OC3570 Operational Meteorology Analysis of Refractive duct trends during July 2002 Pt Sur cruise LCDR John Daziens

Project Definition - Analysis of elevated & surface ducting conditions - Propagation impacts of surface ducting conditions (AREPS)

Standard Atmosphere vs. Surface Ducting

Vaisala RS-80 specifications Sensor Type Range Accuracy Resolution Response/Lag Time Pressure (and Height) capacitive aneroid 1060 to 3 hPa 0.5 hPa 0.1 hPa Temperature capacitive bead -90 to 60 oC 0.2 oC 0.1 oC <2.5 sec Humidity (and Vapor Pressure) thin film capacitor 0 to 100% 2% 1% 1 sec

Data Analysis Part I * 21 Rawindsonde profiles analyzed (Full & “Up Downs”)

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:

Modified Refractivity Properties Modified Refractivity The modified refractivity (M) is used to determine how radar rays are bent relative to the earth’s 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

NO SURFACE DUCTING Elevated Duct

Determine Elevated Duct Trends Data Analysis Part II: Determine Elevated Duct Trends

Downward Analysis: (14 Rawindsondes)

Data Smoothing Benefits Up / Down Downward Leg Ambiguous Elevated Duct (~800m) SMALL Lower Level Duct

Elevated Duct Height Analysis

Elevated Duct Thickness Analysis

EM Frequencies Trapped by Duct

Propagation Modes: Atmospheric & EM Regions Alt (km) GROUND WAVE SKYWAVE SCATTERING SPACEWAVE 400 300 200 150 100 50 Ionophere Ionophere Scatter Volume SAT-COM Ionosphere Communication Meteor scatter Line of site microwave Ducting(surface) Ionoscatter 1500Km range D-layer Daytime Mesosphere Stratosphere Troposcatter 400 km range 10 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

Trend Analysis Lowest elevation for “significant” ducting 100m = “Significant” Thickness 190600Z 200300Z

Large Thickness High Elevation

Trapping Layer Formation Initial T After Subsidence Height 9.8 0K/km e Vertical Velocity

Surface Duct Detection: Rawindsonde vs. Kite Methods Elevated Duct

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.