R. A. Brown 2003 U. Concepci Ó n

High Winds Study - Motivation UW PBL Model says U 10 > 35 m/s Composite Storms show high winds Buoy limits: <24 m/s Effects: Weather forecasts, Climatic Fluxes and heat balances R. A. Brown 2003 U. Concepci Ó n

Topics of Discussion Explanations for the Observations, or Lack of Observations Explanations for Lack or Presence of High Winds in various Models New observations, models R. A. Brown 2003 U. Concepci Ó n

What about High Winds? U 10 > 25 m/s, > 40 m/s > 55 m/s ……. R. A. Brown 2003 U. Concepci Ó n

NSCAT Revelation There exist large regions of High Winds (1000km 2 /storm) that nobody knows of…… These do not appear in: GCM analyses Buoy data Climate data Satellite data R. A. Brown 2003 U. Concepci Ó n

High Winds Study - Motivation High Marine Surface Winds do not appear in: –Buoy data (U < 23 m/s) –Climate records –General Circulation Models –Satellite sensor algorithms High Marine Surface Winds do appear in: –Ocean Meteorology Ship reports –Dedicated Airplane PBL Flights –Dropsondes in Hurricanes –A PBL model that includes OLE Higher winds imply: – higher heat fluxes in climatology – higher ocean stress --- revised ocean mixed layer models. R. A. Brown 2003 U. Concepci Ó n

The Measurement of very high winds Some Met. Ship records have sustained winds ~ 45 m/s. About 2-3 events/year Some airplane measurements ~ 35 50’; ’; ’. Rare buoys ~ 45 m/s. Rare towers ~ 45 m/s. Pressure gradients V G ~ 60 m/s U 10 ~ 40 m/s R. A. Brown 2003 U. Concepci Ó n

Buoys No ocean measurements > 23 m/s Tilting in High Seas Displacement Height Effects Meteorology Ships Poor Surface ‘Truth’ Blocking effects of ship Height effects of masts R. A. Brown 2003 U. Concepci Ó n

10-m wind 3-m buoy R. A. Brown 2003 U. Concepci Ó n

R. A. Brown 03 The buoys in high winds, high seas Buoy ~ 3 m Sheltering: The high waves place the buoy in shelter and/or turbulent wake of the waves yielding low winds Displacement height: When surrounding topography is rough, the sensor is ‘displaced’ downward to reflect its lower position in a more turbulent boundary layer =lower winds Wave height ~ 10 m 10-m wind R. A. Brown 2003 U. Concepci Ó n

R.A. Brown, 1997, 2000 Planetary Boundary Layer Model Winds Comparison with Dropwindsonde Observations in Tropical Cyclones Robert A. Brown University of Washington Department of Atmospheric Science and Lixin Zeng E.W. Blanch Co. Minneapolis MN Case Studies R. A. Brown 2003 U. Concepci Ó n

Abstract The value of surface winds predicted by the University of Washington two-layer similarity planetary boundary layer (PBL) model are compared with NOAA/HRD GPS dropwindsonde observations and the surface wind analyses of a numerical weather prediction model. These three wind products compare fairly well at moderate wind speeds. However, at high wind speeds, the dropsondes see much higher winds than either model. When the dropsonde pressures are used to furnish input to the UW PBL model, the surface winds match the dropwindsonde observations considerably better. This is consistent with the unique characteristic of the UW PBL model accounting for the nonlinear effects of organized large eddies. These transport momentum and heat fluxes more efficiently than the smaller scale local turbulence, predicting higher winds with mesoscale variability. R.A. Brown, 1997, 2000 R. A. Brown 2003 U. Concepci Ó n

Comparisons Between Windfields and Dropsondes Hurricane 1 Hurricane 2 R. A. Brown 2003 U. Concepci Ó n

The surface wind speeds from the ECMWF analysis (+) and the UWPBL model (*) vs. the dropwindsonde observations. R. A. Brown 2003 U. Concepci Ó n

High Winds State-of-the-Art Summary –There are suggestions of high wind regions (1000s km 2 ) with corresponding high ocean stress and air-sea fluxes in theory and observations. –Surface “truth” measurements from ships of opportunity, buoys, current satellite algorithms and numerical models are deficient at high winds. R. A. Brown 2003 U. Concepci Ó n

The surface layer relation, hence U 10 {u*(  o )} works well. Global, smooth U 10 (x,y,t) are available †. CONCLUSIONS † The PBL relation with OLE, hence V G (  o ) or  P(  o ), works well. Global P(x,y,t) are available †. There is almost no surface truth --- buoy or GCM surface winds with U 10 > 25 m/s. The U 10 model function can be extrapolated to about 35 m/s. There are indications that  o responds to the sea state up to U 10 ~ 40 m/s., H-pol ~ 60 m/s? Climatological u* and heat fluxes need to be revised. The nonlinear equilibrium PBL model is right. R. A. Brown 2003 U. Concepci Ó n