Analysis of geographic and orographic influence in Spanish monthly precipitation

Abstract

Precipitation is a major concern in water resources studies. Being a main variable, the inefficiency of historical ground network, particularly at higher altitudes where precipitation and runoff augmentations are expected, constitutes a major drawback. This work analyses the competence of Spanish historical precipitation network and explores the physiographic influence of elevation and orientation at a national scale. The usefulness of slopes is also explored. Nearly 12 000 monthly precipitation series recorded from the 19th century until the hydrological year 2004/2005 over a high‐resolution topographic map (200 m) of Spanish territory are used. Comparable statistics and precipitation lapse rates are managed once a completion of gaps is accomplished. Then, Spanish yearly rates range from 0.3 to 1.2 mm m−1, reaching 1.5 mm m−1 in Northern Iberian Peninsula, diminishing at highest altitudes. Conclusions address the inefficiency and uncertainties revealed by historical ground networks as well as the variable relationship existing between precipitation and physiographic parameters, such as altitude and orientation.

Development of a hybrid model to interpolate monthly precipitation maps incorporating the orographic influence

“…Existing gaps in recorded rainfall series were filled with regression‐based data. Basis of the completion model as well as a description of available data may be found in Álvarez‐Rodríguez et al ().…”

“…A digital elevation model (DEM) has been composed joining Spanish and a Portuguese DEM to derive its main physiographic features as described in Álvarez‐Rodríguez et al (). Figure shows the digital aspect model (DAM, cell angle at which terrain slope faces, counterclockwise from East) obtained considering relative elevation surrounding each cell of a DEM.…”

“…To reflect orographic influence and the underestimation of precipitation given, a collation of pseudo precipitation records was then added to original records. Pseudo precipitation records were estimated by linear regression analysed in certain Spanish regions (Estrela et al, ; Álvarez‐Rodríguez et al, ). Regions of approximately 5,000 km 2 were delimitated considering windward and leeward location.…”

“…Álvarez‐Rodríguez et al () described some basis to improve spatial estimates of rainfall for the Iberian Peninsula and Spanish Islands. They concluded that precipitation over this territory depends on its complex orographic structure and predominant weather types.…”

“…In Spain, precipitation tends to be positively correlated with altitude although this relationship varies depending on seasonality and location. Annual precipitation lapse rates (PLR) were found to range from 0.3 to 1.2 mm/m, reaching 1.5 mm/m in the Northern Iberian Peninsula and diminish at higher altitudes (Álvarez‐Rodríguez et al, ). This would justify the use of non‐linear functions in precipitation‐altitude regression analysis as it will be shown in this paper.…”