Quantifying polynya ice production in the Laptev Sea with the COSMO model

Arctic flaw polynyas are considered to be highly productive areas for the formation of sea-ice throughout the winter season. Most estimates of sea-ice production are based on the surface energy balance equation and use global reanalyses as atmospheric forcing, which are too coarse to take into account the impact of polynyas on the atmosphere. Additional errors in the estimates of polynya ice production may result from the methods of calculating atmospheric energy fluxes and the assumption of a thin-ice distribution within polynyas. The present study uses simulations using the mesoscale weather prediction model of the Consortium for Small-scale Modelling (COSMO), where polynya area is prescribed from satellite data. The polynya area is either assumed to be ice-free or to be covered with thin ice of 10 cm. Simulations have been performed for two winter periods (2007/08 and 2008/09). When using a realistic thin-ice thickness of 10 cm, sea-ice production in Laptev polynyas amount to 30 km3 and 73 km3 for the winters 2007/08 and 2008/09, respectively. The higher turbulent energy fluxes of open-water polynyas result in a 50-70% increase in sea-ice production (49 km3 in 2007/08 and 123 km3 in 2008/09). Our results suggest that previous studies have overestimated ice production in the Laptev Sea

The land surface water and energy budgets over the Tibetan Plateau

Tibetan Plateau plays an important role in the Asian Monsoon and global general circulation system. Due to the lack of quantitative observations and complicated cold season processes in high elevation terrain, however, the land surface water and energy budgets are still unexplored over this special region. In this study, the water and energy balances are analyzed in detail based on recently released land surface “reanalysis” data produced by NASA Global Land Data Assimilation System by three different land models, which first ingest all available ground and satellite data into the data assimilation system over the Tibetan Plateau. The major land surface energy and water components in the annual variability are compared. The model and data assimilation skills and deficiencies are also discussed. The total heat fluxes in the transition from heat source to heat sink is observed at the west edge of the TP during winter. But, the area and intensity is far less than the previous hypothesized. The Budyko curve for hydrology indicates that the TP is a typical dry and arid climate where evaporation is mainly controlled by precipitation

Improved meteorology and surface fluxes in mesoscale modelling using adjusted initial vertical soil moisture profiles

The Regional Atmospheric Modeling System (RAMS) is being used for different and diverse purposes, ranging from atmospheric and dispersion of pollutants forecasting to agricultural meteorology and ecological modelling as well as for hydrological purposes, among others. The current paper presents a comprehensive assessment of the RAMS forecasts, comparing the results not only with observed standard surface meteorological variables, measured at FLUXNET stations and other portable and permanent weather stations located over the region of study, but also with non-standard observed variables, such as the surface energy fluxes, with the aim of evaluating the surface energy budget and its relation with a proper representation of standard observations and key physical processes for a wide range of applications. In this regard, RAMS is assessed against in-situ surface observations during a selected period within July 2011 over Eastern Spain. In addition, the simulation results are also compared with different surface remote sensing data derived from the Meteosat Second Generation (MSG) Spinning Enhanced Visible and Infrared Imager (SEVIRI) (MSG-SEVIRI) as well as the uncoupled Land Surface Models (LSM) Global Land Data Assimilation System (GLDAS). Both datasets complement the available in-situ observations and are used in the current study as the reference or ground truth when no observations are available on a selected location. Several sensitivity tests have been performed involving the initial soil moisture content, by adjusting this parameter in the vertical soil profile ranging from the most superficial soil layers to those located deeper underground. A refined adjustment of this parameter in the initialization of the model has shown to better represent the observed surface energy fluxes. The results obtained also show an improvement in the model forecasts found in previous studies in relation to standard observations, such as the air temperature and the moisture fields. Therefore, the application of a drier or wetter soil in distinct soil layers within the whole vertical soil profile has been found to be crucial in order to produce a better agreement between the simulation and the observations, thus reiterating the determining role of the initial soil moisture field in mesoscale modelling, but in this case considering the variation of this parameter vertically

Global and direct solar radiation at surface over Iberian Peninsula: variability, trends and forecasting

Besides being the key to Earth's climate, global solar radiation at the surface ( ) is one of the most valuable renewable resources. This way, an adequate knowledge of the solar resource is critical as an assessment for a strategic planning of projects related to the production of solar energy. Therefore, the main goals of this thesis is to analyze past changes and variability of solar radiation fluxes in Portugal and Iberia Peninsula (IP) using observational available measurements, ERA−40 and NCEP/NCAR reanalysis datasets and, predict and characterize the solar radiation at the surface over Iberian Peninsula based on numerical weather prediction models. In a first part, this study is dedicated to the analysis of temporal and spatial variability of based on ground-based stations, as well as in ERA−40 and NCEP/NCAR reanalysis. Parametric and non-parametric tests are applied to detect trends in both reanalysis and ground-based observations. Cloud cover obtained from reanalysis is also used to examine the possible causes of the observed long-term changes in . In a second stage, is presented an assessment of the W model at high resolution ( 5 ) against observations and with another configuration. After a bias removal process, a and cloud cover climatology was obtained for IP (1950−2010 period). Finally, the performance of IFS/ECMWF is evaluated to predict Direct Normal Irradiance (DNI) over Évora city at very short (1 hour) and short term (1 to 3 days), for one year period. It is also described a new methodology to compute DNI attenuation using in situ observational data in order to estimate the transparency of the atmosphere in the absence of cloud cover datasets. To improve IFS/ECMWF outputs is also tested a bias correction methodology; Resumo: A Radiação Solar Global e Direta à Superfície na Península Ibérica: Variabilidade, Tendências e Previsão A radiação solar é um dos recursos energéticos renováveis mais valiosos. Na Península Ibérica (PI) estão em instalação muitos sistemas comerciais e de investigação para o aproveitamento da energia solar. Neste contexto, o conhecimento do fluxo de radiação solar que incide na superfície terrestre e da sua evolução torna-se de extrema importância. Pretende-se com este trabalho estudar a distribuição espacial, a variabilidade e as tendências da radiação solar de pequeno comprimento de onda ( ) à superfície, na PI e em Portugal, a partir de dados observacionais e das reanálises ERA−40/NCEP assim como, prever e caracterizar a radiação com base em modelos de previsão numérica do tempo. Na primeira parte deste estudo, efetua-se uma análise da variabilidade temporal e espacial da radiação recorrendo a estações terrestres, bem como a dados de reanálise ERA−40 e NCEP/NCAR. Para o efeito utilizam-se testes paramétricos e não paramétricos a fim de detetar tendências nas séries em estudo. A cobertura de nuvens obtida a partir das reanálises é também usada para avaliar as possíveis causas da variabilidade da radiação observada. Numa segunda etapa do estudo, obteve-se uma climatologia a 5 de resolução da radiação solar à superfície com base em simulações com o modelo regional − , para a PI, e para o período 1950−2010. Os resultados das simulações foram validados recorrendo a estações de observação e a uma outra simulação , com outra configuração, previamente validada. Na construção da climatologia e de nuvens foi aplicado um método de pós-processamento para remoção do viés. Finalmente, avalia-se o desempenho do modelo IFS, do ECMWF na previsão da radiação DNI a curto e médio prazo, sobre a região. Propõe-se uma nova metodologia para estimar a transparência da atmosfera e testa-se uma metodologia de correção de viés

Improving Forecasts Of Winter Storm Tracks Using A Local Ensemble

Winter storms can affect millions of people, with impacts such as disruptions to transportation, hazards to human health, reduction in retail sales, and structural damage. Blizzard forecasts for Alberta Clippers can be a particular challenge in the Northern Plains, as these systems typically depart from the Canadian Rockies, intensify, and impact the Northern Plains all within 24 hours. The purpose of this study is to determine whether probabilistic forecasts derived from a local physics-based ensemble can improve specific aspects of winter storm forecasts for three Alberta Clipper cases. Verification is performed on the ensemble members and ensemble mean with a focus on quantifying uncertainty in the storm track, two-meter winds, and precipitation using the MERRA and NOHRSC SNODAS datasets. This study finds that addition improvements are needed to proceed with operational use of the ensemble blizzard products, but the use of a proxy for blizzard conditions yields promising results