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