Roland B. Stull and Boundary Layer Experiment—1983 Edwin W. Eloranta

Department of University of Wisconsin Madison, WI 53706

Abstract flat pasture by ANL. This system measured the three components of velocity, as well as the thermal structure Interactions between fair-weather cumulus clouds and mixed-layer of the lowest 1.5 km of the boundary layer. ANL also thermals were the focus of a one-month field experiment in Oklahoma. erected a 5 m tower equipped with chemistry and fast- This experiment, called Boundary Layer Experiment—1983 (BLX83), response turbulence sensors, installed a net radiometer, combined remote sensors, surface observations, balloon platforms, and aircraft measurements to study the kinematics at the top of the and launched kytoons that provided profiles of the daytime convective boundary layer. Emphasis was placed on the lowest 800 m of the boundary layer. In addition, a stereo study of the entrainment zone, and on the relationship between indi- camera system was used at the ANL site to provide vidual thermals as identified by and turbulent motions and photographs of local cloud conditions. fluxes as measured by aircraft and . 2) An unmanned Portable Automated Mesonet (PAM II) station, which was designed and operated by NCAR, and also was located at the ANL site. In addition to the 1. Introduction standard variables of mean pressure, temperature, hu- midity, rainfall, and wind speed and direction, this sta- A field experiment was conducted in Oklahoma for the pur- tion provided net radiation data. pose of measuring the interaction between the boundary 3) The UW lidar system (Kunkel et al, 1977; Sroga et al., layer and fair-weather cumulus clouds. This experiment, 1980), which was located on a small ridge approxi- called Boundary Layer Experiment—1983 (BLX83), ran mately 3 km south-southwest of the ANL site. The lidar from 25 May through 18 June 1983. made range height indicator (RHI) and plan position Four organizations participated in the experiment: the indicator (PPI) scans in the direction of the ANL site; University of Wisconsin (UW), Argonne National Labora- thus, the lidar scanned the boundary layer over the tory (ANL), the National Center for Atmospheric Research ANL sensors. An automatic, time-lapse camera photo- (NCAR), and the National Severe Storms Laboratory (NSSL). graphed the clouds along the field of view of the lidar. Additional support was provided by the Air Weather Service The NCAR Queen Air aircraft made 20 flights over the at Tinker Air Force Base, and by the Army at Ft. Sill. primary field site. The Queen Air was equipped with a turbu- Emphasis was placed on measuring the turbulence struc- lence gust probe, forward- and side-looking automatic cam- ture at the top of the boundary layer. In particular, cloud-base eras, a Johnson-Williams liquid water content sensor, a micro- fluxes and the nature of the entrainment zone were probed wave refractometer, a Lyman-alpha , a dew-point using a sodar, lidar, kytoon, and aircraft. In order to prop- hygrometer, fast-response resistance , inertial erly scale these measurements within the framework of simi- navigation equipment, upward- and downward-looking visi- larity theories, supporting measurements were made of sur- ble and IR radiometers, and a radiometric skin temperature face fluxes, mixed-layer thickness, advection, and subsidence. sensor (RAF, 1981; Kelley and Lackman, 1976). Turbulence These latter measurements were aided by surface turbulence- sensors were sampled 20 times per second; other sensors were flux sensors, radiometers, Doppler radar, and a mesonet- sampled once per second. work of surface weather and rawinsonde stations. Most afternoons, the NSSL Doppler radar at Norman col- lected clear air boundary layer data every half hour. This data can provide one measure of boundary layer divergence and subsidence. In addition, NSSL had an array of surface 2. Equipment Stationary Automated Mesonetwork (SAM) stations in a tight pattern in the Oklahoma City area, and operated the Figure 1 shows the arrangement of BLX83 observing systems. KTVY instrumented 444 m tower to collect temperature, The primary field site was just southeast of Chickasha, Okla. humidity, and wind data. (approximately 45 km southwest of Norman). The following Surrounding the primary field site were 12 additional equipment was in operation at this site: PAM II stations arranged in a circle having a radius of 50 km (see Table 1). These second-generation PAM stations relayed 1) A three-component Doppler sodar system, placed in a 5 min average data to Boulder, Colo., via satellite. This circle of stations was split into two circles near Oklahoma City so that the urban influence could be isolated. © 1984 American Meteorological Society Beyond this circle of surface stations was a triangle of

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FIG. 1. Location of instrument systems in Oklahoma during the BLX83 field experiment.

3. Operations

The field program began on 25 May 1983 with some "shake- upper-air Rawinsonde Observation (RAOB) stations. down" soundings and initial operations of the sodar and flux Soundings were usually taken at 0600, 1000, 1400, and 1800 tower. The following day also was a "shakedown" day, with local time (Central Daylight Time = GMT — 5 h) on days a training flight and some limited lidar observations. Coor- the Queen Air flew data collection missions. The National dinated data collection began on 27 May and continued until Weather Service (NWS) at Will Rogers Airport took their 18 June (ANL terminated operations on 16 June). routine synoptic soundings at 0700 and 1900 local time. At The Operations Log and Data Inventory (Stull, 1983a) the southwest corner of the triangle, soundings were made describes each day's data collection periods and data avail- from one of two Ft. Sill sites, depending on Army commit- ability in detail. Descriptions of the equipment, schedules, ments. personnel, and experiments also are covered, along with

TABLE 1. Positions of the 13 Portable Automated Mesonet (PAM II) stations and the four rawinsonde (RAOB) launch sites during BLX83. Sites FSI and FSW are considered as one site because only one or the other was used, depending on Army constraints. The PAM stations and the Canton RAOB equipment were provided by NCAR.

Name Elevation Latitude Longitude No. (town) (m) (N) (W) Remarks

PAM II: 1 Chickasha 325.8 35 02 03.1 97 51 24.4 Near sodar at primary field site 2 Will Rogers 375.8 35 21 21 97 36 02 16 km S of airport 3 Piedmont 384.0 35 39 07 97 45 31 0.8 km N of town 4 Luther 338.6 35 44 23 97 14 34 10 km NNW of town 5 Shawnee 312.1 35 21 00 96 57 00 At RAOB (SNL) site 6 Byars 338.9 34 52 55 97 09 17 5 km WNW of town 7 Ratliff 317.3 34 27 53 97 32 47 3 km NW of town 8 Duncan 370.9 34 28 31 98 02 58 11 km SW of town 9 Cache 424.0 34 39 00 98 41 24 20 km W of FSI 10 Carnegie 440.1 35 00 08 98 31 26 16 km SE of town 11 Binger 483.1 35 19 13 98 24 58 6 km W of town 12 Cherokee 489.2 35 33 22 98 14 22 2 km N of gift store 13 Cogar 475.8 35 21 14 98 10 08 5 km NW of town RAOB: SNL Shawnee 312.1 35 21 00 96 57 00 At airport CAN Canton 502.9 36 04 48 98 40 48 At abandoned airport FSI Ft. Sill 360.0 34 27 36 98 24 36 0600 and 1000 soundings FSW Cache 424.0 34 39 00 98 41 24 Near Ft. Sill, soundings by request OKC Oklahoma City 391.1 35 24 97 36 Routine 0000 GMT and 1200 GMT at Will Rogers airport

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TABLE 2. BLX 83 flight summary. Twenty NCAR Queen Air (N306D) flights were conducted during the BLX83 field program. Most of these flights were in the vicinity of Chickasha, Okla.

Flight Date Start Duration Data rating (#) (1983) Type of mission (CDT) (hours) (subjective)

1 26 May Shakedown and training 1228 1.7 Poor 2 27 May Entrainment zone 1034 2.5 Excellent 3 28 May Entrainment zone 1425 3.6 Excellent 4 4 June Terrain mapping 1058 3.3 Excellent 5 7 June Training and refractivity 0930 1.3 Fair 6 7 June Cloud base 1217 3.3 Excellent 7 7 June Entrainment zone 1630 2.1 Very good 8 8 June Refractivity and cloud base 1409 3.5 Very good 9 9 June Refractivity and cloud base 1429 3.6 Excellent 10 10 June Cloud base 1258 1.1 Poor 11 12 June Cloud base 1006 2.7 Excellent 12 12 June Cloud base 1417 2.8 Excellent 13 14 June Entrainment zone 1406 3.3 Excellent 14 15 June Entrainment zone 0750 2.4 Good 15 15 June Cloud base 1319 2.4 Good 16 16 June Entrainment zone 1104 2.0 Very good 17 17 June Cloud base 1213 2.3 Excellent 18 17 June Cloud base 1536 1.8 Very good 19 18 June Landsat comparison 1045 1.8 Very good 20 18 June Cloud base 1405 2.4 Very good

FIG. 2. Lidar-generated RHI scan obtained on 4 June 1983 at 1008 CDT, showing clear convective plumes along a path over the ANL site, which was located 3.3 km from the lidar. This display shows the influence of shear on the plumes and shows entrainment of clear air into the boundary layer. Aerosol-laden air and clouds appear white, while cleaner air is dark in this computer enhancement. Unauthenticated | Downloaded 10/06/21 02:42 AM UTC Bulletin American Meteorological Society 453 daily 1500 GMT synoptic weather maps for the continental mid-mixed-layer legs, and mid-cloud-layer legs to de- United States and forecaster remarks during the observation termine scaling variables such as free convection scal- period. ing velocity. Most operations were conducted during daylight hours so 2) Entrainment Zone Pattern: In addition to the surface-flux that the evolution of the cloud-topped convective boundary legs and soundings, additional legs were flown at 1.2, layer could be studied. On occasion some special soundings, 1.1, 1.0, 0.9, 0.8, 0.6, and 0.3 times the average mixed- and ANL and lidar data collection periods, were extended layer depth. During the experiment we noted that the into the night. aircraft sounding, lidar RHI scan, and sodar profiles agreed very closely on the average depth of the mixed layer. 3) Terrain Mapping: This pattern was flown once. The Queen Air flew 10 low-level east-west legs that were dis- 4. Aircraft flights tributed evenly across a square area 50 km on a side and centered on the primary field site. The purpose of this Twenty flights, each of approximately 3 h duration, were flight was to determine the effect of land use on the dis- flown near the primary field site. A summary of the flights is tribution of the thermals that were generated. shown in Table 2. A Scientist's Flight Log (Stull, 1983b) for 4) Landsat Comparison: This pattern was flown once to these flights is available from the UW Meteorology Depart- coincide with a Landsat pass over the primary field site ment. Four types of flight patterns were performed: at 1126 CDT on 18 June 1983. The purpose of this 1) Cloud Base Pattern: Repeated flight legs along the lidar flight was to determine accurately the size distribution beam just under cloud base were flown. Included in this and radiative characteristics of a field of cumulus and racetrack pattern were soundings, surface-flux legs, altocumulus clouds by aircraft.

FIG. 3. Same as Fig. 2, except on 1 June 1983 at 1336 CDT. A convective layer is apparent under a thin stratiform layer. A dust plume produced by agricultural activities is evident at a range of 4 km. Unauthenticated | Downloaded 10/06/21 02:42 AM UTC 454 Vol. 65, No. 5, May 1984

FIG. 4. Lidar-generated PPI scan obtained 4 June 1983 at 1005 CDT with the lidar scanning plane ele- vated to 6°. Cross sections of convective plumes are shown. Plume areal coverage decreases at longer ranges, which correspond to higher altitudes. Streeting of these clear air convective structures also is evident.

5. Lidar operations mixed layer, as well as cloud-droplet growth, produces un- mistakable lidar signatures of cloud base, penetrative con- The UW pulsed ruby lidar recorded digital data on the vection, and entrainment-zone characteristics. backscattered light intensity as a function of the slant range Several different angular scanning sequences were em- for 3 X 105 separate shots during 115 h of operation. Each ployed. During all data sessions, occasional RHI scans (Figs. shot provided a profile of atmospheric structure along a 7.68 2 and 3) were recorded to depict atmospheric structure at km path, which was split into 1024 intervals for digitizing. ranges between 1 and 7.68 km on a vertically aligned angular These profiles were corrected for shot-to-shot variations in sector above the horizon. This maximum scan angle was ad- laser energy, and for inverse-squared light attenuation, prior justed between 15° and 30° for each observation period to to storing on magnetic tape. In addition, a real-time software allow viewing of the entire atmospheric mixed layer. To facili- system produced color-enhanced displays showing RHI and tate data comparisons, the lidar, for all RHI scans, was PPI slices through the boundary layer. These pictures, such pointed directly over the ANL sodar site. as those shown in Figs. 2,3, and 4, provided information nec- Two types of azimuthal angle scans were employed: a wide- essary for operational decisions, flight planning, and lidar angle PPI scan (Fig. 4) to depict atmospheric structure in the system quality control. horizontal, and a triple-angle scan to provide lidar-observed Boundary layer thermals and other turbulence structures vertical profiles of wind speed, wind direction, and turbu- are evident in these displays because of the disparity in aero- lence intensity (Eloranta et al., 1975; Sroga et al, 1980). The sol concentration with height. Most aerosols are produced angular width of the PPI scans was selected during each ob- near the surface, and are drawn into the bases of thermals. servation period as a compromise between wide angular cov- Carried up with the rising air, they enhance their lidar re- erage and frequency of observation. The sector size selected turns. Hydroscopic aerosol swelling near the top of the varied between 22° (about four scans per minute) and 40°

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(about one scan per minute). layer dynamics can be extended beyond that obtained with During most periods of simultaneous lidar and aircraft laboratory tank and computer simulation studies. Ultimate observations, the lidar scanning alternated between short pe- applications include better moisture and temperature models riods of RHI and PPI modes. The elevation angle of the PPI for agriculture, better understanding of the conditions preva- scan was selected to place the top of the mixed layer at ranges lent just prior to severe storm initiation, better estimates of slightly greater than the distance to the ANL sodar site. This air quality in the air near the ground, and better turbulence provided both vertical and horizontal views of convective and cloud estimates for flight safety. elements for comparison with aircraft data, ANL sodar data, and ANL stereo cloud photographs. During certain periods, triple-angle scans were substituted for the wide-angle PPI scans in order to allow comparisons of winds and turbulence Acknowledgments. This research was supported by Grant ATM- measured from the aircraft, lidar, sodar, and kytoon data. 8211842 from the National Science Foundation. Partial support for lidar operations was provided by U.S. Army Grant DAAG 29-80-K- 0070. Support for the participation by Argonne Laboratory was provided by the U.S. Environmental Protection Agency by Intera- gency Agreement DW930060-01-0 to the U.S. Department of 6. ANL operations Energy. Support for limited nighttime studies came from National Science Foundation Grant ATM-8210685. NOAA's support through the National Severe Storms Laboratory is gratefully acknowledged. ANL was interested primarily in the ventilation of pollutants The efforts of many people contributed to the success of this through cumulus clouds. Vertical velocities and standard de- experiment. NSSL was host to the visiting research groups in viations of vertical velocities were measured within the whole BLX83, and was invaluable in the logistics, radar support, and inter- boundary layer, including occasionally at cloud base, using actions with the residents of Oklahoma. Richard Doviak, Bob the sodar system. The stereo camera system sampled the Rabin, J. T. Dooley, Jean Lee, Les Showell, and the many other people at NSSL deserve our special thanks. In addition, the radio- cloud field at intervals ranging from 30 s to 4 min, depending sonde teams from the United States Air Force 6 Weather Squadron on the wind speed, so that any interactions between cumulus at Tinker Air Force Base and the Army Artillery Board at Ft. Sill did clouds and boundary layer structures such as thermals could an excellent job gathering upper-air data as part of the special re- be documented. search RAOB network. If no clouds were present, then temperature structure func- The people from the National Center for Atmospheric Research (NCAR) who participated in BLX83 should be commended. Robert tion data were gathered with the sodar in concert with kytoon, Burris, Ed Brown, Peter Hildebrand, and David McFarland were lidar, RAOB, and aircraft measurements of the top of the part of the NCAR aircraft program. The sound advice from Bob boundary layer. Coordinated lidar and sodar observations McBeth contributed to the success of the RAOB program. Fred were made to study the development and structure of Brock, Julian Pike, Gerry Albright, Steve Semmer, John Militzer, Pat Grundmeier, Errol Korn, and Richard Bobka did an excellent ground-based thermals. job with the deployment of NCAR's new PAM II system. They all Ozone profiles were made in the early morning and evening demonstrated the value of a unified support organization such as under statically stable conditions using the kytoon. These NCAR to the meteorological research community. NCAR is spon- observations were timed to coincide with research flights of sored by the National Science Foundation. the NCAR King Air, which was in the area for about a week Marv Wesely, Rich Coulter, Dave Cook, Tim Martin, and Dave Hart of Argonne National Laboratory displayed teamwork and dedi- doing nocturnal boundary layer studies under the direction cation in their participation in BLX83. They were often operating of Lenschow from NCAR. Deposition data on sulfates, their equipment on site from before sunrise until late at night in ozone, and particulates were measured at the 5 m tower using harsh weather conditions. eddy correlation techniques. Finally, the research assistants from UW who contributed in many ways to the experiment deserve our thanks: Patricio Aceituno, The Queen Air flights did not measure chemistry or par- Reinout Boers, Merrilee Carlson, Tim Crum, Bob Chojnacki, ticulates, and thus cannot provide a direct measure of the Richard Ferrare, Dan Forrest, Louis Garand, Craig Kunitani, Dierk flux of those constituents into the cloud base. However, the Polzin, and Nick Wilde. Niels Nelson, also from UW, drove the lidar aircraft did measure the mass flux in portions of the cloud van between Madison, Wis., and Chickasha, Okla., in rain storms that often made travel difficult. base. Such information will be combined with pollutant con- In a list of acknowledgments such as this, the names of deserving centration information to estimate pollutant flux into the people might inadvertantly be omitted. We apologize to those peo- cloud layer. ple, but thank them for their contributions to BLX83.

7. Summary References BLX83 provided an integrated set of measurements aimed at studying how the convective structure of the daytime atmos- Eloranta, E. W., J. M. King, and J. A. Weinman, 1975: The determi- nation of wind speeds in the boundary layer by monostatic lidar. J. pheric boundary layer interacts with fair weather cumulus Appl. Meteor., 14, 1485-1489. clouds. The predominant structures observed were thermals, Kelley, N. D., and R. L. Lackman, 1976: Description of standard mechanical eddies, cumulus humilis clouds, and cumulus output data products from NCAR Research Aviation Facility air- mediocris clouds. Attention was focused on the entrainment craft. NCAR Res. Aviat. Facil. Bull. 9, NCAR, Boulder, Colo., 77 pp. zone at the top of the mixed layer. (Available from NCAR, P.O. Box 3000, Boulder, CO 80307.) As data analysis proceeds, our understanding of mixed- Kunkel, K. E., E. W. Eloranta, and S. T. Shipley, 1977: Lidar obser-

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vations of the convective boundary layer. J. Appl. Meteor., 16, tions Log and Data Inventory. Meteorology Department, Univer- 1306-1311. sity of Wisconsin, Madison, Wis., 72 pp. (Available from the Mete- RAF, 1981: Queen Air: Overview and summary of capabilities. orology Department, University of Wisconsin, 1225 W. Dayton NCARRes. Aviat. Facil. {RAF) Bull. 2, NCAR, Boulder, Colo., 10 St., Madison, WI 53706.) pp. (Available from NCAR, P.O. Box 3000, Boulder, CO 80307.) —, 1983b: Boundary Layer Experiment—1983 (BLX83) Scientist's Sroga, J. T., E. W. Eloranta, and T. Barber, 1980: Lidar measure- Flight Log. Meteorology Department, University of Wisconsin, ment of wind velocity profiles in the boundary layer. J. Appl. Madison, Wis., 100 pp. (Available from the Meteorology De- Meteor., 19, 598-605. partment, University of Wisconsin, 1225 W. Dayton St., Madison, Stull, R., 1983a: Boundary Layer Experiment—1983 (BLX83) Opera- WI 53706.) •

announcements1

Satellite workshop University of Michigan announces two summer conferences The Wisconsin Meteorological Satellite Workshop (WMSW) will be held at the Space Science and Engineering Center (SSEC) at the Two summer engineering conferences are scheduled for June 1984 University of Wisconsin-Madison from 16 July to 3 August 1984. at the University of Michigan. "Infrared Technology: Fundamen- It is intended to offer meteorologists a hands-on experience with tal and System Applications/7 will be held 18-22 June, and covers the latest advances in satellite meteorology, and is being spon- radiation theory, radiative properties of matter, atmospheric prop- sored by the Cooperative Institute for Meteorological and Satel- agation, optics, and detectors. It also emphasizes system design lite Studies (CIMSS). and the interpretation of target and background signals. The Enrollment in the workshop is limited and priority will be given "Advanced Infrared Technology" conference, 25-29 June, pre- to non-U. S. scientists who do not have a strong background in sat- sents the advanced technology needed for modern, state-of-the- ellite meteorology and to participants who enroll for the entire art, active/passive infrared and optical systems. Presentations three-week program. Instructors will be personnel from SSEC, the cover atmospheric propagation, detectors and focal plane array National Environmental Satellite Data and Information Service technology, discrimination characteristics of targets and back- (NESDIS), and from other selected institutions as expertise dic- grounds, and system designs. Familiarity with fundamentals of tates. All technical sessions will be held at the Meteorology and infrared is a prerequisite. For more information, contact Viola E. Space Science Building at the University of Wisconsin-Madison. Miller, Engineering Summer Conferences, 200 Chrysler Center, The workshop will be set up in modular format with each of the North Campus, Ann Arbor, MI 48109 (tel.: 313-764-8490). one-week modules being self-contained, as follows: 1) The Basics (16-20 July); 2) Satellite Data—A Survey (23-27 July); and 3) Sat- ellite Data-Applications (30 July-3 August). The fee for this workshop is $500 for the entire three-week ses- sion, or $250/week for individual weeks. The fee does not include housing or food service, which will be available at University dor- mitories at extra cost. For additional information, contact David Suchman, Space Science & Engineering Center, University of Wisconsin-Madison, 1225 West Dayton Street, Madison, WI 53706 Deadlines Calendar (tel.: 608-262-5772). Fellowships, grants, etc. 15 June 1984 Macelwane Annual Award (this issue, p. 471) 15 June 1984 Hanks and Orville Scholarships 'Notice of registration deadlines for meetings, workshops, and (this issue, p. 471) seminars, deadlines for submittal of abstracts or papers to be pre- Other sented at meetings, and deadlines for grants, proposals, awards, 13 August 1984 NCAR Research Aviation Facility nominations, and fellowships must be received at least three panel meeting months before deadline dates.—News Ed. (April 1984 BULLETIN, p. 400) •

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