Comparison of Radiosonde and Profiler Data with ACARS Data for Describing the Great Plains Low-Level Jet Ross W. Bradshaw Meteorology Program, Dept. of Geological and Atmospheric Sciences, Iowa State University, Ames, IA Mentor: Daryl Herzmann Dept. of Agronomy, Iowa State University, Ames, IA

Motivation: General interest in aviation Possible decommissioning of radiosondes in favor of ACARS in near future Wanted to test data on a feature normally difficult to observe

ACARS: Aircraft Communications, Addressing, and Reporting System American Airlines, United Airlines, Delta Airlines, Northwest Airlines, FedEx, and UPS have sensors on all their aircraft, as well as some business jets and other airlines Sensors record temperature, onboard computers calculate wind speed and direction Used in most numerical models already - RUC heavily dependant on ACARS observations

David Helms – NOAA’s Office of Science and Technology FY08 – Start elimination of redundant soundings Example: Southwest Airlines –450 Boeing 737’s –8 destinations daily (16 soundings daily) –Total of 7,200 soundings per day Expand sensors to record water vapor, turbulence, icing, and air quality Available to public in near real-time NWS cost reduction of 4 million dollars per year

Radiosonde (purple) and WVSSII (black) Comparison April 26, 2005

12 Hour time-lapse of United States ACARS measurements 68,000 Observations/Day

ACARS Sensor

Methods: Checked climatological data from Southeast Nebraska for nocturnal thunderstorm occurrences Used Iowa State’s meteorology data archive to acquire wind profiler data Found ten cases with low-level jet occurrence in great plains for 2005 and 2006 warm seasons

24 June Haviland, KS profiler as viewed through Gempak Altitude (m) Time (UTC)

Low-level jet instances evaluated during warm seasons of 2005 and 2006 DateLocationTime (UTC)Time (LST) 24 June 2005Haviland, KS0300 – – June 2005Haviland, KS0300 – – July 2005McCook, NE0300 – – July 2005Haviland, KS0300 – – July 2005Vici, OK0000 – – May 2006Vici, OK0000 – – July 2006Haviland, KS0000 – – August 2006Haviland, KS0000 – – August 2006Haviland, KS0000 – – August 2006Hillsboro, KS0000 – – 1200

Methods: Wichita Mid- Continent Airport in Wichita, KS chosen as the ACARS reference point ACARS data acquired from Earth Systems Research Lab, Global Systems Division (ESRL, GSD) Wichita, KS Airport Hillsboro, KS Profiler Haviland, KS Profiler McCook, NE Profiler Vici, OK Profiler

Data and Analysis: Radiosonde and profiler data collocated with ACARS by altitude Comparisons made with data separation, altitude of airplane, and wind speeds for each observation source

Data Point Separation Schwartz and Benjamin (1995) found that distance separation of 60 km or more create too much difference in wind speeds The overall average distance separation of this study was 187 km with a standard deviation of 48 km This is outside of what Schwartz and Benjamin consider acceptable

24 June 2005 – Distance separation between Haviland, KS profiler and ACARS observation

Airplane Altitude In overall study, the airplane altitude: –Mean was 8,770 m (~325 hPa) –Median was 10,556 m (~240 hPa) –Standard deviation was 3,530 m Most low-level jets exist below 2,500 m In a comparison of altitude vs. observed wind from the ACARS data, near surface observations showed sharp increase in wind speed

31 July 2006 – ACARS reported altitude and ACARS observed wind speed

Observed Winds Wind direction was consistent with all observations which agrees with the findings of Lord et al. (1984) The wind speed measurements are the most inconsistent with the radiosondes –Inconsistency most likely due to difference in amount of observations

Scatter plot for all cases combined of ACARS wind speed against profiler wind speed

Case with least correlation: 10 August 2006 – ACARS wind speed against profiler wind speed

Case with most correlation: 31 July 2006 – ACARS wind speed against profiler wind speed

Conclusions: Radiosondes only provide observations at 00 UTC and 12 UTC, missing most of the low-level jet occurrence Radiosonde network too sparse –Only 2 year-round radiosonde sites in Kansas

Conclusions: ACARS system failed to accurately locate and diagnose the low-level jet –Most ACARS data restricted to upper atmosphere, fails to produce sufficient near-surface observations –Too much separation between sources to make accurate data comparison Profiler network sufficient in locating the Great Plains low-level jet –3 to 4 profilers in each Great Plains state –Observation times only separated by 6 min –Makes observation every 250 m –Proven accurate

Future Studies: More airports could be used in a larger study Wider range of data including more cases Study other mesoscale phenomena

Acknowledgements: Daryl Herzmann (Iowa State University) –For helping acquire and organize data Dr. Eugene Takle (Iowa State University) –For guidance in completing the project Thank you both very much!

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