refractivity in the coastal atmospheric boundary layer
DESCRIPTION
Refractivity in the Coastal Atmospheric Boundary Layer. Stephen Burk and Tracy Haack Naval Research Laboratory Monterey, CA. Strength ( M). Height. top. Thickness (= top-base). base. Modified Refractivity, M. Refractivity in the Coastal Atmospheric Boundary Layer. . Q. Height. - PowerPoint PPT PresentationTRANSCRIPT
Refractivity in the Coastal Atmospheric Boundary Layer
Stephen Burk and Tracy HaackNaval Research Laboratory
Monterey, CA
Refractivity in the Coastal Atmospheric Boundary Layer
Hei
ght
Q
base
top
Strength (M)
Thickness (= top-base)
Modified Refractivity, M
Hei
ght
Potential Temperature &Specific Humidity
COAMPSTM 27km grid
Cook & Burk, 1992, BLM, 58, 151-159.Burk & Thompson, 1997, JAM, 36, 22-31.Haack & Burk, 2001, JAM, 40, 673-687.Burk, Haack, Rogers, & Wagner, 2003, JAM, 349-367.
INDIA
SAUDIARABIA
Wallops 2000EM PropagationField Experiment
from NSWCDD/TR-01/132
COAMPSTM Wallops Island
DTG: 10-12 Apr 2000 Triple nest: 27-9-3 km Vertical: 40 levels
10-m Winds/SLPSST/SLP
DMDZ/THETA
Hei
ght (
m)
x = 3 km
x = 27 km
April 10, 20001200 UTC
April 11, 20001200 UTC
April 12, 20001200 UTC
EDH(m)
RH(%)
T(0C)
U(m/s)
Dots = COAMPSTM forecast values
Ta
IR
Obs from Davidson, NPS
3 am LT10 Apr 2000
Norfolk*
Wallops
COAMPSTM SST and Ground Temperature
*284
297
COAMPSTM Sensible Heat Flux (W/m2);near surface streamlines
11 Apr 2000
3 am LT 3 pm LT
0
0
0
60
20
-20
400
20
60
40
20
0
0
0
0
20
-20
COAMPSTM Evaporation Duct Height (m)11 Apr 2000
3 am LT 3 pm LT
4
6 10
12
24
2
4
8
28
base
top
Strength (M)
Modified Refractivity, M
Hei
ght
hourly fields from 00 UTC 11 Apr-2300 UTC 12 Apr 2000
Animation of two 24h COAMPSTM forecasts of:40m(shaded); 50m streamlines; & dM/dz = 0 isosurface (white)
Horizontal: Evaporation Duct Height (shaded) & StreamlinesVertical: Potential Temperature (shaded & contoured)“Clouds”: Trapping Layer (DMDZ=0 isosurface)
0
1 km
North South
M Crossection
(a)
M CrossectionShaded with dM/dz
(b)
1800 UTC 12 Apr 2000 COAMPSTM
Looking toward SE across Tidewater PeninsulaRed Isosurface dM/dz = 157 M-units/km subrefractionWhite isosurface dM/dz = 0 M-units/km trapping layer
(c)
Mixing Ratio (g/kg), Shaded;Potential Temperature (K),contoured
1800 UTC 12 Apr 2000 COAMPSTM
Duct parameters from COAMPSTM
1800 UTC 12 Apr 2000Wallops Island
Duct Base Height (m) Duct Thickness (m) Duct Strength (M-units)
0
100
200
300
400
500
0
100
200
300
0
3
6
9
12
15
18
Summary
• COAMPSTM forecasts both evaporation ducts and elevated and/or surface based ducts
• To date, most modeling studies of refractivity/propagation have focused on subsidence dominated, strongly capped BL’s (e.g., CA coast in summer; Persian Gulf)
• Intensive Observation Periods of the Wallops-2000 propagation field experiment are addressed here using COAMPSTM at high resolution. Model refractivity will be inserted into propagation codes for comparison with prop measurements.
• New insights into refractivity structure in frontal regions are emerging
• Accurate forecasting of major synoptic features (e.g., frontal boundaries) can be of greater importance than extremely high model resolution in defining local refractive structure/ EM propagation conditions. Mesoscale ensembles may be very useful in this context.