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Drought is one of the main natural factors in declining tree-ring growth and the production of agricultural crops in Algeria. This paper addresses the variability of growing conditions for wheat in Algeria with climatic data and a tree-ring reconstruction of January–June precipitation from ten Pinus halepensis tree-ring chronologies. A regression-based reconstruction equation explains up to 74% of the variance of precipitation in the 1970–2011 calibration period and cross validates well. Classification of dry years by the 30% percentile of observed precipitation (131 mm) yields a maximum length of drought of five years (1877–1881) and increasing frequency of dry years in the late 20th and early 21st centuries. A correlation-based sensitivity analysis shows a similar pattern of dependence of tree-growth and wheat production on monthly and seasonal precipitation, but contrasting patterns of dependence on temperature. The patterns are interpreted by reference to phenology, growth phases, and – for wheat – agricultural practices. [ABSTRACT FROM AUTHOR]

Earth-to-air heat exchanger (EAHE) is used for heating and/or cooling of dwelling and buildings in arid regions. In the present paper, experiments are performed to investigate the efficiency of an earth-to-air heat exchanger without external devices (fans, air blowers, etc.). The climatic conditions of the region of Bechar, which is located in the Southwest of Algeria, are considered. The EAHE is made of a PVC pipe with 66 m in length and 0.11 m in diameter. It was buried at a depth of 1.5 m in the agricultural zone, where the annual undisturbed subsoil temperature at 1.5 m is 28 °C. An increase of 19% in the relative humidity (RH) of EAHE has been observed in the humidification regime. While a decrease of 27% in RH has been reached in the dehumidification regime. For the hygrometric regime, the daily working regime was 62.5% of dehumidification (from 00 h to 09 h and from 18 h to 23 h) and 37.5% of humidification (from 10 h to 17 h). The EAHE technique has excellent potential for the enhancement of building hygrometry in arid regions. • The performance of an earth to air heat exchanger is studied by experiments. • The exchanger is used to provide the thermal comfort inside houses in arid regions. • The study is achieved in the region of Bechar, which is located in the Southwest of Algeria. • The studied region is known by its hard environment and arid climate. • The exchanger under investigation acts without external devices (fans, air blower, etc.). [ABSTRACT FROM AUTHOR]