Coupling an ocean wave model to an atmospheric general circulation model

A coupled model, consisting of an ocean wave model and an atmospheric general circulation model (AGCM), is integrated under permanent July conditions. The wave model is forced by the AGCM wind stress, whereas the wind waves modify the AGCM surface fluxes of momentum, sensible and latent heat. We investigate the following aspects of the coupled model: how realistic are the wave fields, how strong is the coupling, and how sensitive is the atmospheric circulation to the spatially and temporally varying wave field. The wave climatology of the coupled model compares favorably with observational data. The interaction between the two models is largest (although weak) in the storm track in the Southern Hemisphere. Young windsea, which is associated with enhanced surface fluxes is generated mostly in the equatorward “frontal” area of an individual cyclone. However, the enhancement of the surface fluxes is too small to significantly modify the climatological mean atmospheric circulation

The 2010 Pakistan floods: high-resolution simulations with the WRF model

Abstract HKT-ISTP 2013 B

Estimativa do índice de área Foliar (IAF) e biomassa em pastagem no estado de Rondônia, Brasil

Medidas mensais da altura da pastagem, biomassa total, variações de biomassa viva e morta, a área específica foliar (SLA) e o Índice de Área de Folha (IAF) de fevereiro de 1999 a janeiro de 2005 na Fazenda Nossa Senhora (FNS) e em Rolim de Moura (RDM) entre Fevereiro a Março de 1999, Rondônia, Brasil. A pastagem predominante é Urochloa brizantha (Hochst. ex A. Rich) R. D. Webster (99% na FNS e 76% em RDM), com pequenas manchas de Urochloa humidicula (Rendle). A altura média anual da grama foi de ~0,16 m. Com o pastejo, o mínimo mensal foi de 0,09 m (estação seca) e máximo de 0,3 m sem pastejo (estação úmida). O IAF, biomassa total, material morto, vivo e SLA tiveram valores médios de 2,5 m2 m-2 , 2202 kg ha-1, 2916 kg ha-1 e 19 m2 kg-1 respectivamente. A média mensal da biomassa foi 4224 kg ha-1 em 2002 e 6667 kg ha-1 em 2003. Grande variação sazonal do material vivo e morto, sendo mais alto o vivo durante a estação úmida (3229 contra 2529 kg ha-1), sendo o morto maior durante a seca (2542 contra 1894 kg ha-1). O nível de água no solo variou de -3,1 a -6,5 m durante as estações. Em médias anuais os IAF foram de 1,4 em 2000 a 2,8 em 2003 e o SLA entre 16,3 m2 kg-1 em 1999 e 20,4 m2 kg-1 em 2001. As observações do Albedo variaram de 0,18 para 0,16 em relação aos altos valores de IAF

High-Resolution Simulations of the 2010 Pakistan Flood Event: Sensitivity to Parameterizations and Initialization Time

Estimating the risk of flood-generating precipitation events in high-mountain regions with complex orography is a difficult but crucial task. Quantitative precipitation forecasts (QPFs) at fine resolution are an essential ingredient to address this issue. Along these lines, the ability of the Weather Research and Forecasting (WRF) Model, operated at 3.5-km grid spacing, to reproduce the extreme meteorological event that led to the 2010 Pakistan flood and produced heavy monsoonal rain in the Indus basin is explored. The model results are compared with Tropical Rainfall Measuring Mission (TRMM) rainfall estimates, the available ground measurements, and radar observations from the CloudSat mission. In particular, the sensitivity of the WRF simulations to the use of different convective closures (explicit and Kain-Fritsch) and microphysical parameterizations (WRF single-moment 6-class microphysics scheme and Thompson) is analyzed. The impact of using different initial conditions, associated with a different initialization day, is also examined. The use of the new-generation Distributed Simulation and Stimulation System NASA Earth Observing System Simulators Suite radar simulator allows a more accurate and extensive representation of the mesoscale processes and of the interaction with the complex orography. The results reported here indicate that the quality of the large-scale initial conditions is a prominent factor affecting the possibility of retrieving a realistic representation of this event when using a nonhydrostatic regional model