clouds and radiation recent hot topics stefan kinne
DESCRIPTION
overview look at combined solar + IR netflux for CERES SRBAVG (the new ToA reference) SRB ISCCP IPCC-model median CERES is about 20W/m2 larger than IPCC modeling 10W/m2 larger than SRB 8W/m2 larger than ISCCPTRANSCRIPT
clouds and radiation
… recent hot topics
Stefan Kinne
348 ?CERES
165 ?CERES
Question: how to balance the incoming extra 20W/m2 by CERES at the surface ?
overview look at combined solar + IR netflux for
CERES SRBAVG (the new ToA reference) SRB ISCCP IPCC-model median
CERES is about 20W/m2 larger than IPCC modeling 10W/m2 larger than SRB 8W/m2 larger than ISCCP
all-sky netflux at surface
all-sky diff-netflux at surf
diagnostics diagnose … why ?
solar down fluxes all-sky CE (all-sky minus clear-sky)
IR down fluxes all-sky CE (all-sky minus clear-sky)
all-sky dn-solar at surface
all-sky diff-dn-solar at surf
CE dn-solar at surface
CE diff-dn-solar at surface
all-sky dn-IR at surface
all-sky diff-dn-IR at surf
CE dn-IR at surface
CE diff dn-IR at surface
different definitions of the clear-sky fluxcloud-free skyall sky
satellite clear-sky: only data from cloud-free areas modeled clear-sky: (= cloud-free) data with cloud removed… but in ‘cloudy columns’ there is more water vapor than in ‘clear-columns’
model simulations underestimate the derived cloud radiative effect … as it includes the increased water vapor in cloudy regions
expected are …
• overestimates to– OLR (IR up at ToA)– IR dn at surface– IR divergence– solar divergence
• underestimates to – solar transmission– solar reflection
JJA
CRFCERES (Wm-2)
-10 0 10 20 30 40 50 60 70 80 90 100 110 120
CR
F du
e to
UTW
cha
nge
(Wm
-2)
0
2
4
6
8
10
12
14
16
OLR error~ 10W/m2 !
B.J.Sohn (2005)
modeled cloud-effect biases on fluxes
OLR error (B.J. Sohn, 2010)theoretical simulations
IPCC-modeling minus CERES (obs)
• divergence
• cloud effect on up-flux
• cloud effect on dn-flux
solar IR
OLR effects are smaller due to compensating differences in cloud altitude
ISCCP (model based) minus CERES (obs)
• divergence
• cloud effect on up-flux
• cloud effect on dn-flux
solar IR
lack of absorbing aerosol in tropics for ISCCP explains unexpected sA bias
take-home messages
- data products of the same name often do not mean the same (not identical by definition)- water vapor is expected often to be larger near clouds … thus clear-sky definitions in modeling by differing from observations introduce biases-interestingly, expected differences often do not fully materialize due to other inconsistencies (e.g ancillary data of aerosol)- careful assessments of data-products and assumptions are essential prior to conclusions