Lewis J. Allison, Joseph Steranka, Meteorological applications oi G. Thomas Cherrix, and Ernest Hilsenrath the Nimbus 4 Temperature- Goddard Space Flight Center Humidity Infrared Radiometer, NASA, Greenbelt, Md. 20771 0.7 micron channel data Abstract radar depiction chart produced at 0745 GMT, 30 April 1970, by the National Severe Storms Forecast Center Mid-tropospheric circulation features under essentially (NSSFC), Kansas City, Mo. Note the similarity in the clear sky conditions have been noted in the data of the two heart-shaped areas which extend through central 6.7 /am channel of the Nimbus 4 Temperature-Humidity Oklahoma and Texas and the radiation pattern shown Infrared Radiometer (THIR) while at the same time on the BULLETIN cover. these features were undetected by the 11.5 /mi channel of the same instrument. The characteristic response The color system which processed the 6.7 /mi data of the 6.7 /am channel to atmospheric water vapor emis- was adapted from the Application Technology Satellite sion is primarily from the 250-mb (10.5 km) to 500-mb (ATS) Spin Scan Experiment (Allison 1971, Allison et al., (5.5 km) levels with a peak contribution at 350 mb 1971). The blue, green, and yellow colors represent (8 km). Dry and moist patterns seen in the 6.7 ^m IK intervals of "cold" brightness values from 200 to data on 21 February 1971 have been integrated into a 219K recorded over high dense cirriform clouds. Note 400-mb moisture analysis over the United States. This the similarity in position of the radar depiction of 50 analysis provided more detailed and timely information to 60,000-ft thunderstorm tops and the blue and green than was conventionally available about the advection areas (200-21 OK). Using the temperature profile obtained of dry air aloft prior to development of the Mississippi from Tinker Air Force Base, Okla., at 1200 GMT, Tornado of February 1971. The derivation of middle to the cloud tops at Tornado A and B (209K) range upper atmosphere flow patterns from the Nimbus 4 from 80 mb (58,000 ft, 17.7 km) to 70 mb (61,000 ft, THIR, 6.7 ^m data under cloud-free conditions has a 18.7 km) which was in good agreement with WSR-57 direct application on a global scale for the GARP radar data recorded at 0739 GMT at Oklahoma City, and World Weather Watch Programs. Okla. Two wedges of warm brightness values (red to violet 235 to 255K) are shown penetrating from the This month's BULLETIN cover contains an unusual color analysis of the 6.7 /tm channel data from the Nimbus 4 Temperature-Humidity Infrared Radiometer (THIR), recorded over the Oklahoma City tornadoes at approximately midnight (0730 GMT) on 30 April 1970. Two tornadoes had moved through an established net- work of surface and upper air stations in central Oklahoma, operated by the National Severe Storms Laboratory (NSSL), Norman, Okla. (Barnes et al., 1971). At the time of satellite passage, the tornadoes were located approximately 25 mi northwest of Okla- homa City (35.9N, 97.3W and 35.5N, 97.6W) where they caused considerable damage to the suburban residential area (Environmental Data Service, 1970). These storms were classified as a Miller (1967) Type-B severe weather pattern and were characterized by a high-level southwesterly jet, dry air at the 700-mb level overriding a northward flowing current of warm moist air from the Gulf of Mexico, and a deepening open FIG. 1. Radar summary chart at 0745 GMT, 30 April wave along an extended cold front at the surface 1970, showing the location of the Oklahoma City tornadoes (Greene, 1971; Henderson, 1971). Fig. 1 shows the (NSSFC, NOAA). 526 Vol. 53, No. 6, June 1972 Unauthenticated | Downloaded 10/09/21 02:51 PM UTC Bulletin American Meteorological Society FIG. 2. (a) At left, the spectral response of the Nimbus 4 THIR, 6.7 ^M channel, (b) At right, the weighting function curves, based upon standard atmosphere assumptions, of the Nimbus 3 MRIR, 6.5-7.0 /xm channel and the Nimbus 4 THIR 6.7 /mi channel. Both radiometers measure the emission of an integrated moisture column from approximately 250 mb (10.5 km) to 500 mb (5.5 km) with a peak contribution at 350 mb (8 km). east and west along 34N to 36N, between the two large masses of thunderstorms. These patterns indicate the massive intrusion of dry air over the NSSL research network at the 400-mb level near tornado A (Hender- son, 1972, private correspondence). The Nimbus 4 Temperature-Humidity Infrared Radiometer (THIR) The THIR flown on Nimbus 4 was a scanning bolometer radiometer which in some respects was similar to the High Resolution Infrared Radiometer (HRIR) used on previous Nimbus satellites. It contained 2 channels: a 10.5-12.5 fjim "window" channel that provided night and day cloud top or surface temperatures with a ground resolution of 5n mi, and a 6.3-7.0 fim "water vapor absorption" channel, which peaked at 6.9 fim (Fig. 2a) and sensed the integrated moisture content of the upper atmosphere from 250 mb (10.5 km) to 500 mb (5.5 km) (Fig. 2b) with a ground resolution of 13 n mi at the sub-satellite point (Nimbus Project, 1970; TIROS N, 1971). The radiation data in analog form are stored on the satellite, read out to ground stations at Rosman, N. C., and Fairbanks, Alaska, and trans- mitted to Goddard Space Flight Center. These data are then gridded by a CDC 924 computer, and a black and white photofacsimile film strip is produced FIG. 3. Photofacsimile film strip of 6.7 /mi data re- for ready analysis. Approximately 6 to 8 grey scale corded at approximately 0900 GMT, during orbit 4607, 17 intervals of brightness temperatures can be delineated March 1971, over the Gulf of Alaska. Superimposed is the by the eye in the photographic print. An example of track of the NASA CV 990 aircraft flying at 240 mb (11 6.7 yum data recorded at approximately 0900 GMT km) at 1900 GMT, 17 March 1971, with hygrometer mea- surements, in parts per million by mass (ppm). A polar jet during orbit 4607 on 17 March 1971 is shown in Fig. 3. stream is shown at its 0000 GMT 18 March 1971 position. 527 Unauthenticated | Downloaded 10/09/21 02:51 PM UTC Vol. 53, No. 6, June 1972 Superimposed is the track of the NASA CV 990 aircraft values (Moller and Raschke, 1964; Allison and Warnecke, with four in situ measurements of water vapor from 1965; Fritz and Rao, 1967; Raschke and Bandeen, 1967; an aluminum oxide hygrometer (mixing ratio in parts Beran et al., 1968; Hanel and Conrath, 1970). Nordberg per million by mass) at the 240-mb level (Hilsenrath and et al. (1966) had described moisture patterns in the Coley, 1971). The driest reading (4 ppm) is shown over 6.4 to 6.9 Aim data from the Nimbus 2 Medium Resolu- the dark grey area on the northwest edge of a 80-90 kt tion Infrared Radiometer (MRIR) which were related polar jet stream. This jet stream is shown in its 0000 to air masses, frontal systems, and jet streams. Recent GMT, 18 March 1971 position where it had remained studies by Holub and Shenk (1972) also used the nearly stationary during this day. Lighter grey areas, 6.5 to 7.0 /mi data from the Nimbus 3 MRIR in a relating to increased moisture content of 9, 10, and multispectral technique to locate and describe upper 14 ppm were recorded as the plane flew through level troughs and jet streams and to discriminate be- scattered cirrus clouds. The aircraft was above the tween cloud types in the vertical. The usefulness of 300-mb tropopause at 1900 GMT, 17 March 1970. The the 6.7 /tm channel in tropical cyclone research to height of the tropopause was verified from the 0000 indicate intensification and wave pattern dynamics GMT, 18 March 1970 Ship P radiosonde (50N, 145W). of Tropical Depression Blanche, 1969 (Fett et al., 1972) The 4-ppm aircraft humidity reading near the jet and Hurricane Camille, 1969 (Shenk and Fujita, 1971) stream was typical of previous balloon frost point has been demonstrated. hygrometer measurements made by Mastenbrook (1971) It was only recently noted that the higher resolution in the lower stratosphere. 6.7 iim data from Nimbus 4 THIR has clearly depicted intense mid-tropospheric circulation patterns which Meteorological examples of Nimbus 4 THIR data were not visible in the 11.5 /mi data. The following Earlier studies of the 6.0-6.5 /mi data from TIROS figures of nighttime THIR data show selected examples satellites have interpreted the emission in the funda- of these features taken from the Nimbus 4 Data mental water vapor band as measurements of mean Catalogs, Vol. 1, 5 (1971): vertical relative humidity and cloud top brightness FIG. 4. Photofacsimile film strips of 6.7 nm and 11.5 /tm data over a closed 500-mb low off the west coast of the FIG. 5. Photofacsimile film strips of 6.7 /tm and 11.5 /tm United States during orbit 1934(N), 30 August 1970, at data over a 500-mb high over the western United States approximately 0845 GMT. during orbit 2565(N), 16 October 1970 at 0840 GMT. 528 Unauthenticated | Downloaded 10/09/21 02:51 PM UTC Bulletin American Meteorological Society Fig. 4: 30 August 1970, Orbit 1934(N). A 500-mb of the white and grey patterns in the 6.7 /tm closed low is shown off the west coast of the U.S.