Acknowledgment: Trinh Tuan Long for TC movie and tracks Interannual variability of heavy rainfall over Central Vietnam Kim Nguyen, Jack Katzfey and John McGregor 9-14 th December 2012 Melbourne

OUTLINES Conformal Cubic Atmospheric Model (CCAM) simulation forced by ERA-Interim at 20 km over Vietnam The periods will be studied: April-May, June-July-August (JJA) and September- October-November (SON) Large scale circulation Heavy Rainfall (95 th ) are compared against APHRODITE (0.25 degree), CMAP and GPCP Simulations of tropical cyclones and related rainfall

Central Vietnam South China Sea Bay of Bengal Tibetan Plateau Thailand Cambodia Laos North South Vietnam CCAM SURFACE ELEVATION Elevation (meter) 20km resolution region

1.Southwesterly from Bay of Bengal 2.Cross-equatorial flow from the Southern Hemisphere June to August September to November Northeasterly originated from Mongolia and northern China merges with easterly flow from the Pacific MEAN CIRCULATION MSLP AND 1000 hPa WIND

HEAVY RAINFALL (95 th PERCENTILE) mm/day CMAPGPCP APHRODITECCAM

APHRODITE CCAM INTER_ANNUAL VARIABILITY OF RAINFALL EXTREME (mm/day) AVERAGED OVER o E, o N

MONTHLY DISTRIBUTION OF HEAVY RAIN DAYS OVER CENTRAL VIETNAM APHRODITE heavy rain days: APR-MAY 5%, JJA 41%, SON 53% heavy rain amount: APR-MAY 4%,JJA 37%, SON 56.4% CCAM Heavy rain days: APR-MAY 8%, JJA 32%, SON 57% Heavy rain amount: APR-MAY 8%, JJA 30%, SON 58%

ANOMALOUS RAINFALL AND WIND AT 850hPa September to November 1.Day -3, disturbance located west of Philippine 2.Day -2, disturbance propagates westward closer to the VN east coast but heavy rainfall has yet to arrive in Central Vietnam

ANOMALOUS RAINFALL AND WIND AT 850hPa September to November Deficiency of rainfall over Eastern China but surplus of rainfall over Central Vietnam Cyclonic circulation located over east coast of VN The above pattern is similar for April-May and June -July-August season

Anomalous (925 hPa) air TEMPERATURE CCAM APRIL-MAY Anomalous (925 hPa) air MOISTURE warm and moist air cold and dry air warm and dry air

JUNE-JULY-AUGUST CCAM Anomalous 925 hPa air TEMPERATURE Anomalous 925 hPa air MOISTURE trough line (ITCZ) warm and moist air cold and dry air

CCAM Anomalous 925 hPa air TEMPERATURE SEPTEMBER-OCTOBER-NOVEMBER Anomalous 925 hPa air MOISTUE trough line (ITCZ) Similar to JJA season, except ITCZ shifted south warm and moist air cold and dry air

Presentation title | Dr Kim Chi Nguyen 13 | TROPICAL CYCLONE The data on this site are provided from the National Weather Service via the NOAAPORT satellite data service. All the images are generated using the Weather Processor (WXP) analysis package which is available from Unisys. National Weather ServiceNOAAPORTWeather Processor (WXP)

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OBS CCAM Linda Keith

AREA-AVERAGED RAINFALL OVER CENTRAL VIETNAM APHRODITE AND CCAM 1980 (neutral)

AREA-AVERAGED RAINFALL OVER CENTRAL VIETNAM APHRODITE AND CCAM 1982 (strong El Nino) Aphrodite (60 mm/d) CCAM (40 mm/d) 5-day-mean rainfall from CMAP and GPCP around mm/day

AREA-AVERAGED RAINFALL OVER CENTRAL VIETNAM APHRODITE AND CCAM 1988 (strong La Nina) No TC found

Presentation title | Presenter name 19 | AREA-AVERAGED RAINFALL OVER CENTRAL VIETNAM APHRODITE AND CCAM 1992 (neutral) Oct 21Jun-1Jul

Presentation title | Presenter name 20 | AREA-AVERAGED RAINFALL OVER CENTRAL VIETNAM APHRODITE AND CCAM 1997 (strong El Nino) APHRODITE 25 Sep 48 mm/d CCAM 26 Sep 65 mm/d

Presentation title | Presenter name 21 | AREA-AVERAGED RAINFALL OVER CENTRAL VIETNAM APHRODITE AND CCAM 2000 (weak La Nina)

Presentation title | Presenter name 22 | AREA- AVERAGED RAINFALL OVER CENTRAL VIETNAM 2001 (neutral) APHRODITE CCAM

Presentation title | Presenter name 23 | AREA-AVERAGED RAINFALL OVER CENTRAL VIETNAM APHRODITE AND CCAM (1997 strong El Nino) APHRODITE 25 Sep 48 mm/d CCAM 26 Sep 65 mm/d

CONCLUSIONS 1.CCAM capture the APHRODITE mean extreme rainfall pattern, but it under estimates the APHRODITE extreme amount over South and North Vietnam. However CCAM extreme rainfall amount seems to agree with those of CMAP and GPCP. 2.Heavy rainfall season is from June to November with peak in October. The study shows that contribution into extreme rainfall days/amount as followed; April-May 8%, June to August 30% and September to November close to 60%. 3.The study shows that heavy rainfall in April-May seems to be due to cold surge from Mongolia and northern China, whereas heavy rainfall in June to August and September to November appears due to the tropical cyclone disturbances embedded in the ITCZ. 4.CCAM captures well the APHRODITE daily rainfall distribution and TC related rainfall peaks

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APR-MAY (925 hPa) air temperature and wind NCEP

JJA (925 hPa) air temperature and wind APHRODITE

SON (925 hPa) air temperature and wind APHRODITE

ANOMALOUS RAINFALL AND WIND AT 850 hPa April to May 1.Similar to above but for Day -2 and Day -3 2.Day -3, disturbance is located east of the Philippine and propagates westward 3.Day -2 it is located just west of the Philippine 4.Disturbances in SCS but heavy rainfall has yet to arrive in Central Vietnam

ANOMALOUS RAINFALL AND WIND AT 850 hPa April to May Deficiency of rainfall over Eastern China but surplus of rainfall over Central Vietnam Cyclonic circulation located middle VN Even though this season only contributes 5 to 8% to the total but its rainfall anomaly is large and spreads over much wider region

JUNE to AUGUST Anomalous 925 hPa air MOISTURE and wind CCAM

APR-MAY Anomalous (925 hPa) air TEMPERATURE and wind CCAM 1.Day -5 warmer than normal over China and East China Sea 2.Day -2 sharp temp gradient along the east coast of China due to cold air advected from northern China and Mongolia. In SCS, disturbance (anti- cyclonic circulation) is located just west of the Philippine and propagates west ward 3.Day -1 the disturbance is closer to the VN east coast and cold air has entered into the region but heavy rainfall has yet to arrive in Central Vietnam 4.Collaborative between disturbance and the cold air surge causing heavy rainfall in Central Vietnam

Presentation title | Presenter name 35 | APR-MAY Anomalous (925 hPa) air MOISTURE and wind CCAM 1.Day -5 warmer and moist air than normal over China and East China Sea 2.Day -2 dry and cold air appears over east China due to cold air surge 3.Day -1 even though cold air had arrived over central VN but drier air only reaches north VN 4.ONSET: interaction between cold air surge and warmer air from SCS due to disturbance causing heavy rainfall in Central Vietnam

CCAM SON Anomalous 925 hPa air TEMPERATURE and wind

SON Anomalous 925 hPa air MOISTURE and wind CCAM

Anomalous 925 hPa air TEMPERATURE SON Anomalous 925 hPa air MOISTUE

JUNE-JULY-AUGUST CCAM Anomalous 925 hPa air TEMPERATURE Anomalous 925 hPa air MOISTURE

JUNE-JULY-AUGUST CCAM Anomalous 925 hPa air TEMPERATURE Anomalous 925 hPa air MOISTURE

CCAM Anomalous 925 hPa air TEMPERATURE SON Anomalous 925 hPa air MOISTUE

ANOMALOUS RAINFALL AND WIND AT 850 hPa June to August 1.Similar to above but for Day -2 and Day -3 2.Disturbances has established in SCS but heavy rainfall has yet to arrive in Central Vietnam

ANOMALOUS RAINFALL AND WIND AT 850 hPa June to August Deficiency of rainfall over Eastern China but surplus of rainfall over Central Vietnam Cyclonic circulation shifted slightly north