High Spatiotemporal Resolution Planetary Boundary Layer Dynamics Across
the Israeli Coast-Mountain-Valley Terrain Unraveled by WRF Simulations
Abstract
The west-east terrain cross-section along ~150km of the
northern part of Israel is characterized by a
coastal-plain—mountain—valley structure; hereafter denodet iCMV.
However, the boundary layer height (BLH) evolution mechanism across the
iCMV has not yet been fully unraveled. We use Weather Research and
Forecasting (WRF) simulations and ceilometer measurements to decipher
the iCMV BLH evolution mechanism during a late summertime period, where
the daily maximal BLH at the mountainous city of Jerusalem (JrM; 800m
above sea-level) varies by ~1000m. We first verify the
BLH simulated by 5 model configurations (with 4 different BL schemes).
The RMSE for the 3 best configurations are around 160 and 200m for the
coastal and JrM areas, respectively. An analysis of the modeled daily BL
evolution reveals a general mechanism. At the early morning, the
up-slope flows and synoptic forcing conspire to induce a surface flow
convergence (SurFCon) zone. For pronounced westerly (easterly) general
flow, the SurFCon is induced east (west) of JrM. Assisted by the inland
propagating sea-breeze front, the SurFCon is advected eastwards during
the afternoon. The SurFCon zone is accompanied by a substantial vertical
wind column and a locally-elevated BLH. The more western the
morning-time SurFCon is, the more likely the elevated BLH will pass
during midday through JrM, with a higher daily maximum BLH. At the late
afternoon, the SurFCon zone arrives at the valley bottom and collapses.
The dependence of the mechanism upon the synoptic regime, and the
corresponding temperature and humidity dynamics, require further study.