MSU Ch 4 Daily Lower Stratosphere Temps with Limb93 Correction V001 (MSULST) at GES DISCEntry ID: GES_DISC_MSULST_V001
Abstract: Section 1. General Description
Spencer and Christy (1990) demonstrated that accurate estimates of global
atmospheric temperatures could be derived from the Microwave Sounding Units
flown on NOAA's TIROS-N series of satellites. The MSU's have been
... continuously operating for more than 14 years collecting measurements of the
thermal emission of radiation by molecular oxygen at four frequencies near 60
The four MSU channels have contribution functions (CF's) determined by their
wavelength and the atmospheric profile of oxygen. MSU channel 1 has a CF peak
near the surface, and is influenced strongly by temperature and liquid water
near the surface. The channel 2 CF is dominated by a wide peak near 50 kPa.
Channel 3 peaks near the tropopause (25 kPa) and the Channel 4 CF has a
somewhat sharper peak in the lower stratosphere (7 kPa).
Spencer and Christy (1992 a,b) demonstrated that the MSU calibrations have been
very stable, with a precision of monthly satellite measurements of 0.01 deg C
for the global mean.
A. Channel 4 Lower Stratospheric Retrieval.
Spencer and Christy (1993) developed a deep-layer lower stratospheric
temperature retrieval using MSU channel 4. The MSU channel 4 CF lies nearly
entirely in the stratosphere with a peak near 7 kPa. They validated their 2.5
grid point data against rawinsondes, finding correlation's with single-station
data as high as .99. The stratospheric retrieval corrects the channel 4 data
for scan angle differences across the scan line (Limb93), and removes known bad
scan lines. The data have been inter calibrated to remove calibration
differences between satellites and to correct for differences between local
orbit crossing times (e.g., 2:30 a.m. vs. 7:30 a.m.), and to remove diurnal
differences (a.m. vs. p.m.).
B. MSU Calibration.
The Limb93 retrievals use calibrated MSU data. The MSU brightness temperatures
for all four channels were linearly calibrated using the radiometric counts
measured viewing the earth scene as compared to the difference between the
radiometric measurement while viewing a warm calibration load and a similar
view of deep space (assumed to be 2.5K). For information on the calibration
procedure, the user is referred to the TOVS MSU Pathfinder User's Guide.
Section 2. MSU Limb93 Data File Structure
The MSU Limb93 data files are given in HDF structure. Every file contains 365
Scientific Data Sets (366 for leap years), one for each day of the year. Each
SDS contains a two dimensional data set, the x dimension is longitude and the y
dimension is latitude. The grid is composed of 144 (longitude) by 72
(latitude) 2.5 by 2.5 degree grid boxes. The first grid box is centered at
88.75 N 178.75 W. The data structure for the SDS data is int16, and the data
are given in hundreths of Kelvin degrees.
Section 3. Algorithm Description
Lower Stratosphere Deep Layer Mean Temperature (LST).
Each SDS gives the lower stratospheric temperature (Ch 4) for a day. The
stratospheric temperature retrieved is simply the black body temperature
linearly calibrated from the radiometric counts in MSU channel 4 at each
The stratospheric retrieval is calculated for each footprint of the MSU scan
line, the latitude and longitude of the footprint are calculated and the
appropriate limb correction (Limb93) is applied based on latitude, longitude,
month, and scan angle. Next, the footprint data are assigned to the
appropriate grid box. North (south) of 66.7N (S) the footprint data are
assigned to adjoining grid boxes in a weighted method depending on footprint
latitude. After all the a.m. and p.m. orbits are processed, a horizontal
averaging is used to fill some of the empty grid boxes.
Data Set Citation
Dataset Originator/Creator: Spencer R., Christy J.R.
Dataset Title: MSU Ch 4 Daily Lower Stratosphere Temps with Limb93 Correction
Version: 001Online Resource: http://disc.sci.gsfc.nasa.gov/services/opendap/documents/lim93_read...
Start Date: 1979-01-01Stop Date: 1993-12-31
Latitude Resolution: 2.5 degree
Longitude Resolution: 2.5 degree
Horizontal Resolution Range: 250 km - < 500 km or approximately 2.5 degrees - < 5.0 degrees
Temporal Resolution: Daily
Temporal Resolution Range: Daily - < Weekly
Distribution Media: On-line
Distribution Format: HDF, Binary
Role: TECHNICAL CONTACT
Email: gsfc-help-disc at lists.nasa.gov
Goddard Earth Sciences Data and Information Services Center Code 610.2 NASA Goddard Space Flight Center
Province or State: MD
Postal Code: 20771
Spencer, R.W., and J.R. Christy, 1993: Precision lower stratospheric
temperature monitoring with the MSU: Technique, Validation, and Results
1979-1991. J. Climate, 6, 1194 1204.
Spencer, R.W. and J.R. Christy, 1992a: Precision and radiosonde validation
... of satellite grid point temperature anomalies, Part I: MSU channel 2.
J. Climate, 5, 847-857.
Spencer, R.W. and J.R. Christy, 1992b: Precision and radiosonde validation
of satellite grid point temperature anomalies, Part II: A tropospheric
retrieval and trends 1979-90. J. Climate, 5, 858-866.
Spencer, R.W. and J.R. Christy, 1990: Precise monitoring of global
temperature trends from satellites. Science, 247, 1558-1562.
Creation and Review Dates
DIF Creation Date: 2008-11-12
Last DIF Revision Date: 2009-07-21