R. A. Brown 2005 AGU

The Satellite + PBL Model The Satellite + PBL Model calculation of surface pressurecalculation of surface pressure

• The microwave scatterometers, radiometers, SARs and altimeters have now provided nearly three decades of inferred surface winds over the oceans. These can all be converted to excellent surface pressure fields.

R. A. Brown 2005 AGU

• Often these products are revolutionary, changing the way we view the world.

R. A. Brown 2005 AGU

fV + K Uzz - pz / = 0 fU - K Vzz + pz / = 0The solution, U (f, K,p ) was found by Ekman in 1904.

State of The analytic solution for a PBL

fV + K Uzz - pz/ = 0 fU - K Vzz + pz/ = A(v2w2)Solution, U (f, K,p ) found in 1970. OLE are part of solution for 80% of observed conditions (near-neutral to convective).

Unfortunately, this was almost never observed.

The complete nonlinear solution for OLE exists, including the 8th order instability solution, effects of variable roughness, stratification and baroclinicity, 1996. Integrated into MM5, NCEP (2005)

Unfortunately, this scale was difficult to observe.

R. A. Brown 2005 AGU

SLP from Surface WindsSLP from Surface Winds

• UW PBL similarity model

joins two layers:

The nonlinear Ekman solution

10 10( , , , , , )G

f P T SST q CSu

10

10logN

o

uU

k z u

to the log layer solution.

Use the “inverse” PBL model to estimate from satellite . Use vector math to get non-divergent field UG. Use Least-Square optimization to find best fit SLP to swaths:There is extensive verification from ERS-1/2, NSCAT, QuikSCAT

G

10NU

P (UG) = P(U10) → P(U10)

R. A. Brown 2005 AGU

The nonlinear solution applied to satellite surface winds The nonlinear solution applied to satellite surface winds yields accurate surface pressure fields. These data show:yields accurate surface pressure fields. These data show:

* The agreement between satellite and ECMWF pressure fields indicate that both the Scatterometer winds and the nonlinear PBL model (VG/U10) are accurate within 2 m/s.

* A 3-month, zonally averaged offset angle <VG, U10> of 19° suggests that the mean marine PBL state is near neutral (the angle predicted by the nonlinear PBL model).

* Swath deviation angle observations can be used to infer thermal wind and stratification.

* Higher winds are obtained from pressure gradients and used as surface truth (rather than GCM or buoy winds).

* VG (pressure gradients) rather than U10 could be used to initialize GCMs

R. A. Brown 2005 EGUR. A. Brown 2005 AGU

• The nonlinear PBL solution applied to satellite surface winds provides sufficient accuracy to determine surface pressure fields from satellite data alone.

Patoux, J. and R.A. Brown, 2002: A Scheme for Improving Scatterometer Surface Wind Fields, J. Geophys. Res., 106, No. 20, pg 23,985-23,994

R. A. Brown 2005 AGU

R. A. Brown 2004 EGUR. A. Brown 2005 AGU

Dashed: ECMWFSolid: UW-Quikscat

R. A. Brown 2005 AGU

The UW PBL Model is now global

ECMWF analysis

QuikScat analysis

Surface Pressures

J. Patoux & R. A. Brown

Raw scatterometer winds

UWPressure field smoothed

JPL Project Local GCM nudge smoothed = Dirth (with ECMWF fields)

R. A. Brown 2005 EGUR. A. Brown 2005 AGU

To get smooth synoptic wind fields from a scatterometer

R. A. Brown 2005 AGU

OPC Sfc Analysis and IR Satellite Image 10 Jan 2005 0600 UTC

UWPBL 10 Jan 2005 0600 UTC

GFS Sfc Analysis 10 Jan 2005 0600 UTC

a b

c d

QuikSCAT 10 Jan 2005 0709 UTC

996

982

999

991

996

984

OPC 08 Jul 2005 GFS 08 Jul 2005

1001

992

996

996

1003

QuikSCAT 08 Jul 2005 UWPBL 08 Jul 2005

dc

a b

R. A. Brown 2005 AGU

• Surface pressures as surface ‘truth’ yield high wind predictions. This suggests that the global climatology surface wind record is too low by 10 – 20%.

Brown, R.A., & Lixin Zeng, 2001: Comparison of Planetary Boundary Layer Model Winds with Dropwindsonde Observations in Tropical Cyclones, J. Applied Meteor., 40, 10, 1718-1723; Foster & Brown, 1994, On Large-scale PBL Modelling: Surface Wind and Latent Heat Flux Comparisons, The Global Atmos.-Ocean System, 2, 199-219.

R. A. Brown 2005 AGU

• There is evidence from the satellite data that the secondary flow characteristics of the nonlinear PBL solution (Rolls or Coherent Structures) are present more often than not over the world’s oceans. This contributes to basic understanding of PBL modelling and air-sea fluxes.

Brown, R.A., 2002: Scaling Effects in Remote Sensing Applications and the Case of Organized Large Eddies, Canadian Jn. Remote Sensing, 28, 340-345; Levy G., 2001, Boundary Layer Roll Statistics from SAR. Geophysical Research Letters. 28(10),1993-1995.

R. A. Brown 2005 AGU

• The dynamics of the typical PBL revealed in remote sensing data indicate that K-theory in the PBL models is physically incorrect. This will mean revision of all GCM PBL models as resolution increases.

Brown, R.A., 2001: On Satellite Scatterometer Model functions, J. Geophys. Res., Atmospheres, 105, n23, 29,195-29,205; Patoux, J. and R.A. Brown, 2001: Spectral Analysis of QuikSCAT Surface Winds and Two-Dimensional Turbulence, J. Geophys. Res., 106, D20, 23,995-24,005; Patoux, J. and R.A. Brown, 2002: A Gradient Wind Correction for Surface Pressure Fields Retrieved from Scatterometer Winds, Jn. Applied Meteor., Vol. 41, No. 2, pp 133-143; R.A. Brown & P. Mourad, 1990: A Model for K-Theory in a Multi-Scale Large Eddy Environment, AMS Preprint of Symposium on Turbulence and Diffusion, Riso, Denmark. On the Use of Exchange Coefficients and Organized Large Scale Eddies in Modeling Turbulent Flows. Bound. Layer Meteor., 20, 111-116, 1981.

R. A. Brown 2005 AGU

Programs and Fields available onPrograms and Fields available onhttp://pbl.atmos.washington.eduhttp://pbl.atmos.washington.edu

QuestionsQuestions to rabrown, neal orto rabrown, neal or jerome jerome @atmos.washington.edu@atmos.washington.edu

• Direct PBL model: PBL_LIB. (’75 -’05) An analytic solution for the PBL flow with rolls, U(z) = f( P, To , Ta , )

• The Inverse PBL model: Takes U10 field and calculates surface pressure field P (U10 , To , Ta , ) (1986 - 2005)

• Pressure fields directly from the PMF: P (o) along all swaths (exclude 0 - 5° lat.?) (2001) (dropped in favor of I-PBL)

• Global swath pressure fields for QuikScat swaths (with global I-PBL model) (2005)

• Surface stress fields from PBL_LIB corrected for stratification effects along all swaths (2006)

R. A. Brown 2005 AGU

Station B

2 - 5 km

Hazards of taking measurements in the Rolls

Station A

1-km

RABrown 2004

U

V Mean Flow Hodograph

Z/ 1

2

3

The Mean Wind

The OLE winds

Hodographfrom center zone

Hodographfrom convergent zone

The solution for the PBL boundary layer (Brown, 1974, Brown and Liu, 1982), may be written

U/VG = ei - e –z[e-iz + ieiz]sin + U2

where VG is the geostrophic wind vector, the angle between U10 and VG is [u*, HT, (Ta – Ts,)PBL] and the effect of the organized large eddies (OLE) in the PBL is represented by U2(u*, Ta – Ts, HT)

U/VG ={(u*), U2(u*), u*, zo(u*), VT(HT), (Ta – Ts), }

Or U/VG = [u*, VT(HT), (Ta – Ts), , k, a] = {u*, HT, Ta – Ts},

for = 0.15, k= 0.4 and a = 1

Since: VG = (u*,HT, Ta – Ts) n(P, , f)

Hence P = n [u*(o , k, a, ), HT, Ta – Ts, , f ] fn(o)

This may be written:

In particular,

R. A. Brown 2005 AGU

1980 – 2005: Using surface roughness 1980 – 2005: Using surface roughness as a lower boundary condition on the as a lower boundary condition on the PBL, considerable information about PBL, considerable information about the marine atmosphere and the PBL the marine atmosphere and the PBL has been inferred from satellite data.has been inferred from satellite data.

The symbiotic relation between surface backscatter data and the PBL model has been beneficial to both.

• The PBL model has established superior ‘surface truth’ winds and pressures for the satellite model functions.

• Satellite data have shown that the nonlinear PBL solution with Organized Large Eddies (OLE) is observed most of the time.