1. Multi-satellite Precipitation Analysis (MPA) George Huffman, Bob Adler, Dave Bolvin, Eric Nelkin NASA/GSFC

2. Theory / Schematic Algorithm Inputs InstrumentExperimental Real- Time (3B42RT) TRMM Version 6 3B42 TRMM Combined Instrument (TCI) –TSDIS TMITSDIS SSM/IFNMOCRSS AMSRTSDIS AMSUNESDIS IRNOAA/CPC (4 km geo- IR) NOAA/CPC (4 km geo- IR, 1° IR histograms) Gauge Analysis–GPCC (monitoring) NOAA/CPC (CAMS)

3. Theory / Schematic (cont.) Algorithm Process The “real” MPA is the post-real-time Version 6 3B42 The current real- time 3B42RT that runs 10 hr after real time is a first look We plan to replace the 10-hr run with a 4-hr “early” and 7- hr “final” to better support operations Instant- aneous SSM/I TRMM AMSR AMSU 30-day HQ coefficients 3-hourly merged HQ 3-hourly IR Tb Hourly HQ-calib IR precip 3-hourly multi-satellite (MS) Monthly gauges Monthly SG Rescale 3-hourly MS to monthly SG Rescaled 3-hourly MS Calibrate High-Quality (HQ) Estimates to “Best” Merge HQ Estimates Match IR and HQ, generate coeffs Apply IR coefficients Merge IR, merged HQ estimates Compute monthly satellite-gauge combination (SG) 30-day IR coefficients

4. Theory / Schematic (cont.) IR Calibration Data Cube 3-hr/0.25° matched HQ and IR, aggregated for a month on overlapping 3°x3° blocks

5. Theory / Schematic (cont.) Strengths and Weaknesses of Underlying Assumptions “All” MW are used Aggregating MW to 3-hr maps introduces time errors at fine scale Intercalibration of MW and cal. of IR to MW traceable; good, except bad if the calibrator goes bad Different calibrators are used for RT (TMI) and V.6 (TCI and gauge) VAR scheme for IR assumes that instantaneously colder clouds rain more VAR scheme for IR takes calibration from a month of data; stable, but stiff HQ-VAR combination scheme is priority - HQ, else VAR; minimum assumptions, but introduces boundaries

6. Theory / Schematic (cont.) Planned Modifications / Improvements Current (3 February) Update the RT VAR calibration coefficients every 3 hr (vs. 5 days) Introduce AMSR, AMSU in RT in addition to TMI, SSM/I Just recomputed February–May due to programming, uh, feature Short-term 10-hr latency lowered to 7-hr in RT (the “final”) Introduce “early” 4-hr RT Long-term Approximate TCI and gauge calibrations for RT (so closer to V.6) Ameliorate or audit out deficient input data in light-rain, cold-surface areas High-latitude estimates based on NASA SRT TOVS and AIRS Fine-scale error estimates (REM2D?) Evaluate CST to replace VAR Evaluate B1 (and TOVS, OPI) data to extend back in time

7. Algorithm Output Information Spatial Resolution 0.25°x0.25° Spatial Coverage 50°N-S (60° possible) Update Frequency 3-hr (RT), monthly (V.6) Data Latency 10 hr (RT; plan move to 7 & 4), 2 weeks after month (V.6)

8. Algorithm Output Information (cont.) Source of Real-Time Data Source of Archive Data InstrumentExperimental Real- Time (3B42RT) TRMM Version 6 3B42 TRMM Combined Instrument (TCI) –TSDIS TMITSDIS SSM/IFNMOCRSS AMSRTSDIS AMSUNESDIS IRNOAA/CPC (4 km geo- IR) NOAA/CPC (4 km geo- IR, 1° IR histograms) Gauge Analysis–GPCC (monitoring) NOAA/CPC (CAMS)

9. Algorithm Output Information (cont.) Capability of Producing Retrospective Data (data and resources required / available) Currently 1/98-present (but already based on heterogeneous input data) Could go back to 10/96 with current data sets Likely able to go back to 1/91 by employing B1 data Figuring out how to handle the F8 drop-out would allow us to go back to 7/87 Properly handling TOVS and/or OPI as calibrators might take us back to 1983 At coarser resolution, might be able to go back to 1979