Loading in 2 Seconds...

Comparison of C n 2 Estimations Using Ship, Rawinsonde, and Model Data

Loading in 2 Seconds...

- By
**oshin** - Follow User

- 418 Views
- Uploaded on

Download Presentation
## Comparison of C n 2 Estimations Using Ship, Rawinsonde, and Model Data

**An Image/Link below is provided (as is) to download presentation**

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

Comparison of Cn2 Estimations Using Ship, Rawinsonde, and Model Data

LCDR Richard M. Murphy, USN

14 MAR ’05

Operational Oceanography/OC2570

- Review Cn2 (little bit of math)
- Data Collection
- Analysis/Results
- Conclusions

- index of refraction (n), f(p,T,q)
- for optics n more dependent on T fluctuations, for RF propagation more dependent on q fluctuations
- importance of gradient wrt height

- Monin-Obukhov Similarity Theory (physical quantities scaled w/ turbulent fluxes of heat & momentum, sfc layer assumed horizontally homogeneous & stationary, fluxes assumed constant, can specify at single height)
- Cn2 = A2 CT2 + AB CTq + B2 Cq2 (where A & B are fcn’s of ∂n/∂T and ∂n/∂q, respectively)
- Cx2 = [x’(0) - x’(d)]2/d2/3
- scaled parameters u*, T* & q* are f(w’,u’,T’,q’)

- u* = uk/[ln(zu/L) – “stuff”] (“stuff” depends on atmospheric stability), similar eqn’s for T*&q*
- modified Matlab code from Prof. Guest to calculate optical Cn2 (runbulk.m, bulkland.m): changed zveg=0, CDn10 decrease by ½, iterative scheme to 0.5%
- one run w/ measured data (from rawinsonde z/u/Tair/press/RH, from UDAS SST/RHsfc)
- another run using combination of measured data & assumed 100% RHsfc (press from model or sat sounding [1000 or 1010 mbars])

- Rawinsondes: balloon-mounted RS80-15L’s recording time, wind dir/speed, temp, dew point, RH, pressure, height, ascent rate, refractivity, modified refractivity, & vapor pressure
- 10 launches over 4-day cruise logging lat/long
- used for simple plots of T&Td/ vs press & RH&NI/MI vs height
- data points for Prof. Guest’s Cn2 Matlab functions (zu, u, Tair, RH, press) [2nd data pt 15-23m]

- UDAS Ship data: continuous data feed from RV Pt Sur; recording date, GMT, lat/long, COG/SOG, T, press, RH, SST w/ IR & boom probe, and salinity
- used for SST & RHsfc data points for Prof. Guest’s Cn2 Matlab functions

- Model data: provided by Prof. Creasey; MM5 & 3km COAMPS(thanks Tara) soundings
- used lowest data points for Tair & press for Prof. Guest’s Cn2 Matlab functions

- Satellite data: GOES-15/16 Tair soundings (provided by Billy Roeting)
- used lowest data points for Tair & press for Prof. Guest’s Cn2 Matlab functions

COAMPS 6hr fcst, T0 OK, T should incr at 950mb, Td high

MM5 12hr fcst, high T0, no sfc inversion, opposite Td trend at sfc

COAMPS Analysis, T & T0 OK, Td low

MM5 6hr fcst, slight elev. inversion not on balloon, Td OK

MM5 6hr fcst, T high, Td starts OK but high

COAMPS Analysis, good T0, moist layer at 950mb at 910mb on balloon

MM5 12hr fcst, high T0, Td trend OK to 950mb

COAMPS 6hr fcst, T0 OK, T high, Td only good to 950mb

COAMPS Analysis, T0 OK, T OK to 920 mb, Td OK to same

MM5 6hr fcst, T0 good, Td good trend but high initial value

MM5 18hr fcst, T0 good trend but high, Td follows

COAMPS Analysis, similar to MM5

MM5 15hr fcst, T0 good but high T, Td same

COAMPS 9hr fcst, T0 good, high T values, Td high

MM5 21hr fcst, T0 good, T high, Td good trend but high

COAMPS 3hr fcst, T high, dry layer at 950mb not on balloon

Balloon/Ship Data

2/5 at 19Z

2/6 at 00Z

2/7 at 21Z

2/6 at 23Z

2/6 at 10Z

2/7 at 12Z

2/8 at 03Z

2/6 at 17Z

2/8 at 21Z

2/8 at 11Z

Balloon/Ship Data

2/6 at 17Z

2/8 at 11Z

2/5 at 19Z

2/7 at 21Z

2/7 at 12Z

2/8 at 03Z

2/6 at 10Z

2/6 at 23Z

2/8 at 21Z

2/6 at 00Z

Data Analysis

- MOS theory uses sfc layer bulk/avg. parameters, sfc layer should be approx. 10% of MBL (≈ 40-50m)
- trend in RH difference most closely approximated Cn2 trend
- lowest MM5 data points too high in atmosphere (1000 mbars [≈ 100-150m], i.e. outside sfc layer)
- some COAMPS data points probably within sfc layer (lowest reading 1010 mbars, [≈ 17-82m])
- lowest satellite data points too high in atmosphere (1000 mbars)
- good agreement between balloon/ship+measured sfc RH and balloon/ship+assumed sfc RH of 100%

Data Analysis

- somewhat good agreement (discounting outlier) of balloon/ship data & balloon/ship/sat data (measured sfc RH)
- MM% & COAMPS model runs not same fcst times, should parallel as closely as possible

- spatial comparison skewed due to different dates/times, need line of buoys/balloons for time series, would also show Cn2 spatial trends toward shore (cross-coast?)

- could utilize ship-mounted scintillometer as baseline instead of measuring specific parameters and then calculating in an equation (along a linear path to/from shore - ship limited to visual range though)

Applications

- communications to units inland (ranges, interference)
- coastal radar coverage on small boats
- lasing targets inland (SpecOps)

References

Abahamid, A., Jabiri, A. et al, 2003: Optical Turbulence Modeling in the Boundary Layer

and Free Atmosphere Using Instrumented Meteorological Balloons. Astronomy

and Astrophysics, 416, 1193-1200.

Davidson, K.L., Schacher, G.E., Fairall, C.W. and A.K. Goroch, 1981: Verification of the

Bulk Method for Calculating Overwater Optical Turbulence. Applied Optics, 20,

no. 17, 2919-2923.

Davidson, K.L. and C. H. Wash, 1998: Describing Coastal Optical Properties with In Situ

and Remote Measurements. Naval Research Reviews, Two, 2-7.

Frederickson, P.A. and K.L. Davidson, 1999: Estimating the Refractive Index Structure

Parameter (Cn2) Over the Ocean Using Bulk Methods. Journal of Applied

Meteorology, 39, 1770-1783.

Hutt, D.L., 1999: Modeling and Measurements of Atmospheric Optical Turbulence Over

Land. Optical Engineering, 38, no. 8, 1288-1295.

Porch, W.M., Neff, W.D. and C.W. King, 1987: Comparisons of Meteorological

Structure Parameters in Complex Terrain Using Optical and Acoustical

Techniques. Applied Optics, 27, no. 11, 2222-2228.

Rachele, H. and A. Tunick, 1993: Energy Balance Model for Imagery and

Electromagnetic Propagation. Journal of Applied Meteorology, 33, 964-975.

Raj, P.E., Sharma, S., Devara, P.C.S. and G. Pandithurai, 1992: Study of Laser

Scintillation in Different Atmospheric Conditions. Journal of Applied

Meteorology, 3, 1161- 1167.

Download Presentation

Connecting to Server..