1. Clare Lee & Anthony Baran
CAESAR sorties
Clare Lee & Anthony Baran
© Crown copyright 2005

2. CAESAR Cirrus and Anvils: European Satellite and Airborne Radiation measurements project
Main Aims:
Study radiative and in-situ cirrus (frontal or convective) properties to improve representation in models
2 Options:
Multi-frequency radiative properties of cirrus
In-situ microphysics for radar intercomparison
© Crown copyright 2005

3. Coincident observations
Want flights in conjunction with:
Satellite A-train – AQUA (AIRS), CloudSat (Radar), Calipso (Lidar)
CloudSat orbit = AQUA orbit + ~1min
Foot print = 1.4km (across track) x (2.5km along track)
and/or Chilbolton radar facility
© Crown copyright 2005

4. Chilbolton 94GHz radar on steerable mount
Lidar, 3GHz radar, 35GHz radar plus standard insts on stand-by
Met Office person at Chilbolton – VHF radio contact
© Crown copyright 2005

5. Chilbolton Flight restrictions
Danger areas/controlled airspace
Chilbolton – can fly directly overhead, but in restricted way
© Crown copyright 2005

6. A-train (AQUA overpass)
16 day repeat cycle
Chilbolton suborbital overpasses (1302Z):
Friday 5th Jan
Sunday 21st Jan
Tuesday 6th Feb
© Crown copyright 2005

7. A-train (AQUA overpass)
Chilbolton suborbital overpasses (0222Z):
Monday 8th Jan
Wednesday 24th Jan
Friday 9th Feb
On website:
Or internally on P: drive
© Crown copyright 2005

8. Option1 - radiative studies of cirrus
Conditions:
Frontal or convective cirrus
Over sea or Chilbolton
Clear sky below
Ideally coincident with satellite overpass: A-train & ENVISAT
Requirements:
Measurement of cirrus
remote sensing from below and above cirrus + orbits (view towards cloud)
In-situ microphysics (e.g. Lagrangian spiral or straight & level runs)
Measurements of atmosphere above and below cloud
aircraft profiles
drop sondes
remote sensing from below and above (view away from cloud)
Sea surface temperature (100ft run)
© Crown copyright 2005

9. Option 1 – Radiative properties
Drop sondes at max alt
orbits
100ft
Runs perpendicular to wind
Advect with air mass
ARIES & SWS to look in same direction, typically towards cloud
© Crown copyright 2005

10. Lagrangian spiral instead to S&L runs
Advecting with wind
To continuously measure same air mass
Runs above cloud
cirrus
fallspeed
~2 ms-1
For 10kft (3km)
@ 2 ms-1
Take 25 mins
266m
Lagrangian spiral descent
Fall with the ice:
Growth rate and changes at different levels
Runs below cloud
© Crown copyright 2005
~ 5 – 10 km

11. Instruments (radiation)
Critical
ARIES
SWS
SID1
2DC
Temp
Humidity
AVAPS
Desirable
MARSS
TAFTS *
SHIMS
CPI *
SID2
FFSSP
2DP
CIPs
Heimann
Core chem (auto)
© Crown copyright 2005

12. Instrument operators ARIES and SWS ARIES SWS
Both instruments must point in the same direction as each other (except during cal)
Majority of time towards cloud (or sea at 100ft)
However, still need some data pointing away to characterise the atmos above and below the cloud (e.g. ~2 mins of 10 min run)
Orbits both view towards cloud for whole time
ARIES
If still unstable for zenith view (shutter open) at high altitudes better to get 30 secs of good data in a 10 min run (with rest of time with shutter closed viewing cals or nadir) than all bad data – let SWS know viewing direction.
SWS
Zenith = 6 deg forward
© Crown copyright 2005

13. Option 2 – Radar intercompaison/validation
Conditions:
Frontal or convective cirrus
Clear sky preferred but not essential
Radar critical - Chilbolton and/or CloudSat
Over sea if only CloudSat
Requirements:
In-situ statistical properties (saw-tooth manoeuvres)
No advection with wind
Drop sondes
Low remote sensing inst requirement
N.B. Chilbolton – 94GHz steerable, all others zenith
© Crown copyright 2005

14. CAESAR – radar intercomparison
CloudSat
wind
Top view
Chilbolton
Trailing edge with Cu behind
cirrus
Leading edge
Side view
© Crown copyright 2005

15. CAESAR – radar intercomparison
Side view
Top view
CloudSat
Trailing edge with Cu behind
Leading edge
top
base
cirrus
No advection – statistical sampling
wind
© Crown copyright 2005

16. Instruments (in-situ)
Critical
SID1
2DC
2DP
CPI *
FFSSP
Temp
Humidity
Desirable
SID2
CIPs
AVAPS
ARIES
SWS
MARSS
TAFTS *
SHIMS
Heimann
Core chem (auto)
© Crown copyright 2005

17. Questions
© Crown copyright 2005