A prognostic pollen emissions model for climate models (PECM1.0)

Abstract

Abstract. We develop a prognostic model of Pollen Emissions for Climate Models (PECM) for use within regional and global climate models to simulate pollen counts over the seasonal cycle based on geography, vegetation type and meteorological parameters. Using modern surface pollen count data, empirical relationships between prior-year annual average temperature and pollen season start dates and end dates are developed for deciduous broadleaf trees (Acer, Alnus, Betula, Fraxinus, Morus, Platanus, Populus, Quercus, Ulmus), evergreen needleleaf trees (Cupressaceae, Pinaceae), grasses (Poaceae; C3, C4), and ragweed (Ambrosia). This regression model explains as much as 57 % of the variance in pollen phenological dates, and it is used to create a climate-flexible phenology that can be used to study the response of wind-driven pollen emissions to climate change. The emissions model is evaluated in a regional climate model (RegCM4) over the continental United States by prescribing an emission potential from PECM and transporting pollen as aerosol tracers. We evaluate two different pollen emissions scenarios in the model: (1) using a taxa-specific land cover database, phenology and emission potential, and (2) a PFT-based land cover, phenology and emission potential. The resulting surface concentrations for both simulations are evaluated against observed surface pollen counts in five climatic subregions. Given prescribed pollen emissions, the RegCM4 simulates observed concentrations within an order of magnitude, although the performance of the simulations in any subregion is strongly related to the land cover representation and the number of observation sites used to create the empirical phenological relationship. The taxa-based model provides a better representation of the phenology of tree-based pollen counts than the PFT-based model, however we note that the PFT-based version provides a useful and climate-flexible emissions model for the general representation of the pollen phenology over the United States.

A prognostic pollen emissions model for climate models (PECM1.0)

“…4.3). It has been reported that wind-driven pollen production has increased historically and is expected, potentially, to increase in the near future (R. Zhang et al, 2014;Lake et al, 2017;Confalonieri et al, 2007;Ziello et al, 2012). Some of more effective improvements to the emissions model would be to create a pollen production model that is sensitive to multiple environmental factors such as soil moisture, temperature, and nutrient status (Jochner et al, 2013).…”

“…Zhang et al, 2015a). Only recently have regional-scale modeling studies of pollen dispersion been conducted for Europe, and they have been used to assess the impacts of climate change on airborne pollen distributions (Sofiev and Prank, 2016;Lake et al, 2017). In contrast to most meteorological pollen models, climate models require long-term (e.g., decadal-to century-scale) emissions at a range of resolutions covering continental regions up to the global scale.…”

Effect of intra-urban temperature variation on tree flowering phenology, airborne pollen, and measurement error in epidemiological studies of allergenic pollen

“…Pollen input from external regions depends on the quantity of pollen produced and its transport to the study area. Oaks are very abundant in forests across much of the United States and are expected to be some of the most prolific producers of pollen on a national scale (Wozniak and Steiner, 2017), potentially leading to relatively high external inputs of oak pollen. In cities, absolute oak abundance is low to moderate (Pennington et al, 2010;White et al, 2014;Woodall et al, 2010), potentially resulting in a relatively lower ratio of local to external pollen compared to other genera.…”

“…One potential source of variation in pollen concentrations is the timing of flowering (Devadas et al, 2018). Phenology (the timing of life history events) has been well studied (Polgar and Primack, 2011), and the flowering of temperate trees primarily depends on temperature although precipitation and photoperiod can play important roles (Gerst et al, 2017;Ibáñez et al, 2010;Wozniak and Steiner, 2017). Temperature is generally higher in urban areas than surrounding rural areas; the urban heat island effect is widespread and has been documented extensively (Imhoff et al, 2010;Rizwan et al, 2008).…”

Development and evaluation of pollen source methodologies for the Victorian Grass Pollen Emissions Module VGPEM1.0

“…In the USA, the Biogenic Emission Inventory System was adapted to emit birch and ragweed pollen and predicted the timing of the birch pollen peak to within two days (Efstathiou et al, 2011). Wozniak and Steiner (2017) modelled pollen from 13 different taxa based on plant functional type mapping for the USA, which could be used on climatic timescales. In Europe, Helbig et al (2004) simulated hazel and alder pollen emissions and transport across Germany, but did not verify their predictions as no pollen measurements were available.…”