A new 'bio-comfort' perspective for Melbourne based on heat stress, air pollution and pollen.

Humans are at risk from exposure to extremes in their environment, yet there is no consistent way to fully quantify and understand the risk when considering more than just meteorological variables. An outdoor 'bio-comfort' threshold is defined for Melbourne, Australia using a combination of heat stress, air particulate concentration and grass pollen count, where comfortable conditions imply an ideal range of temperature, humidity and wind speed, acceptable levels of air particulates and a low pollen count. This is a new approach to defining the comfort of human populations. While other works have looked into the separate impacts of different variables, this is the first time that a unified bio-comfort threshold is suggested. Composite maps of surface pressure are used to illustrate the genesis and evolution of the atmospheric structures conducive to an uncomfortable day. When there is an uncomfortable day due to heat stress conditions in Melbourne, there is a high pressure anomaly to the east bringing warm air from the northern interior of Australia. This anomaly is part of a slow moving blocking high originating over the Indian Ocean. Uncomfortable days due to high particulate levels have an approaching cold front. However, for air particulate cases during the cold season there are stable atmospheric conditions enhanced by a blocking high emanating from Australia and linking with the Antarctic continent. Finally, when grass pollen levels are high, there are northerly winds carrying the pollen from rural grass lands to Melbourne, due to a stationary trough of low pressure inland. Analysis into days with multiple types of stress revealed that the atmospheric signals associated with each type of discomfort are present regardless of whether the day is uncomfortable due to one or multiple variables. Therefore, these bio-comfort results are significant because they offer a degree of predictability for future uncomfortable days in Melbourne.

On the causes of variability in amounts of airborne grass pollen in Melbourne, Australia.

In Melbourne, Australia, airborne grass pollen is the predominant cause of hay fever (seasonal rhinitis) during late spring and early summer, with levels of airborne grass pollen also influencing hospital admissions for asthma. In order to improve predictions of conditions that are potentially hazardous to susceptible individuals, we have sought to better understand the causes of diurnal, intra-seasonal and inter-seasonal variability of atmospheric grass pollen concentrations (APC) by analysing grass pollen count data for Melbourne for 16 grass pollen seasons from 1991 to 2008 (except 1994 and 1995). Some of notable features identified in this analysis were that on days when either extreme (>100 pollen grains m(-3)) or high (50-100 pollen grains m(-3)) levels of grass pollen were recorded the winds were of continental origin. In contrast, on days with a low (<20 pollen grains m(-3)) concentration of grass pollen, winds were of maritime origin. On extreme and high grass pollen days, a peak in APC occurred on average around 1730 hours, probably due to a reduction in surface boundary layer turbulence. The sum of daily APC for each grass pollen season was highly correlated (r = 0.79) with spring rainfall in Melbourne for that year, with about 60% of a declining linear trend across the study period being attributable to a reduction of meat cattle and sheep (and hence grazing land) in rural areas around Melbourne. Finally, all of the ten extreme pollen events (3 days or more with APC > 100 pollen grains m(-3)) during the study period were characterised by an average downward vertical wind anomaly in the surface boundary layer over Melbourne. Together these findings form a basis for a fine resolution atmospheric general circulation model for grass pollen in Melbourne's air that can be used to predict daily (and hourly) APC. This information will be useful to those sectors of Melbourne's population that suffer from allergic problems.

A new hurricane index for the Caribbean / Un nuevo índice de huracanes para el Caribe / Un novo índice de FuracÕes para o Caribe

A new index for hurricane development is introduced which indicates regions of the tropical ocean where tropical cyclones are likely to be generated and regions where existing cyclones would be spun-down. The index physical basis, which can be computed from the fields of sea surface temperature (SST) and evaporation, is briefly discussed. The principal result is that regions favorable to the development of tropical cyclone development are characterized by strong negative spatial gradients of evaporation with respect to SST, whereas cyclones are likely to be spun-down in regions of strong positive gradients. The application to the Caribbean region indicates a corridor of favorable conditions in the central Caribbean, possibly promoted by the presence of easterly waves, and a southern unfavorable zone that shelters the Venezuelan coast from hurricane impact. The results show in detail the reasons for the variability in hurricane seasons, using 1983 and 2005 as examples. On the large scale, the sign and strength of the SST dipole anomaly between the Pacific and the Atlantic oceans appears to be the controlling influence, a positive anomaly in the Atlantic Ocean leading to hurricane formation. The monthly standard deviation of the hurricane index simulates reasonably well the historical fluctuations in hurricane occurrence in 1979-2005, and using the results of a coupled climate model, it predicts that the hurricane season in 2051-2080 will be lengthened to include an early season maximum in June and another in September-October, in contrast to the current single maximum in September.

Se presenta un nuevo índice de desarrollo de huracanes que indica las regiones del océano tropical donde es probable que se generen ciclones tropicales y regiones donde los ciclones existentes serían atenuados. Se discute brevemente las bases físicas del índice, que pueden ser calculadas de los campos de temperatura la superficie del mar (SST) y de evaporación. El principal resultado es que las regiones favorables al desarrollo de ciclones tropicales están caracterizadas por gradientes espaciales de evaporación fuertemente negativos con respecto a SST, mientras que los ciclones tienden a ser atenuados en regiones con gradientes fuertemente positivos. La aplicación a la región caribeña indica un corredor de condiciones favorables in el Caribe central, posiblemente promovidas por la presencia de ondas del este, y una zona sur desfavorable que protege la costa venezolana del impacto de huracanes. Los resultados muestran en detalle las razones de la variabilidad en temporadas de huracanes, empleando los años 1983 y 2005 como ejemplos. A gran escala, el signo y la magnitud del dipolo de la anomalía en SST entre los océanos Pacífico y Atlántico parece ser la influencia controladora, una anomalía positiva en el Océano Atlántico que lleva a la formación de huracanes. La desviación estándar mensual del índice simula razonablemente bien las fluctuaciones históricas en la ocurrencia de huracanes en 1979-2005 y, empleando los resultados de un modelo climático acoplado, predice que las temporadas de huracanes en 2051-2080 se extenderán para incluir un máximo temprano en junio y otro en setiembre-octubre, en contraste con el máximo único actual en setiembre.

Apresenta-se um novo índice de desenvolvimento de furacões que indica as regiões do oceano tropical onde ha probabilidade de que se gerem ciclones tropicais e regiões onde os ciclones existentes seriam atenuados. Discutem-se brevemente as bases físicas do índice, que podem ser calculadas dos campos de temperatura da superfície do mar (SST) e de evaporação. O principal resultado é que as regiões favoráveis ao desenvolvimento de ciclones tropicais estão caracterizadas por gradientes espaciais de evaporação fortemente negativos em relação à SST, enquanto que os ciclones tendem a ser atenuados em regiões com gradientes fortemente positivos. A aplicação a região caribenha indica um corredor de condições favoráveis no Caribe central, possivelmente promovidas pela presença de ondas do leste, e uma zona sul desfavorável que protege a costa venezuelana do impacto de furacões. Os resultados mostram em detalhe as razões da variabilidade em temporadas de furacões, empregando os anos 1983 e 2005 como exemplos. Em grande escala, o signo e a magnitude do dipolo da anomalia em SST entre os Oceanos Pacífico e Atlântico parece ser a influência controladora, uma anomalia positiva no Oceano Atlântico que leva a formação de furacões. O desvio padrão mensal do índice simula razoavelmente bem as flutuações históricas na ocorrência de furacões no período 1979 a 2005 e, empregando os resultados de um modelo climático acoplado, prediz que as temporadas de furacões entre 2051 e 2080 se estenderão para incluir um máximo no começo de junho e outro de setembro a outubro, em contraste com o atual máximo único em setembro.