ERBS Radiation Budget Data

1
Trends in Tropical Water Vapor (1980-2004) Satell
ite and GCM Comparison
Satellite Observed ---- Model Simulated
__
Total column water vapor over tropical oceans has
increased over the past 20 years Models
accurately reproduce the observed variability and
moistening of the tropical atmosphere.
Held and Soden 2006 Robust Responses of the
hydrological cycle to global warming, J Climate,
19, 3354-3360.
2
Impact of Convectively Detrained Cloud Ice On
Upper Tropospheric Water Vapor
GCM Simulations (IPCC AR4)
Satellite Observations (AIRS/MLS)
Spatial distribution of upper tropospheric water
vapor is strongly correlated with amount of cloud
ice Models capture observed correlation between
cirrus ice and upper tropospheric water
vapor. Water vapor feedback is insensitive to
strength of relationship between cloud ice and
water vapor
John and Soden, 2006 Does convectively-detrained
cloud ice enhance water vapor feedback?, Geophys.
Res Lett., 33, L20701.
3
A Comparison of AIRS Water Vapor Retrievals with
GCM Simulations
Zonal Annual Mean Bias in Relative Humidity
Compared to AIRS Retrievals
ECMWF/NCEP Reanalyses
IPCC AR4 GCMs
Both IPCC AR4 GCMs and NCEP/ECMWF reanalyses
produce a more humid troposphere than indicated
by AIRS retrievals.
John and Soden, 2007 Temperature and humidity
biases in IPCC AR4 models, in preparation.
4
Weakening of the Walker Circulation due to
Anthropogenically-Forced Changes in the
Hydrological Cycle
Observed
Model Simulated
Change in Sea Level Pressure (1861-1992)
Climate models predict a weakening of the Walker
circulation in response to hydrological cycle
changes in a warmer climate. Observations from
20th Century reveal changes in SLP consistent
with model projected weakening of Walker Cell.
Vecchi et al. 2006 Weakening of the tropical
Pacific atmospheric circulation ... Nature, 441,
73-76.