MSU Daily Oceanic Precipitation with Limb93 Correction V001 (MSUOP) at GES DISCEntry ID: GES_DISC_MSUOP_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 GHz.
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. Oceanic Precipitation Data set.
The oceanic precipitation estimates follow the method of Spencer (1993).
Oceanic precipitation is estimated by increased warming in MSU channel 1 over a
threshold. The increased warming is attributable to emission by liquid water
in the lower troposphere. Warming due to air mass differences are removed
using information from the MSU channel 2/3 retrieval. The precipitation
estimate has been calibrated into mm per day rainfall using eight years of rain
gauge data from tropical island locations. A climatological ice mask has been
used to screen out anomalous precipitation over ice covered ocean. Likewise,
the maximum value allowed has been set at 99.9 mm/day to further screen out any
remaining ice influence. Also, because this method only works in the Tropics
and mid-latitudes, the retrieval is only calculated for latitudes 60 S to 60 N.
Spencer (1993) discusses the calibration and demonstrates there is good
agreement between the MSU precipitation estimates and previous climate rainfall
data sets. Because the algorithm methodology uses all orbits in a 24 hour
period to calculate the rainfall estimate, no diurnal information is available
in this data set.
B. MSU Calibration.
The Limb93 precipitation 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
Section 2. MSU LIM93 Oceanic Precipitation 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 tenth of mm/day of rainfall. Land areas, areas at high latitudes
(above 60 degrees), and grid boxes with missing data have a value of -999.
Data Set Citation
Dataset Originator/Creator: Spencer R., Christy J.R.
Dataset Title: MSU Daily Oceanic Precipitation 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
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., 1993: Global oceanic precipitation from the MSU during
1979-92 and comparisons to other climatologies. J. Climate, 6, 1301-1326.
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