Diurnal SST and diurnal rainfall in the Maritime Continent from a 40 - - PowerPoint PPT Presentation

Hyodae Seo Physical Oceanography Department Woods Hole Oceanographic Institution

Diurnal SST and diurnal rainfall in the Maritime Continent

from a 40 km regional coupled model during Nov14-Dec13, 2011

(a) Diurnal amplitude of land and sea surface temperatures

0 500 1000 0 10 20 30 LST [℃] 0 0.5 1.0 1.5 SST [℃]

(b) Topography in the MC domain Sumatra Borneo New Guinea Sulawesi Philippines

Topography [m]

SCOAR regional coupled model

• 40 km O-A resolutions
• Tropical channel
• 5 ensemble members
• Nov 14-Dec 13, 2011

Coupler

Scripps RSM

ROMS SST &

• sfc. current

atmos model / bulk physics:τ, Qflux, FW

WRF

Atmosphere Ocean

6-h ERA-Interim daily HYCOM

Seo et al. (2014): J. Climate Coupled impacts of the diurnal cycle of sea surface temperature on the Madden-Julian Oscillation.

CF1: 1-hr coupling CF1DM: WRF forced with Daily-Mean CF1 SST CF24: 24-hr coupling

Land Ocean

Rainfall time-series over land and ocean

Rainfall over the ocean

Reduced early morning rainfall in both land and ocean

Rainfall over land

Hourly rainfall composites

mm/hr mm/hr

Reduced land-sea thermal contrast during the morning and night hours

℃ ℃

LST MC SST MC

Hourly surface temperature composites

Diurnal amplitude of rainfall

CF1 D-PCP (CF1-CF1DM)/CF1 D-PCP % Change TRMM D-PCP mm/hr CF1DM D-PCP

%

mm/hr

Diurnal amplitude of land surface temperatures

CF1 D-LST Land ONLY CF1DM D-LST Land ONLY

℃

(CF1-CF1DM)/CF1 D-LST % Change % D-SST in CF1

Peak rainfall hours

CF1 Diurnal peak hours TRMM Diurnal peak hour CF1-CF1DM; difference in peak hours CF1DM Diurnal peak hours LST LST hrs

Offshore propagation: Sumatra Similar to Mori et al. 2004

mm/hr LST

200 400 800 600

• rography (meter)

LST

Summary

• Preliminary, 1-month integration, coarse h/v resolutions
• Diurnal fluctuation in SST (with the identical time-mean)
• enhances the diurnal amplitude of rainfall
• modulates the diurnal amplitude of LST as much as 10%
• shifts the rainfall peak by up to ±3 hrs throughout the MC islands
• offshore march of the diurnal rainfall stronger and more coherent
• Plan to use an explicit convection regional coupled model with one-

way and two-way nesting

• To represent the land-diurnal convection, gravity wave response to

convective heating, and land-sea breezes.

• To examine the resulting air-sea interaction and the influence on the

MCS formation, the MC-wide rainfall, and the MJO propagation.