Jan.30, 2007

Improvement of the microwave and infrared SSTs merging method

Futoki Sakaida (Tohoku Univ.)
Substitute for PI Professor Hiroshi Kawamura

SST Group activities of the year 2006
Continuation :- NGSST-O demonstration operation
New researches :- Version up of the MODIS SST algorithm- Development of satellite infrared and microwave SST merging method byDiscrete Wavelet Transform (DWT)- Coastal validation of AVHRR SST to develop the NGSST-Coastal(NGSST-C)

Papers :Hosoda et al., Algorithm and validation of sea surface temperatureobservation using MODIS sensors aboard Terra and Aqua in the western
North Pacific. J. Oceanogr. (in press)
Sakaida et al., Research and development of New Generation Sea Surface
Temperature for open ocean (NGSST-O) and its demonstration operation.
Submitted to J. Oceanogr.

NGSST-O demonstration operation & next
Responding to the GODAE satellite requirements for high-resolution
sea surface temperature (better than 10km and at least daily), we havedeveloped the new generation SST for open ocean (NGSST-O). It is
cloud-free, quality-controlled, daily SSTs which cover the western NorthPacific (13-63N, 116-166E) with the grid size of 0.05 degree and is
produced by merging the AVHRR, MODIS and AMSR-E SSTs.
Demonstration operation of the NGSST-O has been conducted since
September 2003. The NGSST operation system has been developed
through cooperation with JAXA and the other regional operational andR&D agencies. Its demonstration operation continues for more than 3-years without large gaps ofthe product generation.
During the NGSST-O operational demonstration, several merged SSTs, such as the MGDSSTby JMA (Kurihara et al., 2006), has been developed and put in operation. Our demonstration
operation has been leading the transition toward high-resolution SST products merging infrared andmicrowave satellite SSTs.
Near-future challenges are as follows. In the NGSST-O, we did not deal with the diurnal SSTvariations. However, several meteorological/oceanographic applications need six hourly SSTs,
which require explicit treatments of the diurnal SST variations. A challenge of the NGSST-O is toincrease its temporal resolution from one day to six hours. A majority of oceanographic users ofthe high-resolution SST are interested in coastal applications. Since coastal ocean phenomena
have finer temporal/spatial scales, the present NGSST-O (daily and 0.05 degree-gridded) is notsatisfactory for the coastal users. Research and development of NGSST-C (Coastal) are anotherchallenge, which is left for future studies.

New research 1 : SST merging by Discrete Wavelet Transform (DWT)- We works in close collaboration with Professor Guan, Ocean Remote
Sensing Institute, Ocean University of China, on this study.
- The method based on the wavelet analysis technique seems to be
useful for SST merging. The method can keep the oceanic front structure
sharper in the SST merging image.

The flow of the Discrete Wavelet Transform (DWT) merging method
Image-1 (AVHRR)

Merged SST Image

DWTA2

HD2

Decomposition

Merge
VD2

Image-2 (AMSR-E)

DD2AHD

VDDD

IDWT
ReconstructionComparison between OA and DWTObjective analysis (OA)

DWT- It is clear that the DWT method can keep fronts sharper.
- The DWT can not fill in the grids which have no IR and microwave SSTs

New research 2 : Coastal validation of the AVHRR SST# In the background of this study, there are two hopes for satellite SST retrieval inthe coastal seas.
- The first one is that the AVHRR/NOAA would be used to retrieve SST with lessthan 0.6C of RMS-E and within ±0.1C of bias in the coastal seas as well as theopen ocean around Japan.
- The second is that the NOAA's equations would be used in SST retrieval in thecoastal seas around Japan.
** In open ocean, the satellite SST retrieval system has been alreadyconstructed.
** The NOAA's equations are derived using the drifting-buoy measurementsin global open ocean.
** If the NOAA's equations work well in the coastal seas, the SST retrieval
could be simplified. We can use the existent system for the satellite, coastal
SST retrieval.
- Although there are several studies to show unfavorable results for our hopes, we
examine the NOAA's equation again using the high-quality match-up data verycarefully collected in the coastal seas around Japan.

Location of the coastal station (▲) and ferry (＋) with the image examples

Kanagawa
Tokyo

Hiroshima
36

Okinawa
Latitude (degN)

3330

Kouchi27

Miyazaki24
123126

129

132
135
Longitude (degE)

Kagoshima(Ferry)

138

141

Match up data (Coastal Station)● Match up condition :- Time difference is within ±30 minutes- Position difference (navigation accuracy) is within ±1 pixel● Specification & no. of match up data
Name

Table name in the insitu database

Hiroshima

Hiroshima_Kan6

Mooring buoy, WT at 2m, 1 hour

78

Kagoshima

Kagoshima_Ferry

Ferry, WT at 5m, 5 min.

216

Kanagawa

Kanagawa

Mooring buoy, WT at 3m, 10 min.

578

KouchiKouchi_Kuroboku

3 Mooring buoys, WT at 2m, 1 hour

181Miyazaki

Miyazaki_Umisachi

3 Mooring buoys, WT at 1m, 1 hour232

Okinawa

Okinawa_Nirai_Buoy

3 Mooring buoys, WT at 4m, 1 hour

88

Tokyo

Tokyo_Bay_Chiba_Touhyo

Monitoring post, Every 1m frombottom to surface (This study uses
the shallowest WTs as SST.), 1 hour

55

Specification

No. of data

- Total : 1428
- Period：Mar. 2001, May 2002～Dec. 2003
- Satellite : NOAA-16, -17- All coastal stations are located at south of 36N. This (no data at north of 36N) is a problem.

NOAA's operational equations ：Day NLSST Split :A1 T4 + A2 Tsfc ( T4 - T5 ) + A3 ( T4 - T5 ) ( secSZA - 1 ) + A4Night MCSST triple window :A1 T4 + A2 T3 + A3 T5 + { A4 ( T3 - T5 ) + A5 } ( secSZA - 1 ) + A6
NOAA-#

A1A2A3A4A5A6Day

0.911279

0.0808835

0.717441-247.389--Night0.257489

1.25364-0.502818

0.110607

1.12932-274.875

Day

0.936047

0.0838670

0.920848-253.951--Night

0.573174

1.12933-0.690623

0.0721864

1.66172-275.456

1617Tsfc : MCSST derived by NOAA

Result 1Coastal Station (NOAA-16, -17):

Drifting Buoy (NOAA-16 only):No.of data : 1428
Bias : -0.054℃
RMS-E : 0.72℃

No. of data : 917
Bias : -0.086℃
RMS-E : 0.62℃

Coastal Station

30302525201520151010550005101520

In-situ SST (degC)

Drifting Buoy

35

Satellite SST (degC)

Satellite SST (degC)3525303505101520

In-situ SST (degC)253035

SST difference (degC)

Result 2 (Coastal Station, Daytime)
Coastal Station - Daytime76543210-1-2-3

NOAA-16
NOAA-17030

60

90120

150

180

210240270300330360Days from Jan. 1NOAA-16
Coastal Station / Daytime

SZA<45SZA>45NOAA-17

No. of data

Bias(degC)

RMS-E(degC)

No. of data

Bias(degC)

RMS-E(degC)

Summer

167

0.48

0.92

810.42

1.07

Non-summer

197

-0.11

0.63

147

-0.15

0.44

Summer

71

0.08

1.08

50

0.25

0.98

Non-summer

134

0.08

0.62

95

0.25

0.67

SZA : Satellite Zenith Angle
Summer : June-Sept.
Non-summer : Jan.-May, Oct.-Dec.

|Bias|>0.2℃, RMS-E>0.7℃

Result 3 (Coastal Station, Nighttime)
Coastal Station - Nighttime

SST difference (degC)

210-1-2

NOAA-16-3

NOAA-17-4
030

60

90120150

180210240

270300330360Days from Jan. 1

Coastal Station /Nighttime

SZA<45SZA>45NOAA-16

NOAA-17

No. of data

Bias(degC)

RMS-E(degC)

No. of data

Bias(degC)

RMS-E(degC)

Summer40-0.10

0.39

32

0.17

0.37

Non-summer

91-0.500.68

111-0.45

0.61

Summer

27-0.400.56

21-0.020.23

Non-summer50-0.60

0.67

114-0.57

0.65

SZA : Satellite Zenith Angle
Summer : June-Sept.
Non-summer : Jan.-May, Oct.-Dec.

|Bias|>0.2℃, RMS-E>0.7℃

Summary and Conclusion
NOAA's equations have almost same performance, bias of 0.1℃ and RMS-E of 0.6℃, in SST
retrieval at the coastal seas around Japan,
NOAA-16
Coastal Station / Daytime

SZA<45SZA>45NOAA-17

No. of data

Bias(degC)

RMS-E(degC)

No. of data

Bias(degC)

RMS-E(degC)

Summer

167

0.48

0.92

810.42

1.07

Non-summer

197

-0.11

0.63147-0.15

0.44Summer

71

0.08

1.08

500.250.98

Non-summer

134

0.08

0.62

95

0.25

0.67

but, on condition that
(1) Daytime, (2) Non summer (Jan.-May, Oct.-Dec.), and (3) SZA < 45 deg.
Further investigation is need
- to examine the reason why the bias occurs,- to correct the nighttime negative bias,- to correct the daytime positive bias in summer.
In short, NOAA's equations are not for the coastal seas around Japan. It is necessary
to construct the system for the coastal validation.

Summary of today's presentation
Now we try to produce the another high-resolution SST for the coastal applications.
This presentation shows some results our research and development (R&D) studies.
Although our R&D is heading for trouble, we will reach the goal, slowly but surely.
New researches :- Version up of the MODIS SST algorithm- Development of satellite infrared and microwave SST merging method byDiscrete Wavelet Transform (DWT)- Coastal validation of AVHRR SST to develop the NGSST-Coastal(NGSST-C)