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Convective Cloud Research
Current Projects:
1. CSIP
2. COPS
3. ICEPIC
4. RICO
5. APPRAISE
6. VOCALS (AG)
7. In-cloud temperature probe
Possible Future Projects:
Response to themes -- storms; network of sensors...
Constrain -- microphysics in UM (and WRF and MESO-NH?)
Aerosol-Clouds (Amazon) -- Major international effort
Aerosol-Clouds: ICE-T and New Mexico -- Ice in convective clouds and
influence of aerosols
Projects involve many people in ICAS from tea maker (me) to Head of ICAS and
Director of NCAS. Everyone important. ICAS is an excellent group.
Research on initiation of convection:
1. Convecitve Storm Initiation Project (CSIP): Southern England, summers of
2004 and 2005
2. Convective Orograpically-induced Precipitation Study (COPS): Black Forest,
Germany, summer of 2007.
Flash Floods caused by intense rainfall associated with a thunderstorm
In the US, more people die yearly in floods (127 on average) than by
lightning (73), tornadoes (65), or hurricanes (16)
In the UK: “Country in chaos after flash floods and
storms”; a familiar headline now -- return time to
severe events decreasing
CSIP
While there had been:

Considerable research in the US; most recently IHOP_2002
Extensive research in UK: Modelling of case studies; Observational case
studies using MO network instruments and satellite
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There had been no previous UK experiment on convective initiation with which
to compare Met Office model predictions
CSIP was a large international experiment centred on Chilbolton

18 IOPs in 2005; 4 IOPs in 2004
Met Office Model usually performed well, but some
shortcomings in precise location and timings

Lids important; triggering often involves phenomena that act
individually or in concert to overcome lid
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Variety of processes: no “generic triggering mechanism”.
Map of CSIP
Thanks to Cyril Morcrette
COPS
Major international experiment in Black Forest mountains during
summer of 2007.
Questions:
What is the role of upper tropospheric features for convective-scale
QPF
in moderate orographic terrain?
Does location and timing of CI depend on structure of
humidity field in boundary layer?
Does precipitation intensity depend on aerosols?
What are pathways for heat, mass, water vapour and aerosols
associated with thermally-driven flows to enter
clouds?
Map of COPS
COPS and CSIP major objective: Determine location and timing of the
initiation and development of convective storms.
Lids important.
Ways of overcoming Lids:
Convergence lines created by orography, land/sea contrasts, surface moisture
gradients, differential heating


Heating; impact of clouds

In complex terrain: e.g. up-valley flow, elevated heat island;

Gravity waves and cold pools (secondary convection)
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Mesoscale convergence lines and dry intrusions

Combination of processes
Frontal zone with low $\theta_w$ air overrunning a tongue of high
$\theta_w$ air
Lid produced by descending dry intrusion
Lid relatively weak over surface warm pool -- strongest descent had occurred
further upstream and the air was beginning to ascend again
Lid raised due to SW-NE convergence line mostly formed by land-sea roughness
differences
Particular cloud initiated near Dartmoor and had sufficient buoyancy as a result
of
combination of high $\theta_w$ air and solar heating through gap in line
of clouds (Lean et al.\ 2008)
COPS 15 July
Convergence line
+
Up-valley flow
Another COPS objective: understand influence
of aerosols on convective precipitation
- link to MMOCCAA and future expts
Venting of aerosols out of valleys into clouds
 Role of tranformation of aerosols by previous
clouds
 Saharan dust outbreaks

Strong updraft over Murg
associated with increase
in humidity and
concentrationof aerosols
Venting of water vapour and aerosols
from Murg Valley
ICEPIC: Study of the initiation and development of ice and precipitation in
cumulus clouds.
1. First ice -- do the numbers match up with concentration of ice nuclei?
Don't know. Didn't manage this. Only way to do this in individual Cumulus clouds is
to study clouds that are anchored to a feature - New Mexico(2012). Or statistically,
as in RICO - ICE-T (2012?). Also see APPRAISE for mixed-phase layer clouds.
2. There are many more ice particles than ice nuclei -- why?
We showed quantitatively that the Hallett-Mossop process of secondary ice
production can explain the observed rate of production of ice. MAC3 model
results confirm that the HM process is important. However, MAC3 also shows that
supercooled raindrops are important and we didn't observe these.
3. Explain quantitatively with models the production of precipitation -- that means
getting the riming rate correct having explained 2.
The rain rate produced by MAC3 was comparable with the observed rate. BUT,
the concentration of aerosols was critical.
ICEPIC (cont)
4. The UM has errors in the quantity of precipitation.
The interaction of the parametrized autoconversion and ice nucleation process
can lead to an excessively rapid glaciation and vertical development of the
simulated clouds. For example, in simulations of New Mexico clouds,
autoconversion first occurred at and above the freezing level and the raindrops
were then rapidly frozen by accreting primary ice
crystals formed by the parametrized primary nucleation. These frozen raindrops
then grew further by riming and, because this occurs with the temperature
range of -3 to -8 C, acted as efficient centres of secondary ice nucleation via
the Hallett-Mossop process. Similar for ICEPIC clouds.
Critical to get autoconversion right - see results from RICO. Also
freezing -- see APPRAISE and future NM,
ICE-T and CONSTRAIN?
RICO Study of the processes responsible for the formation of warm rain in shallow
maritime cumulus clouds. (Rain In Cumulus over the Ocean)
Result: quantitatively explain the formation of rain in shallow maritim cumulus by
collision and coalescence with MAC3 model using the observed aerosol size
distribution. First time; 50-year old problem.
Observations
MAC3 Model
APPRAISE: Aerosol Properties, Processes And InfluenceS on the Earth's climate
Core position: Zhiqiang Cui -- bin microphysics in LEM. Almost complete. Important
Aerosol Interactions in Mixed Phase Clouds
determine the nucleating ability of specific ice nuclei and the initiation and
development of ice in mixed phase clouds.
• determine how aerosol particles control the cloud microphysics, preciptiation
and dynamics in mixed phase clouds.
• determine the type and phase partitioning of absorbing material above below and within
clouds and the role of this material in ice nucleation.
• reduce the uncertainty in the contribution of indirect radiative forcing by better
understanding of the role of aerosols in the microphysics of mixed phase cloud.

Few flights last winter; most of the flying is in January and February 2009 over Chilbolton
The VOCALS-UK Consortium will deliver new insights into the influence of marine
stratocumulus clouds on global and regional climate and provide much needed
improvements in our ability to quantify the processes that influence stratocumulus
clouds and man’s influences on them.
Alan Gadian
BAe-146
Do-228
C-130
Multi-platform sampling
along the 20°S cross
section will deliver:
1. a synthesised data
set for testing of
climate model
representations of
the SEP boundary
layer.
2. A series of important
case studies
VOCALS
VOCALS:
Bridging the scales between climate and cloud processes
VOCALS will act to bridge the gap between climate models and key cloud
processes by:
1) Diagnosing and testing important aspects of Climate model performance in Sc
cloud regions – nested model resolution is key to this
2) Developing new process knowledge and parameterising it in a way that is
effective for climate models
It will provide process studies with a
climate backdrop to the VOCALS
experiment – an important context
Courtesy Hugh Coe
In-Cloud temperature probe
Joint UFAM/FAAM/NCAR/Met Office project to produce a temperature probe
that works in cloud.
Ophir radiometric probe is primary candidate: see Wei, Blyth and Raymond
(1998; JAS)
Early stages for UK project; possible PhD student