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1.
Summary This paper presents a climatological application of the combination of remote sensing data and multivariate analysis. It proposes a methodology to perform an agroclimatic characterization of a region with the aim of determining homogeneous areas. This methodology is applied to Catalonia, in the northwest of the Mediterranean Sea, in the Iberian Peninsula. To this end various multivariate analysis techniques have been applied to data from 107 meteorological stations and to digitally processed AVHRR images from a NOAA satellite (ground surface temperature and thermal inertia). Values of emissivity and albedo for different land uses and phenomenological states, in addition to the most suitable algorithms for the soil surface temperature, have been obtained. Combining this information with orographic characteristics and the Papadakis classification, a final map is obtained with 68 homogeneous zones for the period between April and October, the most important for the agriculture of the area studied.With 5 Figures 相似文献
2.
Marco Turco Maria-Carmen Llasat Jost von Hardenberg Antonello Provenzale 《Climatic change》2014,125(3-4):369-380
We analyse the observed climate-driven changes in summer wildfires and their future evolution in a typical Mediterranean environment (NE Spain). By analysing observed climate and fire data from 1970 to 2007, we estimate the response of fire number (NF) and burned area (BA) to climate trends, disentangling the drivers responsible for long-term and interannual changes by means of a parsimonious Multi Linear Regression model (MLR). In the last forty years, the observed NF trend was negative. Here we show that, if improvements in fire management were not taken into account, the warming climate forcing alone would have led to a positive trend in NF. On the other hand, for BA, higher fuel flammability is counterbalanced by the indirect climate effects on fuel structure (i.e. less favourable conditions for fine-fuel availability and fuel connectivity), leading to a slightly negative trend. Driving the fire model with A1B climate change scenarios based on a set of Regional Climate Models from the ENSEMBLES project indicates that increasing temperatures promote a positive trend in NF if no further improvements in fire management are introduced. 相似文献
3.
C. Price Y. Yair A. Mugnai K. Lagouvardos M. C. Llasat S. Michaelides U. Dayan S. Dietrich F. Di Paola E. Galanti L. Garrote N. Harats D. Katsanos M. Kohn V. Kotroni M. Llasat-Botija B. Lynn L. Mediero E. Morin K. Nicolaides S. Rozalis K. Savvidou B. Ziv 《Surveys in Geophysics》2011,32(6):733-751
One of the costliest natural hazards around the globe is flash floods, resulting from localized intense convective precipitation over short periods of time. Since intense convective rainfall (especially over the continents) is well correlated with lightning activity in these storms, a European Union FP6 FLASH project was realized from 2006 to 2010, focusing on using lightning observations to better understand and predict convective storms that result in flash floods. As part of the project, 23 case studies of flash floods in the Mediterranean region were examined. For the analysis of these storms, lightning data were used together with rainfall estimates in order to understand the storms?? development and electrification processes. In addition, these case studies were simulated using mesoscale meteorological models to better understand the local and synoptic conditions leading to such intense and damaging storms. As part of this project, tools for short-term predictions (nowcasts) of intense convection across the Mediterranean and Europe, and long-term forecasts (a few days) of the likelihood of intense convection, were developed and employed. The project also focused on educational outreach through a special Web site http://flashproject.org supplying real-time lightning observations, real-time experimental nowcasts, medium-range weather forecasts and educational materials. While flash floods and intense thunderstorms cannot be prevented, long-range regional lightning networks can supply valuable data, in real time, for warning the public, end-users and stakeholders of imminent intense rainfall and possible flash floods. 相似文献
4.
Use of Systematic, Palaeoflood and Historical Data for the Improvement of Flood Risk Estimation. Review of Scientific Methods 总被引：2，自引：0，他引：2
Gerardo Benito Michel Lang Mariano Barriendos M. Carmen Llasat Felix Francés Taha Ouarda Varyl Thorndycraft Yehouda Enzel Andras Bardossy Denis Coeur Bernard Bobée 《Natural Hazards》2004,31(3):623-643
The catastrophic floods recently occurring in Europe warn of the critical need forhydrologic data on floods over long-time scales. Palaeoflood techniques provideinformation on hydrologic variability and extreme floods over long-time intervals(100 to 10,000 yr) and may be used in combination with historical flood data (last1,000 yr) and the gauge record (last 30–50 yr). In this paper, advantages anduncertainties related to the reconstruction of palaeofloods in different geomorphologicalsettings and historical floods using different documentary sources are described.Systematic and non-systematic data can be combined in the flood frequency analysisusing different methods for the adjustment of distribution functions. Technical toolsintegrating multidisciplinary approaches (geologic, historical, hydraulic and statistical)on extreme flood risk assessment are discussed. A discussion on the potential theoreticalbases for solving the problem of dealing with non-systematic and non-stationary data ispresented. This methodology is being developed using new methodological approachesapplied to European countries as a part of a European Commission funded project (SPHERE). 相似文献
5.
The main objective of the present paper is to show a methodology for undertaking rainfall regionalization of a region taking into account the convective features of the precipitation, and useful for establishing homogeneous zones for improving the alert system. This methodology has been applied to a hydrographic region located in northeast Spain, with an area of 16000 km2 and characterized by a highly contrasted topography. Information provided by meteorological radar and 5-min precipitation data for 126 automatic raingauges has been used for the period 1996–2002. The previous analysis done on the basis of the 1927–1981 rainfall rate series for the Jardí raingauge, located in Barcelona, has also been considered. To that end, the first step was to draw up a proposal for classification of the pluviometric episodes. Recourse was had for this purpose to definition of the β parameter, related with the greater or lesser convective character of the event and calculated on the basis of the rainfall intensity at the surface (Llasat, 2001) and, when data are available, on the basis of radar reflectivity. Results show that the threshold of 35 mm/h to characterize convective episodes from raingauge data can be corroborated from the radar point of view when convective precipitation is identified using 2-D algorithms with a reflectivity threshold of 43 dBZ. Once the soundness of the β parameter had been corroborated, it was applied to more than 2900 precipitation episodes recorded in the region, in order to discriminate the features of the different subregions and their time and space distribution throughout the entire series of the samples. Using this definition, 92% of the precipitation events recorded in this region, with accumulated rainfall above 35 mm, are classified as convective ones, representing 95% of the precipitation amount. Application of the β parameter combined with monthly rainfall data allows differentiation of 8 regions with different convective precipitation features. 相似文献
6.
The aim of this paper is to show a climatology of Mesoscale Convective Systems (MCS) in the NE of the Iberian Peninsula, on the basis of meteorological radar observations. Special attention was paid to those cases that have produced heavy rainfalls during the period 1996–2000. Identification of the MCS was undertaken using two procedures. Firstly, the precipitation structures at the lowest level were recognised by means of a 2D algorithm that distinguishes between convective and non-convective contribution. Secondly, the convective cells were identified using a 3D procedure quite similar to the SCIT (Storm Cell Identification and Tracking) algorithm that looks for the reflectivity cores in each radar volume. Finally, the convective cells (3D) were associated with the 2D structures (convective rainfall areas), in order to characterize the complete MCS. Once this methodology was presented the paper offers a proposal for classifying the precipitation systems, and particularly the MCS. 57 MCS structures were classified: 49% of them were identified as linearly well-organised systems, called TS (39%), LS (18%) and NS (43%). In addition to the classification, the following items were analysed for each MCS found: duration, season, time of day, area affected and direction of movement, and main radar parameters related with convection. The average features of those MCS show an area of about 25000 km2, Zmax values of 47 dBz, an echotop of 12 km, the maximum frequency at 12 UTC and early afternoon and a displacement towards E-NE. The study was completed by analysing the field at surface, the presence of a mesoscale low near the system and the quasi-stationary features of three cases related with heavy rainfalls. Maximum rainfall (more then 200 mm in 6 h) was related with the presence of a cyclone in combination with the production of a convective train effect. 相似文献
7.
The main meteorological features of catastrophic rainfall events in Catalonia are described. Data come from several sources listed in the text. Surface and upper air synoptic and some subsynoptic conditions under which these events occur are described. Two kinds of events are identified, depending on the amount of forced lift required to release potential instability: Type A events, which take place on the coastal area when the forcing due to littoral and prelittoral hills is enough, and type B events require a large forced lift and occur near the Pyrenees. Local topographical and mesoscale meteorological conditions turn out to have a relevant role in connection with such events. 相似文献
8.
Marco Turco Maria Carmen Llasat Jost von Hardenberg Antonello Provenzale 《Climatic change》2013,116(3-4):665-678
We analyse the impact of climate interannual variability on summer forest fires in Catalonia (northeastern Iberian Peninsula). The study period covers 25 years, from 1983 to 2007. During this period more than 16000 fire events were recorded and the total burned area was more than 240 kha, i.e. around 7.5% of whole Catalonia. We show that the interannual variability of summer fires is significantly correlated with summer precipitation and summer maximum temperature. In addition, fires are significantly related to antecedent climate conditions, showing positive correlation with lagged precipitation and negative correlation with lagged temperatures, both with a time lag of two years, and negative correlation with the minimum temperature in the spring of the same year. The interaction between antecedent climate conditions and fire variability highlights the importance of climate not only in regulating fuel flammability, but also fuel structure. On the basis of these results, we discuss a simple regression model that explains up to 76% of the variance of the Burned Area and up to 91% of the variance of the number of fires. This simple regression model produces reliable out-of-sample predictions of the impact of climate variability on summer forest fires and it could be used to estimate fire response to different climate change scenarios, assuming that climate-vegetation-humans-fire interactions will not change significantly. 相似文献
9.
Summary Over the last 25 years the term “cold pool” has come to be used in many spheres as a synonym for floods. This has given rise
to a major confusion that has even moved into international scientific and technical circles. In this paper we analyse how
the concept of “cold air pool” has evolved from when it was defined at the beginning of the 20th century down to the present
day, in which the Spanish term “DANA” (similar to a cut-off low) has been introduced in order to avoid existing confusions.
In the course of the paper we take account of cold air pool genesis and their thermal and dynamic characteristics, and we
discuss the factors that have led to them being identified (erroneously) with heavy rainfall events. The study takes as its
basis a systematic analysis of all the cold air pools recorded in Europe, and particularly in the Iberian Peninsula, over
the period 1974–1983, as well as in studies of the floods recorded in eastern Spain since 1950 until nowadays. The discussion
done on the basis of this accurate analysis leads to the identification of a cold air pool as a type cut-off low (COL) and
justifying the use of this more generic term when a structure like this is present in a heavy rainfall event. For a better
illustration of the previous discussion and understanding of the role of COLs in intense rainfall events, we present the episode
of September 1971 in Catalonia, in which over 400 mm were recorded. The analysis was carried out with the MM5 initialised
with the ERA-40 re-analyses. The results show that the role of COLs in the heavy rainfall episodes recorded in Spain is mainly
dynamic, both in terms of the circulation they create at low levels and the potential vorticity anomaly generated. This circulation
draws in very warm, moist and potentially unstable air perpendicularly to the coast and the littoral mountain chains. The
factor of thermal instability, owing to the presence of cold air at medium and higher levels, shows itself to be more important
in zones where this warm moist advection at low levels is not as significant as in the Mediterranean zone. 相似文献
10.
A diagnostic study of the synoptic aspects of two cases of heavy rain producing floods in Catalonia (northeast corner of the Iberian peninsula) is presented. The diagnosis consists in the determination of the area where large scale circulation induces favorable conditions for development of thunderstorms. We identify these conditions as upward quasi-geostrophic forcing, convergence of water vapor at low levels and convective instability in the lower troposphere. A composite chart showing where the three synoptic mechanisms overlap determines the area. Local studies of instability are carried out from upper air data given by the radiosonde ascents of Palma de Mallorca, looking for both the Convective Available Potential Energy and Bulk Richardson number and its temporal evolution during the events. 相似文献