The impact of planetary boundary layer parameterisation over the Yangtze
River Delta region, China - Part I: meteorological simulation
Abstract
The planetary boundary layer (PBL) is the main region for the exchange
of matter, momentum, and energy between land and atmosphere. The
transport processes in the PBL determine the distribution of
temperature, water vapour, wind speed and other physical quantities and
are very important for the simulation of the physical characteristics of
the meteorology. Based on the two non-local (YSU, ACM2) and two local
closure PBL schemes (MYJ, MYNN) in the Weather Research and Forecasting
(WRF) model, seasonal and daily cycles of meteorological variables over
the Yangtze River Delta (YRD) region are investigated. It is shown that
all four PBL schemes overestimate 10-m wind speed and 2-m temperature,
while underestimate relative humidity. Inter-comparisons among the
different PBL schemes show that the MYNN scheme results in closer match
of 2-m temperature and 10-m wind speed to surface observations in
summer, while the MYJ scheme shows the smallest bias of 2-m temperature
and relative humidity in winter. Compared to the observed PBL height
obtained from a micro-pulse lidar system, the MYNN scheme exhibits
lowest mean bias while the ACM2 scheme shows the highest correlation. It
is also found that there is a varying degree of sensitivity of the PBL
height in winter and summer, respectively; a best-performing PBL scheme
should be chosen under different seasons to predict various
meteorological conditions over complicated topography like the YRD
region.