Detailed data format descriptions for the TOVS gridded radiances and analysed geopotential heights
Each dataset contains analysed atmospheric radiances from a number of radiance channels on a global grid for each day in a month. The radiances are for the following radiometer channels:
HIRS 2 Channel 1
HIRS 2 Channel 2
HIRS 2 Channel 3
HIRS 2 Channel 8
HIRS 2 Channel 9 [See
HIRS 2 Channel 17 [ Note 2
MSU Channel 23
MSU Channel 24
SSU Channel 25
SSU Channel 26
SSU Channel 27
The global grid is a regular latitude - longitude grid of grid length 5 degrees. There are 37 latitudes from 90 degrees N to 90 degrees S and 72 longitudes from 180 degrees W to 175 degrees E.
The radiances are obtained from analysis of radiances supplied on an orbital grid by NOAA/NESDIS (as described in Section 2.2 Stage 2.6).
Each day's data consists of 38 records. The first record contains header information about the data while the other 37 records contain the radiances. The days are in chronological order.
There are 1080 items in each record Each item is of type integer * 2. Note that data are scaled as indicated in Note 4.
Missing data are indicated by the value -32768.
The formats of the 38 records are given in the following sections:
ITEM NO. BYTE OFFSET DESCRIPTION COMMENTS
1 0 Grid Type 3 Global Grid
2 2 No of Columns in Grid 72
3 4 No. of Rows in Grid 37
4 6 1st Channel Number See Note 2
5 8 2nd Channel Number " " "
6 10 3rd Channel Number " " "
7 12 4th Channel Number " " "
8 14 5th Channel Number " " "
9 16 6th Channel Number " " "
10 18 7th Channel Number " " "
11 20 8th Channel Number " " "
12 22 9th Channel Number " " "
13 24 10th Channel Number " " "
14 26 11th Channel Number " " "
15 28 Not Used
16 30 Year/Month mm + (yy * 100)
(year = true year -
1990)
17 32 Day/Hour hh + (dd * 100)
18 34 Analysis time window 720 Minutes
19 36 Data Flat for 1st 0 = Invalid Data
Channel Number 1 = Valid Data
Items 20 to 30 are as Item 19 but for the other Channels. The order of the flags is the same as the order of the channel numbers.
ITEM NO. BYTE OFFSET DESCRIPTION COMMENTS
31 60 Hemisphere covered 0 = global
32 62 Number of fields of view 16
per record of orbital
radiance data used in
analysis
33 64 Number of radiance Variable
records used in analysis (0 - no data)
34 66 Spacecraft Code See Note 1
35 68 Search Radius used for 500 km
individual fields of
view in analysis
36 70 Search radius used for a 900 km
record of radiances used
in analysis
37 72 Analysis time window 720 Minutes
38 74 Background weighting in 0 = no background
hundredths
39 76 Number of grid points Variable, See Note 3
with no fields of view (2664 - no data)
within search radius.
40 78 Number of smoothing 25
vectors used in
smoothing analysed data
41 80 Not used
42 82 Not used
43 84 Not used
Items 44 to 1080 are not used and are set to 0.
The data is for row 1 (90 degrees N) of the lat-long grid.
ITEM NO. BYTE OFFSET DESCRIPTION COMMENTS
1 0 Not Used Set to -32768
2 2 Not Used Set to -32768
3 4 Not Used Set to -32768
4 6 1st Channel Radiance for See Notes 4 and 5
1st Longitude (180 degrees W)
Items 5 to 14 are the same as Item 4 but for the 2nd to 11th Channels.
15 28 Not Used
Items 16 to 30 are the same as Items 1 to 15 but for the 2nd longitude (175 degrees W) of the 90 degrees N latitude circle.
Similarly, Items 31 to 1080 are for the 3rd to 72nd longitudes (170 degrees W to 175 degrees E) respectively of the 90 degrees N latitude circle.
The format of each of these records is the same as that of the second record except that the data is for the 2nd (85 degrees N) to the 37th (90 degrees S) latitudes of the lat-long grid.
where :
n = 1 = TIROS-N 2 = NOAA-6 4 = NOAA-7 5 = NOAA-9 6 = NOAA-8 8 = NOAA-11
CHANNEL NUMBER CHANNEL 1 HIRS-2 Channel 1 2 HIRS-2 Channel 2 3 HIRS-2 Channel 3 8 HIRS-2 Channel 8 9 HIRS-2 Channel 9 [ See 17 HIRS-2 Channel 17 [ below 23 MSU Channel 23 24 MSU Channel 24 25 SSU Channel 25 26 SSU Channel 26 27 SSU Channel 27For certain periods HIRS-2 channels 9 and 17 are replaced by MSU channels 21 and 22.
CHANNEL SCALING FACTOR 1 X64 2 X64 3 X64 8 X64 9 X64 17 X4096 21 X262144 22 X262144 23 X262144 24 X262144 25 X64 26 X64 27 X64
True radiance value = radiance value in dataset / scaling factor.
where nn = Spacecraft Number = 01 for TIROS-N = 02 for NOAA-6 = 04 for NOAA-7 = 05 for NOAA-9 = 06 for NOAA-8 = 08 for NOAA-11 yy = Year - 1990 mm = Month G = Generation Number = 1 = Data from SSU Radiance Channels Only = 2 = Data from all Radiance ChannelsUsers should note that the monthly radiance dataset is constructed from daily radiance datasets. Each of these datasets has its own generation number. The generation number used in the monthly radiance dataset name is set equal to the most common generation number amongst the daily radiance datasets.
Each dataset contains analysed tropospheric and stratospheric geopotential heights on a global grid for each day in a month.
The heights are for the levels:
850, 500, 300, 200, 100, 50, 20, 10, 5, 2, 1 HPa
The global grid is a regular latitude - longitude grid of grid length 50. There are 37 latitudes from 90 degrees N to 90 degrees S and 72 longitudes from 180 degrees W to 175 degrees E.
The tropospheric heights (up to and including the 50 Hpa level) are obtained from an operational global analysis, while the stratospheric heights are calculated from the 100 Hpa operational analysis heights and sets of thicknesses on an orbital grid. The latter are retrieved from orbital radiances as measured by HIRS-2, MSU and SSU sounding units.
Each day's data consists of 38 records. The first record contains header information about the data, while the other 37 records contain the heights. The days are in chronological order.
There are 1080 items in each record. Each item is of type integer * 2. Data are scaled as indicated in Note 4.
Missing data are indicated by the value -32768.
The formats of the 38 records are as follows:
ITEM NO. BYTE OFFSET DESCRIPTION COMMENTS
1 0 Grid Type 3 - Global Grid
2 2 No of Columns 72
(longitudes) in Grid
3 4 No of Rows 37
(latitudes) in Grid
4 6 1st Pressure Level (Hpa) 1000 (not used)
5 8 2nd Pressure Level (Hpa) 850
6 10 3rd Pressure Level (HPa) 500
7 12 4th Pressure Level (Hpa) 300
8 14 5th Pressure Level (Hpa) 200
9 16 6th Pressure Level (HPa) 100
10 18 7th Pressure Level (HPa) 50
11 20 8th Pressure Level (HPa) 20
12 22 9th Pressure Level (Hpa) 10
13 24 10th Pressure Level 5
(Hpa)
14 26 11th Pressure Level 2
(Hpa)
15 28 12th Pressure Level 1
(Hpa)
16 30 Year/Month mm + yy * 100)
(Year = True Year -
1900)
17 32 Day/Hour hh + (dd * 100)
hh = 0 GMT before 3/8/79
12 GMT from 3/8/79
18 34 Analysis Time Window 720 Minutes
19 36 Data Flag for 1000 mb 0 = Invalid Data
1 = Valid Data
2 = Interpolated Data
3 = thicknesses
Items 20 to 30 are as Item 19 but for the other heights. The order of the flags is the same as the order of the pressure levels.
ITEM NO. BYTE OFFSET DESCRIPTION COMMENTS
31 60 Hemisphere Covered 0 - Global
32 62 Number of Fields of View 16
per Record of Orbital
Thickness Data used in
Analysis
33 64 Number of Thickness Variable
Records used in Analysis
34 66 Spacecraft Code See Note 1
35 68 Search Radius used for 500 km
Individual Fields of View
in Analysis
36 70 Search Radius used for a 900 km
Record of Thicknesses
used in Analysis
37 72 Analysis Time Window 720 Minutes
38 74 Background Weighting in 0 = No Background
Hundredths
39 76 Number of Grid Points Variable
with no Fields of View See Note 2
within search radius
40 78 Number of smoothing 25 (i.e. truncation at
vectors used in smoothing zonal wave 12)
analysis
41 80 Coverage Code See Note 3
42 82 Time of tropospheric data Usually, but not
always, the same as hh
in item 17
43 84 Interpolation of 50 Hpa 0 = Actual Data
data 1 = Interpolated Data
Items 44 to 1080 are not used and are set to 0
The data is for row 1 (900N) of the lat-long grid.
ITEM NO. BYTE OFFSET DESCRIPTION COMMENTS
1 0 Not Used Set to -32768
2 2 Not Used Set to -32768
3 4 Not Used Set to -32768
4 6 1000 Hpa heights for 1st Not Used. Set to
longitude (180 degrees W) -32768
5 8 850 Hpa heights for 1st See Note 4
longitude (180 degrees W)
Items 6 to 15 are the same as Item 5 but for pressure levels 500, 300, 200, 100, 50, 20, 10, 5, 2 and 1 Hpa.
Items 16 to 30 are the same as Items 1 to 15 but for the 2nd longitude (175 degrees W) of the 90 degrees N latitude circle.
Similarly, Items 31 to 1080 are for the other longitudes (170 degrees W to 175 degrees E) of the 90 degrees N latitude circle.
The format of each of these records is the same as that of the 2nd record except that the data is for latitudes 85 degrees N to 90 degrees S.
n = 1 = TIROS-N 2 = NOAA-6 4 = NOAA-7 5 = NOAA-9 6 = NOAA-8 8 = NOAA-11
0 = NMC + THK#3 Thicknesses (Global 1 = NMC Only (Global) 2 = UKMO(NH) + THK#3 Thicknesses (N Hemi) THK#3 100 Hpa + THK#3 Thicknesses (S Hemi) 3 = UKMO(NH) + THK#3 Thicknesses (N Hemi) THK#3 Thicknesses Only (S Hemi) 4 = UKMO(NH) Only 5 = THK#3 100 Hpa + THK#3 Thicknesses (Global) 6 = THK#3 Thicknesses Only (Global) 7 = No Data 8 = ECMWF + THK#3 (Global) 9 = ECMWF Only (Global) 10 = UKMO(GL) or UKMO(UM) + THK#3 (Global) 11 = UKMO(GL) or UKMO(UM) Only (Global)Where:
NMC = Analysed tropospheric heights (850, 500, 300, 100 and 50 Hpa) from NMC (Washington) THK#3 Thicknss = Analysed stratospheric thicknesses (100-20, 100-10, 100-5, 100-2 and 100-1 HPa) UKMO = Analysed tropospheric heights (850, 500, 300, 100 and 50 Hpa) from the Met Office operational analysis UKMO(NH) = For coverage codes 2, 3 and 4, the UKMO tropospheric heights were produced for the northern hemisphere only using the hemispheric Octagon model. UKMO(GL) = Before 12 June 1991, for coverage codes 10 and 11, the UKMO analyses were produced with the first global weather forecasting model (GL) at UKMO. UKMO(UM) = After 12 June 1991, for coverage codes 10 and 11, the UKMO analyses were produced with the new weather forecasting model at UKMO, the Unified Model (UM) THK#3 100 Hpa = Analysed heights at 100 Hpa from NMC (Washington) ECMWF = Analysed tropospheric heights (850, 500, 300, 100 and 50 Hpa) from ECMWF N Hemi = Data from 90 degrees N to approximately 20 degrees N S Hemi = Data from approximately 20 degrees N to 90 degrees S
M20.SnnHTS#3.YyyMmmG
where
nn = Spacecraft Number = 01 for TIROS-N = 02 for NOAA 6 = 04 for NOAA 7 = 05 for NOAA 9 = 06 for NOAA 8 = 08 for NOAA 11 yy = Year - 1900 mm = Month G = Generation Number = 1 Data from SSU Radiance Channels only = 2 Data from all Radiance Channels
The monthly heights dataset is constructed from daily heights datasets. Each of these datasets has its own generation number. the generation number used in the monthly heights dataset name is set equal to the most common generation number amongst the daily heights datasets.