The Atmospheric Radiation Measurement (ARM) Program: An Overview

1. The Atmospheric Radiation Measurement (ARM) Program:An Overview Robert G. Ellingson Department of Meteorology Florida State University Tallahassee, FL

3. Outline • Where did we start? • What have we done? • Where are we going?

4. Where did we start? 1990: The single largest cause of variability in climate models is the treatment of clouds and their coupling to the earth radiation budget • Cess et al., JGR • Our Changing Planet, USGCRP => the cloud parameterization problem

5. ARM Goal To improve the performance of General Circulation Models (GCMs) by: • Improving the treatment of radiative transfer under clear sky, general overcast, and broken cloud conditions • Improving the parameterization of properties and formation of clouds

6. ARM Questions • If we can specify a cloud field, can we compute the radiative fluxes? => Requires knowledge of cloud properties (3D structure, water path, phase, size, etc.)

7. Need atmospheric observations to -- test hypothesis in process model studies -- analyze for empirical relationships and statistical characteristics

8. ARM Questions • If we can specify a cloud field, can we compute the radiative fluxes? => Requires knowledge of cloud properties (3D structure, water path, phase, size, etc.) • If we can specify the large-scale atmospheric fields, can we predict the cloud field properties? => Requires 3D field of state properties and cloud field properties

9. Need data sets that describe the large scale environment in which clouds form

10. ARM Program Components • Development of ground-based remote sensing facilities • Continuous data acquisition and archival • Data analysis • Physical modeling • Parameterization development and testing

11. What have we done? • Sites • Science

12. Location of Current ARM Sites

13. Southern Great Plains Site Central Facility

14. Southern Great Plains Central Facility

15. North Slope of Alaska Site

16. North Slope of Alaska Site

17. Tropical Western Pacific Site

18. Nauru Manus Island Tropical Western Pacific Site

19. Instrumentation at Sites • 35 GHz Radar (cloud properties) • Lidar (pulsed laser; particle and thin cloud properties ) • Sky imagers (cloud cover) • Broad-band and narrow-band radiometers (solar and infrared radiation) • Microwave radiometer (water vapor and liquid water) • Meteorology sensors (temp, humidity, winds)

20. ARM Science -- Some Examples* • Instrument development and data analysis • Radiation Studies • Model testing and development * Lots of possible choices!

21. Total Sky Imager -- Nauru 99-07-13 1150 99-07-13 1351

22. ARM Raman Lidar

24. ARM Millimeter Cloud Radar (MMCR)

25. 35 GHz Radar Reflectivity (Arctic)

26. Radar data ARM now has 4 radars in operation: • SGP – 4 years of data • TWP Nauru – 2.5 years • TWP Manus – 1+ years • NSA – 2 years

27. ARM Science -- Some Examples* • Instrument development and data analysis • Radiation Studies • Model testing and development

28. The Radiation Questions Can we compute solar transmission and infrared emission accurately • in a clear atmosphere? • in an atmosphere with an overcast, single-layer cloud? • in an atmosphere with broken clouds and/or multiple cloud layers?

29. Clear Atmosphere • Yes • Infrared irradiance to < 5 W/m2 (2%) • Solar direct irradiance to < 0.5% • Solar diffuse irradiance to < 10 W/m2 (if we account for diffuse radiometer offset) • Remaining uncertainty probably due to absorption by trace gas species or aerosol

30. Single Layer Cloud • Maybe (anomalous absorption problem) • Question is whether measured atmospheric absorption in clouds exceeds calculated absorption • Published articles show both Measured = 1.5 * Calculated Measured ~ Calculated

31. Current ARM Role in the Problem • ARESE II Experiment (March, 2000) • Stratus cloud experiment at SGP site • Instrument radiation airplane flying above cloud over central facility • Remote sensing of cloud from ground • Some in cloud sampling with second aircraft • Data released to public after examination and evaluation by ARESE science team

32. Results To Date • Analyzed 3 cloud days • Preliminary results show measured = 1.1 – 1.15 * calculated • Experimental uncertainty • In individual measurements: few % • In net flux (difference): few % to 10 % • Evaluation continues, group of papers to be submitted by end of summer

33. Broken Clouds • Don’t know • Work in progress • Defining 3D cloud properties • Developed 3D radiation codes for solar spectrum • Comparison study of 3D codes

34. ARM Education Outreach Program • ARM Program mandates an education outreach program for each CART site. • Education outreach must be relevant to the needs of the local and regional communities. • Content and management of the program has been determined by the CART Site Manager. • Starting in FY2000, the Education Outreach Program is now integrated across all 3 sites.

35. Check out our Scavenger Hunt !! http://www.arm.gov/docs/education/

36. NSA Classroom visits Classroom visits in Barrow

37. Classroom visits in Atqasuk

38. Curriculum Workshops in the Tropics ARM scientists and regional collaborators present background materials. Teachers practice activities that demonstrate concepts for later use in their classrooms.

39. TWP Teacher Participation Manus: “Atmospheric Pressure” (Module 1, Book 1) Manus: “Making Clouds” (Module 2, Book 1)

40. TWP Teacher Participation Manus: “When Land Ice Melts” (Module 4, Book 1) Port Moresby: “Plant Growth and Carbon Dioxide” (Module 3, Book 2)

41. The educational outreach portion of the ARM Program seeks to provide schools with the materials necessary to use environmental data in the classroom. • ARM data is available online through these web pages. http://outreach.ocs.ou.edu/arm

43. ARM Web Site www.arm.gov

44. Is ARM Still Needed? • IPCC Report (2001) cites largest areas of uncertainty in climate change scenarios: • Cloud feedbacks • Effect of changing particle loading on cloud properties • Too much of what we have learned is not yet incorporated into climate models • Climate models need to be evaluated quantitatively and ARM data are part of the necessary tools

45. ARM Future • Continue to operate ground-based sites • 10 year time series • Transition some sites to permanent facility • Construct mobile facility • Expand science activities in parameter-ization and model development • ARM Fellows at NCEP and ECMWF • Promote model comparison studies • Link to operational testing of climate models

46. ARM Future (2) • Forge stronger links with national programs in hydrology, human health, and satellite remote sensing • NASA Earth Observing System (EOS) • DOE Tropospheric Aerosol Program (TAP) • Forge links with international programs • World Climate Research Programme (GEWEX) • NASA Cloud Radar (Canada) and Lidar (France) • European Space Agency

47. In Conclusion, ARM … • Has a well defined mission in the climate research community • Is a highly successful program in terms of its science impact • Has important questions to address over the next 10 years

48. For More Information Please Contact Tom Ackerman Chief Scientist Pacific Northwest National Laboratory