Anvil Clouds of Mesoscale
Convective Systems
Robert A. Houze, Jr.
University of Washington
ASR Science Team Meetings, Bethesda, 20 November 2014

From space
Mesoscale Convective Systems
2
3
1

Frequency of MCS anvils over tropics
Yuan and Houze 2010

Width & thickness of MCS anvils seen by
CloudSat
Africa Indian Ocean
Yuan and Houze 2010

Internal structure of MCS anvils seen by
CloudSat
Africa Indian Ocean
Yuan, Houze, and Heymsfield 2011

CloudSat CFADs of Large, separated MCSs over the
Maritime Continent

MCS anvil is the result of a life cycle process
Houze 1982

The time-integrated MCS anvil process
Mesoscale Convective
System
Need to understand how anvil is related to the raining region
Extensively studied

Dimensions and hydrometeor content of anvils are determined by the same cloud dynamics that produce the precipitation


Z
AC
A c
Breakdown of the water budget
A s

X
AC
After Houze et al. (1980)


Z
AC A c

X
AC
Convective region water budget
C cu
=
R c
+
E cd
+
A c
+
C
T
R c
E c
A c
C
T
=
=
=
= e
C c a
C c b
C c h
C c with the constraint e + a + b + h
(each height cat.)
=
1


Z
AC A c

X
AC
Stratiform water budget equation
C su
+
C
T
=
R s
+
E sd
+
A s
Rain not simply related to condensation
R s
= e s
(
(
C su
+
C
T
E sd
A s
=
= a C su
( su
+
C
T
+
C
T
)
)
)
where e s
+ a
+ b
=
1


Z
AC A c

X
AC
Total anvil water content


Z
AC A c

X
AC
Dimensions and hydrometeor content of anvils are determined by the same cloud dynamics that produce the precipitation—need to determine them to close the MCS water budget

Anvil clouds observed by WACR at Niamey
Powell et al. 2012

Anvil clouds observed by WACR at Niamey
Powell et al. 2012

Aerosol effect on anvils
Fan et al. 2013

Take-home points:
1.
Larger MCSs are primary producers of anvils over the tropics
2.
Anvils are a product of lifecycle of the MCS  lifecycle studies are critical
3.
Anvil characteristics determined by environment: land, ocean, day, night, …
4.
Anvils not dynamically separate from the precipitating part of the MCS
5.
Anvils and precipitating sectors need to be physically consistent
6.
Anvils and precipitating sectors are linked via the MCS water budget
7.
Latent heating and radiative heating are linked  should not be separated
8.
Anvils are likely affected by the aerosol environment, but…

This research was supported by DOE grant DE-SC0008452 / ER-65460 and
NASA grant NNX13AQ37G

Time-integrated Water Budget
1.17R
0
.37R
.41R
.16R
.60R
.29R
.40R
.13R
GATE —oceanic
(Gamache & Houze 1983)
COPT81 —continental
(Chong & Hauser 1989)


Z
AC A c
Sum over all cloud height categories i

X
AC
R
= å i
R ci
C cu
= å i
C cui
E cd
C
T
A c
= å i
E cdi
= å i
C
Ti
= å i
A ci
For each height category i
R ci
E cdi
=
= e i
C ci a i
C ci
A ci
C
Ti
=
= b i
C ci h i
C ci with the constraint e i
+ a i
+ b i
+ h
(each height cat.) i
=
1

Anvil clouds observed by WACR at Niamey
Powell et al. 2012