Characteristics of aggregation of daily rainfall in a middle-latitudes region during a climate variability in annual rainfall amount

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.

[1]  C. Wikle,et al.  Interdecadal Variation in U.S. Pacific Coast Precipitation over the Past Four Decades , 1996 .

[2]  C. Torrence,et al.  A Practical Guide to Wavelet Analysis. , 1998 .

[3]  S. Manabe,et al.  Simulated ENSO in a Global Coupled Ocean–Atmosphere Model: Multidecadal Amplitude Modulation and CO2 Sensitivity , 1997 .

[4]  Xiaolan L. Wang,et al.  Spatial-Temporal Structures of Trend and Oscillatory Variabilities of Precipitation over Northern Eurasia , 1997 .

[5]  N. Graham,et al.  Recent Trends in Rain Gauge Precipitation Measurements from the Tropical Pacific: Evidence for an Enhanced Hydrologic Cycle , 1996 .

[6]  James W. Hurrell,et al.  Decadal atmosphere-ocean variations in the Pacific , 1994 .

[7]  T. Yamagata,et al.  Decadal Climate Variability in the North Pacific during the Recent Decades , 1997 .

[8]  Omar Abel Lucero,et al.  Relationship between interdecadal fluctuations in annual rainfall amount and annual rainfall trend in a southern mid-latitudes region of Argentina , 1999 .

[9]  Statistical characteristics of interdecadal fluctuations in the Southern Oscillation and the surface temperature of the equatorial Pacific , 2000 .

[10]  Mojib Latif,et al.  Dynamics of Interdecadal Variability in Coupled Ocean–Atmosphere Models , 1998 .

[11]  Linda O. Mearns,et al.  MEAN AND VARIANCE CHANGE IN CLIMATE SCENARIOS: METHODS, AGRICULTURAL APPLICATIONS, AND MEASURES OF UNCERTAINTY , 1997 .

[12]  G. Halliwell.  Decadal and Multidecadal North Atlantic SST Anomalies Driven by Standing and Propagating Basin-Scale Atmospheric Anomalies , 1997 .

[13]  M. Hulme,et al.  Development of a Relationship between Station and Grid-Box Rainday Frequencies for Climate Model Evaluation , 1997 .

[14]  Thomas R. Karl,et al.  Secular Trends of Precipitation Amount, Frequency, and Intensity in the United States , 1998 .

[15]  J. Jensen,et al.  Climatic change and design criteria in water resources management a regional case study , 1996 .

[16]  O. Lucero.  Invariance of the design storm in a region under a rainfall climate change at mid-latitudes , 1998 .

[17]  Connie A. Woodhouse,et al.  Number of winter precipitation days reconstructed from southwestern tree rings , 1997 .

[18]  Clayton L. Hanson,et al.  Stochastic Weather Simulation: Overview and Analysis of Two Commonly Used Models , 1996 .

[19]  Q. Hu,et al.  Interdecadal Variations of Annual Precipitation in the Central United States , 1998 .