1. The Radiative Budget of an Atmospheric Column in Tropical Western Pacific Zheng Liu 1 Thomas Ackerman 1,2, Sally McFarlane 2, Jim Mather 2, University of Washington 1 University of Washington 2 Pacific Northwest National Laboratory

2. Background ► Motivation:  Cloud and water vapor feed back → model sensitivity  Cloud and radiative parameterization → feed back ↓↓ ► Model evaluation:  Need : Radiative budgets at TOA, surface Column absorption, Column absorption,  Limited measurements → start with some atmospheric columns:Manus and Nauru

4. Data Set Description: Observational Dataset ► TOA net SW and LW fluxes:  GMS hourly observations, 0.3 o x 0.3 o grid (about 30km x 30 km) ► Surface SW&LW downward fluxes:  ARM surface measurements, daily averaged from 1-min data ► Surface LW upward fluxes:  NOAA optimum interpolated SST, weekly averaged, 1 o x 1 o grid ► Surface SW upward fluxes:  Assumed sea surface SW albedo (6%)

5. Data Set Description: Radiative Model Calculations ► Computed fluxes and heating rates from ARM column observations  Retrieve vertical profiles of cloud microphysical properties from ARM millimeter wave radar data  Temperature and water vapor profiles from radiosonde launches  Sample the cloud properties every 5 minutes and perform radiative transfer only on the sampled profiles.  Calculate broadband fluxes

6. Data Set Description: Climate Model ► NCAR Community Atmosphere Model (CAM)  T42 resolution  Prescribed SST  Compare values from box over Manus (280 km x 280 km) with observations ► Multi-scale modeling framework (MMF)  Embedded 2D cloud system resolving model (64 columns each 4 km in horizontal dimension)  Prescribed SST  Average 64 column values within Manus gridbox

7. Observation v.s. Radiative Model ► Frequency distribution → day to day comparison ► TOA → Surface → Column absorption ► Page organization: Manus SW CLEAR SW ALL LW CLEAR LW ALL Nauru SW CLEAR SW ALL LW CLEAR LW ALL

10. Remarks ► SW clearsky offset ► SW allsky “cumulus” effects ► Manus is convectively more active than Nauru.

16. Observation v.s. Models ► Observation: Jun 16, 1999 ~ May 21, 2003 ► Climate models: Jan 1, 1999 ~ Dec 31, 1999 ► Radiative model calculation:  Manus: Feb 25, 2000 ~ Jul 31, 2000  Nauru: Mar 9, 1999 ~ Dec 19, 1999

20. Conclusion ► Evaluation of the radiative budget of atmospheric columns can help understand the convective tropics ► Discrepancy between calculations from radiative model and observations is probably due to scene mismatch between TOA and the surface and some 3D effects ► Column SW absorption:  Clear sky: around 90w/m 2  All sky: almost unaffected by cloud for both radative model and climate models almost unaffected by cloud for both radative model and climate models much greater variation according to observational data and bias towards more absorption than clear sky much greater variation according to observational data and bias towards more absorption than clear sky

21. Future work ► Compare with other TOA satellite data sets: ISCCP, CERES ► Compare budget results from CAM run in forecast mode with observational data and climate model version of CAM ► Compare surface radiative budget from satellite with ARM surface measurement

22. Acknowledgements ► Professor Ackerman ► Sally Mcfarlane, Professor Fu, Professor Wood ► All my first year classmates ► All the audience here