Modeling Aerosol-Cloud-Precipitation Interactions in Mountainous Regions: Challenges in the Representation of Indirect Microphysical Effects with Impacts at Subregional Scales

Barros, A. P.; Shrestha, Prabhakar; Chavez, Steven; Duan, Yajuan

doi:10.5772/intechopen.80025

Cited by 6 publications

(8 citation statements)

References 62 publications

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“…A simpler and faster option suggested by Beard and Ochs (1984) is also available in the model. The terminal velocity of hydrometeors is estimated following Beard (1976Beard ( , 1977 in three ranges of the particle diameter (0.5-19 µm, 19 µm-1.07 mm, 1.07-7 mm), though droplets larger than 40 µm do not form in the early stages of cloud development. Another approximation by Best (1950) is also available as an option in the model.…”

Section: Collision-coalescence Growthmentioning

confidence: 99%

Understanding aerosol–cloud interactions through modeling the development of orographic cumulus congestus during IPHEx

2019

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A new cloud parcel model (CPM) including activation, condensation, collision-coalescence, and lateral entrainment processes is used to investigate aerosol-cloud interactions (ACIs) in cumulus development prior to rainfall onset. The CPM was applied with surface aerosol measurements to predict the vertical structure of cloud development at early stages, and the model results were evaluated against airborne observations of cloud microphysics and thermodynamic conditions collected during the Integrated Precipitation and Hydrology Experiment (IPHEx) in the inner region of the southern Appalachian Mountains (SAM). Sensitivity analysis was conducted to examine the model response to variations in key ACI physiochemical parameters and initial conditions. The CPM sensitivities mirror those found in parcel models without entrainment and collision-coalescence, except for the evolution of the droplet spectrum and liquid water content with height. Simulated cloud droplet number concentrations (CDNCs) exhibit high sensitivity to variations in the initial aerosol concentration at cloud base, but weak sensitivity to bulk aerosol hygroscopicity. The condensation coefficient a c plays a governing role in determining the evolution of CDNC, liquid water content (LWC), and cloud droplet spectra (CDS) in time and with height. Lower values of a c lead to higher CDNCs and broader CDS above cloud base, and higher maximum supersaturation near cloud base. Analysis of model simulations reveals that competitive interference among turbulent dispersion, activation, and droplet growth processes modulates spectral width and explains the emergence of bimodal CDS and CDNC heterogeneity in aircraft measurements from different cloud regions and at different heights. Parameterization of nonlinear interactions among entrainment, condensational growth, and collision-coalescence processes is therefore necessary to simulate the vertical structures of CDNCs and CDSs in convective clouds. Comparisons of model predictions with data suggest that the representation of lateral entrainment remains challenging due to the spatial heterogeneity of the convective boundary layer and the intricate 3-D circulations in mountainous regions.

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Section: Collision-coalescence Growthmentioning

confidence: 99%

Understanding aerosol–cloud interactions through modeling the development of orographic cumulus congestus during IPHEx

2019

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“…The WRF-ARW modeling system provides operational weather forecasting in more than four dozen countries and is in use by more than 36 000 people from 162 countries (Powers et al 2017). The effectiveness of the model to address diverse atmospheric conditions over complex Himalayan terrains (Collier and Immerzeel 2015;Karki et al 2017;Barros et al 2018;Regmi et al 2017Regmi et al , 2019Regmi and Maharjan 2015) demonstrates the aptness of using the WRF-ARW modeling system for this region.…”

Section: A Routine Forecast Setup and Initializationmentioning

confidence: 99%

The Weather Hazards Associated with the US-Bangla Aircraft Accident at the Tribhuvan International Airport, Nepal

Regmi

Shrestha

Maharjan

et al. 2020

Weather and Forecasting

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Safe flights over the Tribhuvan International Airport (TIA), Kathmandu, Nepal, remain a considerable challenge. Since the airport opened, there have been 13 aircraft accidents during landings and takeoffs that have claimed 392 lives. A detailed understanding and dependable forecast of atmospheric conditions that may develop over the complex terrain of the midhills of central Nepal Himalaya are yet to be achieved. The present study discusses the near-surface atmospheric conditions possibly associated with the most recent fatal crash at TIA on 12 March 2018 as revealed by the Advanced Research version of the Weather Research and Forecasting (WRF-ARW) Model routine forecast. At the time of the accident, two prominent gap winds were converging in the valley, thereby, forming a crosswind and a mix of strong up- and downdrafts over the airfield. As a result, the near-surface atmosphere was significantly turbulent. Unexpected encounters with such turbulent winds are a likely contributor to the fatal crash. This indicates that the knowledge of near-surface atmospheric conditions, critically needed by pilots in advance, for safe operations over the airfield may be generated with WRF-ARW forecasts.

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“…The aerosol indirect effect (AIE) refers to the role of Aerosol-Cloud-Precipitation-Interactions (ACPI) in modifying the structure of clouds and the timing of the precipitation at the ground due to changes in precipitation efficiency. In mountainous regions, complex atmospheric circulations at multiple scales can further modulate ACPI and consequently significantly impact the spatial allocation of freshwater input into adjacent mountain catchments (e.g., Barros et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…Changes in latent heat in the vicinity of the orographic precipitation maximum contribute to enhancing mountain-valley circulations (Magagi and Barros, 2004;Seo et al, 2020). Barros et al (2018), using aerosol size distribution, chemical composition, and hygroscopicity measured in the inner region of the Central Himalayas by Shrestha et al (2013) during JAMEX (Lau et al, 2008), demonstrated the importance of using regional aerosol properties as opposed to standard continental aerosol on the dynamical evolution of an intense convective storm and modification of the vertical structure of hydrometeors including ice particles and the spatial distribution of precipitation, with implications for regional water resources (Shrestha, 2011). Through aerosol-cloud-radiation feedbacks, Duan (2017) showed that impacts on the surface energy budget result in surface temperature changes in the range of 5-10 K among adjacent slopes in the SAM.…”

Section: Introductionmentioning

confidence: 99%

Aerosol indirect effects on orographic clouds and precipitation

Chavez

Barros

2023

Front. Earth Sci.

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The sensitivity of warm orographic cloud development to aerosol indirect effects was investigated through aerosol-aware Weather Research and Forecast model simulations contrasting aerosol-cloud-precipitation interactions using the default (generic) aerosol and regional aerosol measurements from the Integrated Precipitation and Hydrology Experiment in the Southern Appalachian Mountains for three rainfall events: 1) enhanced local convection; 2) a frontal system, and 3) a tropical system. Using the regional aerosol activation spectrum yields higher number of drops than using the default, smaller cloud droplets and delayed rainfall onset under weak synoptic forcing conditions. Evaluation against aircraft measurements in isolated convective clouds reveals that while the model microphysics falls short of reproducing the vertical structure of nonprecipitating clouds, the liquid water content, and the concentration of cloud droplets near cloud base are in keeping with observations. The simulated cloud vertical structure shows the regional signature of orographic enhancement over the mountains vis-a-vis the adjacent plains. In the inner region, valley-ridge circulations organize the spatial patterns of cloudiness under weak synoptic forcing. The formation of early afternoon low-level clouds over the ridges in the summertime reflects the aerosol indirect effect. By contrast, for large-scale systems with strong and sustained moisture convergence at low levels (frontal and tropical systems), mechanically forced rainfall efficiency is enhanced, there is no delay in the onset of precipitation, and the aerosol indirect effect is negligible. This study shows that the impact of aerosol-cloud-precipitation interactions on the spatial variability of orographic rainfall is conditional on weather regime.

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Modeling Aerosol-Cloud-Precipitation Interactions in Mountainous Regions: Challenges in the Representation of Indirect Microphysical Effects with Impacts at Subregional Scales

Cited by 6 publications

References 62 publications

Understanding aerosol–cloud interactions through modeling the development of orographic cumulus congestus during IPHEx

Understanding aerosol–cloud interactions through modeling the development of orographic cumulus congestus during IPHEx

The Weather Hazards Associated with the US-Bangla Aircraft Accident at the Tribhuvan International Airport, Nepal

Aerosol indirect effects on orographic clouds and precipitation

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