Observational Studies And Numerical Simulations Of Land And Sea Breezes Circulations Over East Areas Of Ningbo

In this paper, the climatological properties of sea and land circulations over east areas of Ningbo China are analyzed according to meteorological datas. Land and sea breezes cases during 11-13 June 2005 over the districts are observed using DigiCORA Tethersonds System. The vertical, time and spacial distributions of sea and land breeze circulations evolution are analyzed with the observational details. The observational results clearly show that upper return currents were detected during the mature sea-breeze cases, and that the sea breeze circulation is complete, and that the land breeze accompanies a subsidence temperature inversion layer. The effects of the weak prevailing winds on the development of the sea and land breeze circulations are studied based on the principles of synoptic meteorology. The observational datas and synoptic analysis show that land and sea breezes over east areas of Ningbo occur in Summer much more than in winter. The land and sea breezes are simulated using the Weather Research and Forecast (WRF) model with 5-km horizontal resolution. Subjective analyses show that expect for 11-13 June, the WRF-predicted onset time and duration of the land and sea breezes agree well with observations, and that there is return flow aloft during sea-breeze cases. The streamline fields of Ningbo in 2006 are simulated by PSU/NCAR MM5 model with 1-km horizontal resolution. MM5 simulations for January, April, July and October show that land and sea breezes over areas of Ningbo occur more in Summer, less in Spring, and least in Autumn and winter, and that sea breeze front, land breeze front or sea breeze convergence zone become evident, and that horizontal penetration of sea breeze is approaching 60-km. Concentration distribution of point pollution source is simulated through CALPUFF Dispersion Model system. Impact of land and sea breezes on pollutant dispersion is discussed. The Dispersion modeling results show that sea and land breezes circulation generally lead to high concentration value zone of pollutant. The simulations of MM5 coupled with CALPUFF model also indicate that sea and land breezes in the Northern Hemisphere commonly clockwise rotate, but counterclockwise rotation may happen because of some factor.