Observing and Understanding the Variability of Water in Weather and Climate
17TH Conference on Hydrology


The Kau storm: Imaging precipitable water using GPS

James Foster, University of Hawaii, Honolulu, HI; and M. Bevis, S. Businger, and Y. L. Chen

A dense network of GPS receivers on the Island of Hawaii is used to examine in detail the water vapor field of the Kau Storm, which generated extreme rainfall (>100 mm/hr) and flash floods over much of the southern and eastern portions of the island on 2 November 2000. With GPS stations distributed from sea level to the highest points on the island (>4000 m) spatial and temporal variations in precipitable water are investigated as the storm passed over the network. The results shed light on the role of the topography in controlling the location and duration of convection and heavy rainfall. The relationship between GPS integrated precipitable water vapor and rain gage data is investigated and implications for vertical motion and divergence aloft are evaluated. Rainfall predictions of the storm provided by the Regional Spectral Model consistently underestimate observed rain fall amounts. Comparison with the GPS derived water vapor, shows that this underestimate is correlated with a consistent underestimate of the integrated precipitable water vapor in the model. This suggests that improvements in the initial water vapor distribution in the mesoscale model, would lead to improvements in the prediction of heavy precipitation.

extended abstract  Extended Abstract (356K)

Joint Poster Session 1, Spatial and Temporal Variability (Joint with the Symposium on Observing and Understanding the Variability of Water in Weather and Climate and the 17th Conference on Hydrology)
Monday, 10 February 2003, 2:30 PM-2:30 PM

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