterization to be practically applied to every river inflow point in global Earth system models at negligible cost.
The global CESM simulations with the EBM show it can have significant impacts on the salinity field of the coastal oceans, with non-negligible impacts in some open ocean areas.
The EBM can further imply in river borne nutrient and contaminants.
Improving the representation ofestuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
qiang.sun@uconn.eduCESM workshop - 2018
Improving the representation ofestuarine processes in CESM
Sun, Q.; Whitney, M. M.; Bryan, F. O. and Tseng, Y. H.
qiang.sun@uconn.edu Slide 16 of 14CESM workshop - 2018
Estuary Box Model (EBM): Implementation in POP2
with
and
Salt
Salt
Salt flux taken outof ocean: with local refence salinity
Salt flux taken fromdeeper to shallower:with local refence salinity
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