Observation, analysis, and modeling of the sea breeze circulation during the NOAA/ARL-JSU meteorological field experiment summer 2009

In this study an attempt is made to simulate the diurnal variations of the coastal land and sea breeze atmospheric circulations over the Mississippi Gulf Coast region. It is known that the characteristics of the coastal circulations are dependent on the local topography and land use patterns and the Mississippi Gulf Coast region assumes importance due to its complex terrain features and land use and houses number of industries.

Observations collected at the locations of Harrison County School and Wiggins Airport, situated normal to the Mississippi Gulf Coast region, during June-2009 as a joint NOAA-ARL and JSU-TLGVRC field experiment, were analyzed to understand the characteristics of the sea breeze circulation. These comprise radiosonde observations collected at 5 times of 0900, 1100, 1300, 1500 and 1700 CST (local US time) for four consecutive days of 16 to 19 June, 2009. The main objective of this field experiment was to study the coastal boundary layer structure associated with the development of sea breeze circulation. During this period, radiosonde observations were collected at the two locations, normal to the Mississippi Gulf Coast, of Harrison County School (30.5N,89.1W) and Wiggins Airport (30.8N,89.13W) at five times (i.e.) 1400, 1600, 1800, 2000 and 2200 UTC daily.

For the modeling part, a high resolution mesoscale model, ARW (Advanced Research WRF), was used to simulate the boundary layer characteristics associated with the sea breeze circulation over the Gulf Coast Region corresponding to this 4-day period. The model was designed to have nested two-way interactive three domains with 36, 12 and 4 km resolutions, with the inner most domain covering the entire Gulf Coast region, and 41 vertical levels of which 30 levels were chosen to be below 500 hPa level so as to fine resolve the boundary layer features. The initial and boundary conditions were provided from NCEP FNL data available at 1 degree interval and the boundary conditions were updated at every 6 hours. The model was integrated for 48 hours starting from 00 and 12 UTC of each day starting from 15 June up to 00 UTC of 18 June 2009.

The model simulated atmospheric fields were used to derive the wind, temperature and humidity parameters corresponding to the two locations and the available observation times. The model results were compared with corresponding observations for validation. The model could simulate the gradual development and strengthening of the sea breeze with the progress of daytime. The model could also simulate the variations in the sea breeze at the two locations which are separated by about 25 miles. From the model output, the horizontal and vertical extent of the sea breeze circulation at different time during the daytime period could be identified. The temperature and humidity variations associated with the sea breeze circulation over the Gulf Coast region were also analyzed. These features were compared with the observations collected at the two locations of Harrison County School and Wiggins Airport. These features are noted to have good correspondence with the observations. This study demonstrates the use of WRF ARW high resolution model in the mesoscale atmospheric prediction applications.