RAIN IMPACT MODEL (RIM) FOR AQUARIUS
Andrea Santos-Garcia1, Maria M. Jacob2, Linwood Jones1, and William Asher3
1 Central Florida Remote Sensing Lab., University of Central Florida, Orlando, FL2 Comisión Nacional de Actividades Espaciales, Argentina
3 Applied Physics Laboratory, University of Washington, Seattle, WA
INTRODUCTION– Impact of rain on the AQ Sea Surface Salinity have been
investigated• For several months of 2012• Over the ITCZ
– AQ Rain Accumulation (RA) product based on CMORPH is used for all comparisons
• Global coverage between ±60°lat• Every 0.5 h
− Spatial integration over AQ IFOV• Assumes circular foot print of 100 km• Uses 13 x 0.25° boxes • weighted average based on antenna beam efficiency
INTRODUCTION – cont.
₋ Ancillary paramenters provided are:• BF (Rain Beam Fill Fraction): area weighted percentage of the beam that
exceeds a threshold of 0.25 mm/hr• PS (Probability of Salinity Stratification): normalized ΔSSS per orbit
between RIM at 10 m and RIM at 0.005 m
₋ The Rain Impact Model (RIM) is an overlay for the AQ-L2 product
₋ RIMSSS (SSS based on RIM) is an empirical model that estimates the SSS under rainy conditions at 0.005 meters depth.
• Model is superposition of rain events using 1D stratification model
• Uses HYCOM as initialization
APPROACH
0 5 10 15 20
32.5
33
33.5
34
34.5
35
Salinity @ 0.005 m in time
Time
Salin
ity [p
su]
Stratification Performance for one single Rain Event
32 32.5 33 33.5 34 34.5 350
0.5
1
1.5
2
Model @ 0.005 m = ½ cmModel On Time
Dep
th [m
]
-20 -15 -10 -5 0 5
32.5
33
33.5
34
34.5
Superposition Model for Multiple Rain EventsDuring last 24 Hours
ToTime
Salin
ity [p
su]
Depth = 0.5 cm
HYCOM Vertical Difussivity
Rain ImpulseFunctions
RESULTS
CONCATENATED RESULTS
32 33 34 35 3632
33
34
35
36
-2 -1 0 1-2.5
-2
-1.5
-1
-0.5
0
0.5
1
AQSSS [psu]
AQanomaly
RIM
anom
aly
RIM
SSS [p
su]
AQanomaly = AQSSS – HYCOMmean RIManomaly = RIMSSS – HYCOMmean
RAIN & NON-RAIN RESULTS
0 50 100 15032
34
36
50 100 150 200 250 300 35032
34
36
0 50 100 150-2
-1
0
1
50 100 150 200 250 300 350-2
-1
0
1
AQsss HYCOM anomaly
0 50 100 15032
34
36
50 100 150 200 250 300 35032
34
36
0 50 100 150-2
-1
0
1
50 100 150 200 250 300 350-2
-1
0
1
AQsss
SamplesSamples
NO PRESENCE OF RAIN WITH PRESENCE OF RAIN
AQ anomaly
RIM anomaly
AQ anomaly RIM anomaly
HYCOM anomaly
Non-rain case: Rain < 0.05 mm/hr
CROSS CORRELATIONS
PROBABILITY OF STRATIFICATION
-2 0 2 4 6 8 10 12 1432
34
36cross correlation=0.9148/0.91936
-2 0 2 4 6 8 10 12 140
5
10
-2 0 2 4 6 8 10 12 140
10
20
-2 0 2 4 6 8 10 12 140
5
10
-2 0 2 4 6 8 10 12 140
5
-2 0 2 4 6 8 10 12 14-2
0
2x 10
-4
-2 0 2 4 6 8 10 12 140
0.5
1
-2 0 2 4 6 8 10 12 1432
34
36cross correlation=0.9148/0.91936
-2 0 2 4 6 8 10 12 140
5
10
-2 0 2 4 6 8 10 12 140
10
20
-2 0 2 4 6 8 10 12 140
5
10
-2 0 2 4 6 8 10 12 140
5
-2 0 2 4 6 8 10 12 14-0.1
0
0.1
-2 0 2 4 6 8 10 12 140
0.5
1Salin
ity [p
su]
AQsss
●HYCOM
RIMsss
Latitude
◊ Previous HYCOM
RIM10 m- RIM0.005 m
Prob
abili
tyO
f Str
atific
ation
Threshold
SUMMARY
• The salinity gradient (surface to 1 – 2 m depth) is time dependent and depends upon the rainfall accumulation • In our analysis we find no evidence of SSS radiometric retrievals errors due
to rain effects• The analysis of AQ SSS measurements in the presence of rain,
requires careful interpretation to account for near-surface salinity stratification
• A beta version of our AQ Rain Impact Model product will be upload to PODAAC next week– We solicit constructive criticism for our AQ RIM and seek collaboration with
ocean modelers