Benchmarking midlatitude atmospheric synoptic variability...
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Benchmarking midlatitude atmospheric synoptic variability in global datasets: a spectral perspective Alessandro Dell’Aquila 1 , Susanna Corti 2 1 ENEA, SSPT -MET -CLIM, Italy [email protected] [email protected] 1901-2010 Time series of the anomalies (with respect to 1979- 2001 period) of index of eastward propagating waves activity H E (a) and index of the planetary standing waves activity H (b), in the ex H E [m 2 ] Spectral process-oriented metrics to measure synoptic waves activity a) Eastward propagating waves activity m 2 ] • We present here a process oriented metric to evaluate global datasets in terms of their capability in reproducing the midlatitude atmospheric synoptic variability. In particular our analysis focuses on high and low frequency atmospheric variability as represented by propagating and standing waves defined following the spatio-temporal spectral decomposition introduced by Hayashi ENEA, SSPT -MET -CLIM, Italy 2 CNR, ISAC, Italy [email protected] waves activity H S (b), in the latitudinal belt 30◦N–75◦N, by the ERA20C, NCEP, NOAA 20th CEN, ERA-Interim, ERA40, and ERA-CLIM ERA20CM, ERA20CM-SP . We apply a 5-years running mean DATASETS TREND H E (m2/yr) ERA20C 1.161 NCEP 2.734 NOAA 20thCen 0.991 tward propagating waves activity inde b) Standing planetary waves activity Anomalies H E [m • We apply this process oriented metric and ad hoc indices introduced to validate the ERA-CLIM simulations and, at the same time, to evaluate signals of multi-decadal variability for planetary and baroclinic waves. The results are compared with a series of different reanalysis products, which assimilate atmospheric observations with increased diversity: from surface-only to surface, upper air and satellite observations (ERA20C, Scatterplot of index of eastward propagating waves activity H E (y- axis), for versus the index of the planetary standing waves activity H S for (x-axis) computed for the Z 500 hPa DJF data averaged in the latitudinal belt 30◦N–75◦N for the overlapping period 1979-2001. The bars stand for +/- 1 temporal standard deviation. The thick lines are ERA40 1.648 ERA20CM-0 0.215 ERA20CM-1 -0.768 ERA20CM-2 -0.094 ERA20CM-SP-0 2.584 ERA20CM-SP-1 0.199 ERA20CM-SP-2 -1.482 East Standing planetary waves activity index H S [m 2 ] Anomalies H S [m 2 ] surface-only to surface, upper air and satellite observations (ERA20C, NOAA 20 th Reanalysis, NCEP, Era-Interim, ERA40 Reanalysis…) Trend for baroclinic activity index H E in reanalysis datasets and ERA-CLIM runs: in bolds are the We follow the Fourier space-time decomposition introduced by Hayashi (1971,1979), assuming complete coherence between the eastward and westward components of standing waves and attributing the incoherent part of the spectrum to real travelling waves. Hayashi spectra allow separation between travelling vs Hayashi Spectra •In the second part of the century all the reanalysis datasets exhibit a good agreement in the representation of synoptic atmospheric variability •A positive trend in the baroclinic activity index H is present in all the reanalysis products for the Reanalysis datasets. The thin solid lines are for the ERA20CM runs while the dashed lines for the corresponding ERA20CM-SP runs with the effects of Stochastic Physics included statistical significant trend (90% Mann Kendall test) In italics the non significant trends, the shaded area are for negative significant trends ( calculated over 1961-2001 DJF period) waves. Hayashi spectra allow separation between travelling vs standing waves of the 1D+1D field (500 hPa: latitudinal belt 30– 75N) P and Q are, respectively, the power and the quadrature spectra of the longitude (k) and the time (t) dependent 500 hPa Z(, t) expressed in ) , ( ) ( ) ( , 2 1 4 1 k k k k E S C Q S P C P k E ) , ( ) ( ) ( , 2 1 4 1 k k k k W S C Q S P C P k E ) ( ) ( , 1 S P C P k E Eastward Propagating waves Westward Propagating waves Total variance •A positive trend in the baroclinic activity index H E is present in all the reanalysis products over the second part of the century , not present in most of the ERA-CLIM AMIP simulations •In the first part of XX century (up to 40s) a clear suppression of high frequency variability is apparent in ERA20C and, to a lesser extent, in the ensembles mean of NOAA 20 th Cent. Rean. •The same kind of signal, but weaker, is found for the low frequency variability in the 40s terms of the zonal Fourier harmonics ) ( ) ( , 2 1 k k T S P C P k E , , , k Q k E k E T S Total variance Standing waves NCEP dataset : Climatological STANDING COMPONENT TOTAL VARIANCE l Wavenumber k l Wavenumber k •High and low frequency variability in ERA-CLIM AMIP simulations do not show a similar suppression of variability during the integrations. •The ERA-CLIM AMIP simulations show a general overestimation of synoptic variance Atmospheric patterns associated to the oscillations of H S Z500 T850 SLP U200 The planetary wave activity index H S H E NCEP dataset : Climatological average over 60 winters of Hayashi spectra for DJF geopotential height at 500 hPa, in the latitudinal belt 30◦ N– 75◦N,. The Hayashi spectra have been obtained by multiplying the spectra by k∕(2ߨ), = 90 days so that equal geometrical areas represent equal variance in log-log plots, and their units are square meter. The LFLW standing (H S ) and the HFHW eastward propagating (H E ) areas are indicative of the planetary and the baroclinic waves activities, respectively. PropagatingEastward Propagating Westward Zonal Zonal Wavenumber k Zonal Zonal Wavenumber k period (day) period (day) •Reanalysis Datasets ERA20C deterministic reanalysis 1901-2010 (Poli et al 2015) NOAA 20 th Century Reanalysis: 1901-2010: Ensemble mean (Compo et al 2012) Correlation between the index of the planetary standing waves activity Hs and mean state of U200, Z500, T850 and SLP for NCEP Reanalysis over the 1951-2010 DJF period. The contour lines are for the corresponding long term mean. In the tippled areas the correlations are statistically significant at 90% (Pearson Z500 T850 SLP U200 The planetary wave activity index H S and mean state associated Spectral region Zonal wave numb. Period Hs: LFLW 2-4 10-45d He: HFHW ≥6 2-7d period (day) period (day) et al 2012) NCEP Reanalysis : 1951-2010 ERA-Interim: 1979-2010 ERA-40: 1961-2000 •ERA-CLIM AMIP runs (Hersbach et al 2014) ERA20CM (members 0, 1, 2): 1901-2010 coefficients) The planetary wave activity index H S and variability associated Correlation between the index of the planetary standing waves activity Hs and band pass 10-45 days variance of Z500 for NCEP Reanalysis over the 1951-2010 DJF period. The contour lines are for the corresponding long term mean. In the tippled areas the correlations are statistically significant at 90% (Pearson coefficients) NCEP Reanalysis ERA20CM-SP, members 0, 1, 2 with Stochastic Physics: 1901-2010 Atmospheric patterns associated to the oscillations of H E Correlation between the index of the baroclinic waves activity H E and mean state of U200, Z500, T850 and SLP for Z500 T850 SLP U200 NCEP ERA20CM SLP Correlation between the index of the baroclinic waves activity H E and mean state of SLP for different The baroclinic waves activity index H E and mean state state of U200, Z500, T850 and SLP for NCEP Reanalysis over the 1951-2010 DJF period. The contour lines are for the corresponding long term mean. In the tippled areas the correlations are statistically significant at 90% (Pearson coefficients) The baroclinic waves activity index H E and variability associated Correlation between the index of the planetary standing waves activity HE and band pass 2-7 days variance of Z500 for NCEP Reanalysis over the 1951-2010 DJF period. The contour lines NCEP Reanalysis ERA20C ERA20CM-SP SLP for different datasets over the 1951-2010 DJF period. New publications related to this activity •Di Biagio V., S. Calmanti, A. Dell'Aquila, P M. Ruti. (2014) Northern Hemisphere winter midlatitude atmospheric variability in CMIP5 models. GRL 41:4, 1277-1282. •Dell’Aquila, A., Corti, S. Weisheimer, A. Hersbach, H., Peubey, C., Simmons A., Poli, P., Berrisford P., Dee, D., (2016) Benchmarking Northern Hemisphere midlatitude atmospheric synoptic variability in centennial reanalysis and numerical simulations .In revision on GRL Reanalysis over the 1951-2010 DJF period. The contour lines are for the corresponding long term mean. In the tippled areas the correlations are statistically significant at 90% (Pearson coefficients) The ERA-CLIM simulations show discrepancies in the representation of patterns associated to baroclinic activity mostly over North Atlantic sector
Transcript of Benchmarking midlatitude atmospheric synoptic variability...
Benchmarking midlatitude atmospheric synoptic variability in global datasets: a spectral perspective
Alessandro Dell’Aquila 1, Susanna Corti 21 ENEA, SSPT-MET-CLIM, Italy
[email protected]@isac.cnr.it
1901-2010 Time series of the anomalies (with respect to 1979-2001 period) of index of eastward propagating waves activity HE (a) and index of the planetary standing waves activity H (b), in the
East
war
d pr
opag
atin
g wav
es ac
tivity
inde
x H E
[m2 ]
Spectral process-oriented metrics to measure synoptic waves activity a) Eastward propagating waves activity
[m2 ]
• We present here a process oriented metric to evaluate global datasets in terms of their capability in reproducing the midlatitude atmospheric synoptic variability. In particular our analysis focuses on high and low frequency atmospheric variability as represented by propagating and standing waves defined following the spatio-temporal spectral decomposition introduced by Hayashi
1 ENEA, SSPT-MET-CLIM, Italy2 CNR, ISAC, Italy
waves activity HS (b), in the latitudinal belt 30◦N–75◦N, by the ERA20C, NCEP, NOAA 20th CEN, ERA-Interim, ERA40, and ERA-CLIM ERA20CM, ERA20CM-SP . We apply a 5-years running mean
DATASETS TREND HE (m2/yr)
ERA20C 1.161
NCEP 2.734
NOAA 20thCen 0.991
East
war
d pr
opag
atin
g wav
es ac
tivity
inde
x
b) Standing planetary waves activity
Anom
alie
s H
E [mdecomposition introduced by Hayashi
• We apply this process oriented metric and ad hoc indices introduced to validate the ERA-CLIM simulations and, at the same time, to evaluate signals of multi-decadal variability for planetary and baroclinic waves. The results are compared with a series of different reanalysis products, which assimilate atmospheric observations with increased diversity: from surface-only to surface, upper air and satellite observations (ERA20C,
Scatterplot of index of eastward propagating waves activity HE (y-axis), for versus the index of the planetary standing waves activity HS for (x-axis) computed for the Z 500 hPa DJF data averaged in the latitudinal belt 30◦N–75◦N for the overlapping period 1979-2001. The bars stand for +/- 1 temporal standard deviation. The thick lines are
ERA40 1.648
ERA20CM-0 0.215
ERA20CM-1 -0.768
ERA20CM-2 -0.094
ERA20CM-SP-0 2.584
ERA20CM-SP-1 0.199
ERA20CM-SP-2 -1.482
East
war
d pr
opag
atin
g wav
es ac
tivity
inde
x
Standing planetary waves activity index HS [m2]
Anom
alie
s H
S [m
2 ]
surface-only to surface, upper air and satellite observations (ERA20C, NOAA 20th Reanalysis, NCEP, Era-Interim, ERA40 Reanalysis…)
Trend for baroclinic activity index HE in reanalysis datasets and ERA-CLIM runs: in bolds are the
We follow the Fourier space-time decomposition introduced byHayashi (1971,1979), assuming complete coherence between the eastward and westward components of standing waves and attributing the incoherent part of the spectrum to real travellingwaves. Hayashi spectra allow separation between travelling vs
Hayashi Spectra
•In the second part of the century all the reanalysis datasets exhibit a good agreement in the representation of synoptic atmospheric variability
•A positive trend in the baroclinic activity index H is present in all the reanalysis products
for the Reanalysis datasets. The thin solid lines are for the ERA20CM runs while the dashed lines for the corresponding ERA20CM-SP runs with the effects of Stochastic Physics included
statistical significant trend (90% Mann Kendall test) In italics the non significant trends, the shaded area are for negative significant trends ( calculated over 1961-2001 DJF period)
waves. Hayashi spectra allow separation between travelling vs standing waves of the 1D+1D field (500 hPa: latitudinal belt 30–75N)
P and Q are, respectively, the power and the quadrature spectra of the longitude (k) and the time (t) dependent 500 hPa Z(, t) expressed in
),()()(, 21
41
kkkkE SCQSPCPkE
),()()(, 21
41
kkkkW SCQSPCPkE
)()(, 1 SPCPkE
Eastward Propagating waves
Westward Propagating waves
Total variance •A positive trend in the baroclinic activity index HE is present in all the reanalysis products over the second part of the century , not present in most of the ERA-CLIM AMIP simulations
•In the first part of XX century (up to 40s) a clear suppression of high frequency variability is apparent in ERA20C and, to a lesser extent, in the ensembles mean of NOAA 20th Cent. Rean.
•The same kind of signal, but weaker, is found for the low frequency variability in the 40s
Z(, t) terms of the zonal Fourier harmonics
)()(, 21
kkT SPCPkE
,,, kQkEkE TS
Total variance
Standing waves
NCEP dataset :Climatological
STANDING COMPONENTTOTAL VARIANCE
Zona
l Wav
enum
berk
Zona
l Wav
enum
berk
•High and low frequency variability in ERA-CLIM AMIP simulations do not show a similar suppression of variability during the integrations.
•The ERA-CLIM AMIP simulations show a general overestimation of synoptic variance
Atmospheric patterns associated to the oscillations of HS Z500 T850 SLPU200The planetary wave activity index
HS
HE
NCEP dataset :Climatologicalaverage over 60 winters of Hayashi spectra for DJF geopotential height at 500 hPa, in the latitudinal belt 30◦N–75◦N,. The Hayashi spectra have been obtained by multiplying the spectra by k߱ ߬ ,(ߨ2)⧵߬ = 90 days so that equal geometrical areas represent equal variance in log-log plots, and their units are square meter.
The LFLW standing (HS) and the HFHW eastward propagating (HE) areas are indicative of the planetary and the baroclinic waves activities, respectively.
Propagating Eastward Propagating Westward
Zona
l
Zona
l Wav
enum
berk
Zona
l
Zona
l Wav
enum
berk
period (day) period (day)
•Reanalysis Datasets
ERA20C deterministic reanalysis 1901-2010 (Poli et al 2015)
NOAA 20th Century Reanalysis: 1901-2010: Ensemble mean (Compo
et al 2012)
Correlation between the index of the planetary standing waves activity Hs and mean state of U200, Z500, T850 and SLP for NCEP Reanalysis over the 1951-2010 DJF period. The contour lines are for the corresponding long term mean. In the tippled areas the correlations are statistically significant at 90% (Pearson
Z500 T850 SLPU200The planetary wave activity indexHS and mean state associatedSpectral region Zonal wave numb. Period
Hs: LFLW 2-4 10-45d
He: HFHW ≥6 2-7d
period (day) period (day)
et al 2012)
NCEP Reanalysis : 1951-2010
ERA-Interim: 1979-2010
ERA-40: 1961-2000
•ERA-CLIM AMIP runs (Hersbach et al 2014)
ERA20CM (members 0, 1, 2): 1901-2010
statistically significant at 90% (Pearson coefficients)
The planetary wave activity index HS and variability associated Correlation between the index of the planetary standing
waves activity Hs and band pass 10-45 days variance of Z500 for NCEP Reanalysis over the 1951-2010 DJF period. The contour lines are for the corresponding long term mean. In the tippled areas the correlations are statistically significant at 90% (Pearson coefficients)
NCEP Reanalysis
ERA20CM-SP, members 0, 1, 2 with Stochastic Physics: 1901-2010
Atmospheric patterns associated to the oscillations of HE
Correlation between the index of the baroclinic waves activity HE and meanstate of U200, Z500, T850 and SLP for
Z500 T850 SLPU200 NCEP ERA20CMSLP Correlation between the index of the baroclinic waves activity HEand mean state of SLP for different
The baroclinic waves activity indexHE and mean state
state of U200, Z500, T850 and SLP for NCEP Reanalysis over the 1951-2010 DJF period. The contour lines are for thecorresponding long term mean. In the tippled areas the correlations are statistically significant at 90% (Pearson coefficients)
The baroclinic waves activity index HE and variability associated Correlation between the index of the planetary standing waves
activity HE and band pass 2-7 days variance of Z500 for NCEP Reanalysis over the 1951-2010 DJF period. The contour lines
NCEP Reanalysis
ERA20C ERA20CM-SPSLP for different datasets over the 1951-2010 DJF period.
New publications related to this activity
•Di Biagio V., S. Calmanti, A. Dell'Aquila, P M. Ruti. (2014) Northern Hemisphere winter midlatitude atmospheric variability in CMIP5 models. GRL 41:4, 1277-1282.
•Dell’Aquila, A., Corti, S. Weisheimer, A. Hersbach, H., Peubey, C., Simmons A., Poli, P., Berrisford P., Dee, D., (2016) Benchmarking Northern Hemisphere midlatitude atmospheric synoptic variability in centennial reanalysis and numerical simulations .In revision on GRL
Reanalysis over the 1951-2010 DJF period. The contour lines are for the corresponding long term mean. In the tippled areas the correlations are statistically significant at 90% (Pearson coefficients)
The ERA-CLIM simulations show discrepancies in the representation of patterns associated to baroclinic activity mostly over North Atlantic sector
