Influence of Saharan Dust and Other Aerosols on Hurricane Nadine (2012) as Revealed by the Comparison of Ensemble Model Results and NASA HS3 Data

2020 ◽  
Author(s):  
Jainn Shi ◽  
Scott Braun ◽  
Zhining Tao ◽  
Jason Sippel
Keyword(s):  
Forest Fires ◽  
Cloud Microphysics ◽  
Saharan Dust ◽  
Weather Research And Forecasting ◽  
Radiation Physics ◽  
Convective Clouds ◽  
Ensemble Simulations ◽  
Goddard Space Flight Center ◽  
Core Simulation ◽  
Aerosol Effects

<p>This presentation will focus on simulations of the early stages of Hurricane Nadine (2012), which interacted with the SAL and never intensified beyond a minimal hurricane. Given the complexity of aerosol effects on cloud microphysics and radiation and their subsequent effects on deep convective clouds, there is a need to assess the combined microphysical and radiative effects of aerosols. We use the Goddard Space Flight Center version of the Weather Research and Forecasting model with interactive aerosol-cloud-radiation physics to study the influence of the SAL and other aerosols (sea salt and black/organic carbon) on Nadine via a series of model sensitivity runs. The results from the control experiment with all aerosols will be compared to the dropsonde and CPL aerosol lidar backscatter data collected during the NASA Hurricane and Severe Storm Sentinel (HS3) field campaign. Comparison of model results and dropsonde data shows evidence of the intrusion of Saharan air into the storm core. Simulation results also show the possible intrusion of biomass-burning aerosols that originated from forest fires in the Northwestern United States a few days before Nadine reached hurricane strength. In addition, we will also present results from three sets of 30-member ensemble simulations: 1) without aerosol coupling, 2) with all aerosols, and 3) with only dust aerosol, to study the aerosol impact on Nadine.</p>

scholarly journals Global anthropogenic aerosol effects on convective clouds in ECHAM5-HAM

2008 ◽  
Vol 8 (7) ◽  
pp. 2115-2131 ◽  
Author(s):  
U. Lohmann
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Hydrological Cycle ◽  
Circulation Model ◽  
Cloud Microphysics ◽  
Convective Precipitation ◽  
Anthropogenic Aerosol ◽  
Convective Clouds ◽  
Double Moment ◽  
Aerosol Effects

Abstract. Aerosols affect the climate system by changing cloud characteristics in many ways. They act as cloud condensation and ice nuclei and may have an influence on the hydrological cycle. Here we investigate aerosol effects on convective clouds by extending the double-moment cloud microphysics scheme developed for stratiform clouds, which is coupled to the HAM double-moment aerosol scheme, to convective clouds in the ECHAM5 general circulation model. This enables us to investigate whether more, and smaller cloud droplets suppress the warm rain formation in the lower parts of convective clouds and thus release more latent heat upon freezing, which would then result in more vigorous convection and more precipitation. In ECHAM5, including aerosol effects in large-scale and convective clouds (simulation ECHAM5-conv) reduces the sensitivity of the liquid water path increase with increasing aerosol optical depth in better agreement with observations and large-eddy simulation studies. In simulation ECHAM5-conv with increases in greenhouse gas and aerosol emissions since pre-industrial times, the geographical distribution of the changes in precipitation better matches the observed increase in precipitation than neglecting microphysics in convective clouds. In this simulation the convective precipitation increases the most suggesting that the convection has indeed become more vigorous.

scholarly journals 3-D model simulations of dynamical and microphysical interactions in pyro-convective clouds under idealized conditions

2013 ◽  
Vol 13 (7) ◽  
pp. 19527-19557 ◽  
Author(s):  
P. Reutter ◽  
J. Trentmann ◽  
A. Seifert ◽  
P. Neis ◽  
H. Su ◽  
...  
Keyword(s):  
Forest Fires ◽  
Aerosol Particles ◽  
Three Dimensional ◽  
Convective Cloud ◽  
Atmospheric Model ◽  
Cloud Microphysics ◽  
Aerosol Concentration ◽  
Activation Process ◽  
Cloud Droplets ◽  
Convective Clouds

Abstract. Pyro-convective clouds, i.e. convective clouds forming over wildland fires due to high sensible heat, play an important role for the transport of aerosol particles and trace gases into the upper troposphere and lower stratosphere. Additionally, due to the emission of a large number of aerosol particles from forest fires, the microphysical structure of a pyro-convective cloud is clearly different from that of ordinary convective clouds. A crucial step in the microphysical evolution of a (pyro-) convective cloud is the activation of aerosol particles to form cloud droplets. The activation process affects the initial number and size of cloud droplets and can thus influence the evolution of the convective cloud and the formation of precipitation. Building upon a realistic parameterization of CCN activation, the model ATHAM is used to investigate the dynamical and microphysical processes of idealized three-dimensional pyro-convective clouds in mid-latitudes. A state-of-the-art two-moment microphysical scheme has been implemented in order to study the influence of the aerosol concentration on the cloud development. The results show that the aerosol concentration influences the formation of precipitation. For low aerosol concentrations (NCN=1000 cm−3), rain droplets are rapidly formed by autoconversion of cloud droplets. This also triggers the formation of large graupel and hail particles resulting in an early and strong onset of precipitation. With increasing aerosol concentration (NCN=20 000 cm−3 and NCN=60 000 cm−3) the formation of rain droplets is delayed due to more but smaller cloud droplets. Therefore, the formation of ice crystals and snowflakes becomes more important for the eventual formation of graupel and hail. However, this causes a delay of the onset of precipitation and its intensity for increasing aerosol concentration. This work shows the first detailed investigation of the interaction between cloud microphysics and dynamics of a pyro-convective cloud using the combination of a high resolution atmospheric model and a detailed microphysical scheme.

scholarly journals Aerosol effects on deep convection: the propagation of aerosol perturbations through convective cloud microphysics

2019 ◽  
Vol 19 (4) ◽  
pp. 2601-2627 ◽  
Author(s):  
Max Heikenfeld ◽  
Bethan White ◽  
Laurent Labbouz ◽  
Philip Stier
Keyword(s):  
Latent Heat ◽  
Cloud Condensation Nuclei ◽  
Cloud Microphysics ◽  
Latent Heating ◽  
Microphysics Scheme ◽  
Convective Clouds ◽  
Wide Range ◽  
Microphysical Processes ◽  
Aerosol Effects ◽  
The Impact

Abstract. The impact of aerosols on ice- and mixed-phase processes in deep convective clouds remains highly uncertain, and the wide range of interacting microphysical processes is still poorly understood. To understand these processes, we analyse diagnostic output of all individual microphysical process rates for two bulk microphysics schemes in the Weather and Research Forecasting model (WRF). We investigate the response of individual processes to changes in aerosol conditions and the propagation of perturbations through the microphysics all the way to the macrophysical development of the convective clouds. We perform simulations for two different cases of idealised supercells using two double-moment bulk microphysics schemes and a bin microphysics scheme. The simulations cover a comprehensive range of values for cloud droplet number concentration (CDNC) and cloud condensation nuclei (CCN) concentration as a proxy for aerosol effects on convective clouds. We have developed a new cloud tracking algorithm to analyse the morphology and time evolution of individually tracked convective cells in the simulations and their response to the aerosol perturbations. This analysis confirms an expected decrease in warm rain formation processes due to autoconversion and accretion for more polluted conditions. There is no evidence of a significant increase in the total amount of latent heat, as changes to the individual components of the integrated latent heating in the cloud compensate each other. The latent heating from freezing and riming processes is shifted to a higher altitude in the cloud, but there is no significant change to the integrated latent heat from freezing. Different choices in the treatment of deposition and sublimation processes between the microphysics schemes lead to strong differences including feedbacks onto condensation and evaporation. These changes in the microphysical processes explain some of the response in cloud mass and the altitude of the cloud centre of gravity. However, there remain some contrasts in the development of the bulk cloud parameters between the microphysics schemes and the two simulated cases.

scholarly journals Global anthropogenic aerosol effects on convective clouds in ECHAM5-HAM

2007 ◽  
Vol 7 (5) ◽  
pp. 14639-14674 ◽  
Author(s):  
U. Lohmann
Keyword(s):  
Liquid Water ◽  
General Circulation ◽  
Hydrological Cycle ◽  
Cloud Microphysics ◽  
Liquid Water Path ◽  
Anthropogenic Aerosol ◽  
Water Path ◽  
Convective Clouds ◽  
Stratiform Clouds ◽  
Aerosol Effects

Abstract. Aerosols affect the climate system by changing cloud characteristics in many ways. They act as cloud condensation and ice nuclei and may have an influence on the hydrological cycle. Here we investigate aerosol effects on convective clouds by extending the double moment cloud microphysics scheme developed for stratiform clouds to convective clouds in the ECHAM5 general circulation model. This increases the liquid water path in the tropics and reduces the sensitivity of the liquid water path with increasing aerosol optical depth in better agreement with observations and large-eddy simulation studies. In simulations in which greenhouse gases and aerosols emissions are increased since pre-industrial times, accounting for microphysics in convective clouds matches most closely the observed increase in precipitation. The total anthropogenic aerosol effect since pre-industrial time is slightly reduced from −1.6 to −1.9 W m−2 when microphysics are only included in stratiform clouds to −1.5 W m−2 when microphysics are included both in stratiform and convective clouds.

scholarly journals Saharan dust and biomass burning aerosols during ex-hurricane Ophelia: observations from the new UK lidar and sun-photometer network

2019 ◽  
Vol 19 (6) ◽  
pp. 3557-3578 ◽  
Author(s):  
Martin Osborne ◽  
Florent F. Malavelle ◽  
Mariana Adam ◽  
Joelle Buxmann ◽  
Jaqueline Sugier ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Forest Fires ◽  
Complex Structure ◽  
Atmospheric Dispersion ◽  
Saharan Dust ◽  
Atmospheric Concentration ◽  
Back Trajectories ◽  
Sun Photometer ◽  
The Uk ◽  
Aerosol Types

Abstract. On 15–16 October 2017, ex-hurricane Ophelia passed to the west of the British Isles, bringing dust from the Sahara and smoke from Portuguese forest fires that was observable to the naked eye and reported in the UK's national press. We report here detailed observations of this event using the UK operational lidar and sun-photometer network, established for the early detection of aviation hazards, including volcanic ash. We also use ECMWF ERA5 wind field data and MODIS imagery to examine the aerosol transport. The observations, taken continuously over a period of 30 h, show a complex picture, dominated by several different aerosol layers at different times and clearly correlated with the passage of different air masses associated with the intense cyclonic system. A similar evolution was observed at several sites, with a time delay between them explained by their different location with respect to the storm and associated meteorological features. The event commenced with a shallow dust layer at 1–2 km in altitude and culminated in a deep and complex structure that lasted ∼12 h at each site over the UK, correlated with the storm's warm sector. For most of the time, the aerosol detected was dominated by mineral dust mixtures, as highlighted by depolarisation measurements, but an intense biomass burning aerosol (BBA) layer was observed towards the end of the event, lasting around 3 h at each site. The aerosol optical depth at 355 nm (AOD355) during the whole event ranged from 0.2 to 2.9, with the larger AOD correlated to the intense BBA layer. Such a large AOD is unprecedented in the UK according to AERONET records for the last 20 years. The Raman lidars permitted the measurement of the aerosol extinction coefficient at 355 nm, the particle linear depolarisation ratio (PLDR), and the lidar ratio (LR) and made the separation of the dust (depolarising) aerosol from other aerosol types possible. A specific extinction has also been computed to provide an estimate of the atmospheric concentration of both aerosol types separately, which peaked at 420±200 µg m−3 for the dust and 558±232 µg m−3 for the biomass burning aerosols. Back trajectories computed using the Numerical Atmospheric-dispersion Modelling Environment (NAME) were used to identify the sources and strengthen the conclusions drawn from the observations. The UK network represents a significant expansion of the observing capability in northern Europe, with instruments evenly distributed across Great Britain, from Camborne in Cornwall to Lerwick in the Shetland Islands, and this study represents the first attempt to demonstrate its capability and validate the methods in use. Its ultimate purpose will be the detection and quantification of volcanic plumes, but the present study clearly demonstrates the advanced capabilities of the network.

scholarly journals Longitudinal variability of the biogeochemical role of Mediterranean aerosols in the Mediterranean Sea

2011 ◽  
Vol 8 (5) ◽  
pp. 1067-1080 ◽  
Author(s):  
E. Ternon ◽  
C. Guieu ◽  
C. Ridame ◽  
S. L'Helguen ◽  
P. Catala
Keyword(s):  
Mediterranean Sea ◽  
Forest Fires ◽  
Saharan Dust ◽  
Aerosol Sampling ◽  
Modest Contribution ◽  
Anthropogenic Contribution ◽  
The Mediterranean ◽  
June July ◽  
Atmospheric Inputs ◽  
Longitudinal Variability

Abstract. The Mediterranean Sea is a semi-enclosed basin characterized by a strong thermal stratification during summer during which the atmosphere is the main source of new nutrients to the nutrient-depleted surface layer. From aerosol sampling and microcosm experiments performed during the TransMed BOUM cruise (June–July 2008) we showed that: (i) the Mediterranean atmosphere composition (Al, Fe, P) was homogeneous over ~28° of longitude and was a mixture with a constant proportion of anthropogenic contribution and a variable but modest contribution of crustal aerosols. This quite stable composition over a one month period and a long transect (~2500 km) allowed to define the Mediterranean atmospheric "background" that characterizes the summer season in the absence of major Saharan event and forest fires, (ii) primary production significantly increased at all tested stations after aerosols addition collected on-board and after Saharan dust analog addition, indicating that both additions relieved on-going (co)-limitations. Although both additions significantly increased the N2 fixation rates at the western station, diazotrophic activity remained very low (~0.2 nmol N L−1 d−1), (iii) due to the presence of anthropogenic particles, the probable higher solubility of nutrients associated with mixed aerosols (crustal + anthropogenic contribution), conferred a higher fertilizing potential to on-board collected aerosol as compared to Saharan dust analog. Finally, those experiments showed that atmospheric inputs from a mixed atmospheric event ("summer rain" type) or from a high-intensity Saharan event would induce comparable response by the biota in the stratified Mediterranean SML, during summer.

scholarly journals How do changes in warm-phase microphysics affect deep convective clouds?

2017 ◽  
Vol 17 (15) ◽  
pp. 9585-9598 ◽  
Author(s):  
Qian Chen ◽  
Ilan Koren ◽  
Orit Altaratz ◽  
Reuven H. Heiblum ◽  
Guy Dagan ◽  
...  
Keyword(s):  
Rain Rate ◽  
Convective Cloud ◽  
Cloud Fraction ◽  
Marshall Islands ◽  
Cloud System ◽  
Main Question ◽  
Convective Clouds ◽  
Deep Convective Clouds ◽  
Aerosol Effects ◽  
Deep Convective Cloud

Abstract. Understanding aerosol effects on deep convective clouds and the derived effects on the radiation budget and rain patterns can largely contribute to estimations of climate uncertainties. The challenge is difficult in part because key microphysical processes in the mixed and cold phases are still not well understood. For deep convective clouds with a warm base, understanding aerosol effects on the warm processes is extremely important as they set the initial and boundary conditions for the cold processes. Therefore, the focus of this study is the warm phase, which can be better resolved. The main question is: How do aerosol-derived changes in the warm phase affect the properties of deep convective cloud systems? To explore this question, we used a weather research and forecasting (WRF) model with spectral bin microphysics to simulate a deep convective cloud system over the Marshall Islands during the Kwajalein Experiment (KWAJEX). The model results were validated against observations, showing similarities in the vertical profile of radar reflectivity and the surface rain rate. Simulations with larger aerosol loading resulted in a larger total cloud mass, a larger cloud fraction in the upper levels, and a larger frequency of strong updrafts and rain rates. Enlarged mass both below and above the zero temperature level (ZTL) contributed to the increase in cloud total mass (water and ice) in the polluted runs. Increased condensation efficiency of cloud droplets governed the gain in mass below the ZTL, while both enhanced condensational and depositional growth led to increased mass above it. The enhanced mass loading above the ZTL acted to reduce the cloud buoyancy, while the thermal buoyancy (driven by the enhanced latent heat release) increased in the polluted runs. The overall effect showed an increased upward transport (across the ZTL) of liquid water driven by both larger updrafts and larger droplet mobility. These aerosol effects were reflected in the larger ratio between the masses located above and below the ZTL in the polluted runs. When comparing the net mass flux crossing the ZTL in the clean and polluted runs, the difference was small. However, when comparing the upward and downward fluxes separately, the increase in aerosol concentration was seen to dramatically increase the fluxes in both directions, indicating the aerosol amplification effect of the convection and the affected cloud system properties, such as cloud fraction and rain rate.

Pathways to the Production of Precipitating Hydrometeors and Tropical Cyclone Development

2016 ◽  
Vol 144 (6) ◽  
pp. 2395-2420 ◽  
Author(s):  
J.-W. Bao ◽  
S. A. Michelson ◽  
E. D. Grell
Keyword(s):  
Tropical Cyclone ◽  
Wrf Model ◽  
Cloud Microphysics ◽  
Weather Research And Forecasting ◽  
Rapid Intensification ◽  
Latent Heating ◽  
Vertical Distributions ◽  
Double Moment ◽  
Microphysical Processes ◽  
Definition Of

Abstract Pathways to the production of precipitation in two cloud microphysics schemes available in the Weather Research and Forecasting (WRF) Model are investigated in a scenario of tropical cyclone intensification. Comparisons of the results from the WRF Model simulations indicate that the variation in the simulated initial rapid intensification of an idealized tropical cyclone is due to the differences between the two cloud microphysics schemes in their representations of pathways to the formation and growth of precipitating hydrometeors. Diagnoses of the source and sink terms of the hydrometeor budget equations indicate that the major differences in the production of hydrometeors between the schemes are in the spectral definition of individual hydrometeor categories and spectrum-dependent microphysical processes, such as accretion growth and sedimentation. These differences lead to different horizontally averaged vertical profiles of net latent heating rate associated with significantly different horizontally averaged vertical distributions and production rates of hydrometeors in the simulated clouds. Results from this study also highlight the possibility that the advantage of double-moment formulations can be overshadowed by the uncertainties in the spectral definition of individual hydrometeor categories and spectrum-dependent microphysical processes.

scholarly journals Size resolved mass concentration and elemental composition of atmospheric aerosols over the eastern Mediterranean area

2003 ◽  
Vol 3 (3) ◽  
pp. 2547-2573 ◽  
Author(s):  
J. Smolik ◽  
V. Ždimal ◽  
J. Schwarz ◽  
M. Lazaridis ◽  
V. Havránek ◽  
...  
Keyword(s):  
Forest Fires ◽  
Eastern Mediterranean ◽  
Saharan Dust ◽  
Eastern Coast ◽  
The Black Sea ◽  
Western Coast ◽  
Gravimetric Analysis ◽  
Air Masses ◽  
Pm10 Mass ◽  
Mass Concentrations

Abstract. A Berner low pressure impactor was used to collect size-segregated aerosol samples at Finokalia, located on the north-eastern coast of Crete, Greece during July 2000 and January 2001. Several samples were also collected during the summer campaign aboard the research vessel "AEGAIEO" in the Aegean Sea. Gravimetric analysis and inversion techniques yielded daily PM1 and PM10 mass concentrations. Further, the samples were analysed by PIXE giving elemental size distributions of Al, Si, K, Ca, Ti, Mn, Fe, Sr, S, Cl, Ni, V, Cu, Cr, Zn, and Pb. The crustal elements and sea-salt had a unimodal supermicron size distribution. Sulphur was found predominantly in submicron fractions. K, V, and Ni exhibited bimodal distribution with a submicron mode produced by forest fires and oil combustion. The anthropogenic elements had broad and not well-defined distributions. The time series for PM1 and PM10 mass and elemental concentrations showed both daily and seasonal variation. Higher mass concentrations were observed during two incursions of Saharan dust. Higher concentrations of S, Cu, Zn, and Pb were encountered in samples collected in air masses arriving from northern Greece or the western coast of Turkey. Higher concentrations of chlorine were found in samples with air masses either originating above the Atlantic Ocean and arriving at Finokalia via western Europe or recirculating over the western coast of the Black Sea.

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