Sensitivity of Simulated Philippine Rainfall to Model Resolution and

Convective Closure Scheme

JOSEFINA ARGETE

Institute of Environmental Science and Meteorology

University of the Philippines

ELLA CECILIA CASTILLO

Climate Studies Division

Manila Observatory

ANA LIZA SOLIS

Climatology & Agrometeorology Branch

PAGASA, Weather Bureau

ObjectivesObjectives

• To test the sensitivity of RegCM3 to different domain resolutions on Philippine rainfall

• To test the sensitivity of the model to 2 convective closure schemes

• To validate the model output with observed values (station data, CRU and XA)

Brief Brief ClimatologyClimatology

Northeast Monsoon Season – (Oct-Mar)

brings relatively warm & humid air masses e.g. much rainfall in northern and eastern part of the country.

Southwest Monsoon Season – (May-September)peak in August, deep current up to 10,000m highAlmost all parts of the island receive high rainfall, max. at coasts and slopes directly exposed to the monsoon.

North Pacific Trades – (Mar-Apr) NE monsoon weakens, islands under influence of trades, easterlies bring warmest air in the Phils.

NCEP REANALYSIS

NCEP REANALYSIS

Input data: ET42, L15 (ECWCRP)

GTOPO30_10MIN

GLCC10MIN_BATS

OISST

Start date=1997052500

End date=1997070100

clat = 14 clon= 120

iproj=“ROTMER”

MethodologyMethodology

60 km 45 km 20 km

No. of grids 55 x 45 63 x 53 163 x 133

ds 60 45 20

nspgx 6(12) 8(16) 18(36)

dt 200 100 60

igcc FC/AS FC FC

Validation dataValidation data

• CRU monthly precip

• Xie-Arkin monthly precip rate

• Observed daily/monthly station rainfall

RESULTS:

60

45

20

PRCC at different Resolutions (FC)

Convective Closure Scheme

Domain for

averaging daily

rainfall

Observed vs. Simulated rainfall

0

5

10

15

20

25

30

35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

days

rr a

mo

un

t (m

m)

observed 20 km 45 km FC

Closure Scheme, 60 km

0

5

10

15

20

25

30

35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

days

rr a

mo

un

t (m

m)

observed FC AS

CONCLUSIONSCONCLUSIONS::

• 60 & 45km res. runs captured the spatial pattern of rr ; details are more evident in 20km res.run

• The run using Arakawa-Schubert Scheme simulated the Philippine rainfall better than the Fritsch-Chappel Scheme

• In general, the model’s prca compared relatively well with the observed rainfall values but tended to overestimate

• The same is true for convective precip (prcc)