Interannual variability and predictability in an ensemble of AMIP climate simulations conducted with the CCC GCM2 |
| |
Authors: | F W Zwiers |
| |
Institution: | (1) Canadian Centre for Climate Modelling and Analysis, Victoria, Canada, CA |
| |
Abstract: | This study considers an ensemble of six 10-year climate simulations conducted with the Canadian Climate Centre 2nd generation
General Circulation Model (CCC GCM2). Each simulation was forced according to the Atmospheric Model Intercomparison Project
(AMIP) experimental protocol using monthly mean sea surface temperatures and sea-ice extents based on observations for January,
1979 to December 1988. One simulation, conducted on a CRAY computer, was initiated from analysed 1 January 1979 conditions
while the remaining 5 simulations, conducted on a NEC computer, were initiated from previously simulated model states obtained
from a long control integration. The interannual variability and potential predictability of simulated and observed 500 hPa
geopotential, 850 hPa temperature and 300 hPa stream function are examined and inter-compared using statistical analysis of
variance techniques to partition variance into a number of components. The boundary conditions specified by AMIP are found
to induce statistically significant amounts of predictable variance on the interannual time scale in the tropics and, to a
lesser extent, at extratropical latitudes. In addition, local interactions between the atmosphere and the land surface apparently
induce significant amounts of potentially predictable interannual variance in the tropical lower atmosphere and also at some
locations in the temperate lower atmosphere. No evidence was found that the atmosphere's internal dynamics on their own generate
potentially predictable variations on the interannual time scale. The sensitivity of the statistical methods used is demonstrated
by the fact that we are able to detect differences between the climates simulated on the two computers used. The causes of
these physically insignificant changes are traced. The statistical procedures are checked by confirming that the choice of
initial conditions does not lead to significant inter-simulation variation. The simulations are also interpreted as an ensemble
of climate forecasts that rely only on the specified boundary conditions for their predictive skill. The forecasts are verified
against observations and against themselves. In agreement with other studies it was found that the forecasts have very high
skill in the tropics and moderate skill in the extratropics.
Received: 18 December 1995 / Accepted: 4 April 1996 |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|