L. Rivas Soriano

Meteorological and geo‐orographical relationships with lightning activity in Castilla‐Leon (Spain)

Some meteorological and geo-orographical factors related to cloud-to-ground flashes in Castilla-Leon (Spain) are studied. The relationship between flash density and the number of days with thunderstorms (thunderdays) is analysed, and a clear dependence and geographical variability is found. It is also shown that flashes have an average delay of four hours with respect to the time of the beginning of convection. The effect on flashes of dry static instability and moisture content is analysed by classifying days into four types according to the average values of the 850–700 hPa temperature difference and the 850 hPa dew-point temperature. A similar classification using the 700 hPa wind direction is used to analyse the effect of the mean-level flow on flashes. The results suggest that the daily number of flashes is mainly affected by the moisture content. Finally, a relationship between the cloud-to-ground flash density and geo-orographical factors (altitude, latitude and longitude) is deduced using multiple linear analysis. Copyright

Study of lightning event duration and flash rate in the Iberian Peninsula using cloud-to-ground lightning data

Abstract The average monthly, seasonal and annual lightning event duration and lightning flash rates over the Iberian Peninsula were estimated using cloud-to-ground lightning flashes for the 1992–1994 period. The total lightning event duration was over 37,000 h year −1 . Maximum values were found during the summer and were seen to be associated with mountainous areas, while minimum values were found during the winter and in the western and southern parts of the Iberian Peninsula. The spatial pattern of lightning event duration exhibited significant seasonal variations. The annual average of the mean and peak lightning flash rate was found to be 8.7 and 78.3 flashes (fl) h −1 , respectively. The temporal and spatial variations in flash rate were similar to those of lightning event duration, but with significant differences. In general, lightning flash rate exhibited fewer temporal and spatial variations than lightning event duration.

Effect of Ice on the Generation of a Generalized Potential Vorticity

Abstract In this work (using Hauf and Holler’s entropy temperature) a potential vorticity is defined that generalizes the moist potential vorticity. This “generalized” potential vorticity is used to analyze the possible effect of ice on changes of potential vorticity. The authors find that the existence of spatial gradients of ice concentration supplies a mechanism to generate “generalized” potential vorticity. An estimate of this “ice solenoid” term shows that there are cases in which this new term and the classic solenoid term could have the same order of magnitude.

Meteorology and forest fires : Conditions for ignition and conditions for development

Following the theoretical model proposed in previous papers in which four types of days and their associated fire risk (daily fire risk, DFR) were defined for each size of fire, the authors conclude that the meteorological conditions that favor the generation of fires must be similar to those that are favorable to their development. In a study of burned areas, comparative results with previous works are obtained, and the parameters DFR and NDFR (normalized DFR) are proven to be in agreement with their previously assigned physical meaning. The development rather than the ignition of forest fires is better described using the DFR and NDFR parameters.

Effects of weather types on hospital admissions for respiratory diseases in Castilla-La Mancha, Spain

The aim of this study is to evaluate the relationship between the risk of hospital admission for respiratory diseases (RD) and the daily weather types during the period 2000-2006. A synoptic climatological approach is used to investigate links between air-mass types (weather situations) and all respiratory hospital admissions in the Castilla-La Mancha (CLM) area in Spain. This afforded the main circulation weather types (CWTs) for the winter and spring periods (since respiratory hospital admissions reached their maximum during these seasons) and the frequency distributions of these types were analyzed. A summary of the main characteristics of the hospital admission series and their distribution over the seven years studied, together with the frequency distributions of the admissions classified by sex and ages, for season, month and for each day of the week, is reported. In addition, a comparison between air-mass classification and hospital admissions is made using an admission index (AI). The results reveal different responses of respiratory admission rates to the eight air-mass types identified in winter and in spring. In winter, three air massess southwesterly (SW),anti-cyclonic (A) and hybrid anti-cyclonic southwesterly (HASW), are associated with values 1.5 times higher than the respective average admission rates, while in spring no significant differences are seen.

Medium-Range Forecasting for the Number of Daily Forest Fires

Abstract In an earlier work, the authors introduced an objective forecast model for a 24-h prediction of the number of daily forest fires based on a 2-day lag autoregressive model. The meteorological inputs required for this model (temperature and geopotential height at 850 and 700 hPa and dewpoint at 850 hPa) may be predicted by a medium-range numerical weather forecast model such as that of the European Centre for Medium-Range Weather Forecasts. These predicted meteorological elements may be used to extend the range of daily forest fire forecasting. Since the forest fire forecast model is based on a categorization (type of day), an error in the meteorological predictions may not be an error in the predictive model. A meteorological error will only imply error for the model if it produces a change in the type of day (category). The forecast range for the number of forest fires per day has been extended to five days with this new model. Moreover, assuming that the weather forecast is perfect, a validation...

Generalized Static Energy and Its Conservation

Abstract The theoretical study presented here shows that it is possible to define an energetic parameter that generalizes the dry, saturated, and moist static energies. The properties of the generalized static energy (GSE) are similar to those of dry, saturated, and moist static energies, but GSE can be used in cloudy systems including water vapor, liquid water, and ice, as well as in nonequilibrium conditions. It is shown that GSE is directly related to the entropy and that it is reduced to dry, saturated, and moist static energies when appropriate assumptions are made. It is also shown that GSE is a conservative parameter when irreversibility and mass flux do not exist or are ignored.

Statistical analysis for the spatial validity of a model to forecast the daily number of forest fires

In earlier papers a qualitative and quantitative model was developed for predicting the number of forest fires occurring per day. This model permits the forecast at 00.00 hours Universal Time Convention (UTC) of any day (d), the number of forest fires per day for a range of several days (d tod+5) over a particular region. Input data are the number of forest fires in the region during two preceding days (d−2 andd−1) and the type of day (real and evaluated from radiosonde ford−2,d−1,d and predicted from meteorological medium-range forecasts, i.e. of European Centre, ford+1,d+2,d+3,d+4 andd+5. As this model requires data obtained by radiosonde, particularly temperatures and geopotentials at 850 and 700 hPa and dew points (or specific humidity) at 850 hPa, this study investigates the spatial validity of the model in relation to the distance from the radiosonde station (RS). The highest quality forecast is obtained for the region immediately surrounding the RS, and diminishes with increasing distance from it, this being due to the data obtained from the RS not being representative of the atmospheric column over the region. Hence, the derivation of the critical distance for a particular quality level of measurement. Conversely, fixed quality level implies a specific separation between RS and the region for the prediction, with a higher predictive quality implying a shorter distance.

Temporal and spatial characterization of cloud-to-ground lightning activity over Iberian Peninsula

The quantitative assessment of the impact on society of weather and climate extremes is challenging and recent years have seen a tremendous increase in economic losses from weather hazards. Is necessary to know the changes in the frequency and/or intensity of extreme events to evaluate the trend in losses. So the lightning activity plays a fundamental role as a cause of weather-related deaths, property damages and power system breakdowns. The temporal and spatial distribution of cloud-to-ground lightning activity in the Iberian Peninsula have been studied, using data of years 1992-1994,0ver 2.2 million cloud-to-ground lightning flashes were recorded. The highest lightning activity was found in the summer (79% of all lightning events in the months May to September and the diurnal variation shows a single peak with the maximum at 1700 local time. Just over 11% of all lightning flashes are observed between 0700 and 1100 local time; which represents the contribution of frontal thunderstorms to lightning activity. The lightning polarity changes throughout the year: during the warmer months positive flashes contribute only 5.9 °/0 whereas this percentage increases to 13.1‘Yo in the colder months. The geographical distribution of cloud-to-ground flashes shows a clear relationship with orography, with maximum lightning activity over Pirineos. The average maximum flash density is found to be 3,3 flashes km-zyr-l,