Jianan Chen

The intense and moist winds in a tropical cyclone (TC) environment can produce strong mountain waves and substantially enhanced precipitation over complex terrain, yet few studies investigated how the orographic precipitation in a TC environment might respond to global warming. Here, we use large-eddy simulation to estimate the global warming-induced change in the precipitation over and near an idealized mountain with pseudo-global warming experiments. Two regions in the simulations exhibit locally enhanced precipitation, one over the mountain and the other in the downstream region 25 to 45 km away from the mountain. The enhanced precipitation in both regions is related to the seeder-feeder mechanism, though the enhancement in the downstream regions differs from the conventional definition and is referred as pseudo-seeder-feeder mechanism (PSF). In the PSF mechanism, mountain waves generate an intense cloud formation center in the mid-troposphere above the lee slope, and the resulting precipitation particles drift downstream, intensifying downstream convection when they fall into proper locations and heights. Under warming, the precipitation maximum over the mountain exhibits minimal change, while the precipitation maximum in the downstream region exhibiting sensitivity of around 18 % K-1 intensifies and shifts towards the mountain. The small sensitivity of the first precipitation peak is due to the canceling effects of thermodynamic and dynamic changes. The large sensitivity in the downstream region is mainly due to the strengthening of the wave-induced mid-troposphere cloud formation center which supplies more hydrometeors to the downstream region and enhances precipitation efficiency through the enhanced PSF mechanism.