Evolution of the planetary boundary layer and its simulation over a tropical coastal station Kattankulathur (12.83°N, 80.04°E)

Continuous monitoring of the planetary boundary layer (PBL) height was carried out using simultaneous observations of the micro-pulse lidar (MPL) at Kattankulathur (12.83°N, 80.04°E) and radiosonde and surface meteorological observations at Meenambakkam (13.0°N, 80.18°E) during different seasons in the year 2016 over Chennai, in the Indian east coast region. These observations provide excellent data to evaluate the performance of the five different PBL parameterization schemes from the Weather Research and Forecasting (WRF) model simulation of PBL characteristics over the coastal environment. The simulation experiments were run using Asymmetrical Convective Model version 2 (ACM2), Yonsei University (YSU), Mellor-Yamada-Janjic (MYJ), Mellor-Yamada Nakanishi and Nino level 2.5 (MYNN2), and Bougeault–Lacarrere (BouLac) schemes. The first two schemes are the first-order closure schemes, while the last three schemes are the turbulent kinetic energy (TKE) closure schemes. We have conducted the experiments for dry and wet surface conditions on clear sky days during different seasons. Under the dry surface conditions, the comparison of the simulated PBL height with observation reveals that all the schemes perform well during the daytime. However, during night-time, all the schemes except MYNN2 underestimate the observation. MYNN2 simulates the similar PBL diurnal pattern as detected by MPL. The potential temperature and relative humidity (RH) profiles from radiosonde observations at 00Z and 12Z and their surface observations at every 1-h interval from automatic weather station are also compared with simulated results. In the case of surface parameters, the WRF model underestimates the surface temperature by ~ 2 K and surface relative humidity by ~ 10–20% for the dry surface condition. However, under the wet surface condition, simulated PBL height and surface temperature (RH) overestimate (underestimate) the observation first 8 h after the rainfall.