scholarly journals Quantifying Bioaerosol Concentrations in Dust Clouds through Online UV-LIF and Mass Spectrometry Measurements at the Cape Verde Atmospheric Observatory

2020 ◽  
Author(s):  
Douglas Morrison ◽  
Ian Crawford ◽  
Nicholas Marsden ◽  
Michael Flynn ◽  
Katie Read ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Cape Verde ◽  
Ecosystem Impacts ◽  
Mass Spectral ◽  
Relative Contribution ◽  
Dust Events ◽  
Coarse Aerosol

Abstract. Observations of the long-range transport of biological particles in the tropics via dust vectors are now seen as fundamental to the understanding of many global atmosphere-oceanic biogeochemical cycles, changes in air quality, human health, ecosystem impacts, and climate. However, there is a lack of long-term measurements quantifying their presence in such conditions. Here we present annual observations of bioaerosol concentrations based on online ultraviolet light induced fluorescence (UV-LIF) spectrometry from the global WMO/Global Atmospheric Watch (GAW) observatory on Sao Vicente Cape Verde Atmospheric Observatory. We observe the expected strong seasonal changes in absolute concentrations of bioaerosols with significant enhancements during winter due to the strong island inflow of airmass, originating from the African continent. Monthly median bioaerosol concentrations as high as 45 L−1 were found with 95th percentile values exceeding 130 L−1 during strong dust events. However, in contrast the relative fraction of bioaerosol numbers compared to total dust number concentration shows little seasonal variation. Mean bioaerosol contributions accounted for 0.4 ± 0.2 % of total coarse aerosol concentrations, only rarely exceeding 1 % during particularly strong events under appropriate conditions. Although enhancements in the median bioaerosol fraction do occur in winter, they also occur at other times of the year, likely due to the enhanced Aeolian activity driving dust events at this time from different sources. We hypothesise that this indicates the relative contribution of bioaerosol material in dust transported across the tropical Atlantic throughout the year is relatively uniform, comprised mainly of mixtures of dust and bacteria and/or bacterial fragments. We argue that this hypothesis is supported from analysis of measurements also at Cape Verde just prior to the long-term monitoring experiment where UV-LIF single particle measurements were compared with Laser Ablation Aerosol Particle Time of Flight mass spectrometer (LAAP-ToF) measurements. These clearly show a very high correlation between particles with mixed bio-silicate mass spectral signatures and UV-LIF bio-fluorescent signatures suggesting the bioaerosol concentrations are dominated by these mixtures. These observations should assist with constraining bioaerosol concentrations for tropical Global Climate Model (GCM) simulations. Note here we use the term “bioaerosol” to include mixtures of dust and bacterial material.

scholarly journals Quantifying bioaerosol concentrations in dust clouds through online UV-LIF and mass spectrometry measurements at the Cape Verde Atmospheric Observatory

2020 ◽  
Vol 20 (22) ◽  
pp. 14473-14490
Author(s):  
Douglas Morrison ◽  
Ian Crawford ◽  
Nicholas Marsden ◽  
Michael Flynn ◽  
Katie Read ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Cape Verde ◽  
Ecosystem Impacts ◽  
Mass Spectral ◽  
Relative Contribution ◽  
Dust Events ◽  
Coarse Aerosol

Abstract. Observations of the long-range transport of biological particles in the tropics via dust vectors are now seen as fundamental to the understanding of many global atmosphere–ocean biogeochemical cycles, changes in air quality, human health, ecosystem impacts, and climate. However, there is a lack of long-term measurements quantifying their presence in such conditions. Here, we present annual observations of bioaerosol concentrations based on online ultraviolet laser-induced fluorescence (UV-LIF) spectrometry from the World Meteorological Organization – Global Atmospheric Watch (WMO-GAW) Cape Verde Atmospheric Observatory on São Vicente. We observe the expected strong seasonal changes in absolute concentrations of bioaerosols with significant enhancements during winter due to the strong island inflow of air mass, originating from the African continent. Monthly median bioaerosol concentrations as high as 45 L−1 were found with 95th percentile values exceeding 130 L−1 during strong dust events. However, in contrast, the relative fraction of bioaerosol numbers compared to total dust number concentration shows little seasonal variation. Mean bioaerosol contributions accounted for 0.4 ± 0.2 % of total coarse aerosol concentrations, only rarely exceeding 1 % during particularly strong events under appropriate conditions. Although enhancements in the median bioaerosol fraction do occur in winter, they also occur at other times of the year, likely due to the enhanced Aeolian activity driving dust events at this time from different sources. We hypothesise that this indicates the relative contribution of bioaerosol material in dust transported across the tropical Atlantic throughout the year is relatively uniform, comprised mainly of mixtures of dust and bacteria and/or bacterial fragments. We argue that this hypothesis is supported from analysis of measurements also at Cabo Verde just prior to the long-term monitoring experiment where UV-LIF single particle measurements were compared with laser ablation aerosol particle time-of-flight mass spectrometer (LAAP-ToF) measurements. These clearly show a very high correlation between particles with mixed biosilicate mass spectral signatures and UV-LIF biofluorescent signatures suggesting the bioaerosol concentrations are dominated by these mixtures. These observations should assist with constraining bioaerosol concentrations for tropical global climate model (GCM) simulations. Note that here we use the term “bioaerosol” to include mixtures of dust and bacterial material.

scholarly journals A comprehensive history of climate and habitat stability of the last 800&thinsp,000 years

2019 ◽  
Author(s):  
Mario Krapp ◽  
Robert Beyer ◽  
Stephen L. Edmundson ◽  
Paul J. Valdes ◽  
Andrea Manica
Keyword(s):  
Climate Model ◽  
Temporal Dynamics ◽  
Global Climate ◽  
Global Climate Model ◽  
Regional Scale ◽  
Geological Time ◽  
Comprehensive Overview ◽  
Long Term Stability ◽  
History Of

Abstract. A detailed and accurate reconstruction of the past climate is essential in understanding the interactions between ecosystems and their environment through time. We know that climatic drivers have shaped the distribution and evolution of species, including our own, and their habitats. Yet, spatially-detailed climate reconstructions that continuously cover the Quaternary do not exist. This is mainly because no paleoclimate model can reconstruct regional-scale dynamics over geological time scales. Here we develop a statistical emulator, the Global Climate Model Emulator (GCMET), which reconstructs the climate of the last 800 000 years with unprecedented spatial detail. GCMET captures the temporal dynamics of glacial-interglacial climates as an Earth System Model of Intermediate Complexity would whilst resolving the local dynamics with the accuracy of a Global Climate Model. It provides a new, unique resource to explore the climate of the Quaternary, which we use to investigate the long-term stability of major habitat types. We identify a number of stable pockets of habitat that have remained unchanged over the last 800 thousand years, acting as potential long-term evolutionary refugia. Thus, the highly detailed, comprehensive overview of climatic changes through time delivered by GCMET provides the needed resolution to quantify the role of long term habitat change and fragmentation in an ecological and anthropological context.

scholarly journals Influence of albedo parameterization on surface mass balance in the perspective of Greenland ice sheet modelling in EC-Earth

2016 ◽  
Author(s):  
Michiel Helsen ◽  
Roderik Van de Wal ◽  
Thomas Reerink ◽  
Richard Bintanja ◽  
Marianne Sloth Madsen ◽  
...  
Keyword(s):  
Mass Balance ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
Surface Mass

Abstract. The albedo of the surface of ice sheets changes as a function of time, due to the effects of deposition of new snow, ageing of dry snow, melting and runoff. Currently, the calculation of the albedo of ice sheets is highly parameterized within the Earth System Model EC-Earth, by taking a constant value for areas with thick perennial snow cover. This is one of the reasons that the surface mass balance (SMB) of the Greenland ice sheet (GrIS) is poorly resolved in the model. To improve this, eight snow albedo schemes are evaluated here. The resulting SMB is downscaled from the lower resolution global climate model topography to the higher resolution ice sheet topography of the GrIS, such that the influence of these different SMB climatologies on the long-term evolution of the GrIS is tested by ice sheet model simulations. This results in an optimised albedo parameterization that can be used in future EC-Earth simulations with an interactive ice sheet component.

scholarly journals On the importance of the albedo parameterization for the mass balance of the Greenland ice sheet in EC-Earth

2017 ◽  
Vol 11 (4) ◽  
pp. 1949-1965 ◽  
Author(s):  
Michiel M. Helsen ◽  
Roderik S. W. van de Wal ◽  
Thomas J. Reerink ◽  
Richard Bintanja ◽  
Marianne S. Madsen ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Mass Balance ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Snow Albedo

Abstract. The albedo of the surface of ice sheets changes as a function of time due to the effects of deposition of new snow, ageing of dry snow, bare ice exposure, melting and run-off. Currently, the calculation of the albedo of ice sheets is highly parameterized within the earth system model EC-Earth by taking a constant value for areas with thick perennial snow cover. This is an important reason why the surface mass balance (SMB) of the Greenland ice sheet (GrIS) is poorly resolved in the model. The purpose of this study is to improve the SMB forcing of the GrIS by evaluating different parameter settings within a snow albedo scheme. By allowing ice-sheet albedo to vary as a function of wet and dry conditions, the spatial distribution of albedo and melt rate improves. Nevertheless, the spatial distribution of SMB in EC-Earth is not significantly improved. As a reason for this, we identify omissions in the current snow albedo scheme, such as separate treatment of snow and ice and the effect of refreezing. The resulting SMB is downscaled from the lower-resolution global climate model topography to the higher-resolution ice-sheet topography of the GrIS, such that the influence of these different SMB climatologies on the long-term evolution of the GrIS is tested by ice-sheet model simulations. From these ice-sheet simulations we conclude that an albedo scheme with a short response time of decaying albedo during wet conditions performs best with respect to long-term simulated ice-sheet volume. This results in an optimized albedo parameterization that can be used in future EC-Earth simulations with an interactive ice-sheet component.

scholarly journals Sensitivity study of the REMO regional climate model to domain size

2021 ◽  
Vol 18 ◽  
pp. 157-167
Author(s):  
Réka Suga ◽  
Otília A. Megyeri-Korotaj ◽  
Gabriella Allaga-Zsebeházi
Keyword(s):  
Regional Climate Model ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Regional Climate ◽  
Domain Size ◽  
Sensitivity Study ◽  
Horizontal Resolution ◽  
Precipitation Indices

Abstract. In the framework of the KlimAdat national project, the Hungarian Meteorological Service (OMSZ) is aiming to perform 10 km horizontal resolution simulations with the 2015 version of the REMO regional climate model over Central and Eastern Europe. The long-term simulations were preceded by a 10-year long sensitivity study on domain size, which is summarised in this paper. We selected three different domains embedded in each other, which contain the whole area of the Danube and Tisza river catchments. Lateral boundary conditions were obtained from the 50 km resolution REMO driven by the MPI-ESM-LR global climate model. Simulations were performed for the period of 1970–1980 including 1-year spin-up. Monthly and seasonal means of daily 2 m temperature, precipitation sum and several precipitation indices were evaluated. Reference datasets were E-OBS 19.0 and CarpatClim-HU. We can conclude, that the selection of domain size has a larger impact on the simulation of precipitation, and in the case of the seasonal mean of the precipitation indices, the differences amongst the results obtained on each model domain exceed 10 %. In general, the smallest biases occurred on the largest domain, therefore further long-term simulations are being produced on this domain.

scholarly journals Origins of multi-decadal variability in sudden stratospheric warmings

2021 ◽  
Vol 2 (1) ◽  
pp. 205-231
Author(s):  
Oscar Dimdore-Miles ◽  
Lesley Gray ◽  
Scott Osprey
Keyword(s):  
Climate Model ◽  
Decadal Variability ◽  
Global Climate ◽  
Global Climate Model ◽  
Low Frequency ◽  
Polar Vortex ◽  
Major Influence ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex

Abstract. Sudden stratospheric warmings (SSWs) are major disruptions of the Northern Hemisphere (NH) stratospheric polar vortex and occur on average approximately six times per decade in observation-based records. However, within these records, intervals of significantly higher and lower SSW rates are observed, suggesting the possibility of low-frequency variations in event occurrence. A better understanding of factors that influence this decadal variability may help to improve predictability of NH midlatitude surface climate, through stratosphere–troposphere coupling. In this work, multi-decadal variability of SSW events is examined in a 1000-year pre-industrial simulation of a coupled global climate model. Using a wavelet spectral decomposition method, we show that hiatus events (intervals of a decade or more with no SSWs) and consecutive SSW events (extended intervals with at least one SSW in each year) vary on multi-decadal timescales of periods between 60 and 90 years. Signals on these timescales are present for approximately 450 years of the simulation. We investigate the possible source of these long-term signals and find that the direct impact of variability in tropical sea surface temperatures, as well as the associated Aleutian Low, can account for only a small portion of the SSW variability. Instead, the major influence on long-term SSW variability is associated with long-term variability in amplitude of the stratospheric quasi-biennial oscillation (QBO). The QBO influence is consistent with the well-known Holton–Tan relationship, with SSW hiatus intervals associated with extended periods of particularly strong, deep QBO westerly phases. The results support recent studies that have highlighted the role of vertical coherence in the QBO when considering coupling between the QBO, the polar vortex and tropospheric circulation.

High bit rate ACTS experiments for performing global science - Keck Telescope and global climate model

1996 ◽  
Author(s):  
Larry Bergman ◽  
J. Gary ◽  
Burt Edelson ◽  
Neil Helm ◽  
Judith Cohen ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Bit Rate ◽  
Global Science ◽  
High Bit Rate

scholarly journals A comparison of ship and satellite measurements of cloud properties with global climate model simulations in the southeast Pacific stratus deck

2010 ◽  
Vol 10 (14) ◽  
pp. 6527-6536 ◽  
Author(s):  
M. A. Brunke ◽  
S. P. de Szoeke ◽  
P. Zuidema ◽  
X. Zeng
Keyword(s):  
Diurnal Cycle ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Cloud Fraction ◽  
Cloud Base ◽  
Liquid Water Path ◽  
Cloud Properties ◽  
Southeast Pacific ◽  
Cloud Thickness

Abstract. Here, liquid water path (LWP), cloud fraction, cloud top height, and cloud base height retrieved by a suite of A-train satellite instruments (the CPR aboard CloudSat, CALIOP aboard CALIPSO, and MODIS aboard Aqua) are compared to ship observations from research cruises made in 2001 and 2003–2007 into the stratus/stratocumulus deck over the southeast Pacific Ocean. It is found that CloudSat radar-only LWP is generally too high over this region and the CloudSat/CALIPSO cloud bases are too low. This results in a relationship (LWP~h9) between CloudSat LWP and CALIPSO cloud thickness (h) that is very different from the adiabatic relationship (LWP~h2) from in situ observations. Such biases can be reduced if LWPs suspected to be contaminated by precipitation are eliminated, as determined by the maximum radar reflectivity Zmax>−15 dBZ in the apparent lower half of the cloud, and if cloud bases are determined based upon the adiabatically-determined cloud thickness (h~LWP1/2). Furthermore, comparing results from a global model (CAM3.1) to ship observations reveals that, while the simulated LWP is quite reasonable, the model cloud is too thick and too low, allowing the model to have LWPs that are almost independent of h. This model can also obtain a reasonable diurnal cycle in LWP and cloud fraction at a location roughly in the centre of this region (20° S, 85° W) but has an opposite diurnal cycle to those observed aboard ship at a location closer to the coast (20° S, 75° W). The diurnal cycle at the latter location is slightly improved in the newest version of the model (CAM4). However, the simulated clouds remain too thick and too low, as cloud bases are usually at or near the surface.

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