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43rd Aerospace Sciences Meeting and Exhibit Conference AIAA-200S-02S9 10-14 January 2005, Reno, Nevada

TAMDAR Sensor Validation in 2003 AIRS II

Taumi. S. Dani els' and John J. Murrai NASA Langley Research Center, Hampton, Virginia, 23681

Mark V. A nd erso n ~ , D a ni e l J. Mulall y§, Kri topher R. Jensen" AirDat, LLC. , Evergreen, Co lorado, 80439

Cedric A. Graingertt and David J. Delene** University of No rth Dakota, Grand Forks, North Dakota, 58202

This study entails an assessment of T AMDAR in situ , relative and sensor data from seven flights of the UND Citation II. These data are undergoing rigorous assessment to determine their viability to significantly augment domestic Meteorological Data Communications Reporting System (MDCRS) and the international Aircraft Meteorological Data Reporting (AMDAR) system observational databases to improve the performance of regional and global numerical prediction models. NASA Langley Research Center participated in the Second AUiance Icing Research Study from November 17 to December 17, 2003. TAMDAR data taken during this period is compared with validation data from the UND Citation. The data indicate acceptable performance of the T AMDAR sensor when compared to measurements from the UND Citation research instruments.

I. INTRODUCTION HE Tropospheric Airborne Meteorological Data Reporting (TAMDAR) sensor is designed to mea ure winds, T temperature, humidity, turbul ence and icing from regional commercial aircraft'. AirDat, LLC, developed th e 2 sensor under contract for NASA . A system of TAMDAR sensors and data lin ks on a suffi cient number of aircraft woul d provide hi gh temporal- and spati al-resolution and temperature data in the lower troposphere. Such a system has the potenti al to substantiall y improve weather fo recasting. Moreover, the hi gh-resolution hu midi ty data produced by T AMDAR is unprecedented, and may provide substantial benefits. The meteorological community i keenly in terested in additional observati ons of the lower troposphere and in parti cul ar moisture data as 3 evidenced by the Ameri can Meteorological Society Statement . The University of North Dakota (UND) Cessna Citati on II and the NASA ER-2 parti cipated fro m November 19 to December 14, 2003, a period of overl ap between two separate fie ld campaigns, the Second Alli ance Icing Research Study (AIRS II). AIRS II fli ghts were over Ottawa, Ontario and th e Mirabel Airport outs ide M ontreal, Quebec. To support the campaign, it was necessary to identi fy suitable cases for targeting, prov ide information on the location of sensitive areas, and have th e fac ilitie to control each observing system at short noti ce. Early morning 4 meteorological reports were used fo r daily aircraft routing. Additional informati on can be fo und on th e websites ,5. As part of the development process, the T AMDAR sensor has been tested in various ground-based facili ties and 6 on different atmospheric research aircraft . The subj ect of thi s report is va lidation of T AMDAR sensor usin g data other instruments install ed on the UND Citati on. Additional va lid ati on data came fro m GPS (fTo m the UND Citation). In additi on, other data from two sounding instruments is used for compari son purposes .

• Project Manager, Electromagnetics and Sensors Branch, NASA, MS-473, Hampton, VA 23681 t Atmospheric Scientist, Chemistry and Dynamic Branch, NAS A, MS-401B , Hampton, VA 2368 1 *Pres ident, AirDat LLC, 30746-410 Bryant Dr., Evergreen, CO, 80439 § Vice President, Ai rDat LLC, 30746-410 Bryant Dr. , Evergreen, CO, 80439 •• E ngineer, AirDat LLC, 30746-410 Bryant Dr., Evergreen, CO, 80439 tt Professor, Departme nt of Atmospheri c Sciences, UND, Grand Forks, ND, 58202 *~ Assistant Professor, Department of Atm ospheri c Sciences, UND, Grand Forks, ND, 58202

Ameri can In titute of Aeronautics and Astronautics II. ALLIANCE ICING RESEARCH STUDY II AIRS II objectives were to: a) develop techniques to remotely detect, di agnose and forecast hazard ous win te r conditions at airport , b) improve weather forecasts of aircraft icing conditions, c) improve characteri zation of the 7 aircraft icin g environment and d) improve our understanding of th e icing process and its effect on aircraft ,g In order to support th e AIRS II operati onal obj ecti ves, data was coll ected to: a) in vesti gate the conditi ons associated with supercooled large drop formation, b) determine conditions governing cl oud glaciati on, c) document the spatial di stribution of ice crystal s and supercooled water and th e conditions under which they co-exist, and d) veri fy the response of remote sensors to various cl oud particles, and determine how thi s can be ex pl oited to re motely determine cl oud compositi on.

III. AIRCRAFT INSTRUMENTATION For th e AIRS II fli ghts, th e three main aircraft, the NRC Convair 580, the NASA Twin Otter, and the NCAR C 130 were j oined by the UND Citati on. Icing fli ght confi gurati ons typi call y consisted of the three main aircraft in fli ght pattern s near the Mirabel site. Data from the three main aircraft are not pre ented here and are onl y menti oned fo r completeness. However, data from T AMDAR sensor and th e UND Citati on instruments is pre ented. The UND Citati on aircraft is instrumented for in-situ cl oud phys ics research. For thi s fi eld campaign the T AMDAR sensor pac kage was installed on th e fu selage near th e ship 's pitot probe. In addition, th e aircraft was equipped to deploy NCAR GPS dropsondes. The NASA ER-2 carried the NAST-I instrument. The temperature sounding data were retrieved fro m NAST-I 9 in frared hyperspectral radi ances . NAST-I data were searched for th e locati on where and time when the ER-2 and th e Citation were coll ocated within a delta Latitude <= 0.05°, delta Longitude <=0.05°, and delta time <= 5 min. Mean values for temperature of NAST-I retri evals within the matching cri teri a are computed and reported as NAST­ I temperature data. The temperature accuracy fo r the T AMDAR sensor is ± I 0c. To veri fy this value, a comparison to UND Citati on Rosemount Model 102 Probe sensor data over th e peri od of interest and al so over the entire day's fli ght is made. The Rosemount sen or accuracy is 0.5°C. Both TAMDAR and Rosemount data are corrected for dynami c heating. The T AMDAR sensor has two independent RH sensors, Honeywell HIH seri es thin film capacitive types. As both were reporting very similar values, onl y data from one is used for thi s compari so n. The reported RH accuracy is +/- 5% for down to O°C and below airspeed of Mach 0.4. Above Mach 0.4 th e RH accuracy i +/­ ] 0%. A lack of calibrati on data below O°C fo rces an extrapolati on of the ava il abl e calibration data. While thi s is probabl y valid down to about -40°C, significant measurement differences will be apparent at the lower temperature extremes. With actual calibrati on data at the lower temperatures, the TAMDAR sensor values for relati ve humidity would be in line with the +/- 5% accuracy. To verify the T AMDAR RH values, a compari on to UND Citati on relati ve humidity data is made. There were two sources of relati ve humidity data on the UND Citati on, a tunabl e di ode laser instrument and an EG&G dew point hygrometer. Unfo rtunately, post campaign data analys is revealed th at both these instruments were mi scalibrated. Anoth er source of verifi cati on is GPS drop onde data. The initial values fo r relative humidity are often reported about 60-75 seconds after launch. The values used in thi s paper were converted to Figure 1. November 24, 2003 Flight Track. relati ve humidity with respect to ice using the Hyland lO and Wexler formulation . The T AMDAR sensor computes wind peed and directi on from measured airspeed, aircraft (UND Citati on) magneti c heading, and GPS ground track. TAMDAR wind vector magnitude accuracy is +/-3.08 mls (+/- 6 kn ots). To veri fy thi s value, a comparison to UND Citation nose probe sensor winds is made.

IV. CASE STUDIES For each case study, a description of the fli ght confi gurati on is fo llowed by comparison data. T AMDAR data is validated against the UND Citati on data and compared to sounding data from dropsondes (if avail abl e).

2 Ameri can Institute of Aeronauti cs and Astronauti cs A. November 24, 2003 Case Study On this date, the UND Citation flew an icing mi ss ion as shown in Fig. 1. A cold fron t was approaching the Mirabel area from the we t that was expected to produce signifi cant icing during the evening and early morning hours of the fol lowing day. The Citation was to position in Ottawa with th e expectati on of flying an early morning mission during the icing event on Tuesday, November 25. The Citation fl ew past Ottawa to penetrate the frontal zone and to measure the cloud mi crophysics before the sy tern reached Ottawa. The aircraft took off from Bangor, ME at 1808 UTC and flew through the frontal zone to Lond on, Ontario. Cloud microphysic data were collected at several temperature levels in the fro ntal system. Ice was detected at 2040 UTC and throughout the rest of the flight. The Citation then turned back to the east to pass through the fro ntal zone again and landed in Ottawa at 2155 UTe. The total flight ti me for the mi s ion was 3.8 hours.

2 1.5 · u '"Q) · l" . ar 0.5 .· , o ...t:4...• .:tI, .,t,.• ~.' .,; 0 . . . J..L · -". ... ------;~... .~ 5 ·l.... ~ . ~ .. ~ ~ t l'ti.~:" ~ -0.5 a. !>-~~ . ~ . Q) . ~ 30 ~ -1 ~ • rn f- Qi 20 a: -1.5 10 -2 0 18:00 18:40 19:20 20:00 20:40 18:00 18:40 19:20 20:00 20:40 Time, UTC Time, UTC

Figure 2. Temperature Difference. Figure 3. Relative Humidity Comparison. 2. Temperature 10 15 . 8 f------+------1----~,---__I ci> . .3 10 . ~.,; 6 ~.~--- ~ .,; u , g . '. ~',+,' ! ~ 5 . ~ -\ . l"4 ~. • • - •••• ' ••• Q) . :: .. . '···i· : ;eo~ 2 : - - ' : '};... ~ - ..,'" (5 0 ~~...... ~'" ~!1. • • &:- , to • \ --, ••••-/ ~ c '0 ' .I".(?~ _ I '}"~ .' ~~.; . of. : T . .Q ;',;>~~~~.,1~~ .... 8. 0 -.if"'~~4"~"'''· ·~V . I:t.. ..~• • (/) \ ~ -5 .....: .....: .\~( '. . . . : (5 r--.:-:.;:-... • ~ . • . ~ -2 +-~~---~-~~--r----+----~ 3: " '0 .. 4 +-----11----~.r_---_+----__1 ~ -10 . .

_6 L-___~----~----+_---___1 -15 18:00 18:40 19:20 20:00 20:40 18:00 18:40 19:20 20:00 20:40 Time. UTC Time, UTC Figure 4. Wind Speed Difference. Figure S. Wind Direction Difference.

Shown in Fig. 2 is a time-seri es plot of temperature comparison between the TAMDAR and UND Citation. Over the in itial 2.5 hours of flight (excluding the icing porti on after 2040 UTC), the mean difference is - O.l3°C and the standard deviation is 0.26°e. A systemati c deviation is seen in all the plots at 2000 UTC and is due to recovery from an icing event. 1. Relative Humidity Shown in Fig. 3 is a time-series plot of relative humidity. Over the non-icing portion of the fli ght, the mean difference in relati ve humjdity is - 1.7 % and the standard deviati on is 12%. 2. Wind Sp eed A time-series plot of computed wind speed differences is shown in Fig. 4. The mean di fference is 1.2 mls and the standard deviation is 1.9 m/s. 3. Wind Direction Figure 5 is a time-serie plot of wind direction differences. The mean difference is -l.2° and the standard deviation is 4.4°.

3 American Institute of Aeronautics and Astronautics B. November 25, 2003 Case Study As shown in Fig. 6., the UND Citation took off from Ottawa at 1506 UTe. The forecast was for the low cloud at Mirabel to last onl y a couple of hours, so th e fli ght pl an was adjusted to release dropsondes later and proceed back to Bangor with the hope of finding icing conditions farth er to th e east in northern Maine. Four dropsondes were relea ed at FL370 in the training area with a piral descent down to FL260. The aircraft headed bac k to Bangor at FL270 with the pl an to change altitude when the Citation reached signifi cant cl oudine . A very shall ow low layer of broken stratocumulus wa present that graduall y cleared during the approach to Bangor. A small layer of glaciated altostratus well above FL270 (temperature -42 C) wa observed, but nothing with any icing potenti al was seen to th e east of th e Bangor area, 0 th e aircraft landed at Bangor at 1756 UTe. The total fli ght time fo r the Figure 6. November 25, 2003 Flight Track. ml sion was 2.5 hours. 1. Temperature The plot shown in Fig. 7 is a time-seri e pl ot of temperature differences. The mean difference is O.25 °C and the standard deviati on is O.38 °e.

2 40 1.5 . - 30 - . *oj oj c: 20 _. c: . ;. "i" , " : L~ ~~ '-¥,~ ~-~\:- g 10 -"-.1 ~ ~. * 0.5 fo· ... ·~ is :.- "" ~ ~.! ~ ~ ,t",· ~ 1 ~ I.~:~ 0 .. ,g 0 !, ~ r-.V ~ • \j ::> I . ~~~~~ -~ 041-\ :. :'<.J .. t ;./'i4.- l§ ·0.5 ~, . ~ -10 "..~ Q) . I - t .. a. Q) 'I E -1 . . .., -20 Q) t- ;;; --~. - -1.5 ;.~ . . ~ -30 : ,- ;y -2 -40 I 15:20 16:00 16:40 17:20 18:00 15:20 16:00 16:40 17:20 18:00 Time. UTC Time. UTC Figure 7. Temperature Difference. Figure 8. Relative Humidity Difference.

12 ------,------,------,------, 20 ,------,,------,------,------. on ~ 15 t------~L------_+------~------4 ~'" 10 t--r-----~~------_+------~------.'~

.- "0 .,; -15 . ~ -12 L------~------~------_+------~ -20 15:20 16:40 17:20 18:00 15:20 16:00 16:40 17:20 18:00 Time. UTC Time. UTC Figure 9. Wind Speed Difference. Figure 10. Wind Direction Difference.

2. Relative Humidity Shown in Fig. 8 is a time-seri es pl ot of relative humidity differences. The mean difference in relati ve humidity is -4.9% and the standard deviati on is 9.8%.

4 American Institute of Aeronauti cs and A tronautics l_ --,

3. Wind Sp eed and Direction A time-series plot of computed wi nd speed differences is shown in Fi g. 9. The mean di fference is -0.22 mls and the standard deviation is 20 m/s. Figure 10 is a time-seri es plot of wind directi on differences. The mean difference is 1. 2° and the standard deviation is 9.20.

C. November 30, 2003 Case Study The Citation took off from Bangor at 1624 UTC, arriving over Mirabel at FL350 at about 1730 a hown in Fig. 11 . A spiral de cent was made over the runway in tersection down to FL40. Clouds were not encountered until about FL72 , where there was a layer about 1000 ft thick. The lower cl oud had tops sli ghtl y above FL40, but variable. Several measurement passe were made along the runway at FL40 going in and out of cloud along the way. In cloud , the Citation encountered light to moderate rime ice and liquid water contents of 0. 1 to 0.4 g/m3. This was fo ll owed by a mjssed approach over th e run way from FL40. The cloud extended down to sli ghtl y below FL20. This was followed by passes at FL70 going west to east and missed approaches from FL70 over the runway going east to west. This profile was carri ed oul several times In general, the liquid water content was hi gher in the Figure 11. November 30, 2003 Flight Track. upper cloud layer, with larger mean values of the droplet sizes. There were a few ice crys tal s in both layers, but the clouds were composed primarily of water droplets. The cloud were well characterized by th e measurements in the hori zontal as well as the verti cal.

- 15 ~------r------.------.------.------. 60 r--'~~~~~----r-----r---~ • Citation • TAMDAR I' Citation • TAMDAR 1 50 t-~==~====~----~----~--~ - 25 ~------~----~------~------~----~ .... () ~4 0 f------_4------~------+_----_4------~ ~ :0 '"E .I ~ - 35 --~----~----~------~------~--~~ £ 30 ~----_4------~------+_----~------~ ~ E Q) ~ ~ -45 ----~~~----_4------~------4__j~__1 1m" . a;cc ~• • ., ' -",,r•~ '+" - ..• •~• . 10 - ' J/hJ...... ~ -:. #3 " ....,.l,,~.~J • • ~ ~- . 'i ' I" -~'":. ~·' 1 '···;,~'(~·~!' ..~·:;' -55 ~------~----_4------~------4_----~ o +_----~------~------+_----_.--~~~ 16:30 16:45 17:00 17:15 17:30 17:45 16:30 16:45 17:00 17:15 17:30 17:45 Time. UTe Time. UTe Figure 12. Temperature Comparison. Figure 13. Relative Humidity Comparison.

60 r-~~c=~~~--r--~-~ 320 I--;::::;=r=:::;::;:;:;:~----I----I--I • Citation • TAMDAR • Citation • TAMDAA ..'" ~ 300 ~'" c ..g 280 +II"I--iH~Io!--.--+_... r.:.- -t-----~---"'W-f4f "~ is -g 260 +------t------'-~"'-----+_---~------''_j 20 ?:

10 T-----~------+------4_------~----~ 2 40 +_----t-----~-----+_--_.-----~ 16:30 16:45 17:00 17:15 17:30 17:45 16:30 16:45 17:00 17:15 17:30 17:45 Time. UTe Time. UTe Figure 14. Wind Speed Comparison. Figure 15. Wind Direction Comparison.

5 Ameri can In stitute of Aeronautics and Astronautics ,r­

1. Temperature Comparison The time-seri es pl ot shown in Fig. 12 is a comparison of temperature data from the initial 75 minutes of fli ght. The high rate turns and encounters with ice invalidate the TAMDAR data during different intervals during the remainder of the fli ght. While error stati sti cs could be computed on individual segme nts, this initial segme nt that includes a take-off sounding a nd 60 minutes of cruise fli ght are uffic ient for this comparison. A mean difference o f - 0.47°C and standard deviation of 1.8°C was computed from this segment. 2. Relative Humidity Comparison Another time-seri es pl ot of data is shown in Fig. 13 for a comparison of relative humidity. The same time interval as describe above is used. The mean difference was -3.1 % and the standard deviation was 6.7%. 3. Wind Speed and Direction Comparison Sho wn in Fig. 14 is a time-seri es comparison of computed wind speed of the same 75-minute segment. The mean difference wa - 1.4 mI and tandard deviation wa 10 mls. A time- erie pl ot of computed wind directi on is shown in Fig. 15. For this segment, the mean differe nce is - 1.5° and the standard deviatio n is 15°.

v. CONCLUSIONS The intent of this paper is to use in-situ te mperature, re lati ve humidity, and winds aloft data from the U D Citation as a re fere nce to compare all other measure me nts against. With the exception of the problems noted with the UND Citation re lative humidity data, the reference data it provided proved to be hi ghl y valuable. The data were coll ected in an extre me environme nt and yet the T AMDAR sensor maintained the desired accuracies. While not presented here, the TAMDAR data for the other parameters showed similarly acceptable performance. This fi e ld campaign was conducted prior to the completion of the TAMDAR sensor develo pment phase. Results were used to help refine the sensor algorithms and improve the performance specificati o ns. In summary, the TAMDAR sensor performed very we ll over the entire period of the fi eld campa ign. The data from this new sensor compares favorabl y with the other in struments. The sensor should be abl e to collect the necessary data to significantly augment do mesti c Me teoro logical Data Communi cati ons Reporting System (MDCRS) and the international A ircraft Meteoro logical Data Reporting (AMDAR) syste m observatio nal data bases.

REFERENCES

1 Danjels, T. S., "Tropospheri c Airborne Meteorological Data Reporting (T AM DAR Sensor Development," 2002-02-153, SAE General Aviation Techn ology Conference and Ex position, April 16- 18, 2002, Wi chita, KS .

2Dan iels, T. S. , Tsoucalas, G. , Anderson, M. , Mul all y, D. , Moninger, W., Mamros h, R., "Tropospheric Ajrbome Meteorological Data Reporting (TAMDAR) Sensor Development," 11th Con! on Aviation, Range, and Aerospace , Hyann i , MA, American Meteorological Society.

3 American Meteorological Society Council, "Support fo r Automated Ob ervati ons from U.S. Commercial Aircraft," Bulletin of the American Meteo rological Society, 84, SIS-S17, Febru ary 2003.

4Murray, J. J. and guyen, L. "NASA Langley ATReC & AIRS- II Satellite Page," [cited ovember 10, 2003], URL: http://www-angl er. larc. nasa. gov/bangor/

5"Alli ance Icing Research Study II Webpage," [cited ovember 19,2003], http://www.airs-i cing. org/AJRSIlIAJRSII.htm

60 ani els, T. S., Tsoucalas, G., Anderson, M., Mul all y, D., Moninger, W. , Mamros h, R. .. ibid.

7Murray, J. J., Smjth Sr, W., Daniels, T., Minni s, P., Kapitzke, M. , Poell et, M., Avery, M., Revercomb , H., McGill , M, Myers, J., "Alliance Icin g Research Study n, Science Pl an Appendix E," [cited November 14, 2003], URL: http://www.airs­ icing.org/ AIRS IIIin side/ MRS I1 .htm

8Hallet, J. , Isaac, G. , Po\itovich, M. , Marcotte, D., Reehorst, A. , Ryerson, C , "AJRS II Science Pl an," [cited Jul y 7, 2003], URL: http://www.ru rs- icing.org/AJRS 1I/2003-07-07 AIR S II Science Pl an. pdf

9Zhou , D. K., Smith, W. L., Li, J., Howell , H. B., Cantwell , G. W. , Larar, A. M., Knuteson, R. 0., Tob in , O. C , Reverco mb , H. E., and Mango, S. A. , 2002: ''Thermodynamic product retri eval meth odology fo r AST-I and va lidati on," Applied Optics. 41, 6957-6967.

IOHyland, R. W. and Wexler, A., "Formul ations for the Thermodynami c Properti es of th e saturated Phases of H20 from 173. 1SK to 473. 1SK," ASHRA E Trans , 89(2A), SOO-SI9 , 1983.

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