ARM Water Vapor Measurements for Validation and Analysis Jim Mather Technical Director for the ARM Climate Research Facility

The ARM Climate Research Facility ARM is a United States Department of Energy climate research user facility. Objectives of the ARM facility: Provide the national and international scientific community with the infrastructure needed for scientific research on global change Global change research includes the study of alterations to climate, land productivity, oceans, water cycle, atmospheric chemistry, and ecological systems 2

Overview: Facility Components Research sites – permanent, mobile, and aerial Instruments and measurements Data processing, data quality, Data Archive Field campaigns – ground-based and airborne 3

Overview: Research Sites Southern Great Plains, SGP (1993) North Slope of Alaska, NSA: Barrow (1998) and Atqasuk (1999) Tropical Western Pacific, TWP: Manus (1996), Nauru (1998), and Darwin (2002) First ARM Mobile Facility, AMF (2005); Second ARM Mobile Facility (2010) ARM Aerial Facility, AAF (2007) 4

Cloud profiles: millimeter radar and lidar Temperature/relative humidity/wind profiles: radiosondes (Vaisala RS-92) Column water: microwave radiometer Column aerosol: solar spectral radiometer In situ aerosol optical and cloud nucleation properties Surface radiation budget: solar and terrestrial IR radiometers Surface meteorology: T/RH/wind Additional instruments being deployed through the Recovery Act Overview: Measurements and Instruments 5

Water Vapor Instrumentation At All Sites Vaisala RS-92 Radiosondes launched 2-4 times/day Radiometrics 2-channel (23 GHz, 31 GHz) Microwave Radiometers (in the process of replacing these instruments with updated versions that include a third 90 GHz channel) – gives column integrated vapor Atmospheric Emitted Radiance Interferometers (AERIs) or equivalent (spectral zenith radiance with 1 cm^-1 resolution) - can be used to derive water vapor profiles Multi-filter Rotating Shadowband Radiometer including a 940 nm channel water vapor channel (there is an array of MFRSRs around the SGP) – can be used to derive column integrated water vapor Surface humidity (including tower profiles at the SGP and NSA)

Water Vapor Instrumentation, Cont. The full array of water vapor instruments were available at the Southern Great Plains beginning in 1996 and operate to the present. Each site was subsequently deployed with this suite with the exception that an AERI has never been deployed on Manus (though that will change this year with the Recovery Act.

Recovery Act: Introduction $60M from DOE Office of Science for investments in instrumentation and research infrastructure 3-dimensional measurements of cloud scale dynamics, microphysics, and precipitation Enhanced measurements of: atmospheric aerosol absorption, scattering, composition and chemistry cloud composition Use new knowledge to improve the predictive performance of climate change models Over 120 individual procurement actions and 50 datastreams 8

Lidars SGP NSA TWP-D TWP-M AMF2 AMF1 SGP NSA TWP-D TWP-M AMF2 AMF1 HSRL Raman Doppler MPL MPL Upgrades Ceilometer HSRL Raman Doppler MPL MPL Upgrades Ceilometer Research Sites Mentoring/Science/Engineering: Rob Newsom and John Goldsmith 9

Raman Lidar - Darwin First light data (water vapor mixing ratio) from the newly installed Raman lidar at the Darwin ARM site. (Plot courtesy Dave Turner). In addition to the new Raman lidar in Darwin, there has been a Raman lidar at the SGP since 1998 (Ferrare et al., 2006, JGR).

Radiometry SGP NSA TWP-D TWP-M AMF2 AMF1 SGP NSA TWP-D TWP-M AMF2 AMF1 Sun Photometer AERI AERI-Extended Range MWR-Three Channel Solar Array Spectrometer Sun Photometer AERI AERI-Extended Range MWR-Three Channel Solar Array Spectrometer Research Sites Mentoring/Science/Engineering: Laurie Gregory, Joe Taylor, Maria Cadeddu, and Connor Flynn 11

Radiometery Spectral radiation data can provide information about water vapor and other gases The Solar Array Spectrometer: Measures zenith radiance and hemispheric irradiance over the range 0.35 – 1.7  m (2.5 nm res. below 1  m and 5 nm above 1  m) AERI: Measures zenith radiance over the range 3-19  m (1 cm -1 res.) 12 A retrieval is being applied to SGP AERI data to derive temperature and water vapor profiles. (Feltz et al., J. Appl. Met.)

Radars SGP NSA TWP-D TWP-M AMF2 AMF1 SGP NSA TWP-D TWP-M AMF2 AMF1 X-Band Precipitation C-Band Precipitation Ka-X Band Cloud Ka-W Band Cloud MMCR Upgrades X-Band Precipitation C-Band Precipitation Ka-X Band Cloud Ka-W Band Cloud MMCR Upgrades Research Sites Mentoring/Engineering: Kevin Widener and Nitin Bharadwaj Value-Added Products: Scott Collis and Karen Johnson 13

Radar Retrievals ARM is deploying a variety of scanning radars including X-band radars at the SGP and NSA sites and C-band radars at the SGP and TWP/Manus sites. While these radars are intended primarily to measure spatial distribution of clouds and precipitation, it has been shown recently that scanning radar data can be used to derive near surface spatial distributions of water vapor. 14 Comparison of low-level water vapor derived from the NCAR S-Pol radar at a point with in situ measurements, overlaying profiles from a Raman lidar (Weckwerth et al., 2005, J. Appl. Met.). While shown here for a point, such a technique can be used to derive spatial variability of low-level water vapor.

Field Campaigns In addition to its continuously operating sites, ARM supports field campaign operations for shorter periods, generally (though not always) in support of the operational sites. Field campaigns can include: Airborne measurements Enhanced radiosonde operations (e.g. increased frequency or spatial networks) Guest instruments See a list of past campaigns

For More Information Contact Jim Mather at or visit the ARM web site: particularly the measurements page dealing with atmospheric moisture: To learn how to propose a field campaign or browse past campaigns: To order data: