European Perspectives on Geostationary Microwave Sounding   Bizzarro Bizzarri CNR Istituto di Scienze dell’Atmosfera e del Clima, Roma, Italy Phone +39.06.4426.1604, Fax +39.06.4423.7615, E-mail bibizzar@tin.it Content European undertaking in the geostationary orbit Principle of MW precipitation & sounding from geostationary orbit GOMAS (Geostationary Observatory for MW Atmospheric Sounding) 2nd GOES Users Conference, Boulder CO, USA, 1-3 October 2002

European undertaking in the geostationary orbit Meteosat 1 was launched on 23 November 1977, first of a pre-operational series (Meteosat 1, 2 and 3). Meteosat 4 was launched on 6 March 1989, first of an operational series (Meteosat 4, 5, 6 and 7) to be used until 2005. All these are spinning satellites, equipped with a 3-channel VIS/IR imager. MSG 1 was launched on 28 August 2002, first of a Meteosat Second Generation series (Meteosat 8, 9, 10 and 11) to be used until 2020. These are still spinning satellites, equipped with a 12-channel VIS/IR imager (SEVIRI) and an Earth Radiation Budget radiometer (GERB). Mission definition of post-MSG, or Meteosat Third Generation, has started, in view of a first launch in 2015. A 1st User Consultation Workshop was held on 13-15 November 2001.

Temperature and humidity profile PARAMETER OBSERVABLE FROM GEO OBSERVABLE   FROM LEO Temperature and humidity profile IR emission from different atmospheric layers by spectroscopy. Emission from different layers by MW/Sub-mm radiometry. IR/MW emission from different atmospheric layers by spectroscopy.  Occultation of signals from GPS received by a LEO satellite. Wind profile Motion of water vapour patches by IR imaging spectrometers with frequent observing cycle. Tracers motion (clouds, water vapour and ozone patches) Tracers motion (clouds, water vapour and ozone patches) measured by Backscattered light from aerosol eddies or Derived by 4-D assimilation of frequent temperature / humidity profiles. measured by VIS/IR image sequences.. overlapping VIS/IR images at high latitudes. molecules by Doppler lidar. Cloud pattern, type, and evolution; water vapour growth Frequent measurement of scattered and emitted radiation in several VIS/IR channels covering atmospheric windows and water vapour absorption bands. Scattered and emitted radiation in several VIS/IR channels covering atmospheric windows and water vapour absorption bands. Precipitation rate Derived by 4-D assimilation of frequent temperature / Correlation with cloud top ice as observed by VIS/IR MW/Sub-mm radiation in absorption bands Correlation with lightning intensity and MW backscattering from raindrops by radar - Profile provided. humidity profiles. radiometry. - Gross profile possible. flashes/time in a given area. MW radiation in atmospheric windows. INSTRUMENT IR sounding spectrometer. VIS/IR imaging radiometer. MW/Sub-mm radiometer. Lightning mapper. LEO technique also applicable to GEO. LEO instruments not applicable to GEO. FEASIBILITY Demonstration mission being developed in US. Current practise. Improvements feasible. To be demonstrated. Demonstrated in LEO. Current or demonstrated. Demonstrated or planned. COLOUR CODE Marginal compliance Poor compliance Fair compliance Good compliance Excellent compliance

(WMO representative of current or near-future, EUM of > 2015) WMO and EUMETSAT requirements for precipitation observation (WMO representative of current or near-future, EUM of > 2015) Requi- G l o b a l N W P Reg Ional N o w c a s t i n g rement Unit W M O E U M   Target Threshold x km 50 100 5 10 3 1 r.m.s. mm/h 0.1 t h 12 0.5 6 0.08 0.03 0.3 delay 4 2

The problem of measuring precipitation   The most long-standing practise makes use of VIS/IR image sequences from GEO: The observing frequency is suitable (15 min with MSG) The measurement is strongly indirect (VIS/IR only “sees” the cloud top) The applicability is mostly addressing convective precipitation. From LEO, MW images are used (from SSM/I, TRMM, in the near future GPM): The measurement is direct for low frequencies (10 GHz), less for high frequencies (90 GHz) The applicability is better for convective precipitation, but extends to all precipitation types The frequency, with GPM, will be around 3 hours Global scale will be served optimally, regional scale to a fair extent For the mesoscale, fusion between LEO MW images and GEO VIS/IR images will be attempted. The ideal would be to extend the MW imagery technique to the geostationary orbit, but: The antenna diameter for a 10-km resolution is 15 m at 90 GHz, 35 m at 37 GHz, 70 m at 19 GHz Polarisation diversity is not practical from the geostationary orbit (large and variable z-angle). GEO requires using higher frequencies and exploiting a different physical principle.

The physical principle for measuring precipitation from GEO   MW observation from LEO makes use of “atmospheric windows”: Most common frequencies: 6 GHz, 10 GHz, 19 GHz, 23 GHz, 37 GHz, 90 GHz, 150 GHz Dual polarisation for roughness effects (over the sea) and scattering from ice (over land). The proposed principle for GEO exploits absorption bands: Profiles of temperature and humidity are measured by more bands at different frequencies Profiles observed exploiting bands of different frequencies are differently sensitive to clouds Absorption bands at very high frequencies enable using antennas of affordable size It is not necessary to differentiate polarisations In absorption bands the measurement is equally effective over sea and land. The precipitation measurement passes through the sounding one, therefore: Many more channels are needed, very narrow (< 1 ‰), with SNR > 100 In exchange, one simultaneously gets: - the temperature vertical profile (also inside clouds) - the humidity vertical profile (also inside clouds) - the columnar content (or gross profile) of liquid water in the cloud - the columnar content (or gross profile) of ice water in the cloud - the precipitation.

Multi-channel image from an airborne radiometer (Gasiewski et al, 1994). Note: In absorption bands (183 and 325 GHz) increasing cloud impact moving from the peak to the window (from 183  1 to 183  3 and 183  7; and from 325  1 to 325  3 and 325  9); In windows (89, 150, 183  7, 220 e 325  9) increasing cloud impact with increasing frequency.

Precipitation images from a cold front on October 7, 1998: NEXRAD precipitation map smoothed to 15 km resolution (left image), and NOAA/AMSU precipitation map obtained using a neural net retrieval technique (right image) (Staelin and Chen, 2000).

NOAA-15 AMSU-B 183+/-7 GHz 15-km resolution imagery of small rain cells over the Eastern U.S on August 2, 2000 (from Staelin and Chen, 2000).

Comparison between the 118/54 GHz profile ratio from the NAST-M microwave radiometer being flown on the NASA ER-2 aircraft and simultaneous EDOP Doppler radar reflectivity observation. Hurricane Bonnie at 17 GMT on August 26, 1998 (Tsou et al, 2001). The ratio 118/54 is unit in the absence of precipitation or above the precipitation cell, and reduces in the presence of precipitation because of higher attenuation from drops and impact from ice scattering at the higher frequency. The agreement between the two vertical cross-sections is striking. Horizontal maps of this information from GEO at 15 min intervals, will resemble a proxy rain radar operating over continental field of view, particularly over oceans and mountainous terrain.

Atmospheric spectrum in the MW/Sub-mm range (Klein and Gasiewski, 2000). Preferred bands - for O2 (temperature): 54 GHz, 118 GHz, 425 GHz; for H2O: 183 GHz, 380 GHz.

Incremental Weighting Functions (IWF) for the selected channels in the bands of oxygen (54, 118 and 425 GHz) and of water vapour (183 and 380 GHz). Note that the sensitivity of 380 and 425 GHz drastically drops in lower troposphere (Klein and Gasiewski, 2000).

Retrieval errors for bands 118, 183, 380 e 425 GHz, stand-alone or associated to an IR sounder of the IASI or AIRS class (“GAIRS”). Temperature on the left hand, humidity on the right. On the left hand, GAIRS + 118 + 425 is compared to GAIRS alone and to 118 + 425 alone. For reference, the EOS/Aqua AIRS + AMSU/A + AMSU/B complex also is shown (Blackwell and Staelin, 1996).

Initiatives for MW/Sub-mm sounding from GEO Early proposals: Staelin D.H. and P.W. Rosenkranz, editors, 1978: "Applications Review Panel: High resolution passive microwave satellites". A report to NASA. Chedin A., D. Pick and R. Rizzi, 1985: "Definition study and impact analysis of a microwave radiometer on a geostationary spacecraft". A report to ESA. Fresh start: Staelin D.H., J.P. Kerekes and F.J. Solman III, 1997: "Final Report of the Geosynchronous Microwave Sounder Working Group". A report to NOAA/NESDIS. Staelin D.H., A.J. Gasiewski, J.P. Kerekes, M.W. Shields and F.J. Solman III, 1998: "Concept proposal for a Geostationary Microwave (GEM) Observatory". A proposal to NASA and NOAA. Bizzarri B., 2000: "MW/Sub-mm sounding from geostationary orbit". A report to EUMETSAT. Current projects: GEM (Geostationary Microwave observatory). GOMAS (Geostationary Observatory for Microwave Atmospheric Sounding).

Horizontal resolution Resolution v/s frequency and antenna diameter Reference user requirements adopted for GOMAS Geophysical parameter Horizontal resolution Vertical resolution Accuracy (r.m.s.) Observing cycle Delay of availability Temperature profile 30 km 2.0 km 1.5 K 1 h 15 min Humidity profile 20 km 20 % Cloud liquid/ice water 5.0 km 50 % 5 min Precipitation rate 10 km - 5 mm/h Resolution v/s frequency and antenna diameter Antenna Ø 54 GHz 118 GHz 183 GHz 380 GHz 425 GHz 1 m 242 km 112 km 73 km 35 km 31 km 2 m 121 km 56 km 36 km 18 km 16 km 3 m 81 km 37 km 24 km 12 km 10 km 4 m 60 km 28 km 8.8 km 7.8 km

GOMAS (Geostationary Observatory for MW Atmospheric Sounding) European sector (1/12 of disk) scanned each 15 minutes. The sector can be moved everywhere inside the visible Earth disk. The satellite can be shifted to serve from USA to India. Simultaneous retrieval of temperature/humidity profiles, cloud liquid/ice water and precipitation.

Radiometric performance assessment for 15 min observing cycle NEDT compliance code Compliant Nearly compliant Compliant on 2 x or 1 h Candidate to be dropped  (GHz)  (MHz) Product resolution IFOV s.s.p. Required NET (K) Expected NET (K) Peak of IWF (s.s.p.) NE T (K) 56.325 50   0.6 0.15 27 km 183.310  0.300 300 0.45 10 km 56.215 0.5 23 km 183.310  0.900 500 0.35 8.5 km 56.025 250 0.07 17 km 183.310  1.650 700 2 x 2 pixels 0.29 7 km 55.520 180 0.4 0.08 13 km 183.310  3.000 1000 (20 km) 24 km 0.3 0.24 6 km 54.950 6 x 6 pixels 0.06 183.310  5.000 2000 0.17 5 km 54.400 220 (60 km) 81 km 8 km 183.310  7.000 4 km 53.845 190 183.310  17.000 4000 0.18 surface 53.290 360 3 km 380.197  0.045 30 2.36 15 km 52.825 0.2 2 km 380.197  0.400 200 0.91 51.760 400 0.1 0.05 1 km 380.197  1.500 0.58 11 km 50.300 380.197  4.000 900 12 km 0.43 9 km 118.750  0.018 6 1.32 34 km 380.197  9.000 118.750  0.035 12 0.93 29 km 380.197  18.000 0.36 118.750  0.080 20 0.72 424.763  0.030 10 3.40 118.750  0.200 100 0.32 19 km 424.763  0.070 2.41 28 km 118.750  0.400 3 x 3 pixels 0.23 424.763  0.150 60 1.39 118.750  0.700 (30 km) 37 km 0.16 424.763  0.300 1.08 18 km 118.750  1.100 424.763  0.600 0.76 118.750  1.500 424.763  1.000 0.54 118.750  2.100 800 0.11 424.763  1.500 600 0.44 118.750  3.000 0.10 424.763  4.000 0.34 118.750  5.000 1 pixel 1.0 (10 km) 1.02

Space Calibration Tube 3” Thick Composite Reflector Azimuth Motor & Compensator Elevation Motor Nodding / Morphing Subreflector Thin Struts Space Calibration Tube Backup Structure 3” Thick Composite Reflector 50-430 GHz Feeds Receiver Package The GOMAS instrument with its 3-m antenna

Space Calibration Tube S-Band Antenna for TT&C     The GOMAS satellite NORTH DIRECTION Space Calibration Tube NADIR Solar Wing 3 -meter Antenna Star Sensors S-band Antenna for TT&C Mass: 860 kg (“dry": 430 kg) Electrical power: 500 W Volume: 3.0 x 3.0 x 3.0 m3 Data rate: 128 kbps (S-band, compatible with MSG LRIT). S-Band Antenna for TT&C S-band antenna for LRIT

List of Proponents of GOMAS (undertaking to implement the scientific programme) P.I.: Bizzarro BIZZARRI, for the CNR Istituto Scienze dell'Atmosfera e del Clima, Roma, Italy Team leader Institute Umberto AMATO CNR Istituto Applicazioni della Matematica, Napoli, Italy Paul MENZEL NOAA/NESDIS Office of Research and Application, Madison Wis., USA John BATES NOAA/NESDIS, National Climatic Data Center, Asheville NC, USA Jungang MIAO Institute of Environmental Physics, University of Bremen, Germany Wolfgang BENESCH Deutscher Wetterdienst, Offenbach, Germany Alberto MUGNAI CNR Istituto Scienze dell'Atmosfera e del Clima, Roma, Italy Stefan BÜHLER Paolo PAGANO Servizio Meteorologico dell'Aeronautica, Roma, Italy Massimo CAPALDO Jean PAILLEUX Météo France, Toulouse, France Marco CERVINO CNR Istituto Science dell'Atmosfera e del Clima, Bologna, Italy Juan PARDO Instituto de Estructura de la Materia, Madrid, Spain Vincenzo CUOMO CNR Istituto Metodologie Avanzate di Analisi Ambientale, Potenza, Italy Federico PORCU' Department of Physics, University of Ferrara, Italy Luigi De LEONIBUS Catherine PRIGENT Dep.nt de Radioastronomie Millimetrique, Observatoire de Paris, France Michel DESBOIS CNRS Laboratoire de Météorologie Dynamique, Palaiseau, France Franco PRODI Stefano DIETRICH CNR Istituto Science dell'Atmosfera e del Clima, Roma, Italy Rolando RIZZI Department of Physics, University of Bologna, Italy Frank EVANS University of Colorado, Atmospheric & Oceanic Sciences, Boulder Co., USA Guy ROCHARD MétéoFrance, Centre de Météorologie Spatiale, Lannion, France Laurence EYMARD CNRS Centre études Environnement Terrestres et Planétaires, Vélizy, France Hans Peter ROESLI MétéoSuisse, Locarno-Monti, Switzerland Albin GASIEWSKI NOAA Environmental Technology Laboratory, Boulder Co., USA Carmine SERIO Dip.nto Ingegneria e Fisica Ambiente, University of Basilicata, Potenza, Italy Nils GUSTAFSSON Swedish Meteorological and Hydrological Institute, Norrköping, Sweden William SMITH NASA Langley Research Center, Hampton VA., USA Georg HEYGSTER Antonio SPERANZA Hydrographic and Mareographic Service, Roma, Italy Marian KLEIN David STAELIN MIT Research Laboratory of Electronics, Cambridge MA., USA Klaus KÜNZI Alfonso SUTERA Department of Physics, University of Roma, Italy Vincenzo LEVIZZANI Jung-Jung TSOU Gian Luigi LIBERTI Chris VELDEN Cooperative Institute for Meteorological Satellite Studies, Madison Wis.,USA Ernesto LOPEZ-BAEZA Dep.nt of Thermodynamics, Faculty of Physics, University of Valencia, Spain Guido VISCONTI Department of Physics, University of L'Aquila, Italy

Conclusions   Strong requirements exist for frequent precipitation observation. From GEO, a new physical principle needs to be exploited. GOMAS is proposed as a demonstration mission. It would be a precursor for future operational applications. From the technical standpoint, and building on the studies conducted in the U.S. on GEM, it is believed that no enabling technology is currently missing. The GOMAS satellite could be developed in time for a launch before 2010, in phase with GPM and possible overlap with GIFTS. It would provide simultaneous retrieval of: - temperature profile (x  30 km) - humidity profile (x  20 km) - cloud liquid/ice water total column and gross profile (x  20 km) - precipitation rate (x  10 km) each 15 minutes ! over  1 / 12 of the disk covering sea and land !