Empirical Mode Decomposition in 2-D space and time: a tool for space-time rainfall analysis and nowcasting

International audienceA data-driven method for extracting information, at temporally predictable scales, from spatial rainfall data (as measured by radar/satellite) is described, which extends the Empirical Mode Decomposition (EMD) algorithm into two dimensions. The EMD technique is used here to separate spatial rainfall data into a sequence of high through to low frequency components. This process is equivalent to a low-pass spatial filter, but based on the observed properties of the data rather than the predefined basis functions used in traditional Fourier or Wavelet decompositions. It has been suggested in the literature that the lower frequency components of spatial rainfall data exhibit greater temporal persistence than the higher frequency ones. This idea is explored here in the context of Empirical Mode Decomposition, to prepare rainfall data for nowcasts based on the temporal evolution of the lower frequency components. The paper focuses on the implementation and development of the two-dimensional extension to the EMD algorithm and it's application to radar rainfall data, as well as examining temporal persistence in the data at different spatial scales

Improved radar rainfall estimation at ground level

International audienceA technique has been developed to provide an estimate of the rainfall reaching the earth's surface by extrapolating radar data contained aloft to ground level, simultaneously estimating unknown data in the radar volume scan. The technique has been developed so as to be computationally fast, to work in real time and comprises the following steps. A rainfall classification algorithm is applied to separate the rainfall into two separate types: convective and stratiform rainfall. Climatological semivariograms based on the rainfall type are then defined and justified by testing, which result in a fast and effective means of determining the semivariogram parameters anywhere in the radar volume scan. Then, extrapolations to ground level are computed by utilising 3-D Universal and Ordinary Cascade Kriging; computational efficiency and stability in Kriging are ensured by using a nearest neighbours approach and a Singular Value Decomposition (SVD) matrix rank reduction technique. To validate the proposed technique, a statistical comparison between the temporally accumulated radar estimates and the Block Kriged raingauge estimates is carried out over matching areas, for selected rainfall events, to determine the quality of the rainfall estimates at ground level

Radar rainfall image repair techniques

International audienceThere are various quality problems associated with radar rainfall data viewed in images that include ground clutter, beam blocking and anomalous propagation, to name a few. To obtain the best rainfall estimate possible, techniques for removing ground clutter (non-meteorological echoes that influence radar data quality) on 2-D radar rainfall image data sets are presented here. These techniques concentrate on repairing the images in both a computationally fast and accurate manner, and are nearest neighbour techniques of two sub-types: Individual Target and Border Tracing. The contaminated data is estimated through Kriging, considered the optimal technique for the spatial interpolation of Gaussian data, where the "screening effect" that occurs with the Kriging weighting distribution around target points is exploited to ensure computational efficiency. Matrix rank reduction techniques in combination with Singular Value Decomposition (SVD) are also suggested for finding an efficient solution to the Kriging Equations which can cope with near singular systems. Rainfall estimation at ground level from radar rainfall volume scan data is of interest and importance in earth bound applications such as hydrology and agriculture. As an extension of the above, Ordinary Kriging is applied to three-dimensional radar rainfall data to estimate rainfall rate at ground level. Keywords: ground clutter, data infilling, Ordinary Kriging, nearest neighbours, Singular Value Decomposition, border tracing, computation time, ground level rainfall estimatio

Comparison of soil moisture fields estimated by catchment modelling and remote sensing: a case study in South Africa

International audienceThe paper compares two independent approaches to estimate soil moisture at the regional scale over a 4625 km2 catchment (Liebenbergsvlei, South Africa). The first estimate is derived from a physically-based hydrological model (TOPKAPI). The second estimate is derived from the scatterometer on board on the European Remote Sensing satellite (ERS). Results show a very good correspondence between the modelled and remotely sensed soil moisture, illustrated over two selected seasons of 8 months by regression R2 coefficients lying between 0.78 and 0.92. Such a close similarity between these two different, independent approaches is very promising for (i) remote sensing in general (ii) the use of hydrological models to back-calculate and disaggregate the satellite soil moisture estimate and (iii) for hydrological models to assimilate the remotely sensed soil moisture

A comparison of ASCAT and modelled soil moisture over South Africa, using TOPKAPI in land surface mode

In this paper we compare two independent soil moisture estimates over South Africa. The first estimate is a Soil Saturation Index (SSI) provided by automated real-time computations of the TOPKAPI hydrological model, adapted to run as a collection of independent 1 km cells with centres on a grid with a spatial resolution of 0.125°, at 3 h intervals. The second set of estimates is the remotely sensed ASCAT Surface Soil Moisture product, temporally filtered to yield a Soil Wetness Index (SWI). For the TOPKAPI cells, the rainfall forcing used is the TRMM 3B42RT product, while the evapotranspiration forcing is based on a modification of the FAO56 reference crop evapotranspiration (ET<sub>0</sub>). ET<sub>0</sub> is computed using forecast fields of meteorological variables from the Unified Model (UM) runs done by the South African Weather Service (SAWS); the UM forecast fields were used, because reanalysis is not done by SAWS. To validate these ET<sub>0</sub> estimates we compare them with those computed using observed meteorological data at a network of weather stations; they were found to be unbiased with acceptable scatter. Using the rainfall and evapotranspiration forcing data, the percentage saturation of the TOPKAPI soil store is computed as a Soil Saturation Index (SSI), for each of 6984 unconnected uncalibrated TOPKAPI cells at 3 h time-steps. These SSI estimates are then compared with the SWI estimates obtained from ASCAT. The comparisons indicate a good correspondence in the dynamic behaviour of SWI and SSI for a significant proportion of South Africa

Stochastic properties of water storage

August 1980.Includes bibliographical references (pages 46-48)

The use of hydrolysed diets for vomiting and/or diarrhoea in cats in primary veterinary practice

Objective To describe responses of cats prescribed a hydrolysed diet with or without concurrent medication for chronic vomiting and/or diarrhoea of undetermined aetiology. Materials and Methods Anonymised records of 512,213 cats under UK veterinary care in 2016 from the VetCompass database were searched using relevant terms for hydrolysed diets. The records of 5000 (90%) of 5569 cats with evidence of receiving a hydrolysed diet were randomly reviewed for gastrointestinal indication, prior and concurrent medication and response after hydrolysed dietary intervention. A poor response was defined as evidence of receiving antibiotic or glucocorticoid treatment for vomiting/diarrhoea at visits after the onset of the diet or death from gastrointestinal signs for at least 6 months follow-up. Results Of 977 cats prescribed a hydrolysed diet for chronic vomiting/diarrhoea, 697 (71%) were first prescribed the diet without concurrent antibiotics or glucocorticoids while 280 (29%) first received the diet with these medications. Thirty-four per cent of cats in the former group and 61% in the latter had a poor response. Cats older than 6 years and cats prescribed antibiotic and/or glucocorticoid for vomiting/diarrhoea before and concurrently with the diet had higher odds of poor response. Clinical Significance Although variations in our observations may reflect severity of signs or prescribing habits of primary-care veterinary surgeons, our study suggests there is merit in trialling a hydrolysed diet first as a sole therapy in cats with chronic vomiting/diarrhoea when diagnostic investigations do not reveal a cause, before resorting to antibiotic and/or glucocorticoid therapy for cases that respond poorly

Disorder predispositions and protections of Labrador Retrievers in the UK

Abstract The Labrador Retriever is one of the most popular dog breeds worldwide, therefore it is important to have reliable evidence on the general health issues of the breed. Using anonymised veterinary clinical data from the VetCompass Programme, this study aimed to explore the relative risk to common disorders in the Labrador Retriever. The clinical records of a random sample of dogs were reviewed to extract the most definitive diagnoses for all disorders recorded during 2016. A list of disorders was generated, including the 30 most common disorders in Labrador Retrievers and the 30 most common disorders in non-Labrador Retrievers. Multivariable logistic regression was used to report the odds of each of these disorders in 1462 (6.6%) Labrador Retrievers compared with 20,786 (93.4%) non-Labrador Retrievers. At a specific-level of diagnostic precision, after accounting for confounding, Labrador Retrievers had significantly increased odds of 12/35 (34.3%) disorders compared to non-Labrador Retrievers; osteoarthritis (OR 2.83) had the highest odds. Conversely, Labrador Retrievers had reduced odds of 7/35 (20.0%) disorders; patellar luxation (OR 0.18) had the lowest odds. This study provides useful information about breed-specific disorder predispositions and protections, which future research could evaluate further to produce definitive guidance for Labrador Retriever breeders and owners

Staffordshire Bull Terriers in the UK: their disorder predispositions and protections

Abstract: Background: The Staffordshire Bull Terrier is a popular dog breed in the UK but there is limited reliable evidence on disorder predispositions and protections within the breed. Using anonymised veterinary clinical data from the VetCompass™ Programme, this study aimed to identify common disorders with predisposition and protection in the Staffordshire Bull Terrier. The study hypothesised that Staffordshire Bull Terriers would have higher odds of aggression compared with non-Staffordshire Bull Terriers. Results: The clinical records of a random sample of dogs of all types were reviewed to extract the most definitive diagnoses for all disorders existing during 2016. A combined list from the 30 most common disorders in Staffordshire Bull Terriers and the 30 most common disorders in non-Staffordshire Bull Terriers was generated. Multivariable logistic regression was used to report the odds of each of these disorders in 1304 (5.8%) Staffordshire Bull Terriers compared with 21,029 (94.2%) non-Staffordshire Bull Terriers. After accounting for confounding, Staffordshire Bull Terriers had significantly increased odds of 4/36 (11.1%) disorders compared to non-Staffordshire Bull Terriers with highest odds for seizure disorder (OR 2.06; 95% CI 1.24 to 3.40; p = 0.005). Conversely, Staffordshire Bull Terriers had reduced odds of 5/36 (13.9%) disorders, with lowest odds for patellar luxation (OR 0.15; 95% CI 0.04 to 0.61; p = 0.008). There was no significant difference in the odds of aggression between Staffordshire Bull Terriers compared with non-Staffordshire Bull Terriers (OR 1.09; 95% CI 0.75 to 1.58; p = 0.644). Conclusions: This study provides a reliable evidence base of breed-specific disorder predispositions and protections that can be used by breeders to optimise breeding decisions. The findings can assist prospective owners of Staffordshire Bull Terriers to make informed decisions when acquiring a dog. From the relative number of predispositions to protections identified, there is no evidence that Staffordshire Bull Terriers have higher overall health problems than non-Staffordshire Bull Terriers