t1edr [ parameter=value ... ] [ inputfile ... ]
Parameters are: af_elevation, method, 1000mb_height, constant_height, wind, centered, satelxy, raindiag.
t1edr derives atmospheric temperature, height and wind profiles from the SSM/T1 TeraScan datasets output by the DMSP ingest functions rtdin and rdsin. t1edr implements the Air Force Global Weather Center (AFGWC) D-matrix algorithm to compute temperature and heights at standard pressure levels, along with the the tropopause temperature and pressure. In addition to the seven SSM/T1 brightness temperatures, the calculation takes into account the latitude zone, elevation, season and viewing angle of each SSM/T1 footprint. The geostrophic winds at the standard pressure levels and thermal winds between these levels are computed as diagnostics based on the derived heights.
The named input files must be SSM/T1 TeraScan datasets output from the DMSP ingest functions rtdin and rdsin. Thus, the input filenames must have the suffix ".t1_s", meaning SSM/T1 sensor dataset. Output filenames are generated to have the same form as the input filenames, except with the suffix ".t1_e", meaning SSM/T1 environmental dataset.
The output datasets contain essentially three dimensions: lines, samples and pressure levels. The number of lines depends on the length of the satellite pass being processed. The number of samples is fixed by the SSM/T1 to be 7 (see centered below). The number of pressure levels is 15. These denote the following fixed-pressure surfaces: 1000, 850, 700, 500, 400, 300, 250, 200, 150, 100, 70, 50, 30, 20 and 10 millibars. These pressure level values are stored in the one-dimensional output variable press_levels.
The temperature, pressure height and wind profiles, along with the layer thickness, are each stored as three-dimensional variables. The vertical dimension of the temperature, pressure height and geostrophic wind profiles is 15 levels, while for the thickness and thermal wind profiles, it is 14 layers. The first layer represents the layer between 1000 mb and 850 mb, the second represents the layer between 850 and 700 mb, and so on. A one-dimensional variable called press_midlevels contains linearly interpolated millibar values signifying the pressure at these layers. The output dataset also contains the following two-dimensional (lines and samples) variables: tropopause pressure, tropopause temperature, rain indicator (Boolean), zone, season, geography type, and elevation.
The zone values indicate:
Zone
----------------------------------
1 : Tropics (< 30 Degrees)
2 : Mid-latitudes
3 : High-latitudes(> 60 Degrees)
The season values indicate:
Season
------------
1 : Fall
2 : Winter
3 : Spring
4 : Summer
The geography values indicate:
Geography
---------------
1 : Ocean
2 : Land
3 : Ice
4 : Coast
Output datasets can be examined using the functions xvu, printvar, contents, burst, stats, etc.
If af_elevation=yes, then the AFGWC elevation dataset is used for the retrieval scheme. This dataset is stored in the form of an "1/8 meso-scale (mesh) grid". Each hemisphere contains 512 x 512 points, with the pole at the center of the grid; therefore the resolution is approximately 1/3 degree. The elevation at each SSM/T1 footprint is assigned the elevation of the grid point that has its center closest to the center of the sensor footprint. If af_elevation=no, then the elevation dataset is the etop05 topography dataset. This dataset is provided at 5 minute intervals over the globe; therefore, the grid contains (12 x 360) x (12 x 180) points (i.e., 1/12 degree resolution). See parameter method to specify options for assigning the elevation value to SSM/T1 footprints when using the etop05 dataset.
Valid responses are [yes or no]. The default is yes.
If af_elevation=no, then the value of method determines the manner in which the etop05 elevation values are assigned to individual SSM/T1 footprints. Since the size of the SSM/T1 footprint near nadir is about 175 km and the etop05 elevation dataset has a resolution of about 9 km (or less), several options are provided for specifying the elevations.
Use the elevation value closest to the sensor footprint center.
Use the mean of the elevation values within an area approximately the size of a SSM/T1 footprint at nadir.
Use the median of the elevation values within an area approximately the size of a SSM/T1 footprint at nadir.
Use the maximum elevation value within an area approximately the size of a SSM/T1 footprint at nadir.
Use the minimum elevation value within an area approximately the size of a SSM/T1 nadir footprint.
Note: processing time is least for method=center.
Valid responses are [center, mean, median, max, min]. The default is mean.
This parameter determines the way the 1000mb height is obtained. This height is the value which the atmospheric thickness are stacked onto to compute the standard pressure heights. If 1000mb_height=contant, then the user is prompted to provide the constant value (in meters). If 1000mb_height=nmc_clim, then the twelve-month global climatology from the National Meteorological Center's 10-year analysis is used. This dataset is on a 2.5 x 2.5 degree rectangular grid.
Valid responses are [constant or nmc_clim]. The default is constant.
If 1000mb_height=yes, then the value of this parameter specifies the height in meters of the 1000mb pressure surface for the profiles in the output dataset.
Valid responses are [>= 0]. The default is 110.0.
If wind=yes, then the geostrophic and thermal winds are calculated from the derived height profiles. The geostrophic winds at a given pressure level are based on the gradients of the height surface at that pressure level. The thermal winds for the layers between pressure levels are calculated as differences between the geostrophic winds at the layer above minus that at the layer below. (See Wallace and Hobbs, 1977). Note: no absolute wind information is available for the calculation so these geostrophic winds are relative, and thus not anchored to a given absolute "known" wind at a given pressure level. The wind variables are output as two components, "east" and "north" (see satelxy below).
Valid responses are [yes or no]. The default is no.
If centered=yes, then the numerical differential scheme to compute the geostrophic winds is the centered differencing scheme, except for edge points. If centered=no, then the differences are averages of two pairs of adjacent points.
Points 1,2,3,4 represent gridpoints. o represents the center grid point. 3 y centered=yes: 1o2 ^ 4 | -->x centered=no: 12 34If centered=yes, then the x derivative is determined from points 2 - 1, and the y derivative is determined from points 4 - 3. The output value is at location 'o' above. Thus the input grid and output grid are the same. If either the x or y derivative is missing then both components of the wind vector are set to missing. Edge lines and samples are calculated based on the 'o' point, and for example, the points 2 and 4 for the vector in the upper left corner of the image.
If centered=no, then the x derivative is determined from average of points 2 - 1 and points 4 - 3, and the y derivative is determined from average of points 3 - 1 and points 4 - 2. If only one pair of the two derivative differences is available, the difference is still computed. If either the x or y derivative cannot be calculated, then both components of the wind vector are set to missing. The output value is at a new point at the center of points 1, 2, 3, 4. Thus in this case, the output grid for the wind vectors has one less line and sample and is shifted by a half line and sample. This option provides a slightly smoother output and will usually result in fewer dropouts.
Valid responses are [yes or no]. The default is yes.
OPTIONAL. Instructs t1edr to output winds that are in satellite coordinates, with along track and along scan components, rather than east and north wind components. In this case, the wind variables have a naming convention of "scan" and "track", rather than "east" and "north".
The default value is no. This parameter can only be set by an explicit specification on the command line.
OPTIONAL. Instructs t1edr to print out diagnostic information for footprints which may be contaminated by precipitation.
The default value is no. This parameter can only be set by an explicit specification on the command line.
This example shows how to execute t1edr on an SSM/T1 dataset created in the manner shown in the EXAMPLES section of rtdin. For this example, raindiag was turned on, and the 1000mb height was set to 110 meters. The output indicates that two profiles may be contaminated by rain.
% t1edr raindiag=y
input file(s) : char(255) ? f11.92351.1415_t1_s
af_elevation : char( 3) ? [yes]
1000mb_height : char( 8) ? [constant]
constant_height: real ? [110]
wind : char( 3) ? [yes]
centered : char( 3) ? [yes]
Processing f11.92351.1415_t1_s
SSMT/1 data starts at 14:15:19.371 GMT on 92/12/16.
*** LIQ H2O > 0.5 KG/M**2 *** LAT= 42.5 LON=-134.9, Line= 12 Sample= 1,
Channel 1 Temp = 247.4, View Angle = 36, View = 4, Zone = 2,
Season = 1, Terrain Type = 1, Precip. Thresh = 245
*** LIQ H2O > 0.5 KG/M**2 *** LAT= 42.0 LON=-131.9, Line= 12 Sample= 2,
Channel 1 Temp = 244.2, View Angle = 24, View = 3, Zone = 2,
Season = 1, Terrain Type = 1, Precip. Thresh = 240
TDF data set f11.92351.1415_t1_e created.
Below is the description of the output dataset given by contents.
% contents f11.92351.1415_t1_e
printout : char( 3) ? [no]
Contents of File: f11.92351.1415_t1_e Page 1
Dimension Size Coord Scale Offset
mt1line 24 y 1 0
mt1samp 7 x 1 0
standard_levels 15 ? 1 0
standard_layers 14 ? 1 0
Attribute Type Units Value
projection long std_projection sensor_scan
et_affine double 1 0 0 1 0 0
satellite string12 f-11
sensor long std_sensor ssmt1
pass_date long std_date 92/12/16
start_time double std_time 14:15:19.371
time_adjust double std_time 00:00:00
attitude double radians 0 0 0
sensor_tilt double radians 0
scan_samples long 7
scan_rates double 0.03125 0.333333 -0.0698132
sensorient double radians 0 0.785398 0 0.628319
-0.628319
orb_elem_date long std_date 92/12/16
orb_elements double 0.237152 0.829383 4e-05
0.0012575 0.697166 0.72245
0.274848
history byte
Variable Type Units
temp_profile short kelvin
press_heights float meters
layer_thick float meters
press_levels float millibars
trop_temp short kelvin
trop_press float millibars
rain_flag byte
zone byte
season byte
geography_type byte
elevation short meters
geos_wind_east short m/s
geos_wind_north short m/s
thrm_wind_east short m/s
thrm_wind_north short m/s
Variable Dimension Size
temp_profile mt1line 24
temp_profile mt1samp 7
temp_profile standard_levels 15
press_heights mt1line 24
press_heights mt1samp 7
press_heights standard_levels 15
layer_thick mt1line 24
layer_thick mt1samp 7
layer_thick standard_layers 14
press_levels standard_levels 15
trop_temp mt1line 24
trop_temp mt1samp 7
trop_press mt1line 24
trop_press mt1samp 7
rain_flag mt1line 24
rain_flag mt1samp 7
zone mt1line 24
zone mt1samp 7
season mt1line 24
season mt1samp 7
geography_type mt1line 24
geography_type mt1samp 7
elevation mt1line 24
elevation mt1samp 7
geos_wind_east mt1line 24
geos_wind_east mt1samp 7
geos_wind_east standard_levels 15
geos_wind_north mt1line 24
geos_wind_north mt1samp 7
geos_wind_north standard_levels 15
thrm_wind_east mt1line 24
thrm_wind_east mt1samp 7
thrm_wind_east standard_layers 14
thrm_wind_north mt1line 24
thrm_wind_north mt1samp 7
thrm_wind_north standard_layers 14
Variable BadValue ValidMin ValidMax Scale Offset
temp_profile 0 -32768 32767 0.01 0
press_heights -999 -3.4028e+38 3.4028e+38 1 0
layer_thick -999 -3.4028e+38 3.4028e+38 1 0
press_levels -3.4028e+38 -3.4028e+38 3.4028e+38 1 0
trop_temp 0 -32768 32767 0.01 0
trop_press 0 -3.4028e+38 3.4028e+38 1 0
rain_flag 255 0 255 1 0
zone 255 0 255 1 0
season 255 0 255 1 0
geography_type 255 0 255 1 0
elevation -32768 -32768 32767 1 0
geos_wind_east -32768 -32768 32767 0.1 0
geos_wind_north -32768 -32768 32767 0.1 0
thrm_wind_east -32768 -32768 32767 0.1 0
thrm_wind_north -32768 -32768 32767 0.1 0
$REFDATA/ssp/t1aabb.tdf, $REFDATA/ssp/af_geog.tdf, $REFDATA/ssp/af_elev.tdf, $REFDATA/bathy/etop05, $REFDATA/ssp/nmc_1000mb.tdf, $SATDATA/f-*/t1dmatrix.tdf
dmsp, ols, ssmt, geoph, rtdin, rdsin, t2edr, miedr, datasets.
System Summary Report Passive Microwave Sounder (SSM/T). Aerojet, Report 5542, CDRL A006, 23 November 1977.
Tactical Applications of DMSP Microwave Temperature Sounders (SSM/T) and Imager (SSM/I) Data. R.G. Isaacs and J.C. Barnes, Atmospheric and Environmental Research, Inc., Cambridge, MA., 1985.
Wallace, J.M. and P.V Hobbs, Atmospheric Science: An Introductory Survey. Academic Press, San Diego, CA. 1977.
Last Update: $Date: 2000/11/20 19:13:50 $