Lanczos Filtering in One and Two Dimensions

Duchon, Claude E.

doi:10.1175/1520-0450(1979)018<1016:lfioat>2.0.co;2

Cited by 2,123 publications

(1,273 citation statements)

References 0 publications

Supporting

Mentioning

1,194

Contrasting

Unclassified

Order By: Relevance

“…The seasonal cycle was smoothed before subtracting the climatology from the daily time series. The relationships with intraseasonal variations are examined by computing anomalies with a Lanczos bandpass filter with cutoff periods of 10 and 90 days and 151 weights (Duchon 1979;Jones et al 1998) (henceforth called intraseasonal anomalies). A dense network of stations in Brazil was used to construct daily gridded precipitation maps.…”

Section: Datamentioning

confidence: 99%

The South Atlantic Convergence Zone: Intensity, Form, Persistence, and Relationships with Intraseasonal to Interannual Activity and Extreme Rainfall

2004

View full text Add to dashboard Cite

The characteristics of intensity, geographical location, and persistence of the South Atlantic convergence zone (SACZ) during the austral summer are investigated. Intensity and spatial features of the SACZ are identified by performing a factor analysis of structural properties of outgoing longwave radiation (OLR) data. The first two leading factors explain 65% of the total variance of structural properties and characterize the SACZ according to intensity and location (oceanic versus continental). An index is constructed based on the magnitude of the factor scores to identify intense (weak) and oceanic (continental) SACZ. The intense SACZ category is associated with negative OLR anomalies over a large area of tropical South America, extending from the western Amazon to the Atlantic Ocean. The weak SACZ category is observed with positive OLR anomalies over tropical South America and negative OLR anomalies over southeastern South America. Oceanic and continental aspects of the SACZ are related to a midlatitude wave train pattern. The Madden-Julian oscillation (MJO) modulates intense SACZ events with persistence longer than 3 days. Interannual variability of persistent events indicates that the ratio of oceanic to continental SACZ as well as their frequency depends on the phase of El Niño-Southern Oscillation (ENSO). Occurrence of extreme rainfall in Brazil is discussed in the context of variations in the SACZ and MJO. Intense (weak) SACZ increases (decreases) the 95th daily rainfall percentile over centraleastern Brazil compared to the climatology. Oceanic (continental) SACZ increases (decreases) the 95th daily rainfall percentile over southeastern Brazil. The MJO phase characterized by suppression of convective activity over Indonesia and enhancement over the central Pacific increases the 95th daily rainfall percentile over northnortheastern Brazil, whereas opposite features are observed for the phase of the MJO characterized by the enhancement of convection over Indonesia and suppression over the central Pacific.

show abstract

Section: Datamentioning

confidence: 99%

The South Atlantic Convergence Zone: Intensity, Form, Persistence, and Relationships with Intraseasonal to Interannual Activity and Extreme Rainfall

2004

View full text Add to dashboard Cite

show abstract

“…To reveal the short-term variations of SAT over land and their possible relations with E1 Nifios and volcanic eruptions, we applied a high-frequency-pass Lanczos digital filter [Duchon, 1979] to the time series of the monthly mean SAT anomalies over land at each grid point to remove variations with timescales longer than l0 years. Figure 1 Second, for each season we compute the composite surface temperature anomalies, SAT over land and SST over the ocean, for each of the 16 categories listed in Table Table 2 for SAT in DJF was statistically significant, we randomly drew 23 years out of the total 48 years of DJF data with volcanic years excluded, constructed two composites (one using the first 12 years of randomly drawn data and the other using the remaining 11 years of randomly drawn data), and calculated the pattern correlations between these two composites for SAT and SST.…”

Section: Indices Of Surface Temperature Anomaliesmentioning

confidence: 99%

Identification and separation of Mount Pinatubo and El Niño‐Southern Oscillation land surface temperature anomalies

Yang¹,

Schlesinger²

2001

J. Geophys. Res.

View full text Add to dashboard Cite

“…Figure 3 illustrates the time behavior of the temperature reconstructions considered here. The annual data have been standardized for ease of comparison and smoothed with a Lanczos filter (Duchon, 1979) having a frequency cutoff of 50% at 100 years to emphasize variation with periods of 100 years or longer. It is of interest that the variance passed by these filters is, in most cases, only a small fraction of the total variance of the unfiltered series, usually less than 5%.…”

Section: Interpretation Of the Climate Recordmentioning

confidence: 99%

Was there a ?medieval warm period?, and if so, where and when?

1994

View full text Add to dashboard Cite

Abstract. It has frequently been suggested that the period encompassing the ninth to the fourteenth centuries A.D. experienced a climate warmer than that prevailing around the turn of the twentieth century. This epoch has become known as the Medieval Warm Period, since it coincides with the Middle Ages in Europe.In this review a number of lines of evidence are considered, (including climatesensitive tree rings, documentary sources, and montane glaciers) in order to evaluate whether it is reasonable to conclude that climate in medieval times was, indeed, warmer than the climate of more recent times. Our review indicates that for some areas of the globe (for example, Scandinavia, China, the Sierra Nevada in California, the Canadian Rockies and Tasmania), temperatures, particularly in summer, appear to have been higher during some parts of this period than those that were to prevail until the most recent decades of the twentieth century. These warmer regional episodes were not strongly synchronous. Evidence from other regions (for example, the Southeast United States, southern Europe along the Mediterranean, and parts of South America) indicates that the climate during that time was little different to that of later times, or that warming, if it occurred, was recorded at a later time than has been assumed. Taken together, the available evidence does not support a global Medieval Warm Period, although more support for such a phenomenon could be drawn from high-elevation records than from low-elevation records. The available data exhibit significant decadal to century scale variability throughout the last millennium. A comparison of 30-year averages for various climate indices places recent decades in a longer term perspective.

show abstract

Lanczos Filtering in One and Two Dimensions

Cited by 2,123 publications

References 0 publications

The South Atlantic Convergence Zone: Intensity, Form, Persistence, and Relationships with Intraseasonal to Interannual Activity and Extreme Rainfall

The South Atlantic Convergence Zone: Intensity, Form, Persistence, and Relationships with Intraseasonal to Interannual Activity and Extreme Rainfall

Identification and separation of Mount Pinatubo and El Niño‐Southern Oscillation land surface temperature anomalies

Was there a ?medieval warm period?, and if so, where and when?

Contact Info

Product

Resources

About