Search Results
shown in Fig. 1 , three nested domains (D01, D02, and D03) were introduced to the model with horizontal resolutions of 36, 12, and 4 km, respectively. D03 covered metropolitan areas such as Guangzhou, Shenzhen, and Hong Kong, where considerable amounts of aerosols are emitted into the atmosphere. The corresponding time steps were 120, 40, and 13.3 s. There were 31 unevenly spaced vertical levels from the surface to a fixed pressure of 50 hPa. No observational data were assimilated in any of the
shown in Fig. 1 , three nested domains (D01, D02, and D03) were introduced to the model with horizontal resolutions of 36, 12, and 4 km, respectively. D03 covered metropolitan areas such as Guangzhou, Shenzhen, and Hong Kong, where considerable amounts of aerosols are emitted into the atmosphere. The corresponding time steps were 120, 40, and 13.3 s. There were 31 unevenly spaced vertical levels from the surface to a fixed pressure of 50 hPa. No observational data were assimilated in any of the
Review of Aerosol–Cloud Interactions: Mechanisms, Significance, and Challenges, or dry condition ( Fan et al. 2009 , 2012b , 2013 ; Li et al. 2008b ; Khain et al. 2005 , 2008a ; Tao et al. 2007 ; Lebo et al. 2012 ; Lebo and Seinfeld 2011 ). On the other hand, numerous observational studies showed the increased cloud-top height and cloud cover with an increase of aerosol loading (e.g., Andreae et al. 2004 ; Koren et al. 2010 ; Li et al. 2011 ; Niu and Li 2012 ). Fan et al. (2013) revealed a new cloud invigoration mechanism–microphysical invigoration induced by
, or dry condition ( Fan et al. 2009 , 2012b , 2013 ; Li et al. 2008b ; Khain et al. 2005 , 2008a ; Tao et al. 2007 ; Lebo et al. 2012 ; Lebo and Seinfeld 2011 ). On the other hand, numerous observational studies showed the increased cloud-top height and cloud cover with an increase of aerosol loading (e.g., Andreae et al. 2004 ; Koren et al. 2010 ; Li et al. 2011 ; Niu and Li 2012 ). Fan et al. (2013) revealed a new cloud invigoration mechanism–microphysical invigoration induced by
Effect of Aerosols on Freezing Drops, Hail, and Precipitation in a Midlatitude Stormtheir growth rate. Hail in the dry growth regime—that is, when its surface is dry—cannot collect ice particles. In contrast, hail particles growing in the regime of wet growth are covered by a liquid water film and can collect ice particles. Fall velocities of FDs, graupel, and hail also depend on the growth regime, since dry and wet surfaces have different surface roughness. Equally, the wet growth process determines the vertical distribution of latent heat release from freezing, which influences
their growth rate. Hail in the dry growth regime—that is, when its surface is dry—cannot collect ice particles. In contrast, hail particles growing in the regime of wet growth are covered by a liquid water film and can collect ice particles. Fall velocities of FDs, graupel, and hail also depend on the growth regime, since dry and wet surfaces have different surface roughness. Equally, the wet growth process determines the vertical distribution of latent heat release from freezing, which influences
precipitation processes. 1 This can occur when collision–coalescence is suppressed in the lower portions of polluted deep convective clouds as a result of high droplet concentrations and reduced droplet sizes. However, the presence of deeper clouds and/or clouds with a larger upper-tropospheric cloud cover [cf. Fig. 2 in Rosenfeld et al. (2008) ] does not have to imply more vigorous convection. Changes in cloud microphysics, for instance, leading to changes in the partitioning between cloud condensate
precipitation processes. 1 This can occur when collision–coalescence is suppressed in the lower portions of polluted deep convective clouds as a result of high droplet concentrations and reduced droplet sizes. However, the presence of deeper clouds and/or clouds with a larger upper-tropospheric cloud cover [cf. Fig. 2 in Rosenfeld et al. (2008) ] does not have to imply more vigorous convection. Changes in cloud microphysics, for instance, leading to changes in the partitioning between cloud condensate
Effects of Urban Plume Aerosols on a Mesoscale Convective Systemmicrophysics scheme. Aerosols are activated as CCN in a separate module and provided as condensation nuclei (CN) to the microphysics ( Abdul‐Razzak and Ghan 2000 ), which tracks the mass mixing ratio and number concentration of five hydrometeor species and water vapor (mass only): 1) cloud drop, 2) raindrop, 3) ice, 4) snow, and 5) graupel. Sources and sinks of these hydrometeors include accretion, heterogeneous freezing, melting, self-collection, sublimation, evaporation, deposition, condensation
microphysics scheme. Aerosols are activated as CCN in a separate module and provided as condensation nuclei (CN) to the microphysics ( Abdul‐Razzak and Ghan 2000 ), which tracks the mass mixing ratio and number concentration of five hydrometeor species and water vapor (mass only): 1) cloud drop, 2) raindrop, 3) ice, 4) snow, and 5) graupel. Sources and sinks of these hydrometeors include accretion, heterogeneous freezing, melting, self-collection, sublimation, evaporation, deposition, condensation
Distinct Impacts of Aerosols on an Evolving Continental Cloud Complex during the RACORO Field Campaign). Progress has also been made to elucidate the aerosol–cloud–radiation feedback on regional and global scales ( Tie et al. 2003 ). Several studies have revealed that a reduced cloud cover, lowered cloud optical thickness, or a short cloud lifetime occurs for low- and midlevel clouds with absorbing aerosols ( Johnson et al. 2004 ; Zhang et al. 2008 ; Allen and Sherwood 2010 ; Sakaeda et al. 2011 ; Li et al. 2013 ). Fan et al. (2008) have shown that ARE induces a decrease in relative humidity
). Progress has also been made to elucidate the aerosol–cloud–radiation feedback on regional and global scales ( Tie et al. 2003 ). Several studies have revealed that a reduced cloud cover, lowered cloud optical thickness, or a short cloud lifetime occurs for low- and midlevel clouds with absorbing aerosols ( Johnson et al. 2004 ; Zhang et al. 2008 ; Allen and Sherwood 2010 ; Sakaeda et al. 2011 ; Li et al. 2013 ). Fan et al. (2008) have shown that ARE induces a decrease in relative humidity
Mechanisms Contributing to Suppressed Precipitation in Mt. Hua of Central China. Part I: Mountain Valley Circulation. 2009 ; Rosenfeld et al. 2007 ; Givati and Rosenfeld 2004 ; Jirak and Cotton 2006 ; Muhlbauer and Lohmann 2008 ; Saleeby et al. 2013 ; Guo et al. 2014 ; Xiao et al. 2014 ). Through the IN effect, Fan et al. (2014) and Muhlbauer and Lohmann (2009) found increased precipitation through enhanced snow formation. Enhanced orographic precipitation associated with dust particles that serve as IN to enhance ice formation is supported by observations in the western United States ( Ault et al. 2011
. 2009 ; Rosenfeld et al. 2007 ; Givati and Rosenfeld 2004 ; Jirak and Cotton 2006 ; Muhlbauer and Lohmann 2008 ; Saleeby et al. 2013 ; Guo et al. 2014 ; Xiao et al. 2014 ). Through the IN effect, Fan et al. (2014) and Muhlbauer and Lohmann (2009) found increased precipitation through enhanced snow formation. Enhanced orographic precipitation associated with dust particles that serve as IN to enhance ice formation is supported by observations in the western United States ( Ault et al. 2011
Aerosol- and Droplet-Dependent Contact Freezing: Parameterization Development and Case Study; Niehaus et al. 2014 ; W. Cantrell 2015, personal communication), for dust particles with different mineralogies. Taken together, these data cover the complete temperature range over which contact freezing is thought to occur. There is considerable spread in the data, particularly at warmer temperatures. Nevertheless, the particle surface-area-normalized freezing efficiency (m −2 ) can be described by the temperature-dependent function: where A = 1.223 × 10 7 , and B = −2.686 × 10 −1 , and were
; Niehaus et al. 2014 ; W. Cantrell 2015, personal communication), for dust particles with different mineralogies. Taken together, these data cover the complete temperature range over which contact freezing is thought to occur. There is considerable spread in the data, particularly at warmer temperatures. Nevertheless, the particle surface-area-normalized freezing efficiency (m −2 ) can be described by the temperature-dependent function: where A = 1.223 × 10 7 , and B = −2.686 × 10 −1 , and were
