The Influence of Mesoscale Orography on a Coastal Jet and Rainband

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Abstract
The role of mesoscale orography along the central California coast in the development and evolution of a coastal jet and rainband is investigated using a high-resolution, triply nested, nonhydrostatic numerical model. Comparison of the model simulations, which use horizontal grid increments of 5 and 2 km on the inner computational meshes, with a coastal mesoscale observation network indicates that the finescale structure of the jet and rainband dynamics are adequately simulated, although phase and orientation errors occur. The observed and simulated near-surface winds have maximum speeds that exceed 22 m s−1 and a direction nearly parallel to the coastline and topography. Force balance analysis indicates that blocking in the lowest 500 m and flow over the coastal range above this layer contribute to mesoscale pressure perturbations, including pressure ridging upstream of the coastal mountains, which forces the ageostrophic dynamics of the coastal jet. Pressure perturbations associated with the to... Abstract The role of mesoscale orography along the central California coast in the development and evolution of a coastal jet and rainband is investigated using a high-resolution, triply nested, nonhydrostatic numerical model. Comparison of the model simulations, which use horizontal grid increments of 5 and 2 km on the inner computational meshes, with a coastal mesoscale observation network indicates that the finescale structure of the jet and rainband dynamics are adequately simulated, although phase and orientation errors occur. The observed and simulated near-surface winds have maximum speeds that exceed 22 m s−1 and a direction nearly parallel to the coastline and topography. Force balance analysis indicates that blocking in the lowest 500 m and flow over the coastal range above this layer contribute to mesoscale pressure perturbations, including pressure ridging upstream of the coastal mountains, which forces the ageostrophic dynamics of the coastal jet. Pressure perturbations associated with the to...

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