NASA Technical Reports Server (NTRS) 20180000532: On the Limitations of Variational Bias Correction

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by  NASA Technical Reports Server (NTRS)

On the limitations of variational bias correction
Isaac Moradi1,2, Will Mccarty1, Ronald Gelaro1
1. GMAO/GSFC/NASA, 2. ESSIC, University of Maryland
98thAMSAnnualMeeting|7–11January2018
AustinConventionCenter|Austin,TX,U.S.A
January 10, 2018
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io 8, 517–540, 2015
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of tropical RH in the
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lower and middle
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troposphere
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No reliable water vapor measurements io
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Uncertainties in our knowledge of the tropospheric humidity
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e TitlePage
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factors influencing the amount of water vapor
Abstract Introduction
concentration of water vapor in many regions of the atmosphere |
trend of tropospheric water vapor D Conclusions References
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No reliable long-term data record u
Tables Figures
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MERRA ECMWF GPS-RO (cid:74) (cid:73)
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Winter Summer r
300 hPa | Back Close
Vergados et al., AMTD, 2015
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Figure 3. Same as Fig. 2, but for the middle-to-upper troposphere. s
IsaacMoradi (98thAMSAnnualMeeting) OnthelimitationsofVarBc January10,2018 2/19 s Printer-friendlyVersion
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538 |
MW Water Vapor Channels
Left: Era Interim, Right: MERRA-2; Top: MHS Chan 3, Bottom: MHS Chan 4
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MW Water Vapor Channels
IsaacMoradi (98thAMSAnnualMeeting) OnthelimitationsofVarBc January10,2018 4/19
Variational Bias Correction
Cost function for 3D-Var Data Assimilation:
Jb Jo
(cid:122) (cid:125)(cid:124) (cid:123) (cid:122) (cid:125)(cid:124) (cid:123)
1 1
J((cid:126)x) = ((cid:126)x −x(cid:126) )TB(cid:126)−1((cid:126)x −x(cid:126) )+ (H((cid:126)x)−(cid:126)y)TR(cid:126)−1(H((cid:126)x)−(cid:126)y)
b b
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y = Tb+(cid:15) +(cid:15)
r s
(cid:15) is the random error (R) and (cid:15) is known as observation bias or
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representativeness error that is taken into account using the variational
bias correction:
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(cid:15) = (cid:80) β p +bangle
s k k
k=1
The control variables (p ) include cloud liquid water (CLW); temperature
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lapse rate; and the square of the temperature lapse rate.
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Change in ECMWF Model Resolution
Difference between obs and ana/fg MHS MetOp-A Observations
IsaacMoradi (98thAMSAnnualMeeting) OnthelimitationsofVarBc January10,2018 6/19
Change in ECMWF Model Resolution
IsaacMoradi (98thAMSAnnualMeeting) OnthelimitationsofVarBc January10,2018 7/19
Variational Bias Correction
IsaacMoradi (98thAMSAnnualMeeting) OnthelimitationsofVarBc January10,2018 8/19
Heterodyne MW Receivers
(a)
er RF RF
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ν ν -ν ν ν +ν
IF LO IF LO LO IF
(b)
er IF RF RF
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ν1ν2 ν-O2 ν-O1 νLOν+O1 ν+O2
νL νL νL νL
frequency
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Uncertainty in Antenna Emissivity
IsaacMoradi (98thAMSAnnualMeeting) OnthelimitationsofVarBc January10,2018 10/19