M. Goldberg
NOAA/NESDIS
Z. Cheng (QSS)


Review

Strategy for using N16 and N15

Comparisons between N16 and N15 observations.

Retrieval Results


Daily, Pentad and Monthly 1x1 grids
- ascending/descending
- July 1998 to present

Products
- Limb adjusted brightness temperatures
- Temperature profile from 0.1 mb to 1000 mb
- Total Precipitable Water – ocean only
- Cloud Liquid Water - ocean only

Accuracy ~ 1.5 K over 3 km layers

Ecmwf forecast - AMSU-A retrieval @ 3mb
Bias = -4.34 , Sdv = 3.4 September 18, 2001
(HALOE -0.25 K, 2.2 K)

ch13
-2.6, 1.35
-.08, 0.26


Algorithm is constant.

Coefficients are not updated.

As a result:
- trends/changes are due to changes in the atmosphere and not due to changes in algorithm or coefficients.


Limb adjust brightness temperatures

Linear regression to solve for atmospheric temperature

Coefficients:
- July 1998 -- limb adjustment coefficients
- July 1998 – Dec 1998 collocated radiosondes to derive regression coefficients
- Synthetic regression used above 10 mb.

Strategy for consistent climate quality NOAA-15
& NOAA-16 AMSU-A temperature product

Goal: To ensure that differences between N15 and
N16 AMSU-A temperature retrievals are due only to atmospheric differences.

Requirements:
- Retrieval coefficients are the same (synthetic).
- All empirical coefficients are from the same time period.
- Compute offsets between N15 and N16


Reconfirmed that asymmetry in AMSU-A exists.

It is different in NOAA-15 and NOAA-16

Differences between NOAA-16 and NOAA-15 are generally small --- especially near nadir.

Differences increase if antenna corrections are applied .

AMSU N16 Asymmetry
4
3
2
1
0
-1
-2
-3
-4
1 2 3 4 5 6 7 8 9
AMSU fov #
10 11 12 13 14 15
1
2
3
15

AMSU N15 Asymmetry
4
3
2
1
0
-1
-2
-3
-4
1 2 3 4 5 6 7 8 9
AMSU fov #
10 11 12 13 14 15
1
2
3
15

AMSU N16 Asymmetry
4
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
-0.2
1 2 3 4
5
6
7
8
9
10
5 6 7 8 9
AMSU fov #
10 11 12 13 14 15 11
12
13
14

AMSU N15 Asymmetry
4
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
-0.2
1 2 3 4
5
6
7
8
9
10
5 6 7 8 9
AMSU fov #
10 11 12 13 14 15 11
12
13
14

AMSU N16-N15 Brightness Temperatures
4 13
3
5
2
6
1
7
0
8
9
-1
10
-2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
11
14
12

AMSU N16-N15 Antenna Temperatures
4 13
3
2
1
0 8
9
-1
10
-2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 11
12
5
6
7
14


Generated annual mean limb adjusted brightness temperature field for both N15 and N16 (Nov 00. –
Oct. 01)

Offsets should be independent of satellite observing time

Averaged ascending/descending for N15 -- mean time of 1:30 pm and compared with ascending N16 data.

Averaged ascending/descending for N16 -- mean time of 7:30 am and compared with descending N15 data.

7
8
5
6
3
4
1
2
9
10
11
12
13 channel n15all – n16asc n15desc – n16all
0.43
0.75
0.54
0.01
0.03
-0.26
0.08
0.14
0.13
0.08
0.14
-0.44
-0.71
0.36
0.7
0.48
-0.03
0
-0.3
0.04
0.13
0.13
0.03
-0.02
-0.7
-1.01
15 0.29
0.11

NOAA 15 NOAA 16 no offsets

NOAA-15 Adjusted NOAA-16


NOAA-16 and NOAA-15 retrievals

Algorithm is very robust and retrievals are accurate.

Model independent retrievals are very important for validating model dependent analyses and climate prediction models.

Microwave observations are very important for monitoring temperature.

New microwave sounders are on the horizon
(SSMIS, ATMS, CMIS).