Transcript Histograms and composites

Histograms and composites
multimodal is always interesting
• qualitative distinction!
• Regimes or modes (literal meaning)
Buoy downwelling
radiation along
Pacific cold tongue as
TIWs go by in the
ocean
Figure 3.16 – Width vs. top height of each EO for 16 June 2006 – 31 May 2008. Distribution is
weighted by total number of pixels (volume) per EO to emphasize larger EOs. Bin size is 10 pixels
(~ km) by 240 m. Width is the horizontal span of the EO.
soundings
climatological time means
must not be iid sums (->normal dist)
The science
• bimodal = 2 “modes” = distinct “regimes”
– wet and dry
– young and old air masses (age since saturation)
• in temporal variations at a point
– convective vs. nonconvective regions
in bimodal climatological mean spatial histograms
Even unimodal can be a basis for
composites, but these aren’t “regimes”
• indeed all similar
• except offset
• indeed very similar
• except offset
Khairoutdinov, Marat, David Randall, 2006:
High-Resolution Simulation of Shallow-to-Deep
Convection Transition over Land. J. Atmos. Sci.,
63, 3421–3436.
High-Resolution Simulation of Shallow-to-Deep
Convection Transition over Land
Marat Khairoutdinov and David Randall
Clouds as connected
regions (have a size)
Nice use of 2dimensional
histograms, and
weighted histograms (=
composites of multiple
fields in each bin)
growing clouds in z and size
all
points
w>
5m/s
• conditional
sampling
• cetegories so
arbitrary
unless there
are multiple
modes in
some
distribution
suppose we want precip flux
•
•
•
•
F = (frequency)(qp)(w)(density)
Product of these 3 distributions (*density)
rare events clearly important
from obs, would need to adjust (sampling)