Millimeter-wave Imaging Radiometer (MIR) Brightness Temperatures, Wakasa Bay, Japan

Summary

This data set includes calibrated brightness temperatures measured over Wakasa Bay in the Sea of Japan in January and February 2003. The MIR was carried on a military-type P-3 aircraft. Brightness temperatures were taken at 57 beam positions covering 100 degrees swath. These data were acquired in support of the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) Wakasa Bay Field Campaign. Data are available in binary format from NSIDC via FTP.

AMSR-E is a mission instrument launched aboard NASA's Aqua Satellite on 4 May 2002. The Wakasa Bay Field Campaign was designed to validate both AMSR and AMSR-E shallow rainfall and snowfall retrieval capabilities.

Citing These Data

Wang, J. Millimeter-wave Imaging Radiometer (MIR) Brightness Temperatures, Wakasa Bay, Japan. Boulder, CO: National Snow and Ice Data Center. Digital media.

Overview Table

Category	Description
Data format	Binary files
Spatial coverage and resolution	30° to 40°N, 130° to 150°E
Temporal coverage and resolution	14 January 2003 to 3 February 2003
File naming convention	Files use the convention "miryyddd.00n" where yy=year, ddd=day of year, n=1 or 2, indicating the file number for a given date.
File size	File sizes range from 1.3 to 15.9 MB.
Parameter(s)	Brightness temperatures (K).
Procedures for obtaining data	Data are available via FTP.

Table of Contents

1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information

1. Contacts and Acknowledgments

Investigator(s) Name and Title

James Wang
NASA/Goddad Space Flight Center (GSFC)

Technical Contact

2. Detailed Data Description

Format

The data are stored in binary files. All values are in four-byte, little-endian IEEE floating point. Each logical record contains one calibrated MIR scan. Each logical record of size 2316 bytes (4 x 579) contains one calibrated MIR scan comprising temporal, spatial, and aircraft attitude information for the nadir position (beam position 29) of the scan, followed by a brightness temperature value for each of 57 beam positions at all seven MIR frequencies.

File Naming Convention

The file naming convention is "miryyddd.00n", where "yy" and "ddd" denote the year and Julian day the data was acquired. The "n" in the extension can be either 1 or 2; multiple files exist only if the processed data for a given day is larger than 15.8 MB. (Note: for 28 January, there is a file "mir03028.nad." During this flight, the MIR operated in a stare (non-scanning) mode for one segment of the flight. So the data file for this segment ends with ".nad" (nadir).)

File Size

File sizes range from 1.3 to 15.9 MB.

Spatial Coverage

Southernmost Latitude: 30° N
Northernmost Latitude: 40° N
Westernmost Longitude: 130° E
Easternmost Longitude: 150° E

Temporal Coverage

Selected dates between 14 January 2003 to 3 February 2003. The following table shows the dates for which data are available.

Day of year	Date
14	1/14
15	1/15
19	1/19
21	1/21
23	1/23
26	1/26
27	1/27
28	1/28
29	1/29
32	2/1
34	2/3
38	2/7

Parameter or Variable

Parameter Description

The parameter for these data is brightness temperatures.

Parameter Range

The following table describes the format of the data.

1	Record Number
2	Month	Real time clock (RTC)
3	Day	Real time clock (RTC)
4	Hour	IRIG
5	Minute	IRIG
6	Second		IRIG
7	Julian Day	Navigation
8	Hour	Navigation
9	Minute	Navigation
10	Second	Navigation
11	Latitude	Degrees
12	Longitude	Degrees (-West, +East)
13	Air Temperature	Degrees celsius
14	Altitude	Feet
15	Pitch	Degrees (+ for nose down)
16	Roll	Degrees (+ for roll right)
17	Heading	Degrees
18- 26	Housekeeping Temperatures
27	Hot average temperature for this scan
28	Cold average temperature for this scan
29	Hot temperature, 8-scan moving average
30	Cold temperature, 8-scan moving average
31- 39	Hot average counts for this scan
40- 48	Cold average counts for this scan
49- 57	Hot counts, 8-scan moving average
58- 66	Cold counts, 8-scan moving average
67-123	57 Brightness temperatures	Degrees Kelvin	89 GHz
124-180	Brightness temperatures	Degrees Kelvin	150
181-237	Brightness temperatures	Degrees Kelvin	183.3 +/-1
238-294	Brightness temperatures	Degrees Kelvin	183.3 +/-3
295-351	Brightness temperatures	Degrees Kelvin	183.3 +/-7
352-408	Brightness temperatures	Degrees Kelvin	220
409-465	Open
466-522	Brightness temperatures	Degrees Kelvin	340
523-579	Open

Sample Data Record

The following figure shows brightness temperature (K) distribution measured on January 14, 2003 in the Sea of Japan for the seven MIR channels. The width of the images is about 14 km and the length is about 90 km. The dark blue areas (low brightness temperature) in the 150, 183±7, 220, and 340 GHz diagrams correspond to snowfall. The blue area in the 89 GHz diagram mostly reflects the ocean surface. The water vapor channels (183±a) strongly respond to water vapor below the aircraft.

Error Sources

A quicklook of the data sets acquired in the Wakasa Bay experiment indicates deterioration in the performance of the 183.3±3 GHz and 340 GHz channels in the latter part of the experiment.

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

Volume of data files is 180 MB.

Software and Tools

View the data with an appropriate application. The investigators have provided a C routine for viewing these data. The routine is named "rdmir.c" and requires the "mir.h" file to run. Both files are included in the data directory.

Related Data Collections

• AMSR-E Validation Data
• AMSR-E Data at NSIDC
• Wakasa Bay Weather Forecast Maps
• TEFLUN MIR Data

4. Data Acquisition and Processing

Sensor or Instrument Description

The Millimeter-Wave Imaging Radiometer (MIR) is an airborne, total power, cross-track scanning radiometer that measures radiation at seven frequencies: 89, 150, 183.3±1, 183.3±3, 183.3±7, 220, and 340 GHz. Researchers can infer brightness temperatures, water vapor profiles, and cloud information from the data gathered by these frequencies. The sensor has a 3 dB beam width of 3.5 degrees at all frequencies. It can cover an angular swath up to ±50 degrees with respect to nadir. In every scan cycle of about 3 seconds, it views two external calibration targets in addition to the 100-degree scene scan; one of these targets is heated to a temperature of 330 K and another remains at the ambient temperature of the aircraft cruising altitude. The temperatures of these calibration targets are closely monitored to within ±0.1 K. The temperature sensitivity for all frequencies is on the order of 0.5 K and the calibration accuracy is about ±1 K in the brightness temperature range of 240-300 K. The measurement accuracy at the low end is less certain; based on the calibration studies in the laboratory, the accuracy near the liquid nitrogen temperature of 77 K is estimated to be ±3 K.

5. References and Related Publications

Wang, J. R. and L. A. Chang. 1990. Retrieval of water vapor profiles from microwave radiometric measurements near 90 and 183 GHz. J. Appl. Meteor. 29(10), 1005-1013.

Wang, J.R., S.H. Melfi, P. Racette, D.N. Whitemen, L.A. Chang, R.A. Ferrare, K.D. Evans and F.J. Schmidlin. 1995. Simultaneous measurements of atmospheric water vapor with MIR, Raman lidar and rawinsondes. J.Appl.Meteor. 34(7) 1595-1607,

Racette, P., R.F. Adler, A.J. Gasiewski, D.M. Jackson, J.R. Wang and D.S. Zacharias. 1996. An airborne millimeter-wave imaging radiometer for cloud, precipitation and water vapor studies. J. Atmos.Ocean.Tech. 13(3), 610-619,

6. Document Information

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document.

AMSR-E	Advanced Microwave Scanning Radiometer - Earth Observing System
FTP	File Transfer Protocol
GSFC	Goddard Space Flight Center
K	Kelvin
MIR	Millimeter-wave Imaging Radiometer

Document Creation Date

March 2004

Document URL

http://nsidc.org/data/docs/daac/nsidc0193_rainfall_wakasa_mir.gd.html