Based upon coupled climate simulations driven by present day and conditions resembling the Marine Isotope Stage 31 (WICE-EXP), insofar the West Antarctic Ice Sheet (WAIS) configuration is concerned, we demonstrate that changes in the WAIS orography lead to noticiable changes in the oceanic and atmospheric circulations. Compared with the present day climate, the WICE-EXP is characterized by warmer conditions in the Southern Hemisphere (SH) by up to 5 • C in the polar oceans and up to 2 • C in the Northern Hemisphere (NH). These changes feed back on the atmospheric circulation weakening (strengthening) the extratropical westerlies in the SH (northern Atlantic). Calculations of the Southern Annular Mode (SAM) show that modification of the WAIS induces warmer conditions and a northward shift of the westerly flow, in particular there is a clear weakening of the polar jet. These changes lead to modification of the rate of deep water formation reducing the magnitude of the North Atlantic Deep Water, but enhancing the Antarctic Bottom Water. By evaluating the density flux we have found that the thermal density flux has played a main role in the modification of the meridional overturning circulation. Moreover, the climate anomalies between the WICE-EXP and the present day simulations resemble a bipolar seesaw pattern. These results are in good agreement with paleorecontructions in the framework of the Ocean Drilling and ANDRILL Programs.4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 442 rium in accelerated global oceanic models.

No abstract

Fire incidence has been linked to multiple factors such as climate conditions, population density, agriculture, and lightning. Recently, fire frequency and severity have induced health problems and contributed to increase atmospheric greenhouse gases. Based on atmospheric susceptibility to fire, this study evaluates the use of a Potential Fire Index (PFIv2) to identify regions prone to fire development, as demonstrated by the satellite detected-fire in the 2001-2016 interval. It is demonstrated that PFIv2 delivers an efficiency by up to 80% in matching the observed fires from Terra/MODIS satellite. The PFIv2 is also able to reproduce more accurately areas with fire activity with respect to its previous version, the PFI. This better performance is linked to the implementation of parameterization of water pressure deficit and atmospheric stability in the lower troposphere, and a new term to represent the effect of surface temperatures, particularly in mid-latitudes and extra-Tropics. To evaluate the performance of the PFIv2 in more details, its comparison to MODIS burned areas demonstrated correlations values higher than 0.6 over the most susceptible regions such as Africa and South America, slightly lower correlation is found where fire does not primary follows the climate annual cycle, and is dominated by high frequency events. These findings indicate that the PFIv2 can be an important tool for decision makers in predicting the potential for vegetation fires development and fire danger.

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.

Based on statistical analyses and Arctic Oscillation (AO) and the Pacific-North American pattern (PNA) induced climate anomalies in the 2001–2020 interval, it has been found that these climate modes drastically influence the fire danger (PFIv2) in differing ways across coastal and inland regions. The AO induces higher fire risk in northern Eurasia and central North America, whereas the PNA increases the fire danger across southern Asia and western North America. Moreover, fires have been predominantly identified, up to 70%, during the positive phases of AO and PNA northward of 50°N, in particular over Alaska, Baltic States and eastern Asia. For coincident positive AO and negative PNA days, a large number of fires have been identified over northwestern North America and northern Eurasia. Spectral analyses demonstrate that weather anomalies related to AO and PNA lead fire danger by 10–20 days, and both modes are significantly correlated to PFIv2 over north America and most of Eurasia. Despite some drawbacks related to the fire danger methods currently applied (PFI and FWI), it is demonstrated that the influence of AO and PNA on potential environmental driven-fires can be anticipated, in some locations on almost 90% of days. Fire danger forecasts are urgently needed and the understanding of factors and conditions, which are able to modify the environmental susceptibility to fire development, are crucial for adequate management to reduce the harmful effects of fire. In this sense, our results reveal that a better prediction of the fire season can be achieved by advanced assessment of the PNA and AO behavior, and shed light on the need to investigate the impact of other modes of climate variability upon wildfire frequency and severity.