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Omar Abel Lucero – One of the best experts on this subject based on the ideXlab platform.

  • Evolution of spatial patterns of subdecadal signals in Annual Rainfall in Southern South America and Southern and Central North America
    Atmospheric Research, 2004
    Co-Authors: Omar Abel Lucero, Norma C. Rodrı́guez

    Abstract:

    Abstract Spatial patterns at different timescales of anomaly of Annual Rainfall in southern South America and southern and central North America are composed of quasi-standing wavelike signals. Emphasis in this research is on subdecadal timescales, short-subdecadal (3 to 6 years) and long-subdecadal (6 to 10 years). Indications were found of the existence in most cases of a slow long-term evolution of spatial patterns superimposed on the within-cycle evolution. There are different types of spatial patterns or regimes. These regimes last several quasi-cycles. The change of regime is abrupt. Spatial patterns of anomaly of Annual Rainfall volume (ARV) in short-subdecadal timescales (average quasi-period is approximately 4 years) are under the influence of the short-subdecadal component of the Southern Oscillation. Correlation coefficient, although statistically significant, is not large. Long-subdecadal spatial patterns of anomaly of Annual Rainfall volume are strongly correlated with the long-subdecadal component of the Southern Oscillation Index (SOI). Average quasi-period of long-subdecadal fluctuations is 8 years. Finally, it was analyzed the partial contribution of fluctuations in different timescales to the total anomaly of Annual Rainfall during the 10 wettest years and the 10 driest years. Findings indicate that in southern South America and in southern and central North America, the contributions are in the order of decreasing magnitude: [ 10 years), and [6 to 10 years).

  • Spatial organization in Europe of decadal and interdecadal fluctuations in Annual Rainfall
    International Journal of Climatology, 2002
    Co-Authors: Omar Abel Lucero, Norma C. Rodrı́guez

    Abstract:

    The spatial patterns of decadal and bidecadal fluctuations in Annual Rainfall in Europe are identified. Filtering of time series of the anomaly in Annual Rainfall is carried out using the Morlet wavelet technique. Reconstruction is achieved by summing the contributions from bands of wavelet time scales; the decadal band and the bidecadal band are composed of contributions from the bands of the (10 to 17 year) and (17 to 27 year) time scales respectively. Results indicate that (1) the spatial organization of the decadal and bidecadal components of Annual Rainfall are standing-wave-like organized patterns. Three standing decadal fluctuations zonally aligned formed the spatial pattern from 1900 until 1931; thereafter the pattern changed into a NW–SE orientation. The decadal band shows an average 12 year period. (2) The spatial organization of the bidecadal component was composed of three standing fluctuations from 1903 to 1986. After 1987, two standing bidecadal fluctuations were located over Europe. The orientation of the bidecadal fluctuations changed during the period under study. Until 1913 the spatial pattern of the bidecadal component was zonally aligned. Since 1913 and until 1986 the three bidecadal fluctuations composing the spatial pattern were aligned SW–NE; starting in 1987, the spatial pattern is composed of two standing fluctuations zonally aligned. The bidecadal spatial pattern shows an average period of 20 to 22 years in length. (3) At the decadal and bidecadal time scales, the first principal component of the spatial field of anomaly in Annual Rainfall and the North Atlantic oscillation (NAO) index are connected. The upper positive third (lower negative third) of values of the first principal component are indicative of an extensive area with positive (negative) anomalies in Annual Rainfall. (4) At the decadal time scale the relative phase between the first principal component and the NAO index changes through the period under study; these changes define three regimes. (i) During the regime covering the period 1900 (start of period under study) to about 1945, at the time of peak values in decadal NAO index there takes place a transition between extremes (a neutral state) of the decadal Rainfall spatial pattern (first principal component takes small absolute values). In addition, for a positive (negative) peak value of NAO index the spatial pattern of Annual Rainfall evolves toward an area of predominantly positive (negative) anomalies. (ii) The second regime starts about 1946 and continues to the early 1980s. At the time of the negative (positive) peak in decadal NAO there is a prevailing spatial pattern of positive (negative) anomalies of decadal Rainfall. (iii) The third regime starts around the late 1970s and continues to the end of the period under study (in 1996). There is a change of relative phase within this period in the late 1980s. In this regime a spatial pattern of prevailing positive or negative anomaly of decadal Rainfall takes place during values of decadal NAO close to zero. (5) At the bidecadal time scale the relative phase between the first principal component and the NAO index remains almost constant through the period under study. The first principal component of the transformed bidecadal component of Annual Rainfall anomalies attains its positive (negative) peak about 3 years before the bidecadal component of NAO reaches its negative (positive) peak. Copyright © 2002 Royal Meteorological Society.

  • Characteristics of aggregation of daily Rainfall in a middle-latitudes region during a climate variability in Annual Rainfall amount
    Atmospheric Research, 2002
    Co-Authors: Omar Abel Lucero, Daniel Rozas

    Abstract:

    Abstract Climate variability in Annual Rainfall occurs because the aggregation of daily Rainfall changes. A topic open to debate is whether that change takes place because Rainfall becomes more intense, or because it rains more often, or a combination of both. The answer to this question is of interest for water resources planning, hydrometeorological design, and agricultural management. Change in the number of rainy days can cause major disruptions in hydrological and ecological systems, with important economic and social effects. Furthermore, the characteristics of daily Rainfall aggregation in ongoing climate variability provide a reference to evaluate the capability of GCM to simulate changes in the hydrologic cycle. In this research, we analyze changes in the aggregation of daily Rainfall producing a climate positive trend in Annual Rainfall in central Argentina, in the southern middle-latitudes. This state-of-the-art agricultural region has a semiarid climate with dry and wet seasons. Weather effects in the region influence world-market prices of several crops. Results indicate that the strong positive trend in seasonal and Annual Rainfall amount is produced by an increase in number of rainy days. This increase takes place in the 3-month periods January–March (summer) and April–June (autumn). These are also the 3-month periods showing a positive trend in the mean of Annual Rainfall. The mean of the distribution of Annual number of rainy day (ANRD) increased in 50% in a 36-year span (starting at 44 days/year). No statistically significant indications on time changes in the probability distribution of daily Rainfall amount were found. Non-periodic fluctuations in the time series of Annual Rainfall were analyzed using an integral wavelet transform. Fluctuations with a time scale of about 10 and 20 years construct the trend in Annual Rainfall amount. These types of non-periodic fluctuations have been observed in other regions of the world. This suggests that results of this research could have further geographical validity.

Hind Meddi – One of the best experts on this subject based on the ideXlab platform.

  • TEMPORAL VARIABILITY OF Annual Rainfall IN THE MACTA AND TAFNA CATCHMENTS, NORTHWESTERN ALGERIA
    , 2014
    Co-Authors: Mohamed Meddi, Ali A. Assani, Hind Meddi

    Abstract:

    Abstract: We analyzed the temporal variability of Annual precipitation measured at five stations in the Macta (14,380 km2) and Tafna (4,949 km2) catchments located in northwestern Algeria, in connection with climate indices over the 1950?2004 period. Analysis of the temporal variability using linear regression and Pettitt test revealed a significant decline in Annual Rainfall in the mid-1970s in both basins. Furthermore, a decrease of at least 20% of total Annual Rainfall is also observed at all five stations. As for the relationship between climate indices and variability of Annual precipitation, canonical correlation analysis shows that, from 1950 to 2004, precipitation at the five stations are negatively correlated with NINO4 and, to a lesser degree, with NAO

  • temporal variability of Annual Rainfall in the macta and tafna catchments northwestern algeria
    Water Resources Management, 2010
    Co-Authors: Mohamed Meddi, Ali A. Assani, Hind Meddi

    Abstract:

    We analyzed the temporal variability of Annual precipitation measured at five stations in the Macta (14,380 km 2 ) and Tafna (4,949 km 2 ) catchments located in northwestern Algeria, in connection with climate indices over the 1950–2004 period. Analysis of the temporal variability using linear regression and Pettitt test revealed a significant decline in Annual Rainfall in the mid-1970s in both basins. Furthermore, a decrease of at least 20% of total Annual Rainfall is also observed at all five stations. As for the relationship between climate indices and variability of Annual precipitation, canonical correlation analysis shows that, from 1950 to 2004, precipitation at the five stations are negatively correlated with NINO4 and, to a lesser degree, with NAO. Copyright Springer Science+Business Media B.V. 2010

Norma C. Rodrı́guez – One of the best experts on this subject based on the ideXlab platform.

  • Evolution of spatial patterns of subdecadal signals in Annual Rainfall in Southern South America and Southern and Central North America
    Atmospheric Research, 2004
    Co-Authors: Omar Abel Lucero, Norma C. Rodrı́guez

    Abstract:

    Abstract Spatial patterns at different timescales of anomaly of Annual Rainfall in southern South America and southern and central North America are composed of quasi-standing wavelike signals. Emphasis in this research is on subdecadal timescales, short-subdecadal (3 to 6 years) and long-subdecadal (6 to 10 years). Indications were found of the existence in most cases of a slow long-term evolution of spatial patterns superimposed on the within-cycle evolution. There are different types of spatial patterns or regimes. These regimes last several quasi-cycles. The change of regime is abrupt. Spatial patterns of anomaly of Annual Rainfall volume (ARV) in short-subdecadal timescales (average quasi-period is approximately 4 years) are under the influence of the short-subdecadal component of the Southern Oscillation. Correlation coefficient, although statistically significant, is not large. Long-subdecadal spatial patterns of anomaly of Annual Rainfall volume are strongly correlated with the long-subdecadal component of the Southern Oscillation Index (SOI). Average quasi-period of long-subdecadal fluctuations is 8 years. Finally, it was analyzed the partial contribution of fluctuations in different timescales to the total anomaly of Annual Rainfall during the 10 wettest years and the 10 driest years. Findings indicate that in southern South America and in southern and central North America, the contributions are in the order of decreasing magnitude: [ 10 years), and [6 to 10 years).

  • Spatial organization in Europe of decadal and interdecadal fluctuations in Annual Rainfall
    International Journal of Climatology, 2002
    Co-Authors: Omar Abel Lucero, Norma C. Rodrı́guez

    Abstract:

    The spatial patterns of decadal and bidecadal fluctuations in Annual Rainfall in Europe are identified. Filtering of time series of the anomaly in Annual Rainfall is carried out using the Morlet wavelet technique. Reconstruction is achieved by summing the contributions from bands of wavelet time scales; the decadal band and the bidecadal band are composed of contributions from the bands of the (10 to 17 year) and (17 to 27 year) time scales respectively. Results indicate that (1) the spatial organization of the decadal and bidecadal components of Annual Rainfall are standing-wave-like organized patterns. Three standing decadal fluctuations zonally aligned formed the spatial pattern from 1900 until 1931; thereafter the pattern changed into a NW–SE orientation. The decadal band shows an average 12 year period. (2) The spatial organization of the bidecadal component was composed of three standing fluctuations from 1903 to 1986. After 1987, two standing bidecadal fluctuations were located over Europe. The orientation of the bidecadal fluctuations changed during the period under study. Until 1913 the spatial pattern of the bidecadal component was zonally aligned. Since 1913 and until 1986 the three bidecadal fluctuations composing the spatial pattern were aligned SW–NE; starting in 1987, the spatial pattern is composed of two standing fluctuations zonally aligned. The bidecadal spatial pattern shows an average period of 20 to 22 years in length. (3) At the decadal and bidecadal time scales, the first principal component of the spatial field of anomaly in Annual Rainfall and the North Atlantic oscillation (NAO) index are connected. The upper positive third (lower negative third) of values of the first principal component are indicative of an extensive area with positive (negative) anomalies in Annual Rainfall. (4) At the decadal time scale the relative phase between the first principal component and the NAO index changes through the period under study; these changes define three regimes. (i) During the regime covering the period 1900 (start of period under study) to about 1945, at the time of peak values in decadal NAO index there takes place a transition between extremes (a neutral state) of the decadal Rainfall spatial pattern (first principal component takes small absolute values). In addition, for a positive (negative) peak value of NAO index the spatial pattern of Annual Rainfall evolves toward an area of predominantly positive (negative) anomalies. (ii) The second regime starts about 1946 and continues to the early 1980s. At the time of the negative (positive) peak in decadal NAO there is a prevailing spatial pattern of positive (negative) anomalies of decadal Rainfall. (iii) The third regime starts around the late 1970s and continues to the end of the period under study (in 1996). There is a change of relative phase within this period in the late 1980s. In this regime a spatial pattern of prevailing positive or negative anomaly of decadal Rainfall takes place during values of decadal NAO close to zero. (5) At the bidecadal time scale the relative phase between the first principal component and the NAO index remains almost constant through the period under study. The first principal component of the transformed bidecadal component of Annual Rainfall anomalies attains its positive (negative) peak about 3 years before the bidecadal component of NAO reaches its negative (positive) peak. Copyright © 2002 Royal Meteorological Society.