Abstract. On April 15 and 19, 1998, two intense dust storms were generated over the Gobi desert by springtime low-pressure systems descending from the northwest. The windblown dust was detected and its evolution followed by its yellow color on SeaWiFS satellite images, routine surface-based monitoring, and through serendipitous observations. The April 15 dust cloud was recirculating, and it was removed by a precipitating weather system over east Asia

A size‐segregated soil dust emission and transport model, Northern Aerosol Regional Climate Model (NARCM), was used to simulate the production and transport of Asian soil dust during the Aerosol Characterization Experiment‐Asia (ACE‐Asia) period from March to May 2001. The model is driven by the NCEP reanalyzed meteorology and has all the atmospheric aerosol physical processes of soil dust: production, transport, growth, coagulation, and dry and wet deposition. A Chinese soil texture map that infers the soil grain‐size distribution with 12 categories was generated to drive the size‐distributed soil dust emission scheme [Alfaro et al., 1997; Marticorena and Bergametti, 1995]. The size distribution of vertical dust flux was derived from the observed surface dust‐size distribution in the desert regions. Parameters applicable to the Asian deserts for the dust emission scheme are assessed. Model simulations were compared with ground‐based measurements in East Asia and North America and with satellite measurements for the same period of time. The model captured most of the dust mobilization episodes during this period in China and reasonably simulated the concentrations in source regions and downwind areas from East China to western North America. About 252.8 Mt of soil dust below d < 40 μm was estimated to be emitted in the East Asian deserts between 1 March and 31 May 2001 with ∼60% attributed to four major dust storms. The vertical dust loadings above 700 hPa correlate reasonably well with Total Ozone Mapping Spectrometer aerosol index (TOMS AI) observations. The sensitivity analysis of model performance to soil size distribution, water moisture, and meteorology was carried out with the observational data to establish the most appropriate parameters and conditions for the Chinese soil dust production and transport.

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In much of North America, variables such as temperature, precipitation, snowpack and streamflow are modulated by modes of large-scale ocean-atmosphere variability such as the Pacific Decadal Oscillation (PDO), El Niño-Southern Oscillation (ENSO) and the Pacific North American Pattern (PNA). In this study, we test the hypothesis that the influence of these modes on air temperature and precipitation in British Columbia (BC), Canada, can be explained in relation to changes in frequencies of synoptic-scale circulation types. A catalogue of 13 circulation types was derived by classifying daily mean sea-level pressure (MSLP) grids from 1948 to 2003. The grids cover BC and the North Pacific and were subjected to a standard pattern recognition algorithm employing principal component analysis followed by cluster analysis on the component scores. The circulation types are generally associated with distinctive patterns of precipitation and air temperature anomalies across BC. Multiple linear regressions for selected stations in BC using the type frequencies as predictors explain up to 75% of the variance of mean winter temperature and 65% of winter precipitation. The frequencies of most circulation types vary significantly between the different phases of ENSO, PDO and PNA in a manner consistent with the temperature anomalies associated with those modes and, to a lesser extent, with the more complex precipitation anomalies. In addition, however, average temperatures and precipitation amounts for some circulation types differ systematically between phases of ENSO and PDO. Subsequent analysis revealed distinct differences among ENSO and PDO phases in the upper-level circulation patterns associated with some surface types. A major part of the teleconnections can be explained through variations in the frequencies of synoptic-scale circulation types, but systematic within-type variability, particularly with PDO and PNA, can additionally influence the surface climate.