OC3570 Operational Meteorology

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OC3570 Operational Meteorology
Analysis of Refractive duct trends during July
2002 Pt Sur cruise
LCDR John Daziens
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Project Definition
- Analysis of elevated surface ducting
conditions - Propagation impacts of surface
ducting conditions (AREPS)
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Standard Atmosphere vs. Surface Ducting
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Vaisala RS-80 specifications
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Data Analysis Part I
21 Rawindsonde profiles analyzed (Full Up
Downs)
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What affects refractivity?

• N is affected by temperature (T in degrees K),
  pressure (P in mbar) and humidity (vapor
  pressure, e, in mbar) in the following manner

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Properties
Modified Refractivity
The modified refractivity (M) is used to
determine how radar rays are bent relative to the
earths curvature where T is temperature in
K P is atmospheric pressure in mb e is
vapor pressure in mb z is height above the
surface in m
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NO SURFACE DUCTING
Elevated Duct
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Data Analysis Part II Determine Elevated Duct
Trends
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Downward Analysis (14 Rawindsondes)
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Data Smoothing Benefits
Up / Down Downward
Leg
Ambiguous Elevated Duct (800m)
SMALL Lower Level Duct
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Elevated Duct Height Analysis
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Elevated Duct Thickness Analysis
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EM Frequencies Trapped by Duct
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Propagation Modes Atmospheric EM Regions
Alt (km)
GROUND WAVE SKYWAVE SCATTERING
SPACEWAVE
400 300 200 150 100 50 0
Ionophere
Ionophere
Scatter Volume
SAT-COM
Ionosphere
Communication
Meteor scatter
Ducting(surface)
Line of site microwave
Ionoscatter 1500Km range
D-layer Daytime
Mesosphere
Stratosphere
Troposcatter 400 km range
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10 Mm 1Mm 100km
10km 1km 100m
10m 1m 10cm
1cm 1mm
Wavelength radio bands frequency
ELF VF VLF LF
MF HF VHF UHF
SHF EHF
30 Hz 300Hz 3KHz
30KHz 300KHz 3MHz 30MHz
300MHz 3GHz 30GHz
300GHz
CONTROLLING INFLUENCE - Number of free electrons
(N) in the IONOSPHERE
CONTROLLING INFLUENCE - Vertical variation of
pressure, temperature, and humidity (P,T,e) of
TROPOSPHERE
CONTROLLING INFLUENCE - Absorption by water vapor
and oxygen molecues in the TROPOSPHERE
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Trend Analysis

• Lowest elevation for
• significant ducting
• 100m Significant
• Thickness

190600Z 200300Z
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Significant Ducting Period
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Large Thickness High Elevation
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Large Thickness High Elevation
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(No Transcript)
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Trapping Layer Formation
Initial
T
After Subsidence
9.8 0K/km
Height
e
0
Vertical Velocity
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Surface Duct Detection Rawindsonde vs. Kite
Methods
Elevated Duct
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Conclusions

• Surface Ducting not evident from rawindsonde
  data (differs from 19July02 Kite Data).
• Diurnal variance of elevated duct height /
  thickness not indicated by analysis.
• Thickness maximum / elevation minimum
  corresponded to period of higher subsidence.