MWR and MWR3C data during MAGIC
M. P. Cadeddu Argonne National Laboratory
First MAGIC Science Workshop, May 5-7, 2014, Brookhaven National Laboratory, Upton, NY, 11973
OVERVIEW
• Overview of MWR and MWR3C instruments
• Data availability
• Instrument calibration
• Retrievals
• Summary
MWR and MWR3C
MWRMWR3C MWR3C rain sensor
MWR
2- frequencies: 23.8 and 31.4 GHzNo azimuth scanningTime resolution ~ 1/20 s in LOS mode and ~1/50s in tip modeCalibration performed using ‘tip curves’Measurements: Sky brightness temperaturesPhysical quantities: Retrieved precipitable water vapor and liquid water path
MWR3C
3- frequencies: 23.834, 30, 89 GHzTime resolution ~ 1/20 s - Azimuth scanning possibleCalibration performed using ‘tip curves’Measurements: Sky brightness temperaturesPhysical quantities: Retrieved precipitable water vapor and liquid water path. Increased sensitivity to small amounts of liquid water.Embedded accelerometer for accurate pointing readings
DATA AVAILABILTIY
MWR
MWR3C: No data until 2012/11/15
CALIBRATION
The MWR and MWR3C use the cloudless sky as a reference to calibrate the noise diode.
Calibration is achieved by plotting airmass vs. opacity and extrapolating the line to airmass zero. Bilateral scan to collect points at different airmasses.
The radiometer needs to be leveled and the pointing accuracy needs to be know within fractions of degrees.
MWR CALIBRATION (continued…)
Mounting the radiometer on a ship causes multiple negative effects due to:
1) Ship listing 2) Ship movement (pitch, roll)
Listing cannot be easily corrected but its effect can be minimized by frequently checking the alignment of the radiometer. Its effect is a deterioration in the calibration.
Expecte
d pointing during ca
libration sc
an
Actual pointing during calibration scan
• Pitch and roll can be corrected if navigation data are available.
• New calibration software was developed to post-processed the data when the navigation data were available.
• Because the MWR needs to scan to low angles we couldn’t use the small angle approximation (θ=p2+r2).
CALIBRATION (continued…)
p
y
r
V
X
Y
Z
Vo
0
o
ε0
v=YPRv0 Y=0
MWR CALIBRATION (continued…)
Equivalent zenith brightness temperature difference between two sides of the scan
RETRIEVALS
ARM provides statistical and physical retrievals of LWP and PWV
Statistical retrievals available in real-time.• MWR linear regression • MWR3C neural network
Physical retrievals MWRRET (not yet available for MAGIC)
PWV RETRIEVALS
MWR STAT
MWR3C NN-Archive
MWR3C NN-reproc
LWP RETRIEVALS-ALL
MWR STAT
MWR3C NN-Archive
MWR3C NN-reproc
LWP RETRIEVALS CLEAR SKY
MWR STAT
MWR3C NN-Archive
MWR3C NN-reproc
RAIN MITIGATION
RAIN MITIGATION (continued)
SUMMARY
MWR and MWR3C data available through most of the deployment
Calibration was corrected for the MWR the MWR3C has embedded accelerometer
MWR statistical retrievals (mwrlos) have high uncertainty (flagged yellow)
MWR3C NN neural network retrievals will be reprocessed with new NN coefficients
Physical retrievals MWRRET are not yet available for MAGIC (may be available upon request from PI)
Care should be used when data are used during rain
For questions or any concern with the data email me [email protected]
For details on ARM microwave radiometer:
M.P. Cadeddu, J.C. Liljegren, D.D. Turner: The Atmospheric Radiation Measurement (ARM) program network of microwave radiometers: instrumentation, data, and retrievals, Atmos, Meas. Tech., 6, 2359-2372, 2013.
THANK YOU
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