Out of the Lab and Into the Air:
Peter Hobbs and the Physics and
Dynamics of Real Clouds
Robert A. Houze, Jr.
University of Washington, Seattle, WA
Peter V. Hobbs Symposium, New Orleans, January 24, 2008
Mason’s Influence
The Physics of Clouds
Sir John Mason, D. Sc., F. R. S.
Preface to 1957 Edition:
“Although the emphasis here is on the micro-physical processes,
it is important to recognize that these are largely controlled by the
atmospheric motions which are manifest in clouds. These macro-physical
features…might more properly be called a dynamics…Progress in cloud
physics has been hindered by a poor appreciation of these interrelations
between processes ranging from nucleation phenomena on the molecular
scale to the dynamics of extensive cloud systems on the scale of hundreds
or thousands of kilometres.
“…Because I am convinced that future progress will be largely
governed by our improved understanding of cloud dynamics, I hope that the
next few years will see a greatly increased effort in this direction…Cloud
dynamics will, I hope …form the subject of a separate volume…”
B. J. M., London
The Physics of Clouds
Sir John Mason, D. Sc., F. R. S.
Preface to 1971 Edition:
“…in the preceding preface written thirteen years ago, reference was made
to the…importance of acquiring a much deeper understanding of the cloud
dynamics…The hopes expressed then for much greater effort and progress
in this direction, and for the appearance of a major text on this aspect of the
subject, have yet to be realized…”
B. J. M., Bracknell
Peter at his desk, 1973
Getting out of the lab and into the clouds by going to the top
of a mountain, 1966
We need a
bigger plane…
Getting out of the lab and into the clouds by buying an
airplane, the B-23 in 1968
Peter’s Love Affair with Ice
Peter’s Opus, 1974
Hobbs (1973)
Aggregates in the real atmosphere
Mountainside
Aircraft
Hobbs (1973)
Fall velocities of real ice particles
Rimed & Unrimed
Aggregates
Graupel
Ice Particle Concentrations in the Real
Atmosphere
Ratio of particles to ice nuclei
Hobbs (1969)
Measurements on Mt. Olympus
104
103
102
10
–2
–14
–26
Estimated Cloud Top Temperature (ºC)
Hobbs (1976)
Measurements aboard the B-23
Maximum ice particle
Concentration (per liter)
104
103
102
101
10
10-1
Cloud Top Temperature (ºC)
Hobbs and Rangno (1985)
Aircraft measurements in various midlatitude clouds
Rangno and Hobbs (2005)
Measurements in tropical convective clouds over the
West Pacific
Largest ice concentration ever observed by Peter ~1000 per liter
Ice Particles in Relation to Cloud
Macro-structure
Matejka, Houze, and Hobb(1980)
Frontal Clouds
Hobbs and Rangno (1985)
Midlatitude Cumulonimbus
Hobbs and Rangno (1985)
Development of Stratus
Peter Hobbs: Radar Pioneer?
1973
CYCLES PROJECT
Use of Single-Doppler Color Display
Baynton, Serafin, Frush, Gray, Hobbs, Houze, Locatelli (1977)
Warm advection seen by color display of
NCAR CP-3 radar deployed in Washington
CYCLES PROJECT
Locatelli and Hobbs (1987)
9 mm cloud radar reflectivity showing fallstreaks in a warm frontal zone
e from
soundings
IMPROVE Project
2001
NCAR S-Pol on a mountain and NOAA S-Prof in a valley
IMPROVE Project
Woods, Stoelinga, Locatelli, and Hobbs (2005)
IMPROVE Project
Woods, Stoelinga, Locatelli, and Hobbs (2005)
IMPROVE Project
Fearless, no-holds-barred-science
LEGACY
•Characteristics of ice particles in real precipitating
clouds (fallspeeds, aggregation,…)
•High ice particle concentrations (negates the
importance of the “ice crystal process” as a
precipitation mechanism)
•Ice particle concentrations and characteristics in
relation to “macro-structure” of real of clouds
(stratus to convection, tropics to arctic, over oceans,
land, and mountains)
Peter Hobbs
1936-2005