Partition in Arctic Mixed-phase Clouds

lovingbangInternet and Web Development

Nov 3, 2013 (4 years and 6 days ago)

79 views

The Seasonal Variation of Liquid
-
ice
Partition in Arctic Mixed
-
phase Clouds
Observed at the NSA Site





Ming Zhao and Zhien Wang

University of Wyoming



September 17, 2009


Outline:

1. Data

2. Seasonal variation of liquid and ice properties in


mixed
-
phase clouds

3. Variations of liquid water fraction with cloud top


temperature LWP, and R
eff
.

4. Linkage between liquid and ice microphysical properties

5. Conclusions and future works



Clouds
: Single layer mixed
-
phase clouds with liquid base
below 2 km and thickness above liquid base less than 1
km.


Instruments
: MMCR, MPL, MWR, and SONDE.


Microphysical properties

Based on a new multiple sensor (MWR+MPL+ MMCR)

approach
:


MPL+MMCR

ice water content and general


effective radius profiles for
ice phase
.


MWR+MPL+ adiabatic cloud model


LWP and


cloud effective radius for
water phase
.


1. Data (1999 to 2003 at the NSA Barrow site)

2. Seasonal Variation of cloud liquid and ice properties

Figure 1: Seasonal variation of LWP, IWP, Reff, and Dge for year between 1999 and 2003

Liquid Water

Ice Water


Liquid

water fraction (LWF)
in
mixed
-
phase clouds is defined as:


LWF=

LWP/(LWP+IWP)


Monthly mean LWF
is between 0.6


and 0.9, with maximum value in



August and minimum value in April


and large interannual variations.


Seasonal trend of
LWFgenerally


follows the cloud


temperature changes
.



Figure 2: Seasonal variation of liquid water
fraction for year between 1999 and 2003

Figure 3:
Monthly frequency distribution of
cloud base temperature

Seasonal variation of liquid water fraction:

3. LWF as a function of cloud top temperature

Figure 4. : 2D scatter plots of normalized data distribution for cloud phase partition and cloud top
temperature. The black circles are mean LWFs for each cloud temperature bin.



Whole cloud layer


Mixed
-
phase layer only


Mean LWF increases with cloud top temperature increases.



Large difference between mixed
-
phase layer and the whole layer indicates
model vertical resolutions do matter in treating LWF in large scale models.




Seasonal variation of LWF:
Mixed
-
phase layer

Figure
5
: 2D scatter plots of normalized data distribution for cloud phase partition and cloud top
temperature

for water layer (different seasons).


Spring: Mar
-
Apr
-
May

Summer: Jun
-
Jul
-
Aug

Fall: Sep
-
Oct
-
Nov Winter: Dec
-
Jan
-
Feb

Seasonal variation of LWF:
whole layer

Figure 6: 2D scatter plots of normalized data distribution for cloud phase partition and cloud top
temperature

for whole layer (different seasons).


Comparing with model simulations and in
-
situ measurements :

Figure
7
:

LWF changes with cloud top
temperature

for
mixed
-
phase
layer (left) and the whole layer
(right). Orange dash line is for all
-
year averaged LWP for each temperature bin. Yellow solid line is for
ECWMF LWF parameterization.


Morrison et al.,
2005

Rotstayn

et al.,
1999

LWF dependency on Cloud Top Temperature, LWP and R
eff

Figure 8. : 2D scatter plot for
liquid water fraction as
function of cloud top
temperature and LWP



High LWP occurs at
warmer cloud temperature
and larger LWP values,
similarly for cloud top
temperature and R
eff
.



At given temperature,
LWF increase with LWP or
R
eff
.




Figure 9. : 2D Scatter plots of
normalized data distribution
between water and ice
properties (all year).

4. Linkage between liquid and ice microphysical properties

Seasonal Variation for LWP and IWC correlation:

Figure 10. : 2D Scatter plots of normalized data distribution between LWP and mean IWC

IWC and LWP correlation


temp influence

Figure 11. : Same as figure 10,
for at different

temperature
range
.

Seasonal Variation for R
eff

and IWC
correlation:

Figure 12. : 2D Scatter plots of normalized data distribution between Reff and IWC (different seasons).

IWC and R
eff
correlation


Temp influence

Figure 13. : Same as figure 12,
for at different temperature
range.

Conclusions and Future Works:

Conclusion
:


Liquid water fraction (LWF) generally increase with cloud top
temperature increase.

--

There are significant seasonal variation of LWF.

--

The LWFs calculated for the mixed
-
phase layer and whole cloud layer
have different temperature dependency.

--

Current LWF parameterizations in models have a large bias for
stratiform mixed
-
phase clouds.



Liquid and ice microphysical properties are closely related. IWC
increase with LWP or R
eff

increase, especially at colder temperature
range.


Future works:


Study the linkage between aerosol and ice formation in mixed
-
phase
clouds.


Better understand ice growth in the arctic mixed
-
phase clouds.