The structure of convective rain cells at mid-latitudes

International audienceRain cells are structures which represent an important component of convective precipitation and a study of their properties represents a necessary step both towards improved stochastic models of small-scale precipitation and for the verification of deterministic high resolution local-area models. The case of intense convective precipitation in the tropics has been analysed in a recent study (von Hardenberg et al., 2003). Here we extend the analysis to mid-latitudes and we present results on the structure of convective rain cells observed by radar measurements in Italy. In particular we consider the average shape of precipitation cells and its dependence on radar resolution and the distributions of ellipticities

Clutter and rainfall discrimination by means of doppler-polarimetric measurements and vertical reflectivity profile analysis

The estimation of rainfall rate and other parameters from radar scattering volume is heavily affected by the presence of intense sea and ground clutter and echoes which appears in anomalous propagation condition. To deal with these non meteorological echoes we present a new clutter removal algorithm which combines the results of previous works. The algorithm fully exploits both the Doppler and polarimetric capabilities of the radar used and the analysis of vertical reflectivity profile in order to achieve the better identification of the meteorological and non-meteorological targets. The algorithm has been applied to the C-band radar of Monte Settepani (Savona, Italy), which runs in a high-topography environment. Preliminary results are presented

Assessing uncertainty in radar measurements on simplified meteorological scenarios

A three-dimensional radar simulator model (RSM) developed by Haase (1998) is coupled with the nonhydrostatic mesoscale weather forecast model Lokal-Modell (LM). The radar simulator is able to model reflectivity measurements by using the following meteorological fields, generated by Lokal Modell, as inputs: temperature, pressure, water vapour content, cloud water content, cloud ice content, rain sedimentation flux and snow sedimentation flux. This work focuses on the assessment of some uncertainty sources associated with radar measurements: </p><ol> <li>absorption by the atmospheric gases, e.g., molecular oxygen, water vapour, and nitrogen; </li> <li>attenuation due to the presence of a highly reflecting structure between the radar and a &quot;target structure&quot;. </li> </ol> RSM results for a simplified meteorological scenario, consisting of a humid updraft on a flat surface and four cells placed around it, are presented

Stochastic downscaling of LAM predictions: an example in the Mediterranean area

International audienceIn the absence of a full deterministic modelling of small-scale rainfall, it is common practice to resort to the use of stochastic downscaling models to generate ensemble rainfall predictions to be used as inputs to rainfall-runoff models. Here we present an application of a novel spatial-temporal downscaling procedure based on a non-linear transformation of a linearly correlated (gaussian) field. This procedure allows for reproducing the scaling properties (if any) of the rainfall pattern and it can be easily linked with meteorological forecasts produced by limited area meteorological models

Air-entrapping capacity in the hair coverage of Malacosoma castrensis (Lasiocampidae: Lepidoptera) caterpillar: a case study.

The moth Malacosoma castrensis (Lasiocampidae) is commonly found along the Northern Germany coasts whose habitat is mainly represented by salt marshes subjected to sea level variations. Surprisingly, terrestrial caterpillars can withstand many hours being flooded by the seawater. The ability to withstand periods of submersion in a terrestrial insect raises the problem of respiration related to avoiding water percolation into the tracheal system. In the present study, we investigated under laboratory conditions the role of water-repellent cuticle structures in oxygen supply in caterpillars of M. castrensis submerged in water. For this purpose, air-layer stability tests using force measurements, and micromorphology of cuticle structures using SEM and fluorescence microscopy were performed. A plastron appeared when a caterpillar is under water. Plastron stability, its' gasses composition, and internal pressure were estimated. The plastron is stabilized by long and rare hairs, which are much thicker than the corresponding hairs of aquatic insects. Thick and stiff hairs with sclerotized basal and middle regions protrude into the water through plastron – water interface, while substantial regions of thin and flexible hairs are aligned along the plastron – water interface and their side walls can support pressure in plastron even below atmospheric pressure. Additional anchoring points between hair's stalk and microtrichia near to the hair base provide enhanced stiffness to the hair layer and prevent hair layer from collapse and water entering between hairs. Advancing contact angle on hairs is more than 90°, which is close to the effective contact angle for the whole caterpillar

Acculturation process and life domains: Different perceptions of native and immigrant adults in italy

Background: Acculturation process has taken up a relevant place in cross-cultural psychology by demonstrating the strong relationships between cultural context and individual behavioral development. Aim: The purpose of this study is to analyse acculturation strategies and attitudes in different life domains of native and immigrant adults living in Italy, following the Relative Acculturation Extended Model (RAEM). Methods: The participants were 250 Italian native and 100 immigrant adults who completed a questionnaire with items to measure their acculturation strategies (real plane) and attitudes (ideal plane), in general and related to different life domains (peripheral and central). Results: Results revealed that the acculturation attitude of immigrants is integration, whereas Italians prefer their assimilation. Conclusion: However, when different life domains are taken into account, immigrants claim to put in practice and prefer integration in most of the domains, whereas Italians perceive immigrants are separated but they prefer their assimilation or integration, depending on the specific domain

Operational verification of a framework for the probabilistic nowcasting of river discharge in small and medium size basins

Forecasting river discharge is a very important issue for the prediction and monitoring of ground effects related to severe precipitation events. The meteorological forecast systems are unable to predict precipitation on small spatial (few km) and temporal (hourly) scales. For these reasons the issuing of reliable flood forecasts is not feasible in those regions where the basin's response to rainfall events is very fast and can generate flash floods. This problem can be tackled by using rainfall nowcasting techniques based on radar observations coupled with hydrological modeling. These procedures allow the forecasting of future streamflow with a few hours' notice. However, to account for the short-term uncertainties in the evolution of fine scale precipitation field, a probabilistic approach to rainfall nowcasting is needed. These uncertainties are then propagated from rainfall to runoff through a distributed hydrological model producing a set of equi-probable discharge scenarios to be used for the flood nowcasting with time horizons of a few hours. Such a hydrological nowcasting system is presented here and applied to some case studies. A first evaluation of its applicability in an operational context is provided and the opportunity of using the results quantitatively is discussed

The flash flood of the Bisagno Creek on 9th October 2014: An “unfortunate” combination of spatial and temporal scales

SummaryOn the 9th October, 2014 a strong event hit the central part of Liguria Region producing disastrous consequences to the city of Genoa where the Bisagno Creek flooded causing one death and lots of damage. The precipitation pattern responsible for the event had peculiar spatial and temporal characteristics that led to an unexpected flash flood. The temporal sequence of rainfall intensities and the particular severity of rainfall showers at small temporal scale, together with the size of the sub-basin hit by the most intense part of the rainfall were the unfortunate concurrent ingredients that led to an “almost perfect” flash flood. The peak flow was estimated to be a 100–200years order return period.The effects of the spatial and temporal scales of the precipitation pattern were investigated by coupling a rainfall downscaling model with a hydrological model setting up an experiment that follows a probabilistic approach.Supposing that the correct volume of precipitation at different spatial and temporal scales is known, the experiment provided the probability of generating events with similar effects in terms of streamflow.Furthermore, the study gives indications regarding the goodness and reliability of the forecasted rainfall field needed, not only in terms of total rainfall volume, but even in spatial and temporal pattern, to produce the observed ground effects in terms of streamflow

Downscaling stream flow time series from monthly to daily scales using an auto-regressive stochastic algorithm: StreamFARM

Downscaling methods are used to derive stream flow at a high temporal resolution from a data series that has a coarser time resolution. These algorithms are useful for many applications, such as water management and statistical analysis, because in many cases stream flow time series are available with coarse temporal steps (monthly), especially when considering historical data; however, in many cases, data that have a finer temporal resolution are needed (daily). In this study, we considered a simple but efficient stochastic auto-regressive model that is able to downscale the available stream flow data from monthly to daily time resolution and applied it to a large dataset that covered the entire North and Central American continent. Basins with different drainage areas and different hydro-climatic characteristics were considered, and the results show the general good ability of the analysed model to downscale monthly stream flows to daily stream flows, especially regarding the reproduction of the annual maxima. If the performance in terms of the reproduction of hydrographs and duration curves is considered, better results are obtained for those cases in which the hydrologic regime is such that the annual maxima stream flow show low or medium variability, which means that they have a low or medium coefficient of variation; however, when the variability increases, the performance of the model decreases

Clutter and rainfall discrimination by means of doppler-polarimetric measurements and vertical reflectivity profile analysis

International audienceThe estimation of rainfall rate and other parameters from radar scattering volume is heavily affected by the presence of intense sea and ground clutter and echoes which appears in anomalous propagation condition. To deal with these non meteorological echoes we present a new clutter removal algorithm which combines the results of previous works. The algorithm fully exploits both the Doppler and polarimetric capabilities of the radar used and the analysis of vertical reflectivity profile in order to achieve the better identification of the meteorological and non-meteorological targets. The algorithm has been applied to the C-band radar of Monte Settepani (Savona, Italy), which runs in a high-topography environment. Preliminary results are presented