Operational assimilation of ASCAT surface soil wetness at the Met Office

Currently, no extensive, near real time, global soil moisture observation network exists. Therefore, the Met Office global soil moisture analysis scheme has instead used observations of screen temperature and humidity. A number of new space-borne remote sensing systems, operating at microwave frequencies, have been developed that provide a more direct retrieval of surface soil moisture. These systems are attractive since they provide global data coverage and the horizontal resolution is similar to weather forecasting models. Several studies show that measurements of normalised backscatter (surface soil wetness) from the Advanced Scatterometer (ASCAT) on the meteorological operational (MetOp) satellite contain good quality information about surface soil moisture. This study describes methods to convert ASCAT surface soil wetness measurements to volumetric surface soil moisture together with bias correction and quality control. A computationally efficient nudging scheme is used to assimilate the ASCAT volumetric surface soil moisture data into the Met Office global soil moisture analysis. This ASCAT nudging scheme works alongside a soil moisture nudging scheme that uses observations of screen temperature and humidity. Trials, using the Met Office global Unified Model, of the ASCAT nudging scheme show a positive impact on forecasts of screen temperature and humidity for the tropics, North America and Australia. A comparison with in-situ soil moisture measurements from the US also indicates that assimilation of ASCAT surface soil wetness improves the soil moisture analysis. Assimilation of ASCAT surface soil wetness measurements became operational during July 2010

High-resolution hydraulic parameter maps for surface soils in tropical South America

Modern land surface model simulations capture soil profile water movement through the use of soil hydraulics sub-models, but good hydraulic parameterisations are often lacking, especially in the tropics. We present much-improved gridded data sets of hydraulic parameters for surface soil for the critical area of tropical South America, describing soil profile water movement across the region to 30 cm depth. Optimal hydraulic parameter values are given for the Brooks and Corey, Campbell, van Genuchten–Mualem and van Genuchten–Burdine soil hydraulic models, which are widely used hydraulic sub-models in land surface models. This has been possible through interpolating soil measurements from several sources through the <i>SOTERLAC</i> soil and terrain data base and using the most recent pedotransfer functions (PTFs) derived for South American soils. All soil parameter data layers are provided at 15 arcsec resolution and available for download, this being 20x higher resolution than the best comparable parameter maps available to date. Specific examples are given of the use of PTFs and the importance highlighted of using PTFs that have been locally parameterised and that are not just based on soil texture. We discuss current developments in soil hydraulic modelling and how high-resolution parameter maps such as these can improve the simulation of vegetation development and productivity in land surface models

BARRA v1.0: the Bureau of Meteorology Atmospheric high-resolution Regional Reanalysis for Australia

The Bureau of Meteorology Atmospheric high-resolution Regional Reanalysis for Australia (BARRA) is the first atmospheric regional reanalysis over a large region covering Australia, New Zealand, and Southeast Asia. The production of the reanalysis with approximately 12&thinsp;km horizontal resolution – BARRA-R – is well underway with completion expected in 2019. This paper describes the numerical weather forecast model, the data assimilation methods, the forcing and observational data used to produce BARRA-R, and analyses results from the 2003–2016 reanalysis. BARRA-R provides a realistic depiction of the meteorology at and near the surface over land as diagnosed by temperature, wind speed, surface pressure, and precipitation. Comparing against the global reanalyses ERA-Interim and MERRA-2, BARRA-R scores lower root mean square errors when evaluated against (point-scale) 2&thinsp;m temperature, 10&thinsp;m wind speed, and surface pressure observations. It also shows reduced biases in daily 2&thinsp;m temperature maximum and minimum at 5&thinsp;km resolution and a higher frequency of very heavy precipitation days at 5 and 25&thinsp;km resolution when compared to gridded satellite and gauge analyses. Some issues with BARRA-R are also identified: biases in 10&thinsp;m wind, lower precipitation than observed over the tropical oceans, and higher precipitation over regions with higher elevations in south Asia and New Zealand. Some of these issues could be improved through dynamical downscaling of BARRA-R fields using convective-scale (&lt;2&thinsp;km) models.</p

Low field electron transport in a GaAs/GaAlAs superlattice

SIGLEAvailable from British Library Document Supply Centre- DSC:D96379 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Validação da assimilação de dados na inferência da refletividade de um radar com o sistema MM5 Validation of data assimilation in the inference of a radar reflectivity with the MM5 system

Em certas ocasiões o Estado do Rio Grande do Sul é assolado por sistemas meteorológico com manifestações atmosféricas atípicas e que se enquadram entre os fenômenos de mesoescala. A impossibilidade dos modelos globais simularem adequadamente diversos efeitos localizados, que ocorrem nas mais variadas regiões do globo, associada ao rápido aumento dos recursos computacionais, vem facilitando e induzindo, cada vez mais, o emprego de modelos de mesoescala para melhorar os conhecimentos sobre eventos anômalos e severos e até mesmo para utilização como ferramenta operacional em alguns centros de previsão do tempo. Para se avaliar a destreza de um modelo de mesoescala em prover previsões de precipitação, em escala espacial e temporal compatível com àquelas de um radar meteorológico Doppler, é implantado todo o sistema de modelagem de mesoescala, que constitui o MM5 na exploração da ocorrência de um evento relativamente severo de precipitação, ocorrido na região próxima da cidade de Canguçu/RS, no dia 11 de janeiro de 2008. O evento foi arbitrariamente selecionado para avaliação do modelo em inferir a refletividade do radar meteorológico instalado na cidade de Canguçu/RS, processando-se com e sem a assimilação de dados convencionais; bem como para abordar a análise da situação termo-hidrodinâmica e sinótica.<br>On certain occasions the Rio Grande do Sul State is affected by atypical weather systems events which are in the category of mesoscale phenomena. The inability of global forecast models to appropriately simulate several localized effects, which occurs over the most different regions, associated to the fast increase of computational resource, is facilitating and increasingly inducing the use of mesoscale models to improve the understanding of anomalous and severe events and also as a necessary and indispensable operational tool. In order to evaluate the skill of mesoscale model to provide precipitation forecasts, with space and time scales compatible with those of a Doppler meteorological radar, a mesoscale modeling system, the MM5, is implemented to explore the occurrence of the relatively severe precipitation event; occurred near the city of Canguçu / RS, on January 11, 2008. The event was arbitrarily selected; to evaluate the model skill in inferring the reflectivity of the meteorological radar, installed in Canguçu / RS, running the MM5 model with and without conventional data assimilations, as well as to get an approach of the thermo-hydrodynamics and synoptic conditions analysis