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Diurnal Cycle of Precipitation Based on CMORPH

Diurnal Cycle of Precipitation Based on CMORPH. Vernon E. Kousky, John E. Janowiak and Robert Joyce Climate Prediction Center, NOAA. CMORPH (CPC Morphing technique).

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Diurnal Cycle of Precipitation Based on CMORPH

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  1. Diurnal Cycle of Precipitation Based on CMORPH Vernon E. Kousky, John E. Janowiak and Robert Joyce Climate Prediction Center, NOAA

  2. CMORPH (CPC Morphing technique) Uses IR data along with passive microwave data to create global rainfall analyses (60N-60S) at high spatial and temporal resolution. CMORPH uses IR only as a transport vehicle, i.e. IR data are NOT used to make estimates of rainfall when passive microwave data are not available. The underlying assumption is that the error in using IR to transport precipitation features is less than the error in using IR to estimate precipitation.

  3. Rationale • Passive microwave (PMW) data provide much better rainfall estimates than IR but these data are spatially and temporally incomplete (instruments on polar orbiting platforms) • IR data are abundant both in space & time (polar & geostationary platforms) • CMORPH combines the superior quality of the PMW-derived precipitation estimates with the excellent sampling characteristics of the IR data

  4. Specifics • Spatial Grid: 0.0728o lat/lon (8 km at equator) • Temporal Resolution: 30 minutes • Domain: Global (60o N - 60o S) • Period of record: Dec. 2002 – present For more information about CMORPH: http://www.cpc.ncep.noaa.gov/products/janowiak/cmorph.html

  5. Comparison: CMORPH and Gridded Analyses (DJF 0203+0304) CMORPH Gridded CMORPH over estimates precipitation by 40-50% over Brazil.

  6. South America: DJF 02-03+03-04 (1mm/d mask)

  7. DJF - South America (1mm mask)

  8. DJF - South America (1mm mask)

  9. Time (UTC) of Max. Precipitation: South America – DJF 2002-03 18-21 UTC 00-03 UTC 12-15 UTC 06-09 UTC 06-09 UTC 12-15 UTC 00-03 UTC 18-21 UTC

  10. Time (LST) of Max. Precipitation: South America – DJF 2002-03 15-18 LST 21-24 LST 08-11 LST 03-06 LST 02-05 LST 09-12 LST 20-23 LST 15-18 LST

  11. Percent Total Precipitation: Diurnal Cycle DJF 2002-03 4 5 6 La Plata Basin 4 5 6 Daytime maximum Nighttime maximum 1 2 3 2 1 3

  12. Diurnal Cycle DJF 02-03 + 03-04

  13. Time-Longitude Diurnal Cycle EQ DJF 2002-03 +2003-04 Rainfall develops along coast during the day and propagates westward through the night and into the next day. Early morning maximum in rainfall over tropical Atlantic.

  14. MAM Mean Diurnal Cycle – EQ-5N Convective rainfall systems start along east coast on day-1 propagate westward, reaching western Amazon on day-3. West Coast East Coast

  15. Time-Longitude Diurnal Cycle 30S DJF 2002-03 +2003-04 Rainfall develops over Andes Mts. During late afternoon, then shifts eastward during the night and following day. Andes East Coast SA

  16. Conclusions • CMORPH precipitation analyses are useful in obtaining a detailed description of the diurnal cycle. • A pronounced diurnal cycle in precipitation is found in many areas of South America. • Daytime peak over high terrain (e.g., Andes Mts., Brazilian Planalto). • Daytime peak near the coast, especially NE South America, associated with sea breeze. • Nocturnal peak in the central La Plata Basin, and inland areas affected by westward propagating sea breeze-induced convection (Amazon Basin).

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