Uncertainties in (energy) budgets

Transcription

1 Uncertainties in (enery) budets Thanks to Michael Mayer, John M. Edwards, Patrick Hyder, Andrea Storto, Marianne Pietschni, Sebastian Stichelberer, Eric Boisseson, Patrick Laloyaux, Elke Rustemeier, Markus Ziese

2 Motivation, Outline Interal budet constraints allow for indirect estimation of difficult to measure quantities. TOA lobal mean radiation imbalance = OHCT+Icemelt Estimation of net surface enery flux pattern Biases and drifts in state quantities such as temperature often have their root in erroneous transports CMIP6 puts more emphasis on budet components reference data needed Ocean, ice and coupled reanalyses open new possibilities Improvements for coupled enery budet formulation Reional budet evaluations Precipitation evaluation ->DWD talk Carbon ->UVSQ talk

3 Improvin the net surface enery flux evaluation Use vertically interated atmospheric total enery budet equation to infer F S indirectly F S Rad TOA F Diverence term requires mass-consistent winds Rad TOA with FS LH SH Rad S A FA

4 Current practice Vertically interated atmospheric total enery budet equation can be used to infer net surface enery flux Diverence term requires mass-consistent winds with F S Rad TOA Inferred F S F FS LH SH Rad S A The patterns look nice and realistic, but

5 Comparison to independent surface flux product Compare implied F S from satellite TOA radiation and reanalysis transports to independent surface flux products here: difference to CERES sfc radiation plus OAflux turbulent fluxes Substantial differences in the tropics, with a pronounced P-E pattern Where does this pattern come from?

6 Take a closer look at budet equation Vertically interated atmospheric total enery budet equation F S Rad TOA F A

7 Take a closer look at budet equation Vertically interated atmospheric total enery budet equation F S Rad TOA p s 1 [ v2 ( m k)] dp 0

8 Take a closer look at budet equation Vertically interated atmospheric total enery budet equation F S Rad TOA 1 [ v2 ( m k)] dp Diverence term can be decomposed as follows: p s p p 1 s s 1 1 [ v 2 ( m k)] dp v2 ( m k) dp ( m k)( v 2) dp p s 0 Moist static enery ( c pt Lvq ) Kinetic enery Advection term Mass diverence term

9 Take a closer look at budet equation Vertically interated atmospheric total enery budet equation F S Rad TOA 1 [ v2 ( m k)] dp Diverence term can be decomposed as follows: p s p p 1 s s 1 1 [ v 2 ( m k)] dp v2 ( m k) dp ( m k)( v 2q) dp p s 0 Moist static enery ( c pt Lvq ) Kinetic enery Advection term Mass diverence term Vertically interated mass diverence reduces to moisture flux diverence (if dry mass is conserved!)

10 Take a closer look at budet equation Vertically interated atmospheric total enery budet equation F S Rad TOA 1 [ v2 ( m k)] dp Diverence term can be decomposed as follows: p s p p 1 s s 1 1 [ v 2 ( m k)] dp v2 ( m k) dp ( m k)( v 2q) dp p s 0 Moist static enery ( c pt Lvq ) Kinetic enery Mass diverence term involves absolute m, i.e. temperature itself!

11 F S Dependency of F S on reference temperature can be written as: 1 ps ps ps 1 c p ( mkelvin k)( v2 q) dp ( mcelsius k)( v2q) dp ( v 2q) dp Field of ΔF S shows lare values with a P-E structure: h 0 What is correct? Shouldn t F S be independent on employed temperature scale? Wm -2

12 Reason for inconsistency Latent heat is treated consistently in 3D enery fluxes, but moisture enthalpy fluxes are NOT! Atmosphere h 0 =0 in the ocean because C scale is used Ocean

13 More complete budet Need to include moisture enthalpy fluxes in lateral AND surface fluxes usin consistent temperature scales! Atmosphere Ocean

14 More complete budet Need to include moisture enthalpy fluxes in lateral AND surface fluxes usin consistent temperature scales! Atmosphere Ocean

15 Practical evaluation Either take into account F p and F e when inferrin F S Atmosphere Ocean

16 Improvement of results More consistent budet formulation improves areement RMS difference drops by 30-40% Improvement seen also with several other flux products Conventional budet formulation improved budet formulation

17 Surface enthalpy fluxes Althouh small compared to h 0 -effect, F p, F e, and F snow exhibit pronounced spatial pattern Additional implications for lobal mean fluxes F p -F e

18 Oceanic Heat Content Estimation Fi. 6: Global 0-300m OHC anomalies with respect to ORA-20C ensemble (10 members) are in liht red, with the ensemble mean in red. CERA20C ensemble (10 members) in rey, with the mean in black, ORAS4 ensemble (5 members) in liht blue with the ensemble mean in blue. An OHC increase of 1x10 8 J/m2 corresponds to a temperature increase of 0.08K averaed over the top 300m. De Boisséson, E., Balmaseda, M. A. and Mayer, M., 2017: Ocean heat content variability in an ensemble of twentieth century ocean reanalyses. Clim. Dyn., DOI /s

19 Rad TOA from CERES and from reconstructions Next step: Evaluate how well do improved budet estimations for Fs, revised Rad TOA, Ocean heat content estimates correlate? Liu, C., et al. (2017), Evaluation of satellite and reanalysis-based lobal net surface enery flux and uncertainty estimates, J. Geophys. Res. Atmos, doi: /2017jd

20 Enery and Freshwater fluxes throuh Arctic Gateways Fi 2: Location of 138 instruments at 41 moorin sites in the Arctic Gateways. Blue crosses: Temperature and salinity measurements (SeaBird microcats). Blue circles: Current and Salinity meters (Aanderaa sinle point current meters). Red circles: Current meters. Green diamonds: ADCP (Acoustic Doppler Current Profiler). Source: Tsubouchi et al. 2017

21 Volume and temperature fluxes throuh Davies strait Fluxes from moored array vs. CGLORSv7 09/ /2006 Common reference temperature for both Temperature fluxes positive from moored array, near neutral from C-CLORS Pietschni et al. 2017, Ocean Science Discussions

22 Net Heat and Freshwater Transport comparison Fi. 4 a) Seasonal cycle of net northward heat fluxes estimated from moored observations, CMCCv5, and ORAS5 ocean reanalyses from data coverin b) seasonal cycle of net northward freshwater fluxes. Shadin indicates standard deviation of the 7 monthly averaes.

23 Conclusions Inconsistency in present enery budet formulation revealed and fixed this is a dianostic problem and hence affects all reanalysis products also much cleaner comparison to climate models Effects of surface enthalpy fluxes should be taken into account in models Explicitly required for CMIP6 reanalyses should follow, especially when coupled Recommendations for better usability of archived enery budet terms: Mass consistent total enery diverence Diverence of moisture enthalpy transports should be stored separately Reional evaluation of lateral oceanic transports Next steps: see if improved formulation improves OHCT-F S -RAD TOA correlation Noise near ororaphy how to best avoid it to et F S over land?

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25 Fi. 9: P-E differences CERA20C minus ERA-Interim averaed over period (upper left), Differences ERA20C minus ERA- Interim (upper riht), Differences ERA20CM minus ERA-Interim (lower left), Difference between ERA-Interim P-E and vertically interated moisture flux diverence (lower riht), yieldin a measure of uncertainty for ERA-Interim P-E.

26 a) ERA-20C b) CERA-20C Fiure 7 BIAS of short term precipitation forecasts from ERA- 20C a) and the CERA-20C ensemble mean b) aainst Full Data Monthly V7 (Schneider et al., 2014). Time interval considered: on 1 spatial resolution with annual temporal resolution.

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28 Mass budet in ERA-Interim Vertically interated mass diverence Indirect estimate of mass diverence

29 Improved self-consistency of ERA-Interim budet

30 Error introduced by consistent vapour enthalpy removal