Transcript Fabry Anlysis of Refractivity Presentation

Analysis of Refractivity
Measurements: Progress and Plans
Frédéric Fabry
McGill University
Montréal, Canada
My IHOP-Related Objectives
• Comparisons of moisture estimates with
other sensors;
• Improvements to the refractivity extraction
code;
• Case analyses.
Comparisons of moisture estimates
Refractivity data is only in NCAR’s possession;
- buried within 1350 GB of S-Pol data files
- that have become available only since
January; downloadable a few GB a shot
 I do not have most of the refractivity data
 This aspect of the work has suffered
Comparisons of moisture estimates
Refractivity
Station data vs radar field average
Time
Improvements to Refractivity Code
Field code worked well, but difficult to use as
a reanalysis tool.
Three areas of focus:
• Improve input data to algorithm (better
calibration, more sophisticated data
selection…);
• Make it easier to change parameters;
• Try a whole new data fitting algorithm using
a variational approach.
Improvements to Refractivity Code
Field run
New run
• Sharper gradients, more noisy fields.
• Artifacts no longer hidden by smoothing.
• Also generated: Field of measurement error.
Rerun of IHOP campaign is in progress.
Cases Analyses
Current focus is on:
- Structure of fronts (moisture vs wind
fronts);
- The nature of the many moisture
discontinuities observed;
- ABL, in particular the time evolution of
moisture;
- Bore cases;
- The odd convection initiation (and lack of)
near S-Pol.
Examples: BL Moistening
Rain accumulation two days before next event; foggy next day
Examples: BL Moistening
Sunny, cool, calm morning; will warm quickly
Anomalous
propagation
echoes
No wind (!)
Maximizes
local effects
Q: Can the Moisture Flux Be Computed?
Assuming vertical homogeneity:
 PW (t )  PW (t  t ) 


 U (t )  U (t  t )  
2

 t  S

h
Flux (t )t  PW (t  t )  PW (t )   h


2
X
h


5min
Precipitable
water change
in BL
i
qi
PW   Pi
g
Horizontal wind
Advection
Vertical
advection
(BL growth)
From radar refractivity N
Height of the Boundary Layer
from FM-CW Profiler radar
Q: Can the Moisture Flux Be Computed?
from Sounding, FM-CW Radar, MIPS
13:52z
17:32z
AGL Height (m)
Mean Depth of MBL
1500
+++++ FM-CW
+++++ MIPS
1000
646m
500
q(g/kg)
θv(K)
V(m/s)
Hour (UTC)
 take the FM-CW as representative of the whole domain
Moisture Flux : Comparisons
ISFF
ISFF
Radar
 Time variability of humidity in the free atmosphere
swamped the flux signal. Too bad…