Analysis of Refractivity Analysis of Refractivity Measurements: Progress and PlansMeasurements: Progress and Plans

FrFrédéric Fabryédéric Fabry

McGill UniversityMcGill University

MontréMontréal, Canadaal, 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

Refr

act

ivit

y

Time

Station data vs radar field average

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

New runField 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 MoisteningRain accumulation two days before next event; foggy next day

Examples: BL Moistening

No wind (!)No wind (!)MaximizesMaximizes

local effectslocal effects

Sunny, cool, calm morning; will warm quickly

Anomalouspropagation

echoes

Q: Can the Moisture Flux Be Computed?

Assuming vertical homogeneity:

Precipitable water change

in BL

SthX

ttPWtPWtt

hUt

hU

tPWttPWttFlux

2

)()(

2

)()()()()(

Horizontal windAdvection

i

ii Pg

qPW

Verticaladvection

(BL growth)

From radar refractivity N

Height of the Boundary Layer from FM-CW Profiler radar

5min

from Sounding, FM-CW Radar, MIPS

13:52z 17:32z

q(g/kg) θv(K) V(m/s)

+++++ FM-CW+++++ MIPS

Hour (UTC)

take the FM-CW as representative of the whole domain

Mean Depth of MBL

AG

L H

eig

ht

(m) 1500

1000

500

646m

Q: Can the Moisture Flux Be Computed?

ISFF

Moisture Flux : Comparisons

RadarISFF

Time variability of humidity in the free atmosphere swamped the flux signal. Too bad…