Open AccessThe characterisation of orographic rainfall
Author(s) -
Gray W R,
Seed A W
Publication year - 2000
Publication title -
meteorological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 59
eISSN - 1469-8080
pISSN - 1350-4827
DOI - 10.1017/s1350482700001559
Subject(s) - orographic lift , radar , precipitation , environmental science , meteorology , rain gauge , orography , transect , precipitation types , atmospheric sciences , climatology , geology , geography , telecommunications , computer science , oceanography
Abstract The Otaki Precipitation Estimation by Radar (OPERA) programme was designed to investigate the processes that lead to enhancement of rainfall over the Tararua ranges of New Zealand. These ranges rise to 1500 m above the coastal plain and enhancement of rainfall by windflow over these hills leads to annual hill‐top rainfall of over four times that upwind. The OPERA experimental campaigns aimed to characterise the enhancement processes by analysing data collected from a transect of high‐resolution rain gauges and a locally deployed, high‐resolution radar, supported by scanning radar and satellite observations. Measurements made during these experiments showed that orographic enhancement led to hill‐top accumulations often twice that upwind, and up to as much as a factor of seven in one case. The data suggest that the most frequent occurring enhancement mechanism was triggered convection. This mechanism leads to an increase in rainfall over the hills of around a factor of two, primarily through an increase in the duration of rain. Seeder/feeder‐type enhancement occurs less frequently but leads to larger enhancements. Copyright © 2000 Royal Meteorological Society