Global Precipitation (Means and Variations): GPM, TRMM and GPCP Robert Adler and Jian-Jian Wang University of Maryland, College Park • Utilize data from GPM multiple instruments and algorithms to develop Global Composite Climatology (GCC) for comparison with and improvement of GPCP. • Analyze large-scale inter-annual variations of rainfall with both PMW and radar observations in relation to surface temperature and understand differences between radar and PMW results. Objectives GPM somewhat higher than GPCP in tropics, but lower in extra-tropics Two-year (2014.03-2016.02) Composite Climatology mm/day TRMM-based Sfc. Temp.-Rainfall Relations (Active vs. Passive Microwave) 1998-1999 El Nino to La Nina Transition (Ocean, 25°S-25°N) GPM-based Sfc. Temp.-Rainfall Relations (Active vs. Passive Microwave) 2014-2016 Neutral to El Nino Transition (Ocean, 25°S-25°N) TRMM Radar does not confirm PMW T-R relations—Attenuation issues? GPM Radar better confirms PMW T-R relations—why different from TRMM? Inter-annual Variation of Ocean (25°S-25°N) Tropical Rain (Active vs. Passive Microwave) TRMM correlation differences in total ocean rain due solely to convective portion (right panel)—Attenuation issues? GPM shows much better correlation differences in convective portion Precipitation Anomalies (2015-2016 El Nino) GPM GPCP Summary Over tropical oceans GPM-based mean estimates slightly higher (~ 5-8%) than TRMM (and GPCP). • Over high latitude oceans GPM-based mean estimates are low compared to GPCP and CloudSat-based estimates. • GPM radar results for 2014-2016 (including El Nino) better agree with surface temperature – rainfall relations for PMW results (including GPCP) than did TRMM radar results. Reasons for this seem to be related to intense convective rainfall near surface better defined with DPR. mm/day Mean Precipitation (mm/day) of Ocean (25°S-25°N) during Mar.-Aug. 2014 (TRMM/GPM Overlap) TRMM Radar ~0%/C GPM Radar ~13%/C PMW ~10%/C Ocean Zonal Mean (March 2014-Feb. 2016) GPCP Equator 45° N 45° S GPCP Artifact GPM GMI DPR GPCP mm/d PMW Radar Comb GPCP 25N- 25S 3.50 3.63 3.37 3.33 65N- 65S 2.70 2.83 2.63 3.07 GPM profile shows higher surface rain (less attenuation?) Total Stratiform Convective Total Stratiform Convective TRMM GPM
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Global Precipitation (Means and Variations): GPM, TRMM and GPCPRobert Adler and Jian-Jian Wang University of Maryland, College Park
• Utilize data from GPM multiple instruments andalgorithms to develop Global Composite Climatology(GCC) for comparison with and improvement of GPCP.
• Analyze large-scale inter-annual variations of rainfallwith both PMW and radar observations in relation tosurface temperature and understand differences betweenradar and PMW results.
Objectives
GPM somewhat higher than GPCP in tropics, but lower in extra-tropics
Two-year (2014.03-2016.02) Composite Climatology
mm/day
TRMM-based Sfc. Temp.-Rainfall Relations (Active vs. Passive Microwave)1998-1999 El Nino to La Nina Transition (Ocean, 25°S-25°N)
GPM-based Sfc. Temp.-Rainfall Relations (Active vs. Passive Microwave)2014-2016 Neutral to El Nino Transition (Ocean, 25°S-25°N)
TRMM Radar does not confirm PMW T-R relations—Attenuation issues?
GPM Radar better confirms PMW T-R relations—why different from TRMM?
Inter-annual Variation of Ocean (25°S-25°N) Tropical Rain (Active vs. Passive Microwave)
TRMM correlation differences in total ocean rain due solely to convective portion (right panel)—Attenuation issues?
GPM shows much better correlation differences in convective portion
Precipitation Anomalies (2015-2016 El Nino)
GPM
GPCP
Summary� Over tropical oceans GPM-based mean estimates slightly higher (~ 5-8%) than
TRMM (and GPCP).
• Over high latitude oceans GPM-based mean estimates are low compared to GPCP and CloudSat-based estimates.
• GPM radar results for 2014-2016 (including El Nino) better agree with surface temperature – rainfall relations for PMW results (including GPCP) than did TRMM radar results. Reasons for this seem to be related to intense convective rainfall near surface better defined with DPR.
mm/day
Mean Precipitation (mm/day) of Ocean (25°S-25°N) during Mar.-Aug. 2014 (TRMM/GPM Overlap)
TRMM Radar ~0%/C GPM Radar ~13%/C PMW ~10%/C
Ocean Zonal Mean (March 2014-Feb. 2016)
GPCP
Equator
45° N
45° S
GPCP Artifact
GPM
GMI
DPR
GPCP
mm/d PMW Radar Comb GPCP
25N-25S
3.50 3.63 3.37 3.33
65N-65S
2.70 2.83 2.63 3.07GPM profile showshigher surface rain(less attenuation?)
Total Stratiform Convective
Total Stratiform Convective
TRM
MG
PM
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