The Satellite

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Surface Pressures from Space
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The Satellite PBL Model calculation 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.

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

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The PBL Model (surface winds to pressures
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State of The analytic solution for a PBL
fV K Uzz - pz /? 0 fU - K Vzz pz
/ ? 0 The solution, U (f, K,?p ) was found by
Ekman in 1904.
Unfortunately, this was almost never observed.
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 scale was difficult to
observe.
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)
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SLP from Surface Winds

• UW PBL similarity model
• joins two layers
• The nonlinear Ekman solution

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
G
(UG) ?P(U10) ? P(U10)
There is extensive verification from ERS-1/2,
NSCAT, QuikSCAT
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The nonlinear solution applied to satellite
surface winds 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
ltVG, U10gt 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
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• 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

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R. A. Brown 2005 AGU
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Dashed ECMWF Solid UW-Quikscat
The UW PBL Model is now global
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Surface Pressures
QuikScat analysis
ECMWF analysis
J. Patoux R. A. Brown
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To get smooth synoptic wind fields from a
scatterometer
Raw scatterometer winds
JPL Project Local GCM nudge smoothed Dirth
(with ECMWF fields)
UW Pressure field smoothed
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Pressure Fields used in NCEP Forecast Analyses
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a
b
996
991
999
996
OPC Sfc Analysis and IR Satellite Image 10 Jan
2005 0600 UTC
GFS Sfc Analysis 10 Jan 2005 0600 UTC
c
d
984
982
UWPBL 10 Jan 2005 0600 UTC
QuikSCAT 10 Jan 2005 0709 UTC
14
GFS 08 Jul 2005
OPC 08 Jul 2005
1003
996
996
b
a
UWPBL 08 Jul 2005
QuikSCAT 08 Jul 2005
1001
992
c
d
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Some Conclusions
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• 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.

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• 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 worlds 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.

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• 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.

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Programs and Fields available onhttp//pbl.atmos.
washington.edu Questions to rabrown, neal
or jerome _at_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)

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Hazards of taking measurements in the Rolls

Hodograph from center zone
Hodograph from convergent zone
1-km
The OLE winds
Station A
3
2 - 5 km
U
2
The Mean Wind
Z/?
1
Station B
V
Mean Flow Hodograph
RABrown 2004
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The solution for the PBL boundary layer (Brown,
1974, Brown and Liu, 1982), may be written U/VG
ei ? - e ze-iz ieizsin ? 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)
This may be written
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
In particular,
Since VG ? (u,?HT, Ta Ts) ? ?n(?P, ?,
f) Hence ?P ?n u(?o , k, a, ?), ?HT, Ta Ts,
?, f ? fn(?o)
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1980 2005 Using surface roughness as a lower
boundary condition on the PBL, considerable
information about the marine atmosphere and the
PBL 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.

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Marine Weather from Satellites and PBL models

• Surface Winds Pressure Fields from Space
• The ability to extract surface pressure maps from
  satellite scatterometer data has been described
  in a series of papers since the 80s. The
  technique has been recently improved for the
  purpose of providing near real-time surface
  pressures for NCEP forecasters. The fields have
  proved more valuable to the forecasters than the
  raw QuikScat winds while providing more detail in
  the pressure fields than ever before.