REALIZING TERACOMPUTING (2003) 1-18
Appl Opt 42 (2003) 5891-5896
A number of techniques to track rainfall patterns by use of radar observations have been developed over the years. We present a method for radar-echo tracking based on Hu invariant moments. The method has been tried on several sequences of test images, and the derived displacement fields were in good agreement with the real motions of the tested objects. For the real data obtained from the conventional meteorological radar in Legionowo the method occasionally failed when changes in the radar echo between observations were too large.
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 129 (2003) 2401-2423
Benefits of increased resolution in the ECMWF ensemble system and comparison with poor-man's ensembles
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 129 (2003) 1269-1288
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 128 (2002) 1641-1670
Nature 415 (2002) 512-514
Increasing concentrations of atmospheric carbon dioxide will almost certainly lead to changes in global mean climate. But because--by definition--extreme events are rare, it is significantly more difficult to quantify the risk of extremes. Ensemble-based probabilistic predictions, as used in short- and medium-term forecasts of weather and climate, are more useful than deterministic forecasts using a 'best guess' scenario to address this sort of problem. Here we present a probabilistic analysis of 19 global climate model simulations with a generic binary decision model. We estimate that the probability of total boreal winter precipitation exceeding two standard deviations above normal will increase by a factor of five over parts of the UK over the next 100 years. We find similar increases in probability for the Asian monsoon region in boreal summer, with implications for flooding in Bangladesh. Further practical applications of our techniques would be helped by the use of larger ensembles (for a more complete sampling of model uncertainty) and a wider range of scenarios at a resolution adequate to analyse average-size river basins.
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 128 (2002) 747-774
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 127 (2001) 685-708
MONTHLY WEATHER REVIEW 129 (2001) 2226-2248
JOURNAL OF CLIMATE 14 (2001) 3212-3226
Nonlinear Processes in Geophysics 8 (2001) 357-371
Operational forecasting is hampered both by the rapid divergence of nearby initial conditions and by error in the underlying model. Interest in chaos has fuelled much work on the first of these two issues; this paper focuses on the second. A new approach to quantifying state-dependent model error, the local model drift, is derived and deployed both in examples and in operational numerical weather prediction models. A simple law is derived to relate model error to likely shadowing performance (how long the model can stay close to the observations). Imperfect model experiments are used to contrast the performance of truncated models relative to a high resolution run, and the operational model relative to the analysis. In both cases the component of forecast error due to state-dependent model error tends to grow as the square-root of forecast time, and provides a major source of error out to three days. These initial results suggest that model error plays a major role and calls for further research in quantifying both the local model drift and expected shadowing times.
A nonlinear dynamical perspective on model error: A proposal for non-local stochastic-dynamic parametrization in weather and climate prediction models
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 127 (2001) 279-304
ATMOSPHERIC SCIENCE LETTERS 2 (2001) 72-80
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 127 (2001) 709-731
Atmospheric Science Letters 2 (2001)
In order to investigate whether climate models of different complexity have the potential to simulate natural atmospheric circulation regimes, 1000-year-long integrations with constant external forcing have been analysed. Significant non-Gaussian uni-, bi-, and trimodal probability density functions have been found in 100-year segments. © 2001 Royal Meteorological Society.
METEOROLOGICAL APPLICATIONS 7 (2000) 163-175
Arctic and Antarctic ozone layer observations: Chemical and dynamical aspects of variability and long-term changes in the polar stratosphere
Polar Research 19 (2000) 193-204
The altitude dependent variability of ozone in the polar stratosphere is regularly observed by balloon-borne ozonesonde observations at Neumayer Station (70°S) in the Antarctic and at Koldewey Station (79°N) in the Arctic. The reasons for observed seasonal and interannual variability and long-term changes are discussed. Differences between the hemispheres are identified and discussed in light of differing dynamical and chemical conditions. Since the mid-1980s, rapid chemical ozone loss has been recorded in the lower Antarctic stratosphere during the spring season. Using coordinated ozone soundings in some Arctic winters, similar chemical ozone loss rates have been detected related to periods of low temperatures. The currently observed cooling trend of the stratosphere, potentially caused by the increase of anthropogenic greenhouse gases, may further strengthen chemical ozone removal in the Arctic. However, the role of internal climate oscillations in observed temperature trends is still uncertain. First results of a 10 000 year integration of a low order climate model indicate significant internal climate variability, on decadal time scales, that may alter the effect of increasing levels of greenhouse gases in the polar stratosphere.
TELLUS SERIES A-DYNAMIC METEOROLOGY AND OCEANOGRAPHY 52 (2000) 391-411