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A Preliminary Look at Variations in Terra Fluxes and Cloud

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A Preliminary Look at Variations in Terra Fluxes and Cloud Powered By Docstoc
					   Variations in CERES-Terra
Fluxes and Cloud Properties with
         SST Anomalies

   Zach Eitzen (SSAI/NASA-LaRC)
     Kuan-Man Xu (NASA-LaRC)
    Takmeng Wong (NASA-LaRC)
         Acknowledgments
• Thanks to David Doelling and Michele
  Nordeen for help with CERES cloud
  property data.
                Motivation
• Recent authors (e.g., Wagner et al. (2008,
  Atmos Chem Phys) have used satellite data to
  examine cloud properties and their changes with
  SST anomaly.
• Others (e.g., Bony et al. 2004, Klein and
  Hartmann 1993, Wood and Bretherton 2006)
  have studied how clouds change with dynamical
  regime and lower-tropospheric stability.
• Here, we look at changes in cloud properties
  with SST anomaly, and attempt to quantify the
  portion of that change that is due to shifts in
  stability within a given dynamical regime.
                Data Sources
• All data is from March 2000-Feb 2005.
• Monthly mean 1x1 degree CERES-EBAF data is used
  for radiative fluxes.
• Monthly mean 1x1 degree CERES Terra SRBAVG Non-
  GEO data is used for optical depth and cloud fraction
  and cloud top height.
• Monthly mean Reynolds SSTs from NOAA.
• ECMWF-Interim data is used for meteorological data,
  including w700 and Estimated Inversion Strength (EIS).
• “Standard” anomalies are calculated by subtracting each
  month’s value from the five-year mean for that month.
• Residual anomalies of cloud and radiative properties are
  calculated by taking the mean anomaly associated with a
  given (w700, DEIS) state and subtracting it from the
  standard anomaly.
Change in total cloud fraction with SST (%/K)
Change in ln(tau) with SST (K-1)
Change in LW CRE with SST (W m-2 K-1)
Change in SW CRE with SST (W m-2 K-1)
Change in Net CRE with SST (W m-2 K-1)
Low cloud regions from Jensen et al. (2008)
Frequency of DEIS-w700 regimes
Average low cloud anomalies
Joint distribution of low cloud
 fraction and SST anomalies
Average low cloud ln(t) anomalies
Average SW CRE anomalies
Average Net CRE anomalies
Changes in properties with SST
Property             Slope with standard   Slope with residual
                     anomalies             anomalies

Low Cloud Fraction   -4.4 % K-1            -1.8 % K-1

Low Cloud ln(t)      -0.103 K-1            -0.049 K-1

LW CRE               1.3 W m-2 K-1         0.5 W m-2 K-1

SW CRE               3.4 W m-2 K-1         2.1 W m-2 K-1

Net CRE              4.7 W m-2 K-1         2.6 W m-2 K-1
                  Summary
• Near the ITCZ, cloud top heights, cloud fraction
  and cloud optical depth all increase with SST,
  leading to little change in net CRE.
• In subtropical boundary-layer cloud regions,
  cloud fraction and cloud optical depth decrease
  with SST, leading to less shortwave cooling.
• Changes in cloud and radiative properties with
  SST have a strong association with changes in
  EIS within each dynamical regime, but there
  appears to be a positive cloud feedback even
  after this is removed.
             Future Work
• Look at additional fields.
• Filter out months with too much high cloud
  occurrence.
• Look at individual regions.
Change in cloud top height with SST (km/K)
Frequency of DEIS-Dw700 regimes
Average LW CRE anomalies
Joint distribution of low cloud ln(t)
        and SST anomalies
Joint distribution of SW CRE and
          SST anomalies
Joint distribution of LW CRE and
          SST anomalies
Joint distribution of Net CRE and
          SST anomalies

				
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posted:4/5/2010
language:English
pages:26