GPM/DPR V07X Product Note

JAXA and DPR algorithm
development team
15th January 2024

GPM/DPR Data Processing Flow
GPM Core Observatory
DPR

Level 0Developed by
JAXA

HK/Science Telemetry• DPR HK
•Attitude• Observation data •Time• Satellite position •DPR Temp. Monitor, etc• Altitude

Level 1algorithm

Ancillary
Data• Satellite Orbital Elements• CAL factors• Scene information, etc.

Engineering values
Level 1
Products
Developed by
DPR Joint JAXANASA Algorithm
TeamLevel 2algorithm• Transmit power• Antenna beam direction• Received power… etc.

Level 2Products

Physical values• Reflectivity factor• Precip. rate
• Precip. type classification(Conv./Strat.)• Particle type(Rain/Snow/Graupel)• DSD (Drop Size Distribution) ,etc.

P2

Updates of the DPR-L1 algorithm for post-boost
operation• Update the VPRF(Variable Pulse Repetition Frequency) table➢ Installed a new VPRF table for post-boost in the DPR-L1algorithm.
➢ Changed the VPRF table version (V3 → V4).
• Altitude information updates➢ DPR-L1 algorithms✓ Store altitude for DPR operation (dprAlt)and real spacecraft
altitude (scAlt) in the DPR-L1 product.
• /swath/navigation/dprAlt : altitude for DPR operation (offsetted to be
between 396.5km and 419.5km)• /swath/navigation/scAlt : real spacecraft altitude• “scAlt” and “dprAlt” was almost same in the pre-boost.
P3

Preliminary evaluation of the DPR-L1 productscAlt (real spacecraft altitude)

Time series of spacecraft altitudes during the period from 13rd Oct. to 17th Nov. 2023. Blue,
red, and green lines denote maximum, minimum, and averaged altitudes within each orbit,
respectively.

4P4Preliminary evaluation of the DPR-L1 productaltitude for DPR operation (dprAlt)

Time series of spacecraft altitudes during the period from 13rd Oct. to 17th Nov. 2023. Blue,red, and green lines denote maximum, minimum, and averaged altitudes within each orbit,respectively.

5P5Preliminary evaluation of the DPR-L1 productof the DPR in terms of spatial resolution and swath width for
Geolocation Specifications
the pre-boost (altitude of 407km) and the post-boost (altitude of 442km),
predicted by the DPR manufacture company (NEC).

442km
0.7°

Spatial resolutionNadir
Scan edge

407km

5.04km×5.04km

5.04km×5.57km

Swathwidth
255.8km

442km

5.48km×5.48km

5.48km×6.05km

277.9km

Satellite altitude

407km

Post:Nov. 23, 2023
Pre: Mar. 16, 2017

0.7°

Cross-track

Along-track

5.0km
5.5km

Distances between adjacent footprints in the cross-track direction (left) and the along-track direction (right)
for the pre-boost(16th March 2017, Black marks) and the post-boost (23rd Nov. 2023, Red marks).

• Compared the footprint and swath width between similar orbits at pre/post boost.
• DPR-L1 data confirmed that changes of the sampling were larger in the cross-track
direction (about 5 km to 5.5 km at the nadir).

P6

Preliminary evaluation of the DPR-L1 productComparisons of the DPR observation area for the pre-boost and the post-boost.

Coverage

One day

8 daysPre-boost

Post-boost

These observed DPR Coverage features were similar to those predicted by the NASA before the boost . P7

Preliminary evaluation of the DPR-L1 productComparisons of the DPR observation area for the pre-boost and the post-boost.

100 %99.9818%

Delta-V maneuver on Nov 17, 2022•

In pre-bost, 100% coverage in 8 days.

•In post-bost, it has not reached 100% after 21 days.

• This coverage tendency is expected
to change with satellite maneuvers.
• The maneuver is expected to change
the orbit elements, thereby covering
all locations.

These observed DPR Coverage features were similar to those predicted by the NASA before the boost . P8

DPR-L2 algorithm development status
Main developments of the L2 algorithm in V07X
(Experimental version) are connected with Preparation (PRE)module.
The PRE module reads the received power data from L1 products, classifies eachfootprint into either rain or no-rain and converts the received power into measured
reflectivity factor at each range bin and into apparent normalized surface cross section.

DPR Joint JAXA-NASA Algorithm Team revised the PRE
module in V07X in terms of the mainlobe clutter detection andthe sidelobe clutter database.
Preliminary evaluation of the DPR-L2 product, corresponding
to V07X, is shown here using the revised algorithms.
DPR team is also working for V07C (Standard version) whichis expected to be released in March 2024.
P9Preliminary evaluation of the DPR-L2 product•

The sensitivity degradation of the DPR is expected owing to the increase ofsatellite altitude.

•Figures below time series of measured radar reflectivity factor (Zm) at storm top
height (STH) over the ocean for the KuPR and the KaPR, respectively.
••Zm at STH is used as an indicator of the sensitivity (e.g., Toyoshima et al. 2015).

They show the sensitivity degradation of about 0.8-0.9dB for KuPR, and about
0.7-0.9dB for KaPR, as expected.

KuFS

Orbit boost

KaFS

Orbit boost~0.7-0.9 dB~0.8-0.9 dB

Angle-bin #21-29

P10

Preliminary evaluation of the DPR-L2 productWe compared precipitation estimates between the pre-boost
and the post-boost.
Pre-boost :Nov 12- Dec 12, 2022
Post-boost :Nov 12- Dec 12, 2023

Please note precipitation distributions during Nov.-Dec. 2023
were affected by effects of the El Nino. Here we show
GSMaP figures for references.
GSMaP (Nov. 2023)

GSMaP (Nov. 2022)

P11

Horizontal distribution of surface precipitation:
KuFS
Post-boost :Nov 12- Dec 12, 2023
Post-boost(07X_20231226)

Pre-boost :Nov 12- Dec 12, 2022
Pre-boost(V07A)

12
P12

Horizontal distribution of surface precipitation:
KaFS
Post-boost :Nov 12- Dec 12, 2023
Post-boost(07X_20231226)

Pre-boost :Nov 12- Dec 12, 2022
Pre-boost(V07A)

13
P13

Horizontal distribution of surface precipitation:
DPRFS
Post-boost :Nov 12- Dec 12, 2023
Post-boost(07X_20231226)

Pre-boost :Nov 12- Dec 12, 2022
Pre-boost(V07A)

14
P14

Zonal mean surface precipitation (KuFS)
precipRateESurface

Full swath
KuPR● : Post-boost〇 : Pre-boost

P15

Zonal mean surface precipitation (KaFS)
precipRateESurface

Full swath
KaPR● : Post-boost〇 : Pre-boost

16
P16

Zonal mean surface precipitation (DPRFS)
precipRateESurface

Full swath
DPR● : Post-boost〇 : Pre-boost

17
P17

Summary
This summarizes preliminary evaluations of V07X.
DPR L1 and L2 algorithms for V07X are working as expected.

DPR-L1 data confirmed that changes of the sampling were larger in the crosstrack direction (about 5 km to 5.5 km at the nadir).
Spatial bias was observed in DPR sampling during post-boost (11th Nov. to 1stDec. 2023), but this is thought to be mitigated by the delta-V maneuver.

With analyzing measured radar reflectivity factor at storm top height over theocean, the sensitivity degradation was found for about 0.8-0.9dB for KuPR,
and about 0.7-0.9dB for KaPR.
Precipitation maps and zonal mean averages of V07X shows reasonable
ranges while the strong El Nino may affect distributions during Nov.-Dec.
2023.

Based on the above results, the DPR team suggests that there is no issue
with the release of V07X.

P18

Plan for DPR release in March 2024
DPR V07X is the experimental version and to be
expected to be used only for the near-real-timeprocessing.
JAXA and the DPR team is working for the finalcode for the standard version as following.
DPR L1
DPR L2&L3

V07B
V07C

We’re targeting the above standard versions as therelease in March 2024.
We will develop algorithms and evaluate more
DPR data before releasing the standard versions.
P19

ReferenceT. Kubota, T. Masaki, G. Kikuchi, M. Ito, T. Higashiuwatoko,K. Kanemaru, N. Takahashi, K. Yamamoto, K. Furukawa, T.
Nio, “Evaluation of effects on Dual-Frequency Precipitation
Radar Observations due to the Orbit Boost of the GPM Core
Observatory”, submitted to Proc. IGARSS 2024.

P20