Advances in the assessment of the MW-IR blended technique for rain rate measurement by remote

1. Advances in the assessment of the MW-IR blended technique for rain rate measurement by remote sensing Vincenzo Levizzani and Francesca Torricella Satellite Meteorology Group ISAC-CNR Italy DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop

2. Previous applications devoted to the production of rainfall accumulations on a 6 to 48 hours basis or more • The application to flood forecasting requires to assess the reliability of the method in producing instantaneousrain rate maps • To this end we work along a few main directions: • Improving (especially over land) the algorithm applied to MW TB; • Assessing the capability of the statistical histogram matching approach • in propagating the information on rainfall between two MW calibrations; • Validation of rain rate fields produced by means of Turk’s technique • comparing them with raingauges measurements (from dense, nearly • homogeneous, short time reporting networks) from literature. DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop

3. Improving over land the algorithm applied to MW TB • Available at SatMet group in Bologna the new GPROF version 6 (Goddard profiling algorithm, Kummerow et al., 2001) • After careful comparison of GPROF5 RR estimates with ground validation • data, authors are releasing the GPROFv6, modified to match PR and ground observations. • We needed to: • adapt the GPROF structure in order to manage SSM/I data, needed for proper coverage of non-tropical areas, i.e. to prepare an interface to adapt SSM/I data to the RU software; • insert the new algorithm in the RU structure, and compare its performances with the NESDIS (Ferraro et al., 1997) algorithm. • test the new algo on weather conditions, geographical areas and cases • relevant to the Projects. DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop

4. The GFROFv6: an algorithm for TRMM/TMI , SSM/I and AMSR-E instruments (McCollum and Ferraro, 2003) The new version eliminates the global high bias with respect to gauges This is done using coincident TMI and PR to derive relationships between RR and TB85V for both stratiform and convective rain The probability of convection is derived form PR-estimates and used to calibrate PMW* predictors of convection The resulting rainfall estimates compare quite well with PR data and GPCP** monthly rainfall product. * Passive MW ** GPCP: Global Precipitation Climatology Project DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop

5. GPROFv6 performances mean monthly rain (1998-2000) Zonal rainfall profiles using the three rainfall products (v5, v6, PR). Overall v6 is relatively unbiased respect to GPCP. overestimation mm underestimation LATITUDE DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop

6. Open issues in GPROFv6 • (applied to SSM/I data) • No rain detected at high • latitudes (where there is less • convective rainfall) • No rain estimation over • frozen surfaces such as • snow MONTHLY MEAN JAN 2002 DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop

7. Assessing the capability of the histogram matching approach in propagating the information on rainfall between two MW calibrations 08:00 UTC 10 Nov 2001 08:03 UTC MW cal The method follows to some extent the evolution of the event before- after the MW calibration Previous calibration: 3 hours old! 08:30 UTC 3 mm/h 25 DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop

8. lon0 grid overpass-1 swath (SSM/I) From the previous slide it is apparent… The RR values are depressed due to the smoothing process involved in the method (i.e. the TB-RR relationships derived from coincident data are averaged on 5 x 5 boxes regions to avoid discontinuities at box boundaries). For non-global applications avoid the smoothing (?) lon0 +lon overpass-2 swath (TMI) lat0 Global grid for geo-locating RR/TB relationships DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop

9. Validation of rain rate fields produced by means of Turk’s technique Validation of an Operational Global Precipitation Analysis at Short Time Scales F. Joseph Turk, Elizabeth E. Ebert, Hyun-Jong Oh, Byung-Ju Sohn, Vincenzo Levizzani, Eric A. Smith, and Ralph Ferraro Proc. 1st IPWG Workshop, Madrid, 23-27 Sept., 2002, in press. Rain gauges-RU scatter plots for several time average intervals (1° spatial scale) Gauges from the AWS (Automated Weather Station) network of the KMA (Korean Meteorological Agency) DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop

10. Validation of rain rate fields produced by means of Turk’s technique 0.5 2 0.5 Gauge averaging time: 2 minutes window centered about the GMS observation time As expected all three parameters improve as either the averaging period is increased or the grid size is coarsened! DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop

11. Validation of rain rate fields produced by means of Turk’s technique 0.5 2 0.5 Gauge averaging time: 20 minutes window centered about the GMS observation time. Sharp improvement when widening the time window. DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop

12. Multispectral characterization of storm top Vincenzo Levizzani, Elsa Cattani, Francesca Torricella and Maria João Costa Satellite Meteorology Group ISAC-CNR Italy DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop

13. Multispectral studies of cloud top to identify severe weather features. For example characterization of plumes of ice crystals and link their formation to precipitation formation mechanisms. The idea is to explore the forecasting potential • Observations of storm top plumes suggest that very small ice crystals are responsible for large increases in the cloud top reflectance field at 3.7 μm. • Radiative transfer simulations using several ice crystal habits indicate that indeed small ice crystals are a likely cause of such high reflectance values. • Only certain types of crystals, whose dimensions are sufficiently small, are compatible with reasonable plumes optical depths and therefore correctly reproduce the observed reflectance and brightness temperature values. DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop

14. Multispectral studies of cloud top with applications to precip. estimations. 8 Nov. 1998 Multispectral image from TRMM VIRS over the Kwajalein Atoll with superimposed PR-derived rain areas (stippled pixels). The graphs report cloud top temperature vs effective radius. While the 3.7 m product (top) correctly identifies the cloud top structure and delimits the various microphysical zones, the 1.6 m channel response (bottom) suffers from contamination from the lower levels in the cloud. Numbers on the graphs refer to the numbered boxes in the image. Research conducted in cooperation with D. Rosenfeld, Hebrew Univ. Jerusalem. DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop

15. Rosenfeld and Lensky, 1998 The classification scheme of convective clouds into microphysical zones according to the shape of the temperature – effective radius relations Note that in extremely continental clouds re at cloud base is very small, the coalescence zone vanishes, mixed phase zone starts at T<-15oC, and the glaciation can occur at the most extreme situation at the height of homogeneous freezing temperature of –39oC. In contrast, maritime clouds start with large re at their base, crossing the precipitation threshold of 14 mm short distance above the base. The deep rainout zone is indicative of fully developed warm rain processes in the maritime clouds. The large droplets freeze at relatively high temperatures, resulting in a shallow mixed phase zone and a glaciation temperature reached near –10oC DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop