Lewis J. Allison, Joseph Steranka, Meteorological applications oi G. Thomas Cherrix, and Ernest Hilsenrath the Nimbus 4 Temperature- Goddard Space Flight Center Humidity 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 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).

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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 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.

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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.

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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. in data, it was possible to draw the 400-mb streamline the 1200 GMT National Meteorological Center (NMC) circulation which closely resembled the conventional analysis and by the spiralling light grey moisture bands wind field (Fig. 6). The streamline analysis was drawn in the 6.7 /mi data. The central portion of the vortex before comparing it with the conventional data. No appears quite dark, indicating a 110-km wide sub- estimate of wind speed was made by this technique. sidence region. No evidence of this circulation is seen By combining the derived streamlines with conven- in the 11.5 /tm data. Dense high clouds appear as tional data, significant synoptic scale features appear white areas on both channels over the Intertropical which could not have been derived from the radiosonde Zone of Convergence, Canada, and the U.S. west data alone. The analysis was extended to a world scale coast. on 16 October 1970 (Fig. 7a), and a quasi-global 400-mb Figs. 5, 6 and 7: 16 October 1970, Orbit 2565(N). wind field (Fig. 7b) was derived which provided wind Clear night skies over western U.S. allow the coastline direction information even over data-sparse regions to be easily discerned in the 11.5 /tm data. The light (Steranka et al., 1972). Wind measurements have been grey pattern over the eastern Pacific is indicative of difficult to obtain over large remote areas of the world stratoform clouds over the California current. due to icing problems of constant level balloons at The 6.7 /tm data show the characteristically spiralling 300 mb and below (Morel et al., 1968; Lally, 1970; anticyclonic dryness associated with a strong high aloft. Masterson, 1971). This satellite radiation wind direction Steranka et al. (1972) plotted the 400-mb level winds technique holds the possibility of overcoming some of over the western United States at 1200 GMT, 16 these difficulties. October 1970. By following the changing orientation Fig. 8: 8 September 1970, Orbit 2055(N). A developed

FIG. 6. (a) At left, photofacsimile film strip of Nimbus 4 THIR 6.7 /tm data over a 500 mb high over the western United States during orbit 2565(N), 16 October 1970, at 0840 GMT. (b) At right, winds at 400 mb from conventional United States radiosonde stations at 1200 GMT, 16 October 1970. Short arrows follow the orientation of the lines of con- trast between the light and dark grey patterns of 6.7 /tm brightness values in Fig. 6a. Conventional streamlines were drawn by following the direction of the conventional wind barbs and short arrows on the radiation chart.

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FIG. 7a. Winds at 400 mb Northern Hemisphere were plotted from radiosonde stations at 00 GMT, 1200 GMT, 16 October 1970, and 00 GMT, 17 October 1970, as shown at the top of the figure. In Southern Hemisphere, 500-mb winds are from radiosonde stations, satellite cloud-derived "bogus" winds, and 300-mb aircraft wind reports, in similar time periods. (Steranka et al., 1972).

FIG. 7b. The short arrows show the derived wind direction at the approximate 400-mb level. These arrows were drawn by following the lines of contrast between the light grey and dark grey patterns of 6.7 /mm brightness values from 70-mm photofacsimile film strips of orbits 2561 to 2574(N) on 16 October 1970. (Steranka et al., 1972).

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Unauthenticated | Downloaded 10/09/21 02:51 PM UTC Bulletin American Meteorological Society subtropical vortex outlined by spiralling light grey Russia. The two northernmost alternating grey bands moisture patterns is shown in the 6.7 /mi data in the in the 6.7 /tm chart are indicative of drier air flowing eastern Pacific Ocean between 15N and 30N. The around the edges of a deepening 500-mb trough over northern edge of the elongated semicircular white Central Russia. The third band at 38N to 32N is band at 40N-42N is related to a 50-60 kt polar jet related to a 80-100 kt polar jet stream (00 GMT, 22 stream at the 500-mb level (1200 GMT NMC analysis). November 1970 NMC analysis) passing through northern Little evidence of the midtropospheric low or the jet India and the Himalaya Mountains. stream appears in the 11.5 /tm data. Fig. 11: 10 November 1970, Orbit 2905(N). Portions Fig. 9: 30 April 1970, Orbit 295(N) and 296(N). The of the Chinese mainland, the Korean peninsula, and northeast to southwest orientation of a 60 to 100 kt the Siberian coastline are clearly revealed in the 11.5 subtropical jet stream (STJ) off Baja California is more /mi data. A trailing cold front is shown oriented east- fully depicted in the 6.7 /cm data than in the 11.5 west along 30N with an occlusion extending from 40N /tm data. Previous studies by Martin and Salomonson to 50N along the eastern edge of the photofacsimile (1970) over the U.S. have related the warmer bright- print. The northwest to southeast grey streak 5° to 10° ness values (dark grey areas along the northern edge north of the surface front in the 6.7 /tm data is the of the STJ) to areas of subsidence. Rodgers and position of a 100 to 120-kt 200-mb polar jet stream Salomonson (1971) describe a synoptic situation in (00 GMT NMC analysis), which is not evident in the which areas of widespread and strong subsidence cor- 11.5 /mi data. The possible relationshhip between the respond closely to areas delineated by high brightness sharpness of the moisture gradient, shown by the temperatures in Nimbus 3, 6.7 /mi MRIR data. dark to light grey tones along the northern edge of the Fig. 10: 21 November 1970, Orbit 3055(N). The 11.5 polar jet stream, and clear air turbulence will be /tm chart shows up the coastline of Saudi Arabia, the the subject of future research (Salomonson, 1969). Persian Gulf, the Aral Sea, and the steppes of Central Fig. 12(a): 21 February 1971, Orbit 4283(N). The intersection of two dark grey lines over Central Mexico is shown in the 6.7 /tm data but is missing in the 11.5 /mi print. The long west to east grey streak indicates dry air advection from 500 to 250 mb on 21 February 1971, 0700 GMT. It is embedded in a 40-50 kt, 200-mb subtropical current (1200 GMT NMC analysis) which ends along the western edge of a "dryline" forming at the Gulf coast. The cloud mass "A" at 89W to 92W, 3IN to 33N, developed from 30-40,000 ft at 00 GMT to 48-55,000 ft at 0845 GMT in severe thunderstorm activity (NSSFC Radar Data). This was the area in which fifty tornadoes in three nearly-parallel storm tracks occurred from 2100 GMT, 21 February 1971, to 0123 GMT, 22 February 1971 (Miller, 1971). The cloudiness between 30N to 40N in the center of each print is related to a developing open wave in eastern Texas and a deepening 500-mb trough east of the Rockies. Fig. 12(b). An analysis was made of the 400-mb winds and humidity (mixing ratio) over the United States on 21 February 1971, 1200 GMT. This level was selected because it corresponded well to the peak of the weighting function curve shown in Fig. 2(b) and the air temperature ranged from —25C to —35C per- mitting the recording of reliable conventional water vapor measurements. Light to dark grey patterns from the 6.7 /mi data from orbit 4283(N) [Fig. 12(a)] at 0710 GMT, 21 February 1971, were integrated into the FIG. 8. Photofacsimile film strips of 6.7 /tm and 11.5 /tm conventional moisture analysis which existed 9-14 hr data over a developed 500-mb low in the subtropical eastern Pacific during orbit 2055(N), 8 September 1970, at prior to the start of the Mississippi Tornado, near approximately 0900 GMT. Jackson, Miss., by using the radiosonde measurements

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FIG. 9. Photofacsimile film strips of 6.7 /tm and 11.5 /tm data over the Oklahoma City tornadoes and the subtrop- ical jet stream flowing northeastward off Baja California on 30 April 1970, orbit 295 and 296 at 0730 GMT and 0915 GMT, respectively. (Note color radiation analysis of 6.7 /tm data on cover.) as benchmarks and conserving the general character Feasibility studies have been initiated between the of the moisture patterns seen in the 6.7 /mi imagery. National Environmental Satellite Service, Washington, Note the moist tongue A, B, and C separating the cold D.C., and Goddard Space Flight Center, Greenbelt, Md., dry polar air in the trough centered at H, from the to operationally process the 6.7 /tm radiation data from warm dry subtropical air, D, E, F, and G flowing to Nimbus E (November 1972, launch date) for use in a the northeast, off Baja California. Many of these Mesoscale Tornado Project at NSSFC Kansas City, Mo., dry and moist details recorded between the 00 GMT and other priority locations (Fett, 1972, private cor- and 12 GMT radiosonde runs were located in regions respondence). Operational use of this channel in 1976 between reporting radiosonde stations. The placement has already been approved for TIROS N, scheduled of the moist tongue A, B at the 400-mb level is only to be launched during the Global Atmospheric Re- an approximation because this light grey pattern search Program (U.S. Committee for the GARP, 1969). generally indicates water vapor emission from the 700-mb to the 200-mb level. At 0000 GMT, 22 Acknowledgments. The authors wish to thank Mr. February 1971, warm dry air was found aloft from Vincent J. Oliver of the National Environmental Satellite 850 mb to 300 mb just to the west of the long-lived Service, NOAA, for his persistent encouragement to tornado tracks in Mississippi. This type of detailed determine the basic meteorological differences between moisture chart locates the intrusions of dry air over the 6.7 /tm and 11.5 /mi channels in the Nimbus 4 lower-level (850 mb) moist air which is responsible for THIR data. We also wish to thank Drs. V. V. Salomon- the convective instability associated with tornado de- son and R. Wexler for helpful discussions during the velopment (Miller, 1967; Purdom, 1971). course of this research.

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FIG. 11. Photofacsimile film strips of 6.7 /mi and 11.5 /mi data over China, Korea, and Siberia during orbit 2905(N), 10 November 1970, at approximately 1630 GMT.

FIG. 10. Photofacsimile film strips of 6.7 /tm and 11.5 /tm data over the Middle East and Russia during orbit 3055(N), 21 November 1970, at approximately 2030 GMT.

FIG. 12a. Photofacsimile film strips of 6.7 /tm and 11.5 /tm data over the southwestern United States and Mexico during orbit 4283(N), 21 February 1971, at approximately 0700 GMT.

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FIG. 12b. Enhanced 400-mb moisture analysis over the United States at 1299 GMT, 21 February 1971. The light to dark grey patterns of moisture from the 6.7 /mm data in Fig. 12a, orbit 4283(N), 21 February 1971 at 0710 GMT, were inte- grated into the conventional radiosonde moisture data. The light grey patterns shown at points A and B indicate water vapor emission generally from the 700-mb to 200-mb level.

References Environmental Data Service, 1970: Storm Data, Vol. 12, No. 4. Asheville, N.C., 46 pp. Allison, L. J., and G. Warnecke, 1965: The interpretation of TIROS radiation data for practical use in synoptic Fett, R., L. J. Allison, and R. Wexler, 1972: A case of weather analysis. NASA TN-D-2851, 38 pp. easterly wave development in the tropical Atlantic Ocean. Allison, L. J., 1971: The applications of the Nimbus Paper presented at the Spring Annual Meeting of the meteorological satellite data. Air Weather Service Tech- Amer. Geophys. Union, 19-21 April 1972, Washington, nical Report 242, AWS, (MAC), U.S. Air Force, Scott D.C. AFB, 111., 261-290. Fritz, S., and P. K. Rao, 1967: On the infrared transmission Allison, L. J., G. T. Cherrix, and H. Ausfresser, 1971: The through cirrus clouds and the estimation of relative application of color display techniques for the analysis humidity from satellites. J. Appl. Meteor., 6, 1088-1096. of Nimbus infrared radiation data. NASA X-651-71-275, Greene, Douglas R., 1971: An indicator of explosive de- Goddard Space Flight Center, Greenbelt, Md. velopment in severe storms. Proc. Seventh Conf. on Severe Barnes, S. L., J. H. Henderson, and R. J. Ketchum, 1971: Local Storms, Amer. Meteor. Soc., Kansas City, Mo., 5-7 Rawinsonde observation and processing techniques of the October 1971, 97-104. National Severe Storms Laboratory. NOAA Tech. Memo., Hanel, R. A., and B. J. Conrath, 1970: Thermal emission ERL NSSL-53, 246 pp. spectra of the and atmosphere from the Nimbus 4 Beran, D. W., E. S. Merrit, and D. T. Chang, 1968: Interpretation of baroclinic systems and wind fields as Michelson interferometer experiment. Nature, 228, 143- observed by Nimbus II MRIR, Final Report 9G43-F. 145. Allied Research Associates, Inc., Concord, Mass. to Henderson, J. H., 1971: The internal structure of a NASA, GSFC, Greenbelt, Md. thunderstorm as revealed by 9w surfaces. Proc. Seventh

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Conf. on Severe Local Storms, Amer. Meteor. Soc., Kansas Science Data Center, Goddard Space Flight Center, City, Mo., 5-7 October 1971, 97-104. Greenbelt, Md., 214 pp. Hilsenrath, E., and R. J. Coley, 1971: Performance of an Nimbus Project, 1971: Nimbus 4 data catalog, Vol. 1, 5. aluminum oxide hygrometer on the NASA CV990 Air- National Space Science Data Center, Goddard Space craft Meteorological Observatory. NASA X-651-71-37, Flight Center, Greenbelt, Md. 14 pp. Nordberg, W., A. W. McCulloch, L. L. Foshee, and W. R. Holub, R., and W. Shenk, 1972: A multispectral study of an Bandeen, 1966: Preliminary results from Nimbus II. extropical cyclone with Nimbus 3 MRIR data. Paper Bull. Amer. Meteor. Soc., 47, 857-872. presented at the Fourth Conference on Weather Fore- Purdom, J. F., 1971: Satellite imagery and severe weather casting and Analysis, Portland, Oreg., 1-4 May 1972. warnings. Proc. Seventh Conf. on Severe Local Storms, Lally, V. E., 1970: Constant-level balloons for sounding sys- Kansas City, Mo., Amer. Meteor. Soc., 120-127. tems. Meteor. Monogr., 11, 392-396. Raschke, E., and W. R. Bandeen, 1967: A quasi-global Martin, F. L., and V. V. Salomonson, 1970: Statistical analysis of troposphere water vapor content from TIROS characteristics of subtropical jet stream features in terms IV radiation. J. Appl Meteor., 6, 468-481. of MRIR observations from Nimbus 2. J. Appl. Meteor9, Rodgers, E. B., and V. V. Salomonson, 1971: A quantitative 508-520. evaluation of the Nimbus water vapor observations as related to middle and upper tropospheric circulation Mastenbrook, H. J., 1971: The variability of water vapor in features. Paper presented at the Fall Annual Meeting of the stratosphere. J. Atmos. Sci., 28, 1495-1501. the Amer. Geophys. Union, San Francisco, Calif., 6-9 Masterson, J. E., 1971: An in situ measurement system for December 1971. GARP using balloons, buoys and a satellite. Paper pre- Salomonson, V. V., 1969: MRIR observations of jet streams. sented at the Eighth Space Congress, Progress in Meteor- Significant accomplishments in science and technnology, ology, Cocoa Beach, Fla., 19 April 1971. NASA SP-251, 15-18. Miller, R. C., 1967: Notes on analysis and severe forecasting Shenk, W., and T. Fujita, 1971: The structure of tropical procedures of the military weather warning center. Air storm Camille over the U.S. as determined from satellite Weather Service Tech. Report 200, AWS (MAC), U.S. Air and conventional measurements. Paper presented at the Force, Scott AFB, 111. Seventh Technical Conference on Hurricanes and Tropical Miller, R. C., 1971: The use of computer products in severe , Barbados, B.W.I., 6-8 December 1971. weather forecasting (the SWEAT index). Proc. Seventh Steranka, J., L. J. Allison, and V. V. Salomonson, 1972: Conf. on Severe Local Storms, Amer. Meteor. Soc., Kansas Improvement of synoptic scale moisture and wind field City, Mo., 1-6. analysis using the Nimbus 4 THIR 6.7 jum observations. Moller, F., and E. Raschke, 1964: Evaluation of TIROS III NASA X-651-72-101, Goddard Space Flight Center, Green- radiation data. NASA Contractor, Report No. CR-112, belt, Md. NASA, Goddard Space Flight Center, Greenbelt, Md. TIROS-N, 1971: Phase A Report, Vol. 1, 2, 3. NASA, God- Morel, P., J. Fourier, and P. Setbon, 1968: The occurrence dard Space Flight Center, Greenbelt, Md. of icing on constant level balloons. J. Appl. Meteor7, U.S. Committee for the GARP, 1969: Plan for U.S. participa- 626-634. tion in the Global Atmospheric Research Program. Nimbus Project, 1970: Nimbus 4 users guide. National Space National Academy of Science, Washington, D.C., 79.

central parts of the north Pacific at 49 minutes after the hour on the same frequencies. The expanded broadcasts now include data on the mid- announcements latitude and tropical areas of their respective oceans. The purpose of the broadcasts is to inform mariners of storm threats, not to provide complete information. NOAA doubles storm information service The National Oceanic and Atmospheric Administration Changes at NCC doubled its storm-information service for deep-water sailors The National Climatic Center at Asheville, N.C., is devel- in the Atlantic and Pacific beginning in April. The pro- oping a synoptic file of global, surface, and upper air data. gram, begun last summer, is a joint effort of the National The surface data will be for 00, 06, 12, and 18 GMT. The Weather Service and the National Bureau of Standards. It upper air data will be for 00 and 12 GMT. Microfilm of the consisted formerly of hourly broadcasts, each lasting about entire synoptic data will cost $65.00 per month. 45 sec, giving information on major storms that cause The Climatic Center will select data from this file to hazardous conditions for ships at sea. The weather broad- make available tabulations of selected data. Microfilm of casts are superimposed on time signals carried by NBS radio these tabulations will be available for the cost of reproduc- stations WWV in Fort Collins, Colo., and WWVH in Kauai, tion—$9.00 per reel. A month of data will occupy one or two Hawaii. reels of film (depending on data receipt from a preselected The new, expanded service consists of two 45-sec broad- network of stations). Tabulations for the period July- casts, 1 min and 15 sec apart, and gives more storm informa- December 1971 will be available about 1 November 1972, tion. Station WWV carries information about storms in the and in subsequent batches of six months of data at six- western north Atlantic and the Gulf of Mexico, now at 10 month intervals thereafter. minutes after the hour on radio frequencies 2.5, 5, 10, 15, 20 and 25 mHz. Station WWVH lists storms in the eastern and (More announcements on page 547)

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