RT info:eu-repo/semantics/bachelorThesis
T1 Análisis de la influencia de las condiciones sinópticas sobre la precipitación en Canarias. Aproximación basada en análisis de componentes principales.
A1 Álvarez Hernández, Aarón
K1 Meteorología
K1 Tipos de tiempo
K1 Componentes Principales
AB The rainfalls in the Canary Islands are very important for the social and economic life of theirpopulation. However, the precipitation has different influences depending on the islands or thezones: there are desert areas and very wet ones.The Alisios winds have an important influence in the humidity of the islands, especially theoccidental ones, that generally have more relief than the rest. That is caused by the Azoresanticyclone, which has more impact in summer months. Nevertheless, this is not the principalcause of the heavy rains in the archipelago: that is principally due to atmospheric disturbancesthat destroy the stability that generate these winds.In this project, the main objective is to characterize the impact of some weather types (WTs) inthe precipitation of the islands making use of two different databases, WRF and SPREAD, inthe period 1st January 1995 – 31st December 2004, which involves ten years of data. To achievethis goal the Principal Components Analysis will be used to determine 4 regions or components,also known as principal components (PC), using the precipitation values registered in thosedatabases. The Jones’s equations and rules will be also applied, which define a classificationmethod to identify different WTs depending on the pressure disturbances in a specific day.To determine this last is necessary the sea level pressure values available in NCEP/NCARReanalysis-1 database.To apply the PCA, a region must be defined to make possible the calculation of the PC. Thechosen area is 27.025o N - 29.975o N, 13.025o W - 18.975o W (see figure 2). Each component hasan associated explained variance, which is related to the corresponding amount of information.It is important to know that the calculated components will be rotated.For the determination of the WTs, another region must be defined. Now, because of the spatialresolution of NCEP/NCAR database, the zone is defined between the coordinates 20o N – 40oN, 10o W – 25oW (see figure 3). With the information that will be extracted from the resultsof applying the Jones’s method tables of values will be computed. The calculation of percentileswill be also applied to determine what WTs are more important for intense precipitation in theCanary Islands.After finishing all this procedure, the results will be discussed. First of all, the WTs classificationhas detected 1266 days of anticyclonic type (WT2), 1234 of directional types (WT1), 993 ofhybrid types (WT0), 74 days of cyclonic type (WT3) and 86 days undefined (U) (see figures 18and 19). With that, the regions obtained applying the PCA will be analysed. To do this, thepercentile 95 will be studied, because it discriminates the light rains against the heavy ones:• WRF database: (see figure 6 and table 13)− W-PC1: this component is formed by Fuerteventura and Lanzarote. There, the WTsthat usually cause heavy rains are the west winds (23.67 % of the accumulated precipitation in the 10 analysed years), the cyclonic type (16.56 % of the accumulatedprecipitation) and the northwest winds (16.41 % of the accumulated precipitation).Other WTs that are less important are the east (14.47 % of the accumulated precipitation) and the northeast winds (10.14 % of the accumulated precipitation).4− W-PC2: this one is formed by the north-western islands of the archipelago, exceptthe northeast of Tenerife and La Palma. The most important WTs in this zoneare the cyclonic type (30.32 % of the accumulated heavy precipitation) and the westwinds (25.03 % of the accumulated precipitation). Also the east (12.86 % of theaccumulated precipitation) and northeast (10.38 % of the accumulated precipitation)winds have influence.− W-PC3: this component considers the island of Gran Canaria and a part of the coastof Santa Cruz de Tenerife. In this region the cyclonic type is again very important(27.55 % of the accumulated precipitation), and also the northeast (18.72 % of theaccumulated precipitation), east (18.28 % of the accumulated precipitation) and westwinds (17.45 % of the accumulated precipitation).− W-PC4: the last component is formed by the northeast of La Palma and Tenerife, a region characterized by laurisilva that stands out because of its moisture. Thenortheast winds are now the most important WT in the region (22.00 % of the accumulated precipitation). The cyclonic type (21.18 % of the accumulated precipitation)and the west (16.40 % of the accumulated precipitation) and east winds (14.29 % ofthe accumulated precipitation) are also important for the rains in the zone.• SPREAD database: (see figure 13 and table 14)− S-PC1: this region includes almost all Fuerteventura, the south of Gran Canariaand some parts in the east of Tenerife. The WTs that cause the heaviest rains in thiszone are the west winds (34.15 % of the accumulated precipitation) and the cyclonictype (33.01 % of the accumulated precipitation). Both WTs amount nearly two thirdsof the intense rains in the region. With less prominence are the east winds (11.55 %of the accumulated precipitation).− S-PC2: this component is formed by the north-western islands, except the northand northeast of Tenerife, and the west of Gran Canaria. There, the most important WTs are the cyclonic type (35.86 % of the accumulated precipitation) and thewest winds (28.27 % of the accumulated precipitation). The southwest winds havealso importance (9.82 % of the accumulated precipitation), but much less than theaforementioned WTs.− S-PC3: this component considers Lanzarote and the north of Fuerteventura. Now,the west winds are so important (43.45 % of the accumulated precipitation), practically the double of the contribution of the cyclonic type (22.63 % of the accumulatedprecipitation). The east winds have less importance (9.98 % of the accumulate precipitation).− S-PC4: this region includes the north of the capital islands. The most importantWTs are the cyclonic type (23.62 % of the accumulated precipitation) and the northwest (18.41 % of the accumulated precipitation) and west winds (15.81 % of the accumulated precipitation). The northeast (14.60 % of the accumulated precipitation)and north winds (10.36 % of the accumulated precipitation) are important too, butto a lesser extent.5The regions W-PC2 and S-PC1 are quite similar, and also the components W-PC4 and S-PC4are slightly similar. Also, for both databases the cyclonic type is very important for the heavyrains in the archipelago, and the west and east winds too. In the other hand, the anticyclonictype hardly ever is the cause of intense precipitations in the Canary Islands, but the south andsoutheast winds have less importance than it. Finally, the northeast winds are important in theentire components calculated using WRF database, but if the SPREAD database is used, thesewinds have more importance in the north of the capital islands.
YR 2019
FD 2019
LK http://riull.ull.es/xmlui/handle/915/16274
UL http://riull.ull.es/xmlui/handle/915/16274
LA es
DS Repositorio institucional de la Universidad de La Laguna
RD 07-may-2024