Diurnal cycle of warm season precipitation in Hainan Island Lei Zhu Supervisor: Paul Markowski, Fuqing Zhang and Zhiyong Meng

Background The diurnal cycle of precipitation is a very important phenomenon on the local weather and climate, is linked with the lives of people. It often links with the topography, the land-sea breeze and even with the LLJ. More than 9 million residents~ On the contrary, it has never been studies in this region (Hainan island). The diurnal cycles of precip have been done a lot of research (Ruppert et al. (2013)).

Hourly precipitation evolution (OBS) cmorph data: 30min, 8km 10 years (2006-2015) average! May June Difference with what the diurnal cycles of precip have been studied: Do not propagate! Seems do not have nocturnal precip!

Experiment design WRF version: 3.7.1 Model resulotion: Horizontal: 9km Vertical: 43 levels GFS FNL data for initial and boundary conditions Initial condition: 0000 UTC averaged over May and June months averaged in 2006-2015 Boundary conditions: Every 6h averaged just like the initial condition Run 1-month (31days) simulation The results are using the average in the last 25 days.

OBS vs. simulation (shaded: hourly precip; contour: terrain>200m) CMORPH CNTL

Lon/lat-time diagrams over the simulation domain average OBS CNTL No_ter OBS CNTL No_ter

RH & UV @850hPa CNTL Mountain affects the water trans and the wind Noter

2nd lowest model level Pertubation UV & precip CNTL Sea breeze is very outstanding. It seems that the convergence of sea breeze is the most important factor to produce rainfall Noter Doubled the CNTL terrain high

2nd lowest model level Pertubation UV & mdbz The mountain seems not the crucial factor for the convective initiation, but it can affect the distribution, intensity and timing of the precip. CNTL Noter Doubled the CNTL terrain high

2nd lowest model level Pertubation UV & 850 W CNTL Terrain produces the gravity wave? Does it is TRUE? Noter

Replace the sea region of the left/right 110°longitude with land The land and sea breezes arise because the water and land have different heating abilities.

Thanks for your attention! Conclusion The diurnal cycle of warm precipitation is very notable in Hainan Island. It also has two distinct features: precipitation does not propagate and no nocturnal precip peak. The precip is induced by the sea breeze convergence at the center of the island! The mountain can intense the rainfall. It also decides the distribution and time of the precip. Thanks for your attention!