Variations in CERES-Terra Fluxes and Cloud Properties with SST Anomalies Zach Eitzen...

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 700 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 (700, EIS) 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 EIS-700 regimes

Average low cloud anomalies

Joint distribution of low cloud fraction and SST anomalies

Average low cloud ln() anomalies

Average SW CRE anomalies

Average Net CRE anomalies

Changes in properties with SST

Property Slope with standard anomalies

Slope with residual anomalies

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

Low Cloud ln() -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 EIS-700 regimes

Average LW CRE anomalies

Joint distribution of low cloud ln() 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