Wind turning in the boundary layer - observations and comparison with CMIP5 models

Transcription

1 in the boundary layer - observations and comparison with CMIP5 models Jenny Lindvall, Gunilla Svensson Department of Meteorology and Bolin Centre for Climate Research, Stockholm University Swedish e-science Research Centre Thanks to Julio Bacmeister, NCAR

2 Introduction We do not have any direct global measurements of surface drag Look at parameters that can constrain what the models should be doing the wind turning in the boundary layer is one of them The angle of wind turning is closely related to the cross-isobaric flow which is important for cyclone development and the large-scale flow

3 Introduction Known modeling problems: Too large cross-isobaric flow Too deep stable PBLs The angle between the near-surface and geostrophic wind is too small The evaluations are generally based on a few point studies (Cabauw ~32 o ) or LES comparisons Recently climatologies of has emerged

4 a) c) Weakly All stable, < Ri <.2 b) d) Unstable, Stable, Sodan ARM SGP.4.2 BCC CSM1.1 HadGEM2 A IPSL CM5A MR Wind CESM1 speed [m s -1 ] Observations Ri < >.2 OB Mean: Mean: Mean:.4.4 OBS:.16.4 OBS:.2.4 OBS: CTRL:.2 CTRL:.3 CTRL: NoTMS:.18 NoTMS:.27 NoTMS:.29 Lon.2 Longtail:.23.2 Longtail:.3.2 Longtail:.44.2 Longtail:.18.2 Longtail:.26!"( Longtail: !"(./ +.1!"(./!"' !"&, !"'./ !"&, w'u'!"' [m 2 s w'u' ] 1234!"& 5627-w'u' 4689:,;*!"% [m 2 s -2 [m 2 15 s -2 ] ] -18.6!"% between near surface and [ o ]./ 1234!"& 5627 in PBL 4689:,;* [ o ]!"% </4=+4689:,;* c) Weakly stable, :,;* </4=+4689:,;*!"$!"%!"$ < Ri <.2 </4=+4689:,;*!"$!"# Studied.4 the angle of windturning at one (two) locations!"$ in CMIP5!"# models! + e)!"#.4!"#.4! + and.3 in several versions of CAM with different surface drag and vertical!"(! +!"(!"'!.2.3!"(!"&.3 diffusion 55 E-!"' C8D:,E*>+FGH!"& E-.1!"' C8D:,E*>+FGH./@+'%.2!"& C8D:,E*>+FGH!"%./@+'%!"% 1234@+'$.2!"&./@+'%!"% 1234@+'$ 5627@+'$!"$ Large.1!"% 1234@+'$ 5627@+'$ 4689:,;*@+'#.6 differences between the models/model versions!"$.1!"$ 5627@+'$ 4689:,;*@+'#!"# </4=+4689:,;*@+'$ d) Stable,!"$ 4689:,;*@+'#!"# </4=+4689:,;*@+'$.5!!"#!"# </4=+4689:,;*@+'$ Ri >.2!!"( Lindvall,.4 J., Svensson, G., and Caballero, R. (216). The impact of changes.4 in parameterizations!!"( of surface drag!"'!.4 and vertical!"(!"& Q-.3 diusion on the large-scale circulation in the Community Atmosphere Model (CAM5).!"' Accepted N>,O*P+D:,E*>+FGH in!"& Climate Dynamics.3 Q-!"' N>,O*P+D:,E*>+FGH./@+#'.3.2!"& N>,O*P+D:,E*>+FGH!"%./@+#'!"% 1234@+##!"&./@+#'!"% 1234@+## 5627@+&"& Svensson,.1 G. and Lindvall, J. (215). Evaluation of Near-Surface Variables.2 and!"$!"% the 1234@+## Vertical 5627@+&"& Structure 4689:,;*@+& of the.2!"$!"$ 5627@+&"& 4689:,;*@+&!"# </4=+4689:,;*@+&"( Boundary Layer in CMIP5 Models. Journal of Climate, 28(13): !"$ 4689:,;*@+&!"# </4=+4689:,;*@+&"(.1 Sodankyla Mean: m) OBS:.12 CTRL:.27 NoTMS:.21 Longtail:.21 Longtail: IG. 12. PDFs of the modeled and observed angle of wind turning over the PBL at the ARM Southern Great ins site for a) all cases, b) unstable (Ri < ), c) weakly stable ( < Ri <.2), d) stable conditions (Ri.2) Wind speed [m s -1 ] ARM SGP Sodankyla ARM SGP Sodankyla )** C8D:,E*>I+ 3;+J+! >,O*P+D:,E*>I+ +J+3;+J+!"!$ Mean: n) OBS:.17 CTRL:.37 NoTMS:.3 Longtail:.28 Longtail:.29 )** C8D:,E*>I+ 3;+J+! N>,O*P+D:,E*>I+!+J+3;+J+!"!$.1.4 All OB 3 Wind speed [m s -1 ] )** C8D:,E*>I+ 3;+J+! N>,O*P+D:,E*>I+!+J+3;+J+!"!$ a) Mean: OBS:.14 CTRL:.37 NoTMS:.32 Longtail:.4 Longtail:.33.6 Uns CTR.4 NoT o) Lon.2 PBL.6 Uns CTR NoT PBL

5 Data IGRA Soundings at over 1 locations (681 included) Limited vertical resolution from Seidel et al, 21 ( ) SPARC High vertical resolution (6 or 1 s) Fewer points (US only) IGRA stations year 199 Models 6-hourly, global data 5 years and 5 models (for now) CMIP5 data + CESM(CLUBB) SPARC stations

6 Data The turning of the wind with height is calculated between the first level above the and 1 m wind (the lowest height in the sounding data set) θ θ The is from a dataset by Seidel et al (21) Diagnosed using a bulk Richardson number (finding first level where Ri bulk >.25) For a fair comparison, the same method is used to calculate the in the models

7 The angle of wind turning - observations

8 Windturning

9 Windturning - seasons

10 Windturning - seasons UTC, JJA 12 UTC, DJF 12 UTC, JJA UTC, DJF

11 PDFs for all observation sites Angle of windturning (sign of the windturning reversed for sites in the Southern Hemisphere) Observations show a wider PDF and larger angles of windturning Models are similar except GFDL Windspeed

12 Angle of windturning vs wind speed - Observations Forest Shrub Grass ALL The turning of the wind increases with wind speed. -5m 5-1m The increase is faster for lower s 1-5m Different surface types (from MODIS data) show the same behavior 5-1m 1-2m 2-3m

13 Angle of windturning vs wind speed 5-1m OBS ACCESS1.3 CESM(CLUBB) GFDL-ESM2M GISS-E2-R HadGEM2-ES m 5-1m 1-5m The models also show an increase of the wind turning with wind speed. The differences in the slope between difference regimes is less in the models

14 Angle of windturning vs wind speed 1-2m 5-1m 1-5m 5-1m OBS ACCESS1.3 CESM(CLUBB) GFDL-ESM2M GISS-E2-R HadGEM2-ES The models also show an increase of the wind turning with wind speed. The differences in the slope between difference regimes is less in the models

15 Angle of windturning vs - Observations Forest Shrub Grass ALL Wind speed 2-4 m/s Wind speed 1-2 m/s Wind speed 5-1 m/s Wind speed 1-5 m/s Wind speed -1 m/s The turning of the wind decreases with Different surface types (from MODIS data) show the same behavior -5 5

16 Angle of windturning vs Wind speed Wind speed Wind speed Wind speed Wind speed 2-4 m/s 1-2 m/s 5-1 m/s 1-5 m/s -1 m/s OBS -5 5 ACCESS1.3 CESM(CLUBB) GFDL-ESM2M GISS-E2-R -5 5 The models also show the decrease of the wind turning with. The spread is smaller in the models. HadGEM2-ES -5 5

17 SPARC - examples International Falls, Minnesota Birmingham, Alabama UTC (afternoon) 12 UTC (morning)

18 and over oceans model differences

19 Outlook Continue the analysis and include more models Use SPARC data to estimate uncertainties in the IGRA data and study what goes on in the vertical Compare the observations with reanalyses Look more closely at polar areas

20 Summary We have used radiosondes to attempt to get a climatology of the wind turning in the PBL Both the angles of windturning and the variations in windturning are smaller in the models than in the observations. The angle of windturning increases with wind speed and decreases with and this is to some extent captured by the observations

21 Thank you!