COPS Workshop, 27-29 February 2008

Long-term water vapour comparison at the ARM Mobile Facility

S. Crewell, U. Löhnert, S. Kneifel (U Cologne) D. Turner (U Wisconsin)

COPS Workshop, 27-29 February 2008

Instrumentation at AMF Radiosondes

IfT Lidar

Microwave Radiometers

- MWRP 12 ch.

- HATPRO - Scanning (Köln)

- MWRLOS 2ch.

- MWRHF

- DPR

GPS

Vertical profiles

MWRPMWRLOSMWRHF

HATPRODPHASE

Integrated Water Vapor (IWV)

COPS Workshop, 27-29 February 2008

Data SetSource Org. Description t Operation

COSMO-DE DWD Model analysis/fore-cast at 3x3 gpoints

15 min 04/01-12/ 31

RS-92 ARM Radiosonde profiles 919 quality checked

4 / day 04/01-12/ 31

GPS GFZ 15 min, 93% 15 min 04/19-12/31

2CH ARM Standard ARM dual channel radiometer

20 s 04/01 - 12/31

MWRP ARM 12 freqs 1 s 04/01 - 12/31

MWRHF ARM 90/150 GHz 1 s 06/20-12/31

HATPRO UKöln scanning 14 freqs 04/20-12/31

DPR UKöln dual pol at 150 GHz 1s 05/02-10/05

Lidar IfT Raman COPS

MSG FUB IWV 3x3 grid 15 min 04/01-12/31

COPS Workshop, 27-29 February 2008

Microwave Signatures

standard atmosphere

liquid water pathLWP=250 gm-2

temperature profilehumidity profile

ν /GHz 31 36 90

90° 9 12 50

COPS Workshop, 27-29 February 2008

TB Intercomparison

Difference in gas absorption from MonoRTM - Rosenkranz

22 GHz water vapor line

continuum at higher freqs

COPS Workshop, 27-29 February 2008

Radiosonde Dry Bias

0 UTC 6 UTC 12 UTC 18 UTC All

N 61 66 68 65 263

RS - GPS 0.3 1.1 -0.1 0.8 -1.5 1.3 -0.3 0.8 -0.4 1.2

RS - Profiler 0.0 0.8 -0.7 0.7 -1.0 0.7 -0.4 0.6 -0.5 0.8

RS - 2 ch 0.2 0.5 -0.5 0.6 -1.4 0.9 -0.6 0.6 -0.6 0.9

AMF April to JuneBias/Std. Deviation in Integrated Water Vapor in kg m-2

COPS Workshop, 27-29 February 2008

Scanning Microwave ObservationsCOPS: Azimuth scans every 15 min

- fixed elevation angle (30°)

- 355°- rotation with 5° resolution

- beamwidth: HATPRO: ~4-2°, IR: ~1°

- scan duration about 5 Min.

Integrated Water Vapor (IWV), liquid water path (LWP) and IR-Temperaturalong slant path for each azimuth angle

COPS Workshop, 27-29 February 2008

Exmple: 14 July 2007

30 deg azimuth scans

Morning strong asymmetry of thehumidity field

Noonstrong humidity reductionof about 5 kgm-2 (in zenith)

13:00-14:30 UTCConvection in the North West

after 15:00humidity increase

see Poster by S. Kneifel

COPS Workshop, 27-29 February 2008

Summary and Outlook

Water vapour absorption Poorly known at higher microwave frequencies calibration analysis

Integrated Water Vapor consistent analysis of all COPS microwave radiometers

(calibration, filtering, quality flags, retrieval algorithms..)

Profiles intercomparisons with IfT Lidar, DLR aircraft lidar

Spatial variabiityMore than 10 % variabilty in IWV(see Poster by Kneifel further analysis of volume scans