ISCCP at 30, April 2013

Concurrent Study of a) 22 – year reanalysis and extension of global

water vapor over both land and ocean (NVAP–M) and

b) the matching ISCCP data setThomas H. Vonder Haar

John M. ForsytheJohn Haynes

Cooperative Institute for Research in the Atmosphere (CIRA)Colorado State University Fort Collins, CO

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NVAP-M (NVAP (NASA Water Vapor Project) – MEaSUREs)

NASA MEaSUREs Program: Making Earth System Data Records for Use in Research EnvironmentsSTC - METSAT

Science and Technology Corporation - Metsat Division, Fort Collins CO

ISCCP at 30, April 2013 2

• Reanalysis and extension (1988-2009) of the heritage NVAP (1988-2001) dataset

• Total (TPW) and layered (LPW) precipitable water• Removes time-dependent biases caused by

dataset and algorithm changes incurred during multi-phase processing.

– Focus on consistent data inputs and peer reviewed processing algorithms through time.

• Back-propagation of modern observations through the entire data period.

– Collaboration with AIRS water vapor project at NASA JPL. (E. Fetzer et al.)

• Global (land and ocean) data with vertical structure information.

• Multiple data products to fit varying user needs.• Highly model-independent

• Now Available at NASA Langley Atmospheric Science Data Center (ASDC). https://eosweb.larc.nasa.gov/project/nvap/nvap-m_table

NASA Water Vapor Project – MEaSUREs

“NVAP-M” refers to the new NVAP-MEaSUREs data set. “Heritage NVAP” refers to the existing dataset described by Randel et al., 1996

Vonder Haar et al. 2012: Weather and climate analyses using improved global water vapor observations. Geophys. Res. Lett., 39, L15802. doi:10.1029/2012GL052094.

Similar in concept to GPCP, ISCCP…

ISCCP at 30, April 2013

NVAP-M: Input DatasetsSSM/I Average TPW September 10, 2004

Retrieved from microwave Tbs intercalibrated by Sapiano et al

75

mm

0

AIRS Version 5 Level 3 Average TPW September 10, 2004

0 mm 75

HIRS Average PW September 10, 2004 500-700 mb layerRetrieved from clear-sky radiances

20

mm

0

GPS TPW Data Points (beginning 1997)(Wang et al. 2007)

SSM/I

AIRS

Sonde HIRS

GPSSapiano et al. (TGRS; 2012) intercalibration; Elsaesser et al. 2008 retrieval.

(IGRA)

(Wang et al.)

Jackson and Bates radiances;Engelen and Stephens (1999) retrieval

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ISCCP at 30, April 2013

SSM/I-F08

SSM/I-F10

SSM/I-F11

SSM/I-F13

SSM/I-F14

SSM/I-F15

HIRS-N09

HIRS-N10

HIRS-N11

HIRS-N12

HIRS-N14

HIRS-N15

HIRS-N16

HIRS-N17

Sonde

AIRS

NVAP-M Climate Product: Sensor Timeline

1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009

More confidence in later period due to increased observations

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ISCCP at 30, April 2013

NVAP-M: A Three-Tiered Product Approach

NVAP-WeatherUsed for weather case studies on timescales of days to weeks

•SSM/I Level 1 C intercalibrated radiances•HIRS cloud cleared radiances •Radiosonde, GPS since 1997•AIRS Level 3 TPW and Layered PW

•Maximizes spatial and temporal coverage

•Not driven by reduction of time-dependent biases

•4x daily•½ degree resolution • TPW and layered precipitable water

•surface to 700 hPa•700 to 500 hPa•500 to 300 hPa• < 300 hPa.

NVAP-ClimateUsed for studies of climate change and interannual variability

•SSM/I Level 1 C intercalibrated radiances•HIRS cloud cleared radiances, + AIRS since 2002

• Radiosonde

•Consistent inputs through time. •Consistent, high quality retrievals. •Less emphasis on spatial and temporal coverage

•Daily•1-degree resolution •TPW • layered precipitable water

•surface to 700 hPa• 700 to 500 hPa• 500 to 300 hPa• < 300 hPa

NVAP-OceanSSM/I-only.

Supplemental Fields•Data source code (DSC) map, indicating the sources used in each grid box .

Heritage NVAP begun in early 1990’s was “one size fits all” approach.

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ISCCP at 30, April 2013

NVAP-M Weather vs. Climate Product

0-6Z

12-18Z

18-24Z

6-12Z

0 mm 75

Weather Product

Climate Product

10 September, 2004

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ISCCP at 30, April 2013

Heritage NVAP

NVAP-M Climate

Global Mean TPW

Dotted lines : Known time-dependent biases due to processing changes

-90°

90°

-90°

90°

Heritage:24.5 mm

NVAP-M: 25.3 mm

Monthly Zonal TPW Anomaly Over Land and Ocean

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ISCCP zonal mean cloud amount anomaly (%)

(Raschke and Kinne (2008))

NVAP-M Climate TPW anomaly (mm)

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ISCCP at 30, April 2013

Correlation Coefficient

Correlation of ISCCP total cloud and NVAP-M total precipitable water vapor monthly anomalies (1988-2007)

NVAP-M Ocean (SSM/I only)

NVAP-M Climate

(SSM/I, AIRS, HIRS, Sondes)

-1.0 1.00.0 Blue areas indicate cloud amount decreases as TPW increases

Subtropical ocean regions show increasing low-level stratus coupled with dry subsidence aloft

Low correlation or negative correlation over land under study

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ISCCP at 30, April 2013

-3.5 +3.5

NVAP-M-Climate 1988-2003

Preliminary - Significance testing in progress

Trend (mm / decade)

ISCCP Monthly Mean Cloud 50 – 100% only

ISCCP Monthly Mean Cloud 0 – 50% only

Insufficient data

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ISCCP at 30, April 2013

At this time, we can neither prove nor disprove a robust trend in the global water vapor data from the NVAP-M Climate data set

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ISCCP at 30, April 2013

0 75Monthly Mean TPW (mm)

from NVAP-M Climate

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ISCCP at 30, April 2013

Summary• NVAP-MEaSUREs represents the first reanalysis of the heritage

NVAP global water vapor data over both land and ocean.

• NVAP-M features intercalibrated radiances, time-consistent retrieval algorithms, climate / weather / ocean processing paths and use of the first 7.5 years of AIRS data

• Data fusion and study with companion climate records such as ISCCP allows increased insight into each data set and natural processes.

• Trend analysis must consider:a) Time-dependent bias due to instruments, calibration, algorithm and

ancillary datab) Changing time/space sampling of observations

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ISCCP at 30, April 2013

• Data now available from NASA Langley Atmospheric Science Data Center: https://eosweb.larc.nasa.gov/project/nvap/nvap-m_table (netCDF format)

• For further information see Vonder Haar, Bytheway, Forsythe, 2012: "Weather and climate analyses using improved global water vapor observations." Geophys. Res. Lett., 39, L16802, doi:10.1029/2012GL052094

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