Air quality forecast systems need reliable and accurate representations of the planetary boundary layer (PBL) to perform well. An important question is how accurately numerical weather prediction ...models can reproduce conditions in diverse synoptic flow types. Here, observations from the summer 2014 HygrA-CD (Hygroscopic Aerosols to Cloud Droplets) experimental campaign are used to validate simulations from the Weather Research and Forecasting (WRF) model over the complex, urban terrain of the Greater Athens Area. Three typical atmospheric flow types were identified during the 39-day campaign based on 2-day backward trajectories: Continental, Etesians, and Saharan. It is shown that the numerical model simulations differ dramatically depending on the PBL scheme, atmospheric dynamics, and meteorological parameter (e.g., 2-m air temperature). Eight PBL schemes from WRF version 3.4 are tested with daily simulations on an inner domain at 1-km grid spacing. Near-surface observations of 2-m air temperature and relative humidity and 10-m wind speed are collected from multiple meteorological stations. Estimates of the PBL height come from measurements using a multiwavelength Raman lidar, with an adaptive extended Kalman filter technique. Vertical profiles of atmospheric variables are obtained from radiosonde launches, along with PBL heights calculated using bulk Richardson number. Daytime maximum PBL heights ranged from 2.57km during Etesian flows, to as low as 0.37km during Saharan flows. The largest differences between model and observations are found with simulated PBL height during Saharan synoptic flows. During the daytime, campaign-averaged near-surface variables show WRF tended to have a cool, moist bias with higher simulated wind speeds than the observations, especially near the coast. It is determined that non-local PBL schemes give the most agreeable solutions when compared with observations.
•Intercomparison of eight PBL parametrization schemes from the WRF model in Athens.•WRF surface, vertical profiles, and PBL height compared with campaign observations.•Largest differences are found of simulated PBL height against lidar observations.•Non-local closure schemes perform best, even under diverse synoptic flow types.
•The β parameter estimates the contribution of convective precipitation to total precipitation.•The β parameter is useful to characterize convective events that can cause flash floods.•Until now, no ...trends in extreme daily precipitation had been observed in the northeast of Spain.•An observed positive trend in flash floods could be partially related to the β increase.•More concentrated and intense convective precipitation events have been observed in Catalonia.
The aim of this paper is to analyse the potential relationship between flash flood events and convective precipitation in Catalonia, as well as any related trends. The paper starts with an overview of flash floods and their trends in the Mediterranean region, along with their associated factors, followed by the definition of, identification of, and trends in convective precipitation. After this introduction the paper focuses on the north-eastern Iberian Peninsula, for which there is a long-term precipitation series (since 1928) of 1-min precipitation from the Fabra Observatory, as well as a shorter (1996–2011) but more extensive precipitation series (43 rain gauges) of 5-min precipitation. Both series have been used to characterise the degree of convective contribution to rainfall, introducing the β parameter as the ratio between convective precipitation versus total precipitation in any period. Information about flood events was obtained from the INUNGAMA database (a flood database created by the GAMA team), with the aim of finding any potential links to convective precipitation. These flood data were gathered using information on damage where flood is treated as a multifactorial risk, and where any trend or anomaly might have been caused by one or more factors affecting hazard, vulnerability or exposure. Trend analysis has shown an increase in flash flood events. The fact that no trends were detected in terms of extreme values of precipitation on a daily scale, nor on the associated ETCCDI (Expert Team on Climate Change Detection and Indices) extreme index, could point to an increase in vulnerability, an increase in exposure, or changes in land use. However, the summer increase in convective precipitation was concentrated in less torrential events, which could partially explain this positive trend in flash flood events. The β parameter has been also used to characterise the type of flood event according to the features of the precipitation. The highest values correspond to short and local events, usually with daily β values above 0.5, while the minimum threshold of daily β for catastrophic flash floods is 0.31.
A observação dos sinais da natureza ao longo da existência humana beneficiou a construção de saberes empíricos sobre o clima. O objetivo deste estudo é descrever aspectos sociais, caracterizar o ...saber local voltado à indicadores meteorológicos de previsão de precipitação a partir do conhecimento de pequenos agricultores residentes ao entorno da Reserva Biológica de Duas Bocas, município de Cariacica, estado do Espírito Santo (ES), sudeste do Brasil, localizada na Bacia Hidrográfica do Rio Duas Bocas. Foram realizadas 50 entrevistas etnográficas semiestruturadas, além da aplicação das observações participante e direta; e utilizado um diário de campo. Os agricultores são em sua maioria do sexo masculino (n=41), atuam na agricultura da região há pelo menos 40 anos e possuem baixa escolaridade com ensino fundamental incompleto principalmente. Os principais cultivos na região são banana, café e mandioca. O verão é a estação com maior produção agrícola por apresentar altas temperaturas e elevados índices pluviométricos. A maioria dos agricultores (n=41; 82%) confia na previsão etnoclimatológica derivada do conhecimento tradicional. A dinâmica atmosférica, o comportamento da fauna e os astros celestes foram os principais indicadores de chuva. O conhecimento etnoclimatológico mostra-se importante na manutenção da prática agrícola na região estudada, já que o sucesso da colheita depende deste saber local.
Precipitation on the Spanish mainland and in the Balearic archipelago exhibits a high degree of spatial and temporal variability, regardless of the temporal resolution of the data considered. The ...fractal dimension indicates the property of self-similarity, and in the case of this study, wherein it is applied to the temporal behaviour of rainfall at a fine (10-min) resolution from a total of 48 observatories, it provides insights into its more or less convective nature. The methodology of Jenkinson & Collison which automatically classifies synoptic situations at the surface, as well as an adaptation of this methodology at 500 hPa, was applied in order to gain insights into the synoptic implications of extreme values of the fractal dimension. The highest fractal dimension values in the study area were observed in places with precipitation that has a more random behaviour over time with generally high totals. Four different regions in which the atmospheric mechanisms giving rise to precipitation at the surface differ from the corresponding above-ground mechanisms have been identified in the study area based on the fractal dimension. In the north of the Iberian Peninsula, high fractal dimension values are linked to a lower frequency of anticyclonic situations, whereas the opposite occurs in the central region. In the Mediterranean, higher fractal dimension values are associated with a higher frequency of the anticyclonic type and a lower frequency of the advective type from the east. In the south, lower fractal dimension values indicate higher frequency with respect to the anticyclonic type from the east and lower frequency with respect to the cyclonic type.
ABSTRACT
This paper presents a regional and seasonal study of extreme point rainfall scaling from 10 min to 2 years. To do this, the highest point‐based rainfall list based on these temporal periods ...was calculated from the Spanish Meteorological Service (AEMET) precipitation databases with more than 11 000 rain‐gauge stations, with the longest series ranging from 1805 to 2014 (209 years). This list constitutes the register of single station largest amounts of precipitation in Spain ever recorded for selected periods, including for example the values for 2 h (193 mm), 24 h (817 mm) or 1 year (5503 mm). Rainfall extremes for 10 min periods are evenly distributed in coastal and inland areas. Daily precipitation extremes are mostly concentrated over the Mediterranean coast while from durations from one month to two years, extremes are located in southern and northwest Spain. Extreme data obtained were compared with existing worldwide rainfall records for equivalent periods. Results indicate that Spanish extreme rainfall scaling relating R depth (in mm) against D duration (in minutes) may be expressed as a potential law R = 21.8 D0.422 (R = 43.6 D0.507 for worldwide data). We propose the upper envelope line (greater or equal to extreme rainfall values) parallel to the potential fit law as a simple method to estimate possible extreme records for different time scales. Using this method, worldwide envelope may be expressed as R = 60.5 D0.507 and the Spanish envelope as R = 39.3 D0.422. Further analysis stratifying results by season and region show that seasonal scaling has more variability than regional scaling. The methodology described can be readily applied to other regions for which detailed rainfall databases exist. Applications of the results include using the scaling found as a reference for classification of heavy precipitation events for temporal scales.
Observed point‐based rainfall extremes for different durations for World (solid circles) and Spain (empty circles). Bold lines correspond to a power‐law fitting and dashed lines to the data upper envelope scaling. Black dotted lines show the proportion with respect to the WE fitting line as reference (i.e. 0.50 corresponds to 50%). Labelled numbers show the episode Id which produced the extreme rainfall (see Table 1).
As alterações climáticas relacionadas ao aquecimento global podem afetar ecossistemas, biomas e ambientes variados, o que vem acarretando amplas discussões no ambiente acadêmico, político e social ...com o intuito de desenvolver métodos para reduzir este processo fortemente influenciado pelas ações antrópicas. No entanto, para se constatar tais mudanças é necessário a utilização de critérios científicos, dessa forma, objetivou-se com este trabalho analisar a variação da precipitação e das temperaturas mínima, máxima e média do ar nas cidades de Lambari e Lavras, situadas no sul do estado de Minas Gerais. Para tanto, foram coletados dados diários de temperatura mínima, média e máxima do ar ao longo do período de 1976 à 2006 oriundos de Estações Climatológicas Principais, instaladas nas cidades citadas. Foram calculadas as temperaturas médias anuais para toda a série por meio da média aritmética dos valores diários, para as temperaturas máximas, mínimas e médias. Para a precipitação pluvial calculou-se o acumulado anual e em seguida foi feita análise de regressão linear para os referidos valores. Os resultados indicaram tendência de aumento da temperatura máxima, média e mínima do ar ao longo do tempo. Quanto à precipitação, não ficou caracterizado uma tendência de acréscimo ou decréscimo, em função do baixo valor do coeficiente de determinação.
Numerical weather prediction models play an increasingly important role in meteorology, both in short- and medium-range forecasting and global climate change studies. The most important components of ...any numerical weather prediction model are the subgrid-scale parameterization schemes, and the analysis and understanding of these schemes is a key aspect of numerical weather prediction. This book provides in-depth explorations of the most commonly used types of parameterization schemes that influence both short-range weather forecasts and global climate models. Several parameterizations are summarised and compared, followed by a discussion of their limitations. Review questions at the end of each chapter enable readers to monitor their understanding of the topics covered, and solutions are available to instructors at www.cambridge.org/9780521865401. This will be an essential reference for academic researchers, meteorologists, weather forecasters, and graduate students interested in numerical weather prediction and its use in weather forecasting.
In this paper, we illustrate a new, simple and complementary ground-based methodologyto retrieve the vertically resolved atmospheric precipitation intensity through a synergy betweenmeasurements from ...the National Aeronautics and Space Administration (NASA) Micropulse Lidarnetwork (MPLNET), an analytical model solution and ground-based disdrometer measurements.The presented results are obtained at two mid-latitude MPLNET permanent observational sites,located respectively at NASA Goddard Space Flight Center, USA, and at the Universitat Politècnicade Catalunya, Barcelona, Spain. The methodology is suitable to be applied to existing and/or futurelidar/ceilometer networks with the main objective of either providing near real-time (3 h latency)rainfall intensity measurements and/or to validate satellite missions, especially for critical lightprecipitation (<3 mm h−1).
•Rainfall data to be used in the hydrological practice is available in aggregated form.•Aggregated form produce the underestimate of annual maximum rainfall depth (Hd).•Errors in the Hd evaluation ...from data with coarse time aggregations are investigated.•Relationships to overcome the underestimate of Hd are presented.
For a few decades the local rainfall measurements are generally obtained by tipping bucket sensors, that allow to record each tipping time corresponding to a well-known rain depth. However, a considerable part of rainfall data to be used in the hydrological practice is available in aggregated form within constant time intervals. This can produce undesirable effects, like the underestimation of the annual maximum rainfall depth, Hd, associated with a given duration, d, that is the basic quantity in the development of rainfall depth-duration-frequency relationships. The errors in the evaluation of Hd from data characterized by a coarse temporal aggregation, ta, and a procedure to reduce the non-homogeneity of the Hd series are here investigated. Our results show that for ta = 1 min the underestimation is practically negligible, whereas for larger temporal aggregations with d = ta the error in a single Hd can reach values up to 50% and in a series of Hd in the average up to 17%. Relationships between the non-dimensional ratio ta/d and the average underestimation of Hd, derived through continuous rainfall data observed in many stations of Central Italy, are presented to overcome this issue. These equations allow to improve the Hd estimates and the associated depth-duration-frequency curves at least in areas with similar climatic conditions. The effect of the correction of the Hd series on the rainfall depth-duration-frequency curves is quantified. Our results indicate that the improvements obtained by the proposed procedure are of the order of 10%.
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