On the roles of deep convective clouds in tropospheric chemistry

On the roles of deep convective clouds in tropospheric chemistry. Wang, C. & Prinn, R., G. JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 105(D17):22269-22297, 9, 2000.
abstract bibtex

The impact of deep convection on tropospheric chemistry has been studied using a cloud-resolving model including integrated dynamics, cloud and aerosol microphysics, gaseous and aqueous chemistry, radiation, and lightning production of NO. Initialized with observational data over the tropical Pacific Ocean, sensitivity runs using a three-dimensional version of the model for short integration times (4 hours) and a two-dimensional version for relatively long integration times (30 hours) have been carried out. The impact of deep convection on tropospheric chemistry is found to occur not only through vertical transport but also by changing UV fluxes land thus the photochemical rates), scavenging soluble species, and producing NO molecules through lightning which then collectively change the main chemical pathways. The formation of large amounts of ice as opposed to liquid water particles is shown to greatly change the efficiencies of gaseous and aqueous reactions, The results suggest that upward transport during deep convection can form a transient layer in the lower stratosphere with relatively high H2O concentrations. This increase in H2O together with enhancement of UV fluxes by upward reflection from the cloud anvils then produces high OH concentrations just above the cloud top. The existence of a deep convective tower and its associated anvils changes the gas phase production of most chemical species by more than a factor of 2. We find that the production of NO through lightning is very important to chemistry in the convective region. In the model runs including lightning, the reduced UV fluxes inside and below the convective tower and anvils and during the nighttime combine with large conversions of NO to NO2 and then to N2O5 and HNO3 to produce reductions of both NO, and O-3 despite the massive lightning production of NO. This is because as many as 28% of the NO, molecules produced by lightning have been terminated through reactions with O-3 and HOx before contributing to O-3 production. Total O-3 in the model domain is reduced by up to 11% relative to the preconvective state. The lowest O-3 mole fractions in the upper troposphere calculated in the simulations are slightly less than 2 ppb, which is an 80% decrease from the initial O-3 mole fraction. Vertical profiles of O-3 from model runs including lightning agree quite well with observations in the upper troposphere, implying that lightning-related O-3 loss in cloud anvil regions can help explain the occasionally observed low O-3 layers in the tropical upper troposphere. The study also indicates that during convection, only 9% of the dissolved SO2 is converted to sulfate so that the aqueous processes only contribute 21% to the total sulfate production inside the model domain (similar to 1000 km wide). This result is caused by the much lower solubility of SO2 relative to H2O2; the conversion of water to ice phase particles that terminates the aqueous chemistry; and the limited coverages and lifetimes of the liquid phase portions of the clouds, This result also suggests that the aqueous sulfate production calculated in global models which neglect the ice phase may be overestimated.

@article{
 title = {On the roles of deep convective clouds in tropospheric chemistry},
 type = {article},
 year = {2000},
 identifiers = {[object Object]},
 pages = {22269-22297},
 volume = {105},
 month = {9},
 id = {ac9f932c-3d7a-3ae8-af79-81f2497818f4},
 created = {2015-05-08T02:33:13.000Z},
 file_attached = {false},
 profile_id = {f8c267c4-4c39-31dc-80fa-3a9691373386},
 group_id = {63e349d6-2c70-3938-9e67-2f6483f6cbab},
 last_modified = {2015-05-08T02:33:13.000Z},
 read = {false},
 starred = {false},
 authored = {false},
 confirmed = {true},
 hidden = {false},
 citation_key = {ISI:000089469100012},
 source_type = {article},
 abstract = {The impact of deep convection on tropospheric chemistry has been studied
using a cloud-resolving model including integrated dynamics, cloud and
aerosol microphysics, gaseous and aqueous chemistry, radiation, and
lightning production of NO. Initialized with observational data over the
tropical Pacific Ocean, sensitivity runs using a three-dimensional
version of the model for short integration times (4 hours) and a
two-dimensional version for relatively long integration times (30 hours)
have been carried out. The impact of deep convection on tropospheric
chemistry is found to occur not only through vertical transport but also
by changing UV fluxes land thus the photochemical rates), scavenging
soluble species, and producing NO molecules through lightning which then
collectively change the main chemical pathways. The formation of large
amounts of ice as opposed to liquid water particles is shown to greatly
change the efficiencies of gaseous and aqueous reactions, The results
suggest that upward transport during deep convection can form a
transient layer in the lower stratosphere with relatively high H2O
concentrations. This increase in H2O together with enhancement of UV
fluxes by upward reflection from the cloud anvils then produces high OH
concentrations just above the cloud top. The existence of a deep
convective tower and its associated anvils changes the gas phase
production of most chemical species by more than a factor of 2. We find
that the production of NO through lightning is very important to
chemistry in the convective region. In the model runs including
lightning, the reduced UV fluxes inside and below the convective tower
and anvils and during the nighttime combine with large conversions of NO
to NO2 and then to N2O5 and HNO3 to produce reductions of both NO, and
O-3 despite the massive lightning production of NO. This is because as
many as 28% of the NO, molecules produced by lightning have been
terminated through reactions with O-3 and HOx before contributing to O-3
production. Total O-3 in the model domain is reduced by up to 11%
relative to the preconvective state. The lowest O-3 mole fractions in
the upper troposphere calculated in the simulations are slightly less
than 2 ppb, which is an 80% decrease from the initial O-3 mole
fraction. Vertical profiles of O-3 from model runs including lightning
agree quite well with observations in the upper troposphere, implying
that lightning-related O-3 loss in cloud anvil regions can help explain
the occasionally observed low O-3 layers in the tropical upper
troposphere. The study also indicates that during convection, only 9%
of the dissolved SO2 is converted to sulfate so that the aqueous
processes only contribute 21% to the total sulfate production inside
the model domain (similar to 1000 km wide). This result is caused by the
much lower solubility of SO2 relative to H2O2; the conversion of water
to ice phase particles that terminates the aqueous chemistry; and the
limited coverages and lifetimes of the liquid phase portions of the
clouds, This result also suggests that the aqueous sulfate production
calculated in global models which neglect the ice phase may be
overestimated.},
 bibtype = {article},
 author = {Wang, C and Prinn, R G},
 journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
 number = {D17}
}

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Initialized with observational data over the\ntropical Pacific Ocean, sensitivity runs using a three-dimensional\nversion of the model for short integration times (4 hours) and a\ntwo-dimensional version for relatively long integration times (30 hours)\nhave been carried out. The impact of deep convection on tropospheric\nchemistry is found to occur not only through vertical transport but also\nby changing UV fluxes land thus the photochemical rates), scavenging\nsoluble species, and producing NO molecules through lightning which then\ncollectively change the main chemical pathways. The formation of large\namounts of ice as opposed to liquid water particles is shown to greatly\nchange the efficiencies of gaseous and aqueous reactions, The results\nsuggest that upward transport during deep convection can form a\ntransient layer in the lower stratosphere with relatively high H2O\nconcentrations. This increase in H2O together with enhancement of UV\nfluxes by upward reflection from the cloud anvils then produces high OH\nconcentrations just above the cloud top. The existence of a deep\nconvective tower and its associated anvils changes the gas phase\nproduction of most chemical species by more than a factor of 2. We find\nthat the production of NO through lightning is very important to\nchemistry in the convective region. In the model runs including\nlightning, the reduced UV fluxes inside and below the convective tower\nand anvils and during the nighttime combine with large conversions of NO\nto NO2 and then to N2O5 and HNO3 to produce reductions of both NO, and\nO-3 despite the massive lightning production of NO. This is because as\nmany as 28% of the NO, molecules produced by lightning have been\nterminated through reactions with O-3 and HOx before contributing to O-3\nproduction. Total O-3 in the model domain is reduced by up to 11%\nrelative to the preconvective state. The lowest O-3 mole fractions in\nthe upper troposphere calculated in the simulations are slightly less\nthan 2 ppb, which is an 80% decrease from the initial O-3 mole\nfraction. Vertical profiles of O-3 from model runs including lightning\nagree quite well with observations in the upper troposphere, implying\nthat lightning-related O-3 loss in cloud anvil regions can help explain\nthe occasionally observed low O-3 layers in the tropical upper\ntroposphere. The study also indicates that during convection, only 9%\nof the dissolved SO2 is converted to sulfate so that the aqueous\nprocesses only contribute 21% to the total sulfate production inside\nthe model domain (similar to 1000 km wide). This result is caused by the\nmuch lower solubility of SO2 relative to H2O2; the conversion of water\nto ice phase particles that terminates the aqueous chemistry; and the\nlimited coverages and lifetimes of the liquid phase portions of the\nclouds, This result also suggests that the aqueous sulfate production\ncalculated in global models which neglect the ice phase may be\noverestimated.","bibtype":"article","author":"Wang, C and Prinn, R G","journal":"JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES","number":"D17","bibtex":"@article{\n title = {On the roles of deep convective clouds in tropospheric chemistry},\n type = {article},\n year = {2000},\n identifiers = {[object Object]},\n pages = {22269-22297},\n volume = {105},\n month = {9},\n id = {ac9f932c-3d7a-3ae8-af79-81f2497818f4},\n created = {2015-05-08T02:33:13.000Z},\n file_attached = {false},\n profile_id = {f8c267c4-4c39-31dc-80fa-3a9691373386},\n group_id = {63e349d6-2c70-3938-9e67-2f6483f6cbab},\n last_modified = {2015-05-08T02:33:13.000Z},\n read = {false},\n starred = {false},\n authored = {false},\n confirmed = {true},\n hidden = {false},\n citation_key = {ISI:000089469100012},\n source_type = {article},\n abstract = {The impact of deep convection on tropospheric chemistry has been studied\nusing a cloud-resolving model including integrated dynamics, cloud and\naerosol microphysics, gaseous and aqueous chemistry, radiation, and\nlightning production of NO. Initialized with observational data over the\ntropical Pacific Ocean, sensitivity runs using a three-dimensional\nversion of the model for short integration times (4 hours) and a\ntwo-dimensional version for relatively long integration times (30 hours)\nhave been carried out. The impact of deep convection on tropospheric\nchemistry is found to occur not only through vertical transport but also\nby changing UV fluxes land thus the photochemical rates), scavenging\nsoluble species, and producing NO molecules through lightning which then\ncollectively change the main chemical pathways. The formation of large\namounts of ice as opposed to liquid water particles is shown to greatly\nchange the efficiencies of gaseous and aqueous reactions, The results\nsuggest that upward transport during deep convection can form a\ntransient layer in the lower stratosphere with relatively high H2O\nconcentrations. This increase in H2O together with enhancement of UV\nfluxes by upward reflection from the cloud anvils then produces high OH\nconcentrations just above the cloud top. The existence of a deep\nconvective tower and its associated anvils changes the gas phase\nproduction of most chemical species by more than a factor of 2. We find\nthat the production of NO through lightning is very important to\nchemistry in the convective region. In the model runs including\nlightning, the reduced UV fluxes inside and below the convective tower\nand anvils and during the nighttime combine with large conversions of NO\nto NO2 and then to N2O5 and HNO3 to produce reductions of both NO, and\nO-3 despite the massive lightning production of NO. This is because as\nmany as 28% of the NO, molecules produced by lightning have been\nterminated through reactions with O-3 and HOx before contributing to O-3\nproduction. Total O-3 in the model domain is reduced by up to 11%\nrelative to the preconvective state. 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This result is caused by the\nmuch lower solubility of SO2 relative to H2O2; the conversion of water\nto ice phase particles that terminates the aqueous chemistry; and the\nlimited coverages and lifetimes of the liquid phase portions of the\nclouds, This result also suggests that the aqueous sulfate production\ncalculated in global models which neglect the ice phase may be\noverestimated.},\n bibtype = {article},\n author = {Wang, C and Prinn, R G},\n journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},\n number = {D17}\n}","author_short":["Wang, C.","Prinn, R., G."],"bibbaseid":"wang-prinn-ontherolesofdeepconvectivecloudsintroposphericchemistry-2000","role":"author","urls":{},"downloads":0},"search_terms":["roles","deep","convective","clouds","tropospheric","chemistry","wang","prinn"],"keywords":[],"authorIDs":[]}