Special Sensor Microwave Imager (SSM/I) Intersensor Calibration and Impact on Precipitation Trend

[email protected] 16, 2008

Special Sensor Microwave Imager (SSM/I) Intersensor Calibration and Impact on

Precipitation Trend

Song Yang, Fuzhong Weng, Banghai Yan, and Ninghai Sun

NOAA/NESDIS/STARCamp Springs, MD 20746

4th Workshop of International Precipitation Working Group (IPWG), Beijing, Oct 13-17, 2008


Outline

• Why need SSM/I TDR Calibration• SCO Calibration Technique• Impacts on TDRs/EDRs/CDRs• Impacts on Rainfall Climate Trend• Conclusions


Ascending Descending

Overall

SSM/I Oceanic Rain-free Ta Difference against Scan Central Pixel before Calibration (60°S-60°N)


SSM/I Monthly Oceanic Rain-free TDR Time Series

before Calibration

SSM/I Intersensor Bias of Oceanic Rain-Free Monthly Mean Ta

Ta (

K)

37V

Ta B

ias

(K)

Oceanic Rain-Free Monthly Mean Ta


F13 provides the stable and longest time series for inter-sensor calibration

SSM/I Orbit Draft


North Pole Region South Pole Region

DMSP Satellite SCO Intersections


Analysis of SCO Pixels Ta - Water t 30 sec & d 3 Km)

19H

22V

F11

F14

F14

F11

Std 5

F11

Std 2

F11

Std 2|Ta| 20

100 140 180 220 260 300 100 140 180 220 260 300 100 140 180 220 260 300 100 140 180 220 260 300


85 H

Bia

s °K

Std 2|Ta|

20

F13-F11 SCO Pixels Ta Bias (Water - with scan angle adjustment)

F13-F14 SCO Pixels Ta Bias - Water (t 30 sec & d 3 Km, with scan angle adj.)


19V 19H 22V 37V 37H 85V 85H Satellite

Surface Type Bias Bias Bias Bias Bias Bias Bias

W 0 0 0 0 0 0 0 0 0 0 0 0 0 0

L 0 0 0 0 0 0 0 0 0 0 0 0 0 0

I 0 0 0 0 0 0 0 0 0 0 0 0 0 0 F08

C 0 0 0 0 0 0 0 0 0 0 0 0 0 0

W -0.16 2.66 -0.12 2.19 -0.20 2.27 -0.16 1.42 -0.09 2.65 -0.30 1.61 -0.29 2.81

L 0.54 1.19 0.33 1.32 0.53 1.32 0.44 1.36 0.49 1.49 0.11 2.31 0.12 2.39

I -0.05 1.23 -0.03 2.01 -0.04 1.10 -0.04 0.91 0 2.13 -0.07 1.19 -0.09 3.96 F10

C 0.11 0.57 0.23 1.13 0.09 0.46 0.08 0.62 0.23 1.22 -0.02 1.20 0.10 1.28

W -0.56 0.55 0.09 1.07 -0.88 1.03 -0.34 0.55 0.39 1.58 -0.92 1.46 -0.17 1.10

L 0.02 1.01 0.21 1.05 -0.17 1.08 -0.19 0.96 0.01 1.04 -0.56 1.69 -0.62 1.56

I 0.23 0.90 0.35 0.98 -0.05 0.92 0.03 0.87 0.28 1.11 -0.26 2.01 -0.24 1.99 F11

C -0.10 1.83 0.21 2.50 -0.42 1.90 -0.07 1.82 0.19 2.58 -0.03 3.32 -0.03 3.49

W -0.43 0.64 0.32 0.54 -0.32 0.85 -0.81 0.45 0.21 0.63 -0.32 0.89 0.32 1.29

L 0 0.85 0.11 0.75 0.10 0.97 -0.42 0.67 -0.06 0.98 -0.01 1.54 0.23 1.30

I 0.06 0.76 0.25 0.87 0.13 0.91 -0.32 0.88 -0.05 0.83 0.23 1.32 0.43 1.33 F14

C 0.20 1.25 0.38 1.85 0.30 1.28 -0.08 1.16 0.25 1.73 0.39 2.67 0.74 2.86

W 0.42 0.65 -0.23 0.55 0.03 0.87 -0.17 0.51 -0.04 0.67 -0.05 0.87 -0.02 1.32

L 0.15 0.85 0.06 0.71 0.02 0.75 -0.02 0.59 -0.04 0.56 -0.02 0.81 -0.09 0.74

I 0.83 0.81 0.23 0.85 0.43 0.83 0.50 0.63 0.30 0.72 0.71 1.19 0.35 1.65 F15

C 0.16 1.10 -0.13 1.55 -0.07 1.08 0.12 1.10 0.09 1.64 0.33 1.91 0.41 2.30

Criteria: | t| 0.5 min; d 3 km; 2 K;Ta| 20 K; : Standard deviation (K) Surface Type Category: W Š Water; L Š Land; I Š Ice; C Š Coast

SSM/I TDR Bias Correction CoefficientsF13 as Reference Satellite


SSM/I Monthly Oceanic Rain-free TDR Time Series after Calibration (F13 as Reference Satellite)


Ta (

K)

37V

Ta B

ias

(K)

Bef

ore

Cal

ibra

tion


Ta B

ias

(K)

37V

Ta (

K)


Aft

er C

alib

rati

on



Before Calibration After CalibrationSSM/I Intersensor Bias of Oceanic Rain-Free Monthly Ta


19V 19H 22V 37V 37H 85V 85H

Ta_Raw (K)

0.59 0.31 0.65 0.59 0.33 0.77 0.85

Ta_Cal

(K) 0.30 0.38 0.48 0.21 0.19 0.40 0.39

Chg (%)

-49 22 -26 -64 -42 -43 -54

Mean SSM/I TDR Absolute BiasF13 as Reference Satellite


SSM/I Monthly Oceanic Rain-free TDR Trend (F13 as Reference Satellite)

Before C

alibration

After C

alibration

19V 19H 22V 37V 37H 85V 85H

S S S S S S S

Before 188.5 -0.92 125.2 -0.11 212.2 -0.74 208.3 -0.62 151.5 -0.18 251.8 -0.72 219.6 -0.46

After 188.2 -0.54 124.9 -0.23 211.9 -0.54 208.0 -0.58 151.4 -0.30 251.5 -0.36 219.3 -0.38

Comparison of SSM/I Monthly Oceanic Rain-free TDR before and after Calibration [(K), S (K/10yr)]


F14 SSM/I Monthly Mean Surface Rainrate for December 2006 from NOAA Heritage Rain Algorithm and Matched TRMM 3B42

BeforeCalib.

AfterCalib.

Matched3B42

0.5°x0.5°grid scale


F14 SSM/I Monthly Mean Surface Rainrates for December 2006 from NOAA Heritage Rain Algorithm

BeforeCalib.

AfterCalib.

Difference(aft - bef)

0.5°x0.5°grid scale

29% bias deduction with calibrated TDR against matched TRMM 3B42 Rain products


F14 SSM/I Monthly Mean Total Precipitable Water (TPW) for December 2006 from NOAA Heritage Rain Algorithm

BeforeCalib.

AfterCalib.

Difference(aft - bef)

11% bias deduction with calibrated TDR against radiosonde measurement


F14 SSM/I Monthly Mean Sea Ice Concentration (%) Near North Pole

Region for December 2006 from NOAA Heritage Algorithm

Before Calib. After Calib. Difference (aft - bef)


GPCP

Climate Trend of Monthly Precipitation from SSM/I and GPCP

SSM/I


Climate Trend of Oceanic Total Precipitable Water Path


The importance of SSM/I intersensor calibration is presented.

NOAA/NESDIS SCO-based calibration scheme can dramatically reduce the intersensor biases of SSM/I TDRs.

Test results indicate that the SSM/I TDR calibration scheme shows significant impacts on EDRs/CDRs.

Although the bias correction of SSM/I TDRs is small, the calibration has a significant impact on TDR’s trend.

The very small decreasing trend of precipitation is evident, however, this trend could not be treated as the “truth” because of uncertainties associated with the calibrations and SSM/I sampling issue.

Conclusions

Documents

Special Sensor Microwave Imager (SSM/I) Intersensor Calibration and Impact on Precipitation Trend