New Interactive Aircraft and Satellite Methodologies for the ...
50
Daniel Rosenfeld and William L. Woodley New insights and methodologies for the operational assessment of seeding potential
Transcript of New Interactive Aircraft and Satellite Methodologies for the ...
Daniel Rosenfeld and William L. Woodley
New insights and methodologies for the operational
assessment of seeding potential
0 5 10 15 20 25 30 35
-30
-20
-10
0
10
20
reff
T [
oC
] m ]
Tha i pre -m ons
Israel dust
Australia urban
IN DO EX polluted
Am azon sm o ke
Ramanathan, V.,
P. J. Crutzen, J.
T. Kiehl, and D.
Rosenfeld, 2001:
Aerosols, Climate
and the
Hydrological
Cycle. Science,
294, 2119-2124.
The cloud particle
size and
precipitation-
forming
processes can be
retrieved by
satellites.
Photo:
Joseph Prospero Clouds rain themselves out in super-clean air
Example of clouds that produce rain very efficiently
Photo:
Joseph Prospero Clouds rain themselves out in super-clean air
Photo:
Joseph Prospero Clouds rain themselves out in super-clean air
Photo:
Joseph Prospero Clouds rain themselves out in super-clean air
Aerosol aircraft: 2006 03 01 01:03Z 900 m
SUPRECIP
2006 03 01 01:03Z 1500 m 3oC
2006 03 01 01:03Z 1500 m 3oC
Rain over sea
The rain is
suppressed in these
shallow clouds
when clouds ingest
the urban aerosols
2006 03 01 01:03Z 1500 m 3oC
Cloud 6
No rain over land
from clouds with
similar depth
2006 03 01 01:18Z 1500 m 3oC
Cloud 8, over Sacramento
No rain over land
from clouds with
similar depth
Cloud 8, over Sacramento
No rain over land
from clouds with
similar depth
4 5
6 7 8
1
10
100
1000
CC
N c
m-3
4
5
6 7
8
1
2
3
800
80
40
70
100
300 600
800
CCN
Concentrations
(cm-3)
Cloud #
Quantification of the increase in CCN and decrease in cloud drop size at height of
1500 m when flying from the ocean to San Francisco and Sacramento.
Cloud #
CCN
Concentrations
(cm-3)
14
Hyderabad, India
22 June 2009
Each point is cloud drop
effective radius as
measured by the aircraft
during 1 second of flight,
or ~100 m cloud path.
Cloud drop effective radius, m
Heig
ht,
m
Aircraft-measured cloud drop effective radius, Re, increases with height
above convective cloud base almost as if the cloud was adiabatic,
regardless of the extent of mixing with dry ambient air.
15
Hyderabad, India
22 June 2009 Re for onset of
significant rain
(> 1 mm/h)
Height for onset
of rain
No rain Rain
Rain develops in the updraft when Re reaches 14 m.
Cloud drop effective radius, re [m]
16
Height, m Temp, °C
7,073 m, -12.2 °C
6,793 m, -11.8 °C
6,124 m, -8.7 °C
5,816 m, -6.8 °C
4,406 m, +1.3 °C
Aircraft measured images of vertical development of
cloud and rain drops in the cloud
The relation between re and depth cloud depth above its base (D) is
uniquely related to CCN.
Hyderabad
26.9.2010
Bareilly
23.9.2009
Bay of Bengal
26.9.2010
Bay of Bengal
27.9.2010
Rosenfeld and Woodley, CAIPEEX-2 Final report to IITM.
Rain No Rain
8
18
Hyderabad, India
22 June 2009
Re for onset of
significant rain
(> 1 mm/h)
Height for onset
of rain
No rain Rain
Cloud drop effective radius can be retrieved
from satellite VIS/IR measurements!
Therefore we can use satellites for
understanding precipitation forming
processes in clouds!
19
MODIS AQUA 2009 06 22 08:30 UT
Red: Visible reflectance
Green: 3.7 m reflectance
Blue: 11 m temperature
Small Drops
Large Drops
-6.8ºC
No rain Rain
Cloud drop effective radius, re [m]
20 0 5 10 15 20
-10
-5
0
5
10
15
20
25
30
CDP_Re[um] r15 r50 r85T
[C
]
AVHRR 20101004 0801
Re [m]
sat=6, sol=32,rel=27
Satellite retrievals validated by aircraft measurements
Aircraft Satellite
re
No rain Rain
21 0 5 10 15 20
-10
-5
0
5
10
15
20
25
30
FSSP_Re[um] r15 r50 r85T
[C
]
MODIS AQUA 20100926.0755
Re [m]
sat=16, sol=30, rel=22
Satellite retrievals validated by aircraft measurements
Aircraft Satellite
Cloud drop effective radius, re [m]
No rain Rain
22 0 5 10 15 20
-10
-5
0
5
10
15
20
25
30
CDP_Re[um] r15 r50 r85T
[C
]
AVHRR 20101004 0801
Re [m]
sat=6, sol=32,rel=27
0 5 10 15 20
-10
-5
0
5
10
15
20
25
30
FSSP_Re[um] r15 r50 r85T
[C
]
MODIS AQUA 20100926.0755
Re [m]
sat=16, sol=30, rel=22
Satellite accuracy can separate well between different situations
Aircraft Satellite
Cloud drop effective radius, re [m]
No rain Rain
The mean radar-measured rain volumes of convective cells as a function of
maximum precipitation echo top height for cells growing on days with weak or
strong coalescence (onset of warm rain above or below 5 km).
Data are from Thailand. Rosenfeld and Woodley, Meteor. Monographs, 2003.
MODIS Pixel size = 1000 m
NPP VIIRS Pixel size = 375 m
26
Learning from Nature what makes clouds rain
• Cloud drops form small near cloud base and grow with height. The cloud must grow at least to the height at which cloud drop re exceeds 14 micron in order to rain.
• The cloud drop size is determined primarily by the aerosol content of the air mass and secondarily by cloud base updraft speed.
• Therefore, differences in air mass aerosol content can cause large difference in cloud precipitation capability.
27
Hygroscopic Seeding
• Clouds that are slow to produce rain, because their drops are too
small, can still produce precipitation by introducing large soluble
particles that form larger drops, which then collect the rest of the
smaller cloud drops and become rain drops.
• The effectiveness of the seeding agent depends on its ability to form
large numbers of rain drops in the seeded cloud volume.
• Cloud seeding cannot further enhance rain from clouds that have
already naturally sufficiently large drops so that they produce rainfall
already efficiently.
• Therefore, cloud seeding has the best potential to add rain from
deep clouds with small drops.
28
Glaciogenic Seeding
• Clouds that are slow to produce rain, because their drops are too small, can still produce precipitation by freezing of the cloud drops into ice precipitation particles.
• The objective of glaciogenic seeding is the promotion of ice in such clouds, assuming that the added ice would accelerate the conversion of the small cloud drops into large ice precipitation particles.
• Glaciogenic cloud seeding cannot further enhance rain from clouds that have already naturally sufficient amounts of ice. This can be caused by natural seeding by desert dust, which produces ice quickly in the clouds.
• Therefore, Glaciogenic cloud seeding has the best potential to enhance rain from deep clouds with small drops and little amounts of ice.
The relation between re and depth cloud depth above its base (D) is
uniquely related to CCN.
Hyderabad
26.9.2010
Bareilly
23.9.2009
Bay of Bengal
26.9.2010
Bay of Bengal
27.9.2010
Rosenfeld and Woodley, CAIPEEX-2 Final report to IITM.
Rain No Rain
8
0ºC
4700 m, +3.2ºC. Max LWC=2.45 gm-3.
No rain.
5530 m, -1.6ºC. Max LWC=2.91 gm-3.
No rain.
6270 m, -4.8ºC. Max LWC=1.05 gm-3.
Isolated supercooled rain drops
6720 m, -8.1ºC. Max LWC=1.66 gm-3.
Supercooled rain drops
7350 m, -11.8ºC. Max HWLWC=0.87 gm-3.
Rain drops and large freezing rain drops.
7700 m, -14.7ºC. Max LWC=1.45 gm-3.
Small rain drops, large freezing rain
drops and small graupel.
8130 m, -17.1ºC. Max LWC=0.49 gm-3.
Frozen drops, small graupel and crystals.
Glaciogenic seeding of
deep supercooled
clouds is expected to
initiate ice precipitation
at lower levels, and
also release more
latent heat of freezing
with dynamic effects
33 Large ice crystal collects small supercooled cloud drops
Rimed crystal Graupel
35 Cloud particle effective radius, m
Clo
ud
top
te
mpe
ratu
re, °C
Water
Mixed phase
Ice, glaciated
Satellite measurements of
glaciation temperature, Tg
Ice particles can be
detected because they
are much larger than
the cloud drops that
produced them
0.8 m
3.9r m
10.8 m
Cb
-32C
Fog St AC
Snow
10.8 m
Cb
-32C
Fog St AC
Snow
Ci
10.8 m
Cb
-32C
Fog St AC
Snow
10.8 m
Cb
-32C
Fog St AC
Snow
Ci
10.8 m
Cb
-32C
Fog St AC
Snow
10.8 m
Cb
-32C
Fog St AC
Snow
Ci
0.8 m
3.9r m
10.8 m
0.8 m
3.9r m
10.8 m
0.8 m
3.9r m
10.8 m
0.8 m
3.9r m
10.8 m
0.8 m
3.9r m
10.8 m
0.8 m
3.9r m
10.8 m
0.8 m
3.9r m
10.8 m
0.8 m
3.9r m
10.8 m
The general view of the dry ice-seeded racetrack pattern in supercooled cloud layer
37 minutes after the start of the seeding and 24 minutes after the end of the
seeding. The cloud layer extended between 4500 and 6800 feet over Utica, New
York, with top temperature of -5.6C.The picture was taken at 24 November 1948
15:21 from an altitude of 17,630 feet. (From Langmuir,1961).
3-D(12.0 m) Microphysical RGB
Daniel Rosenfeld, Xing Yu and Jin Dai, 2005: Satellite retrieved
microstructure of AgI seeding tracks in supercooled layer clouds.
Journal of Applied Meteorology, 44, 760-767.
The Hail Seeding Conceptual Model
• Heavy seeding of AgI in the updrafts of the feeder clouds of the
potential hailstorm produces a large concentration of ice crystals at
temperatures < -10oC.
• These ice crystals grow as graupel as they compete for the available
cloud water.
• This large number concentration of ice hydrometeors depletes the
supercooled cloud water before the hydrometeors can grow to the size of
damaging hail.
Expected impact on indicated T-re relations:
• Increased indicated effective radius at T< -10oC
• Warmer glaciation temperature.
0 5 10 15 20 25 30 35
-50
-40
-30
-20
-10
0
10
reff
T [
oC
]
m ]
1
4
5
0 5 10 15 20 25 30 35
-50
-40
-30
-20
-10
0
10
T [
oC
]
1
4
5
dsd98191_52N_104W b
2: UnSeeded
3: Seeded
Alberta, 10 July 1998 22:15 GMT
Rosenfeld and Woodley, Meteor. Monographs, 2003.
Glaciation temperature of clouds is colder for clouds with smaller supercooled
drops. Therefore, in such clouds:
•Glaciogenic seeding is more effective in enhancing mixed phase precipitation by
nucleating directly more ice crystals, and also:
•Hygroscopic seeding makes larger drops that freeze at higher temperatures.
From Rosenfeld et al., GRL 2011
Summary • The potential seedability can be assessed by satellites,
and used for planning of seeding research flights, operations and evaluation of seeding effects.
• Essential parameters for the precipitation forming processes and cloud seedability are: – Cloud base height and T,
– Height and T of rain threshold of re=14 m.
– Glaciation temperature.
– Cloud top height, T, re and phase.
• Seeding without the direction of satellite and/or cloud physics aircraft for monitoring cloud properties is like shooting in the dark.
• Using satellite extensively is necessary for focusing the use of aircraft to the right time and place, and for extending the aircraft measurements to a regional scale.
