ARM Water Vapor Measurements for Validation and Analysis

Jim MatherTechnical Director for the ARM Climate Research Facility

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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

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Overview: Facility Components

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

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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)

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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

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

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Lidars

SGP

NSA

TWP-D

TWP-M

AMF2

AMF1

HSRL

Raman

Doppler

MPL

MPL Upgrades

Ceilometer

Research Sites

Mentoring/Science/Engineering: Rob Newsom and John Goldsmith

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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

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

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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 mm (2.5 nm res. below 1 mm and 5 nm above 1 mm)

AERI: Measures zenith radiance over the range 3-19 mm (1 cm-1 res.)

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A retrieval is being applied to SGP AERI data to derive temperature and water vapor profiles. (Feltz et al., 2003. J. Appl. Met.)

Radars

SGP

NSA

TWP-D

TWP-M

AMF2

AMF1

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

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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.

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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

http://www.arm.gov/campaigns/table

For More Information

Contact Jim Mather at Jim.Mather@pnl.gov

or visit the ARM web site: http://www.arm.gov/

particularly the measurements page dealing with atmospheric moisture:

http://www.arm.gov/measurements/atmmoist

To learn how to propose a field campaign or browse past campaigns:

http://www.arm.gov/campaigns

To order data:

http://www.archive.arm.gov/