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					CHARACTERIZATION OF INTER-SATELLITE
 DIFFERENCES IN RETRIEVED RAINFALL

                                          Dr. F. Joseph (Joe) Turk
          Naval Research Laboratory, Marine Meteorology Division
                                              Monterey, CA 93943
                            (831)-656-4888 turk@nrlmry.navy.mil




                                         Third IPWG Workshop
                                          Melbourne, Australia
                                            23-27 October 2006
           Inter-Sensor Rainfall Characteristics

In light of program changes, launch delays, etc, the future microwave
(MW) sensor suite likely to be composed of different sensor types (as it is
today)

Radar/radiometer, different channels on MW radiometers, conical & cross
track scanning instruments, spatial resolutions, etc.

Retrieved rainfall characteristics likely to be different between sensors –
varying as a function of rainfall rate, latitude, season, background, etc.

Combining MW sensors is an ongoing research topic for GPM (in radiance
space and rainfall space)

Data assimilation techniques may assimilate “rainy radiances” from a
suite of inter-calibrated MW sensors; however,

High Resolution Precipitation Products (HRPP) will need to blend/merge
these sets of disparate observations
PEHRPP Suite 4: "Big picture" comparisons (coordinator: ?)
       Catch any artifacts not noticed in detailed statistics of above suites
         • obvious systematic changes on a latitude line, related to availability of
           certain data types
         • changes in time series, related to data availability
       Validation of large-scale quantities and characteristics against bulk
        quantities, existing products (GPCP, CMAP, etc.), streamflow data
        sets, water budgets, and subjective judgment
       Focus on thousands of kilometers and monthly time scales
     LOCAL OBSERVATION TIMES OF DMSP and NOAA SATELLITES


                     0                                        0

                                                       F-16
        NOAA-17

                                               F-15
                                                      F-13

18                                     6 18                                     6
                                                F-14
      NOAA-15


           NOAA-16

                     NOAA-18




                     12                                       12
     NOAA Satellites as of Late 2006          DMSP Satellites as of Late 2006
       Ascending Descending                     Ascending Descending
                   Dataset Preparation

 Nearly three years (2004-current) of DMSP, NOAA, TRMM
(WindSat since 6/06, Aqua since 4/05, F-16 since 2/06,
NOAA-18 since 11/05)

 From each orbit file, rain histogram is binned by date,
latitude and surface (0.2 mm hr-1 steps)

 First step is to analyze up-front rain/no-rain screening
differences amongst various sensors

 Second step is to analyze (non-zero) light rain differences
Middle Latitudes   Rain/No-Rain Discrimination


                         Northern Hemisphere
                               30N-40N




                         Southern Hemisphere
                               40S-30S
Rain Detection - Middle Latitudes - Over Ocean
 DMSP F-13, F-14, F-15 (SSMI), F-16 (SSMIS)
                                              Northern Hemisphere
                                                    30N-40N
                                               More “no-rain” events in
                                                 summer seasons

                                                 SSMI’s well matched
      winter    summer    winter   summer
                                               SSMIS flags more no-rain
                                              values in both hemispheres

                                             F-15 RADCAL issue apparent
                                                after mid-August 2006

                                              Southern Hemisphere
                                                    40S-30S

                                                     COLOR LEGEND
       summer    winter   summer    winter             F-13 (SSMI)
                                                       F-14 (SSMI)
                                                       F15 (SSMI)
                                                      F-16 (SSMIS)
Rain Detection - Middle Latitudes - Over Ocean
TRMM-TMI/PR, Aqua-AMSR-E, Coriolis-WindSat
                                              Northern Hemisphere
                                                    30N-40N

                                             PR has about 2-3% more no-
                                                rain events than TMI

      winter    summer    winter   summer    TMI & AMSR-E well matched

                                               WindSat lacks 85 GHz
                                              capability which improves
                                                   rain screening


                                              Southern Hemisphere
                                                    40S-30S

                                                    COLOR LEGEND
       summer    winter   summer    winter            TRMM (PR)
                                                      TRMM (TMI)
                                                     Aqua (AMSR-E)
                                                    Coriolis (WindSat)
   Rain Detection - Middle Latitudes - Over Ocean
NOAA-15, NOAA-16, NOAA-17 (AMSU), NOAA-18 (MHS)
                                                 Northern Hemisphere
                                                       30N-40N
                                                 Seasonality signal not well
                                                represented at high latitudes

                                                   AMSU and MHS well-
         winter    summer    winter   summer
                                                       matched

                                                 Slight differences likely due
                                                to AM and PM crossing time
                                                           difference


                                                Southern Hemisphere
                                                      40S-30S

                                                        COLOR LEGEND
          summer    winter   summer    winter           NOAA-15 (AMSU)
                                                        NOAA-16 (AMSU)
                                                        NOAA-17 (AMSU)
                                                        NOAA-18 (MHS)
                           The Problem

•   At the direction of US Strategic Command (USSTRATCOM) and in
    coordination with the NPOESS IPO-ADO for DMSP operations, the
    satellite operations control center activated the radar calibration
    (RADCAL) suite on DMSP F15, August 14, 2006.

•   The RADCAL beacon operates at 150MHz & 400 MHz. On-orbit testing
    conducted in August 2005, confirmed that transmissions from the
    RADCAL 150Mhz Beacon produced interference in the SSMI 22GHz
    vertical polarization (22V) channel and that the 400Mhz Beacon
    interfered with SSMT-2 channel 4 performance.

•   The SSMT-2 on F15 has since been declared "red" or non-operational
    due to an unrelated component failure.

•   Users of the SSMI data must be aware that the 22V channel used in,
    ocean surface wind speeds, snow classification and depth, and rain rate
    calculations, etc., will be dramatically degraded during RADCAL Beacon
    transmission
            F-15 and F-16 Intercomparison (Post-RADCAL)
       16 September 2006 Ocean-Only Center Beam Position


                                                               F-15 and F-16
   Channel   F-15 SSMI   F-16 SSMIS   F-15 SSMI   F-16 SSMIS   synchronization:
              Mean TB      Mean TB     Std Dev      Std Dev
 19V          198.7        199.4        13.3        13.2       F-13:   1833 local
                                                               F-14:   1758 local
 19H          137.4        136.9        20.5        20.3       F-15:   2010 local
                                                               F-16:   2012 local
 22V          237.5        225.9        22.2        21.8
                                                               Good agreement at
 37V          217.2        217.7        10.0         9.9       non-22 channels,
                                                               max 0.7K difference
 37H          162.6        162.3        18.3        18.0
                                                               However, the
 85V 91V*     258.8        259.1        12.8        12.8
                                                               statistics are
 85H 91H*     231.3        230.7        24.0        23.7       dominated by no-
                                                               rain pixels (~ 95%)


*85 GHz on SSMI, 91 GHz on SSMIS                     Data courtesy of Gene Poe, NRL
    DMSP F15-F16                                         DMSP F15-F16
22V Channel Statistics                F-15           22V Channel Statistics
                               RADCAL Beacon
     Pre-RADCAL              Activated 14 Aug 2006       Post-RADCAL
  01-13 August 2006                                    15-28 August 2006




+/-70 Latitudes Over-Water
Impacts of Radcal Beacon Interference on
           F15 SSM/I Products


 Saturated water vapor   Missing clouds and precipitation
                       Scattering Index Conceptualized
scattering materials: Tv(22) > Tv(85)                   absorbing materials: Tv(22) < Tv(85)
precipitation, dry snow, aged sea ice,                  clouds, melting snow, new sea ice,
          glacial ice, deserts                                  vegetation, wet soil

                                  shading denotes
                                 water vapor thermal
  19                                  emission                               19
 GHz 22         85 91                                                       GHz 22       85 91


                                Material          19V         22V   85V
                           Precip over water     240      270       < 240
                           Precip over land      260      260       < 240
                           Dry Snow              250      240       210
               91 GHz      Clouds over land      275      275       280
             scatters a
             little more   New sea ice           250      245       255
            than 85 GHz
                           Wet soil              265      270       275
     Colder TB as                                                              Warmer TB as
                                           (typical values)                 frequency increases
 frequency increases
                    Scattering Index Computation
scattering materials: Tv(22) > Tv(85)       absorbing materials: Tv(22) < Tv(85)
precipitation, dry snow, aged sea ice,      clouds, melting snow, new sea ice,
          glacial ice, deserts                      vegetation, wet soil


  Oceanic:
  SI85= (-174.4 + 0.715*TB19v + 2.439*TB22v - 0.00504*TB22v*TB22v) - TB85v

  Land:
  SI85= (451.9 - 0.44*TB19v - 1.775*TB22v + 0.00574*TB22v*TB22v) - TB85v


             Estimation of the non-        If SI85 > 10 then Rain ~ log(SI85)
            scattering contribution of     (after screens for ice, deserts, etc
           the 85 GHz measurements         using polarization checks)


       SSMIS vs. SSMI:
       For scattering materials, 91 GHz scatters a bit more than 85 GHz
       For absorbing materials, 91 GHz emits (absorbs) more than at 85 GHz
SSMI-SSMIS High Frequency Channel Differences Most
       Pronounced Over Heavy Convection

                       25 minutes
 Cyclone Xangsane   time separation   Cyclone Xangsane
   F-15 SSMI 85H                       F-16 SSMIS 91H
SSMI-SSMIS High Frequency Channel Differences Most
       Pronounced Over Heavy Convection

                      34 minutes
Cyclone Xangsane   time separation   Cyclone Xangsane
  F-15 SSMI 85H                       F-16 SSMIS 91H
Rain Detection - Middle Latitudes - Over Land
 DMSP F-13, F-14, F-15 (SSMI), F-16 (SSMIS)
                                             Northern Hemisphere
                                                   30N-40N
                                              More “no-rain” events in
                                                 winter seasons

                                               SSMI’s well matched
     winter    summer    winter   summer
                                              SSMI and SSMIS similar

                                            F-15 RADCAL issue apparent
                                               after mid-August 2006


                                             Southern Hemisphere
                                                   40S-30S

                                                    COLOR LEGEND
      summer    winter   summer    winter             F-13 (SSMI)
                                                      F-14 (SSMI)
                                                      F15 (SSMI)
                                                     F-16 (SSMIS)
 Rain Detection - Middle Latitudes - Over Land
TRMM-TMI/PR, Aqua-AMSR-E, Coriolis-WindSat
                                              Northern Hemisphere
                                                    30N-40N

                                                Very similar to DMSP

                                             TMI “oscillation” likely due to
      winter    summer    winter   summer      sampling repeat cycle




                                              Southern Hemisphere
                                                    40S-30S

                                                      COLOR LEGEND
       summer    winter   summer    winter              TRMM (PR)
                                                        TRMM (TMI)
                                                       Aqua (AMSR-E)
                                                      Coriolis (WindSat)
   Rain Detection - Middle Latitudes - Over Land
NOAA-15, NOAA-16, NOAA-17 (AMSU), NOAA-18 (MHS)
                                                Northern Hemisphere
                                                      30N-40N
                                                2-3% less no-rain events
                                                   than DMSP shows

                                                NOAA-17 crossing time
         winter    summer    winter   summer
                                                  difference evident

                                                 NOAA-15:   1736 local
                                                 NOAA-16:   1526 local
                                                 NOAA-17:   2219 local
                                                 NOAA-18:   1343 local

                                                Southern Hemisphere
                                                      40S-30S

                                                      COLOR LEGEND
          summer    winter   summer    winter         NOAA-15 (AMSU)
                                                      NOAA-16 (AMSU)
                                                      NOAA-17 (AMSU)
                                                      NOAA-18 (MHS)
Sub-Tropical Latitudes Rain/No-Rain Discrimination




                           Northern Hemisphere
                                 10N-20N


                          Southern Hemisphere
                                20S-10S
Rain Detection – Sub Tropics - Over Ocean
DMSP F-13, F-14, F-15 (SSMI), F-16 (SSMIS)
                                            Northern Hemisphere
                                                  30N-40N
                                            More “no-rain” events in
                                             winter-spring seasons

                                           SSMI’s well matched except
    winter    summer    winter   summer
                                              F-15 post-RADCAL

                                            SSMIS flags more no-rain
                                           values in both hemispheres



                                           Southern Hemisphere
                                                 40S-30S

                                                  COLOR LEGEND
     summer    winter   summer    winter            F-13 (SSMI)
                                                    F-14 (SSMI)
                                                    F15 (SSMI)
                                                   F-16 (SSMIS)
  Rain Detection – Sub Tropics - Over Ocean
TRMM-TMI/PR, Aqua-AMSR-E, Coriolis-WindSat
                                              Northern Hemisphere
                                                    30N-40N

                                             PR and TMI are closer than
                                              they are in mid latitudes

      winter    summer    winter   summer    TMI & AMSR-E well matched

                                             WindSat screening better in
                                              sub-tropics than in mid-
                                                     latitudes


                                              Southern Hemisphere
                                                    40S-30S

                                                     COLOR LEGEND
       summer    winter   summer    winter             TRMM (PR)
                                                       TRMM (TMI)
                                                      Aqua (AMSR-E)
                                                     Coriolis (WindSat)
    Rain Detection – Sub Tropics - Over Ocean
NOAA-15, NOAA-16, NOAA-17 (AMSU), NOAA-18 (MHS)
                                                Northern Hemisphere
                                                      30N-40N

                                                 NOAA datasets begin to
                                               show some seasonality and
                                                   are well-matched
        winter    summer    winter   summer
                                               About 3% more no-rain pixels
                                                  flagged relative to TMI




                                                Southern Hemisphere
                                                      40S-30S

                                                       COLOR LEGEND
                                                       NOAA-15 (AMSU)
         summer    winter   summer    winter
                                                       NOAA-16 (AMSU)
                                                       NOAA-17 (AMSU)
                                                       NOAA-18 (MHS)
Tropical Latitudes   Rain/No-Rain Discrimination




                            Northern and Southern
                                Hemispheres
                                    5S-5N
  Rain Detection – Tropics - Over Ocean
DMSP F-13, F-14, F-15 (SSMI), F-16 (SSMIS)



                                   SSMI’s well matched

                                 SSMIS flags more no-rain
                                values in both hemispheres

                               F-15 RADCAL issue apparent
                                  after mid-August 2006




                                       COLOR LEGEND
                                         F-13 (SSMI)
                                         F-14 (SSMI)
                                         F15 (SSMI)
                                        F-16 (SSMIS)
   Rain Detection – Tropics - Over Ocean
TRMM-TMI/PR, Aqua-AMSR-E, Coriolis-WindSat



                               PR and TMI are closer than
                                they are in mid latitudes

                              TMI & AMSR-E well matched

                              WindSat screening gradually
                              improves moving from mid-
                                 latitudes to the tropics




                                      COLOR LEGEND
                                        TRMM (PR)
                                        TRMM (TMI)
                                       Aqua (AMSR-E)
                                      Coriolis (WindSat)
      Rain Detection – Tropics - Over Ocean
NOAA-15, NOAA-16, NOAA-17 (AMSU), NOAA-18 (MHS)



                                About 3% more no-rain pixels
                                   flagged relative to TMI




                                         COLOR LEGEND
                                         NOAA-15 (AMSU)
                                         NOAA-16 (AMSU)
                                         NOAA-17 (AMSU)
                                         NOAA-18 (MHS)
Middle Latitudes    Light Rain Detection
              (Non-zero rain < 2 mm hr-1)

                      Northern Hemisphere
                            30N-40N




                      Southern Hemisphere
                            40S-30S
Light Rain Detection - Middle Latitudes - Over Ocean
    DMSP F-13, F-14, F-15 (SSMI), F-16 (SSMIS)
                                                 Northern Hemisphere
                                                       30N-40N

                                                SSMIS picks up about half as
                                                 much “light rain” relative to
                                                    the SSMI’s, in both
         winter    summer    winter   summer           hemispheres




                                                 Southern Hemisphere
                                                       40S-30S

                                                         COLOR LEGEND
          summer    winter   summer    winter              F-13 (SSMI)
                                                           F-14 (SSMI)
                                                           F15 (SSMI)
                                                          F-16 (SSMIS)
Light Rain Detection - Middle Latitudes - Over Ocean
  TRMM-TMI/PR, Aqua-AMSR-E, Coriolis-WindSat
                                                 Northern Hemisphere
                                                       30N-40N
                                                  TMI and AMSR-E detect
                                                about twice as much rain in
                                                 this interval relative to PR
         winter    summer    winter   summer
                                                WindSat detects much more
                                                owing to a looser rain/no-rain
                                                            screen

                                                    Not sure about N-S
                                                  hemisphere differences

                                                 Southern Hemisphere
                                                       40S-30S

                                                         COLOR LEGEND
          summer    winter   summer    winter              TRMM (PR)
                                                           TRMM (TMI)
                                                          Aqua (AMSR-E)
                                                         Coriolis (WindSat)
 Light Rain Detection - Middle Latitudes - Over Ocean
NOAA-15, NOAA-16, NOAA-17 (AMSU), NOAA-18 (MHS)
                                                  Northern Hemisphere
                                                        30N-40N
                                                 Little to no sensitivity to light
                                                   rain over ocean at these
                                                  latitudes (over land better)
          winter    summer    winter   summer




                                                 Southern Hemisphere
                                                       40S-30S

                                                          COLOR LEGEND
           summer    winter   summer    winter            NOAA-15 (AMSU)
                                                          NOAA-16 (AMSU)
                                                          NOAA-17 (AMSU)
                                                          NOAA-18 (MHS)
Light Rain Detection - Middle Latitudes - Over Land
    DMSP F-13, F-14, F-15 (SSMI), F-16 (SSMIS)
                                                Northern Hemisphere
                                                      30N-40N
                                                   SSMI’s well matched

                                                 SSMI-SSMIS difference
                                                     much smaller
        winter    summer    winter   summer
                                                F-15 RADCAL issue more
                                               apparent over-land than over-
                                                          ocean



                                                Southern Hemisphere
                                                      40S-30S

                                                        COLOR LEGEND
         summer    winter   summer    winter              F-13 (SSMI)
                                                          F-14 (SSMI)
                                                          F15 (SSMI)
                                                         F-16 (SSMIS)
Light Rain Detection - Middle Latitudes - Over Land
  TRMM-TMI/PR, Aqua-AMSR-E, Coriolis-WindSat
                                               Northern Hemisphere
                                                     30N-40N

                                                Slightly more light rain
                                               detected by PR than TMI

        winter    summer    winter   summer    No WindSat data over land




                                               Southern Hemisphere
                                                     40S-30S

                                                      COLOR LEGEND
         summer    winter   summer    winter            TRMM (PR)
                                                        TRMM (TMI)
                                                       Aqua (AMSR-E)
                                                      Coriolis (WindSat)
 Light Rain Detection - Middle Latitudes - Over Land
NOAA-15, NOAA-16, NOAA-17 (AMSU), NOAA-18 (MHS)
                                                  Northern Hemisphere
                                                        30N-40N

                                                    Over land and at middle
                                                  latitudes, AMSU/MHS light
                                                 rain detection is very similar
          winter    summer    winter   summer               to DMSP




                                                 Southern Hemisphere
                                                       40S-30S

                                                         COLOR LEGEND
           summer    winter   summer    winter           NOAA-15 (AMSU)
                                                         NOAA-16 (AMSU)
                                                         NOAA-17 (AMSU)
                                                         NOAA-18 (MHS)
Tropical Latitudes   Heavy Rain Detection
                (Non-zero rain > 5 mm hr-1)




                        Northern and Southern
                            Hemispheres
                                5S-5N
Heavy Rain Detection - Tropics - Over Ocean
 DMSP F-13, F-14, F-15 (SSMI), F-16 (SSMIS)
                                              Northern Hemisphere
                                                    30N-40N
                                            Difficult to assess- since even
                                                 with a 30-day running
                                             average there are relatively
                                                 few pixels > 5 mm hr-1
     winter    summer    winter   summer




                                             Southern Hemisphere
                                                   40S-30S

                                                     COLOR LEGEND
      summer    winter   summer    winter              F-13 (SSMI)
                                                       F-14 (SSMI)
                                                       F15 (SSMI)
                                                      F-16 (SSMIS)
 Heavy Rain Detection - Tropics - Over Ocean
TRMM-TMI/PR, Aqua-AMSR-E, Coriolis-WindSat
                                              Northern Hemisphere
                                                    30N-40N

                                             PR has about 2-3% more no-
                                                rain events than TMI

      winter    summer    winter   summer    TMI & AMSR-E well matched

                                               WindSat lacks 85 GHz
                                              capability which improves
                                                   rain screening


                                              Southern Hemisphere
                                                    40S-30S

                                                    COLOR LEGEND
       summer    winter   summer    winter            TRMM (PR)
                                                      TRMM (TMI)
                                                     Aqua (AMSR-E)
                                                    Coriolis (WindSat)
   Heavy Rain Detection - Tropics - Over Ocean
NOAA-15, NOAA-16, NOAA-17 (AMSU), NOAA-18 (MHS)
                                                 Northern Hemisphere
                                                       30N-40N
                                                Seasonality signal not picked
                                                   up at these latitudes

                                                   AMSU and MHS well-
         winter    summer    winter   summer
                                                       matched

                                                 Slight differences likely due
                                                to AM and PM crossing time
                                                           difference


                                                 Southern Hemisphere
                                                       40S-30S

                                                        COLOR LEGEND
          summer    winter   summer    winter           NOAA-15 (AMSU)
                                                        NOAA-16 (AMSU)
                                                        NOAA-17 (AMSU)
                                                        NOAA-18 (MHS)
                              Summary

 A rich “GPM” constellation exists today – employ current systems to
address issues related to merging MW datasets

 NESDIS algorithm for over-ocean high latitudes: Issues known and
being improved – also should examine other AMSU-based algorithms

 DMSP F-15 RADCAL issue: Radiance-level offset being characterized
and a “fix” may be possible for precipitation datasets

 Bring in light rain statistics from CloudSat - averaged across long
timescales

 May develop on improved SSMIS EDR suite after F-17 launch



        All of these topics are relevant to the GPM
F15 – F14 Differences For Two-Week Periods Before and After
           RADCAL Activation on 14 August 2006




                                                 Pre-RADCAL SDR
                                                 differences being
                                                 fixed
Passive Microwave Constellation Local Observation Times
            Jakarta, Indonesia (6.1S 106.8E)
Passive Microwave Constellation Revisit Times
   (Including NOAA Cross-Track Sounders)
        Jakarta, Indonesia (6.1S 106.8E)

                                           Percent of
                                           Year That
                                         Revisit Is Less
                                         Than (Hours):
   6-Hour Level
                                             6 (97%)
                                             5 (94%)
                                             4 (81%)
                                             3 (52%)



                                            NOTE:
                                            Percent of
                                            year, not
                                            percent of
                                            total points
Passive Microwave Constellation Observation Times
     San Francisco, California (37.8N 122.4W)
Passive Microwave Constellation Revisit Times
   (Including NOAA Cross-Track Sounders)
  San Francisco, California (37.8N 122.4W)

                                           Percent of
                                           Year That
                                         Revisit Is Less
                                         Than (Hours):
   6-Hour Level
                                             6 (100%)
                                             5 (98%)
                                             4 (89%)
                                             3 (69%)


                                            Aqua and
                                            NOAA-18
                                              to the
                                             rescue
Passive Microwave Constellation Observation Times
Helsinki, Finland (60.1N 25.0E) No TRMM Coverage
  Passive Microwave Constellation Revisit Times
     (Including NOAA Cross-Track Sounders)
Helsinki, Finland (60.1N 25.0E) No TRMM Coverage

                                            Percent of
                                            Year That
                                          Revisit Is Less
                                          Than (Hours):
     6-Hour Level
                                              6 (100%)
                                              5 (97%)
                                              4 (88%)
                                              3 (81%)

				
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