Out of the Lab and Into the Air:Out of the Lab and Into the Air:Peter Hobbs and the Physics and Peter Hobbs and the Physics and

Dynamics of Real CloudsDynamics of Real Clouds

Robert A. Houze, Jr.Robert A. Houze, Jr.University of Washington, Seattle, WAUniversity of Washington, Seattle, WA

Peter V. Hobbs Symposium, New Orleans, January 24, 2008Peter V. Hobbs Symposium, New Orleans, January 24, 2008

Mason’s InfluenceMason’s Influence

The Physics of CloudsThe Physics of CloudsSir John Mason, D. Sc., F. R. S.Sir John Mason, D. Sc., F. R. S.

Preface to 1957 Edition:Preface to 1957 Edition:

“Although the emphasis here is on the micro-physicalmicro-physical processes, it is important to recognize that these are largely controlled by the atmospheric motions which are manifest in clouds. These macro-physicalmacro-physical features…might more properly be called a dynamicsdynamics…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., LondonB. J. M., London

The Physics of CloudsThe Physics of CloudsSir John Mason, D. Sc., F. R. S.Sir John Mason, D. Sc., F. R. S.

Preface to 1971 Edition: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., BracknellB. J. M., Bracknell

Peter at his desk, 1973Peter at his desk, 1973

Getting out of the lab and into the clouds by going to the top Getting out of the lab and into the clouds by going to the top of a mountain, 1966of a mountain, 1966

We need a bigger plane…

Getting out of the lab and into the clouds by buying an Getting out of the lab and into the clouds by buying an airplane, the B-23 in 1968airplane, the B-23 in 1968

Peter’s Love Affair with IcePeter’s Love Affair with Ice

Peter’s Opus, 1974Peter’s Opus, 1974

Mountainside

Aircraft

Hobbs (1973)Hobbs (1973)

Aggregates in the real atmosphereAggregates in the real atmosphere

Fall velocities of real ice particlesFall velocities of real ice particles

Rimed & Unrimed Aggregates

Graupel

Hobbs (1973)Hobbs (1973)

Ice Particle Concentrations in the Real Ice Particle Concentrations in the Real AtmosphereAtmosphere

Hobbs (1969)Hobbs (1969)Measurements on Mt. OlympusMeasurements on Mt. Olympus

Rat

io o

f pa

rtic

les

to ic

e nu

clei

–2 –14 –26Estimated Cloud Top Temperature (ºC)

102

103

104

10

Hobbs (1976)Hobbs (1976)Measurements aboard the B-23Measurements aboard the B-23

104

103

102

101

10-1

10Max

imum

ice

part

icle

C

once

ntra

tion

(per

lite

r)

Cloud Top Temperature (ºC)

Hobbs and Rangno (1985)Hobbs and Rangno (1985)Aircraft measurements in various midlatitude cloudsAircraft measurements in various midlatitude clouds

Rangno and Hobbs (2005)Rangno and Hobbs (2005)Measurements in tropical convective clouds over the Measurements in tropical convective clouds over the

West PacificWest Pacific

Largest ice concentration ever observed by Peter ~1000 per liter

Ice Particles in Relation to Cloud Ice Particles in Relation to Cloud Macro-structureMacro-structure

Matejka, Houze, and Hobb(1980)Matejka, Houze, and Hobb(1980) Frontal Clouds Frontal Clouds

Hobbs and Rangno (1985)Hobbs and Rangno (1985)Midlatitude CumulonimbusMidlatitude Cumulonimbus

Hobbs and Rangno (1985)Hobbs and Rangno (1985)Development of StratusDevelopment of Stratus

Peter Hobbs: Radar Pioneer?Peter Hobbs: Radar Pioneer?

19731973

Warm advection seen by color display of NCAR CP-3 radar deployed in Washington

CYCLES PROJECTCYCLES PROJECTUse of Single-Doppler Color DisplayUse of Single-Doppler Color Display

Baynton, Serafin, Frush, Gray, Hobbs, Houze, Locatelli (1977)Baynton, Serafin, Frush, Gray, Hobbs, Houze, Locatelli (1977)

9 mm cloud radar reflectivity showing fallstreaks in a warm frontal zone

e from soundings

CYCLES PROJECTCYCLES PROJECTLocatelli and Hobbs (1987)Locatelli and Hobbs (1987)

IMPROVE ProjectIMPROVE Project20012001

NCAR S-Pol on a mountain and NOAA S-Prof in a valleyNCAR S-Pol on a mountain and NOAA S-Prof in a valley

IMPROVE ProjectIMPROVE ProjectWoods, Stoelinga, Locatelli, and Hobbs (2005) Woods, Stoelinga, Locatelli, and Hobbs (2005)

IMPROVE ProjectIMPROVE ProjectWoods, Stoelinga, Locatelli, and Hobbs (2005) Woods, Stoelinga, Locatelli, and Hobbs (2005)

IMPROVE ProjectIMPROVE Project

Fearless, no-holds-barred-science Fearless, no-holds-barred-science

LEGACYLEGACY

•Characteristics of ice particles in real precipitating Characteristics of ice particles in real precipitating cloudsclouds (fallspeeds, aggregation,…) (fallspeeds, aggregation,…)

•High ice particle concentrationsHigh ice particle concentrations (negates the (negates the importance of the “ice crystal process” as a importance of the “ice crystal process” as a

precipitation mechanism)precipitation mechanism)

•Ice particle concentrations and characteristics in Ice particle concentrations and characteristics in relation to “macro-structure” of real of cloudsrelation to “macro-structure” of real of clouds

(stratus to convection, tropics to arctic, over oceans, (stratus to convection, tropics to arctic, over oceans, land, and mountains)land, and mountains)

Peter HobbsPeter Hobbs

1936-20051936-2005