## 2 Literature Review
### Climate in the Canary Islands  
Some of the climatic characteristics of the Canary Islands have been thoroughly studied by several authors [30; 31; 32]. The average trade winds blow mainly against the north side of the islands, and these rise over the island slopes due to the orography leading to condensation and cloud growth resulting in three layers: (1) a layer of fresh and moist air at low levels, (2) a subsidence inversion layer with temperature increase, and (3) a layer of dry and clear air at high levels. However, the movement of these winds below 1000 m is very affected by the abrupt orography such as small valleys, forests, cliffs, etc., which lead and channel the winds at lower levels (Figure 2). The most significant precipitation occurs when disturbances break the inversion layer that are associated with low pressure or due to disturbances in upper levels (troughs), which cannot be detected at the surface level and are only evident when upper layers are analyzed [31]. The latter are the disturbances causing rainfall in the oriental islands with lower orography, but these also significantly affect the rest of the islands in the archipelago. Despite all of the above, according to several authors, the climate in the Canary Islands is generally stable with a high signal-to-noise ratio in meteorological observations [30], which is why it is relatively easy to determine an actual \"trend\" over time as the background fluctuations do not vary significantly. Nevertheless, other authors consider that these relatively low precipitation rates, on the contrary, introduce higher noise in the time series of rainfall measurement [33], which makes their study more complicated. This is one of the aspects that has led to the use of climatic studies based on statistical techniques [34] as long as a complete meteorological database is used. Although the relief is the main factor that affects the local rainfall distribution [31], the combination of the above-mentioned factors makes rainfall prediction difficult at the local level. A temporal analysis of the rainfall distribution on the island of Tenerife shows that it is not homogeneous over the period of time analyzed (1976 to 2016). However, certain seasonality is observed over the months from January  
Figure 2: Orographic model of the Tenerife Island (Google Maps). to March and from October to December. High precipitation rates are observed over certain periods, which do not always coincide with the traditionally rainier months of the year (Figure 3). In the present work, global and local meteorological parameters are used for the development of a predictive model. Global parameters are associated with precipitation and meteorological phenomena occurring in the archipelago on average, an issue which has been already studied by other authors. For instance, in [35], the authors relate the NAO index and heavy rainfall in the winter season in Spain; in [31], the authors highlight the importance of predicting global parameters and their relationship with rainfall in the Canary Islands and use it to characterize precipitation rates in the archipelago, and, in [34], to predict the intensity of monsoon rains in India. We obtained local parameters from measurements of meteorological stations and from reanalysis of databases from NOAA (NCEP/NCAR Reanalysis). In this study, we worked with the following parameters for the development of a rainfall predictive model in the island of Tenerife. On the one hand, NAO global parameter and local reanalysis parameters: (1) Sea Level Pressure (\(SLP\)); (2) Sea Surface Temperature (\(SST\)) and (3) geopotential height 500-hPa (\(GPH\)). On the other hand, local parameters from meteorological stations: (1) monthly accumulated rainfall and monthly measurements of (2) temperature, (3) wind speed, (4) pressure, and (5) relative humidity. More information on the units of the meteorological parameters can be found in Appendix A.