We present a technique for in situ measurement of the vertical and spatial stratigraphic distribu... more We present a technique for in situ measurement of the vertical and spatial stratigraphic distribution of snow optical grain size with a coupled contact illumination probe and field spectroradiometer. Accurate measurements of optical-equivalent grain size are critical for modeling radiative properties of snow such as spectral albedo and microwave emission. Measurements of the spectral reflectance of the snow-pit surface are
ABSTRACT Black carbon (BC) in snow lowers its albedo, increasing the absorption of sunlight, lead... more ABSTRACT Black carbon (BC) in snow lowers its albedo, increasing the absorption of sunlight, leading to positive radiative forcing, climate warming and earlier snowmelt. A series of recent studies have used prescribed-aerosol deposition flux fields in climate model runs to assess the forcing by black carbon in snow. In these studies, the prescribed mass deposition flux of BC to surface snow is decoupled from the mass deposition flux of snow water to the surface. Here we compare prognostic- and prescribed-aerosol runs and use a series of offline calculations to show that the prescribed-aerosol approach results, on average, in a factor of about 1.5–2.5 high bias in annual-mean surface snow BC mixing ratios in three key regions for snow albedo forcing by BC: Greenland, Eurasia and North America. These biases will propagate directly to positive biases in snow and surface albedo reduction by BC. The bias is shown be due to coupling snowfall that varies on meteorological timescales (daily or shorter) with prescribed BC mass deposition fluxes that are more temporally and spatially smooth. The result is physically non-realistic mixing ratios of BC in surface snow. We suggest that an alternative approach would be to prescribe BC mass mixing ratios in snowfall, rather than BC mass fluxes, and we show that this produces more physically realistic BC mixing ratios in snowfall and in the surface snow layer.
Quinn, P.K., A. Stohl, A. Baklanov, M.G. Flanner, A. Herber, K.Kupiainen, K.S. Law, J. Schmale, S... more Quinn, P.K., A. Stohl, A. Baklanov, M.G. Flanner, A. Herber, K.Kupiainen, K.S. Law, J. Schmale, S. Sharma, V. Vestreng, and K. von Salzen, The Arctic, Radiative forcing by black carbon in the Arctic in “State of the Climate in 2013”, Bull. Amer. Meteor, Soc., 95 (7) S124 – 125, 2014.
... Modulator or Trigger? Charlie Zender, Mark Flanner, and Jim Randerson Department of Earth Sys... more ... Modulator or Trigger? Charlie Zender, Mark Flanner, and Jim Randerson Department of Earth System Science, University of California, Irvine ... Roy. Soc. Lon-don A, Math. and Phys. Sci., 430(1880), 577591. Colarco, PR, OB Toon, O. Torres and PJ Rasch, 2002: Determining ...
Abstract The testing results of combustion chamber structure of hypersonic ramjet were used, whic... more Abstract The testing results of combustion chamber structure of hypersonic ramjet were used, which finished the analysis to structure random vibration response of combustion chamber shell. Meanwhile, both of them were compared, which gave us a satisfied ...
: Imaginary refractive index and single scattering albedo for dust comprising 47% Quartz, 25% Ill... more : Imaginary refractive index and single scattering albedo for dust comprising 47% Quartz, 25% Illite, 25% Montmorillonite, 2% Limestone, 0.8% Hematite (i.e., 0.6% Fe).
ABSTRACT The contemporary global distribution of fire emissions reflects a combination of factors... more ABSTRACT The contemporary global distribution of fire emissions reflects a combination of factors linked with ecosystems, the hydrological cycle, and human activity. Humans are increasingly appropriating aspects of the fire regime in many biomes, using fire as a tool in deforestation, pasture maintenance, agriculture, and logging. Compared with other carbon loss pathways from terrestrial ecosystems, fire is unique because its consequences for the climate system are amplified via multiple agents, including the production of methane and ozone greenhouse gases, direct and indirect aerosol effects, black carbon deposition on snow and sea ice, and changes in surface albedo. Here we assess the magnitude of different forcing agents associated with a change in the fire regime in boreal forest ecosystems. We then estimate how these agents may differ for fire in temperate and tropical biomes. As a part of our analysis, we present an initial attempt to estimate the contribution of fire emissions to contemporary radiative forcing from land use change. In a final step, we assess the role of fire as a loss pathway from terrestrial ecosystems over the next several centuries, its relationship with drought, and its potential to contribute to both positive and negative feedbacks between the carbon cycle and climate.
Black carbon (BC) in the atmosphere results from biomass and fossil fuel combustion. It alters ch... more Black carbon (BC) in the atmosphere results from biomass and fossil fuel combustion. It alters chemical and physical properties of the atmosphere and snow albedo, yet little is known about BC emission or deposition histories. Monthly resolved measurements of BC in an ice core indicate that concentrations in central Greenland precipitation varied greatly during the period of record from 1788
Although the influence of El~Niño on inducing drought in equatorial Southeast Asia is relatively ... more Although the influence of El~Niño on inducing drought in equatorial Southeast Asia is relatively well understood, less is known about feedbacks between El Niño, biomass burning and aerosol forcing in this region Fires associated with El~Niño are a new phenomenon, arising from recent increases in human population and agriculture. We examined the impact of El Niño-induced fire aerosols on regional climate using the Community Climate System Model (CCSM), and the Global Fire Emissions Dataset (GFED) for 1997--2006. In our first experiment, we forced the CCSM and a slab ocean model (SOM) with two single-year emissions datasets, one representing a high fire year (1997) and the other a low fire year (2000). In our second experiment the CCSM, coupled with a data ocean model (DOM) of fixed sea surface temperatures (SSTs), was forced with multi-year emissions, consisting of the 10 year GFED record plus an additional 'buffer' year of 'mean' fire emissions. Climate responses to fire aerosols in the two experiments were determined by analyzing ensembles of forty (SOM) and five (DOM) simulations, respectively.Our results show links between fire, aerosols, and decreases in regional precipitation. The inclusion of fire emissions and their climate effects generally improves agreement between simulations and several satellite datasets, including MODIS, MISR and ISCCP. In the first experiment, fires produce aerosol optical depth (AOD) anomalies of 1.0--1.4 over the areas with the most fire in 1997. In the areas with the highest aerosol concentration, solar absorption by these carbonaceous aerosols increases solar heating rates between the surface and 100 hPa upwards of 0.2--0.3 K day-1 during the peak fire season (August--October). This intense heating stabilizes the troposphere, suppresses convection, and ultimately decreases precipitation the region. In peak fire season, fire-emitted aerosols reduced precipitation by more than 30% in the areas of highest AOD. This reduces soil moisture by 1--2% nearly uniformly in the region. These results suggest that recent increases in deforestation and fire emissions in equatorial Southeast Asia may intensify El~Niño-induced drought.
ABSTRACT Smoke from annual burning in the Amazon causes large reduction in surface insolation and... more ABSTRACT Smoke from annual burning in the Amazon causes large reduction in surface insolation and increases the diffuse fraction of photosynthetically-active radiation (PAR). These effects have competing influence on gross primary production (GPP). Recent studies indicate that the sign of net influence depends on aerosol optical depth, but the magnitude of smoke's effect on continental-scale carbon cycling is very poorly constrained and may constitute an important term of fire's net impact on carbon storage. To investigate widespread effects of Amazon smoke on surface radiation properties, we apply a version of the NCAR Community Atmosphere Model with prognostic aerosol transport, driven with re-analysis winds. Carbon aerosol emissions are derived from the Global Fire Emissions Database (GFED). We use AERONET observations to identify model biases in aerosol optical depth, single-scatter albedo, and surface radiative forcing, and prescribe new aerosol optical properties based on field observations to improve model agreement with AERONET data. Finally, we quantify a potential range of smoke-induced change in large-scale GPP based on: 1) ground measurements of GPP in the Amazon as a function of aerosol optical depth and diffuse fraction of PAR, and 2) empirical functions of ecosystem-scale photosynthesis rates currently employed in models such as the Community Land Model (CLM).
Black carbon (BC) has been measured in snow and ice cores at levels that climate models predict a... more Black carbon (BC) has been measured in snow and ice cores at levels that climate models predict are high enough to be the second leading cause in arctic ice melt and glacial retreat after greenhouse gas warming. BC deposited on snow reduces the snow surface albedo; however, in addition to BC content, snow albedo also depends on sky cover, solar
The Tibetan Plateau (TP) has long been identified to be critical in regulating the Asian monsoon ... more The Tibetan Plateau (TP) has long been identified to be critical in regulating the Asian monsoon climate and hydrological cycle. The snowpack and glaciers over the TP provide fresh water to billions of Asian people, but the TP glaciers have been retreating faster than those anywhere else in the world. In this study a series of experiments with a global climate model are designed to simulate radiative forcing (RF) of black carbon (BC) in snow, and to assess the relative impacts of anthropogenic CO2 and carbonaceous particles in the atmosphere and snow on the snowpack over the TP and subsequent impacts on the Asian monsoon climate and hydrological cycle. Results show a large BC content in snow over the TP, especially the southern slope, with concentration larger than 100 µg/kg. Because of high aerosol content in snow and large incident solar radiation, the TP exhibits the largest surface RF induced by BC in snow compared to other snow-covered regions in the world. The BC-induced snow albedo perturbations generate surface RF of 5-15 W/m2 during spring. BC-in-snow increases the surface air temperature by around 1.0oC averaged over the TP and reduces spring snowpack over the TP more than pre-industrial to present CO2 increase and carbonaceous particles in the atmosphere. As a result, runoff increases during late winter and early spring but decreases during late spring and early summer, i.e. a trend toward earlier melt dates. The snowmelt efficacy, defined as the snowpack reduction per unit degree of warming induced by the forcing agent, is 1-4 times larger for BC-in-snow than CO2 increase during April-July, indicating that BC-in-snow more efficiently accelerates snowmelt because the increased net solar radiation induced by reduced albedo melts the snow more efficiently than snow melt due to warming in the air. The TP also influences the South (SAM) and East (EAM) Asian monsoon through its thermodynamical forcing. During boreal spring, aerosols are transported by southwesterly and some particles are deposited to the snowpack over the TP. While BC in the atmosphere directly absorb sunlight and warm the air, the darkened snow surface polluted by BC absorbs more solar radiation and increases the skin temperature, which warms the air above through sensible heating. Both effects enhance the upward motion of air and spur deep convection along the TP during the pre-monsoon season, resulting in earlier onset of the SAM and increase of moisture, cloudiness and convective precipitation over northern India. BC-in-snow has a more significant impact on the EAM in July than CO2 increase and carbonaceous particles in the atmosphere. Contributed by the significant increase of both sensible heat flux associated with warm skin temperature and latent heat flux associated with increased soil moisture with long memory, the role of the TP as a heat pump is elevated from spring through summer as the land-sea thermal contrast increases to strengthen the EAM. As a result, both southern China and northern China become wetter, but central China becomes drier - a near-zonal anomaly pattern that is consistent with the dominant mode of precipitation variability in East Asia.
We present a technique for in situ measurement of the vertical and spatial stratigraphic distribu... more We present a technique for in situ measurement of the vertical and spatial stratigraphic distribution of snow optical grain size with a coupled contact illumination probe and field spectroradiometer. Accurate measurements of optical-equivalent grain size are critical for modeling radiative properties of snow such as spectral albedo and microwave emission. Measurements of the spectral reflectance of the snow-pit surface are
ABSTRACT Black carbon (BC) in snow lowers its albedo, increasing the absorption of sunlight, lead... more ABSTRACT Black carbon (BC) in snow lowers its albedo, increasing the absorption of sunlight, leading to positive radiative forcing, climate warming and earlier snowmelt. A series of recent studies have used prescribed-aerosol deposition flux fields in climate model runs to assess the forcing by black carbon in snow. In these studies, the prescribed mass deposition flux of BC to surface snow is decoupled from the mass deposition flux of snow water to the surface. Here we compare prognostic- and prescribed-aerosol runs and use a series of offline calculations to show that the prescribed-aerosol approach results, on average, in a factor of about 1.5–2.5 high bias in annual-mean surface snow BC mixing ratios in three key regions for snow albedo forcing by BC: Greenland, Eurasia and North America. These biases will propagate directly to positive biases in snow and surface albedo reduction by BC. The bias is shown be due to coupling snowfall that varies on meteorological timescales (daily or shorter) with prescribed BC mass deposition fluxes that are more temporally and spatially smooth. The result is physically non-realistic mixing ratios of BC in surface snow. We suggest that an alternative approach would be to prescribe BC mass mixing ratios in snowfall, rather than BC mass fluxes, and we show that this produces more physically realistic BC mixing ratios in snowfall and in the surface snow layer.
Quinn, P.K., A. Stohl, A. Baklanov, M.G. Flanner, A. Herber, K.Kupiainen, K.S. Law, J. Schmale, S... more Quinn, P.K., A. Stohl, A. Baklanov, M.G. Flanner, A. Herber, K.Kupiainen, K.S. Law, J. Schmale, S. Sharma, V. Vestreng, and K. von Salzen, The Arctic, Radiative forcing by black carbon in the Arctic in “State of the Climate in 2013”, Bull. Amer. Meteor, Soc., 95 (7) S124 – 125, 2014.
... Modulator or Trigger? Charlie Zender, Mark Flanner, and Jim Randerson Department of Earth Sys... more ... Modulator or Trigger? Charlie Zender, Mark Flanner, and Jim Randerson Department of Earth System Science, University of California, Irvine ... Roy. Soc. Lon-don A, Math. and Phys. Sci., 430(1880), 577591. Colarco, PR, OB Toon, O. Torres and PJ Rasch, 2002: Determining ...
Abstract The testing results of combustion chamber structure of hypersonic ramjet were used, whic... more Abstract The testing results of combustion chamber structure of hypersonic ramjet were used, which finished the analysis to structure random vibration response of combustion chamber shell. Meanwhile, both of them were compared, which gave us a satisfied ...
: Imaginary refractive index and single scattering albedo for dust comprising 47% Quartz, 25% Ill... more : Imaginary refractive index and single scattering albedo for dust comprising 47% Quartz, 25% Illite, 25% Montmorillonite, 2% Limestone, 0.8% Hematite (i.e., 0.6% Fe).
ABSTRACT The contemporary global distribution of fire emissions reflects a combination of factors... more ABSTRACT The contemporary global distribution of fire emissions reflects a combination of factors linked with ecosystems, the hydrological cycle, and human activity. Humans are increasingly appropriating aspects of the fire regime in many biomes, using fire as a tool in deforestation, pasture maintenance, agriculture, and logging. Compared with other carbon loss pathways from terrestrial ecosystems, fire is unique because its consequences for the climate system are amplified via multiple agents, including the production of methane and ozone greenhouse gases, direct and indirect aerosol effects, black carbon deposition on snow and sea ice, and changes in surface albedo. Here we assess the magnitude of different forcing agents associated with a change in the fire regime in boreal forest ecosystems. We then estimate how these agents may differ for fire in temperate and tropical biomes. As a part of our analysis, we present an initial attempt to estimate the contribution of fire emissions to contemporary radiative forcing from land use change. In a final step, we assess the role of fire as a loss pathway from terrestrial ecosystems over the next several centuries, its relationship with drought, and its potential to contribute to both positive and negative feedbacks between the carbon cycle and climate.
Black carbon (BC) in the atmosphere results from biomass and fossil fuel combustion. It alters ch... more Black carbon (BC) in the atmosphere results from biomass and fossil fuel combustion. It alters chemical and physical properties of the atmosphere and snow albedo, yet little is known about BC emission or deposition histories. Monthly resolved measurements of BC in an ice core indicate that concentrations in central Greenland precipitation varied greatly during the period of record from 1788
Although the influence of El~Niño on inducing drought in equatorial Southeast Asia is relatively ... more Although the influence of El~Niño on inducing drought in equatorial Southeast Asia is relatively well understood, less is known about feedbacks between El Niño, biomass burning and aerosol forcing in this region Fires associated with El~Niño are a new phenomenon, arising from recent increases in human population and agriculture. We examined the impact of El Niño-induced fire aerosols on regional climate using the Community Climate System Model (CCSM), and the Global Fire Emissions Dataset (GFED) for 1997--2006. In our first experiment, we forced the CCSM and a slab ocean model (SOM) with two single-year emissions datasets, one representing a high fire year (1997) and the other a low fire year (2000). In our second experiment the CCSM, coupled with a data ocean model (DOM) of fixed sea surface temperatures (SSTs), was forced with multi-year emissions, consisting of the 10 year GFED record plus an additional 'buffer' year of 'mean' fire emissions. Climate responses to fire aerosols in the two experiments were determined by analyzing ensembles of forty (SOM) and five (DOM) simulations, respectively.Our results show links between fire, aerosols, and decreases in regional precipitation. The inclusion of fire emissions and their climate effects generally improves agreement between simulations and several satellite datasets, including MODIS, MISR and ISCCP. In the first experiment, fires produce aerosol optical depth (AOD) anomalies of 1.0--1.4 over the areas with the most fire in 1997. In the areas with the highest aerosol concentration, solar absorption by these carbonaceous aerosols increases solar heating rates between the surface and 100 hPa upwards of 0.2--0.3 K day-1 during the peak fire season (August--October). This intense heating stabilizes the troposphere, suppresses convection, and ultimately decreases precipitation the region. In peak fire season, fire-emitted aerosols reduced precipitation by more than 30% in the areas of highest AOD. This reduces soil moisture by 1--2% nearly uniformly in the region. These results suggest that recent increases in deforestation and fire emissions in equatorial Southeast Asia may intensify El~Niño-induced drought.
ABSTRACT Smoke from annual burning in the Amazon causes large reduction in surface insolation and... more ABSTRACT Smoke from annual burning in the Amazon causes large reduction in surface insolation and increases the diffuse fraction of photosynthetically-active radiation (PAR). These effects have competing influence on gross primary production (GPP). Recent studies indicate that the sign of net influence depends on aerosol optical depth, but the magnitude of smoke's effect on continental-scale carbon cycling is very poorly constrained and may constitute an important term of fire's net impact on carbon storage. To investigate widespread effects of Amazon smoke on surface radiation properties, we apply a version of the NCAR Community Atmosphere Model with prognostic aerosol transport, driven with re-analysis winds. Carbon aerosol emissions are derived from the Global Fire Emissions Database (GFED). We use AERONET observations to identify model biases in aerosol optical depth, single-scatter albedo, and surface radiative forcing, and prescribe new aerosol optical properties based on field observations to improve model agreement with AERONET data. Finally, we quantify a potential range of smoke-induced change in large-scale GPP based on: 1) ground measurements of GPP in the Amazon as a function of aerosol optical depth and diffuse fraction of PAR, and 2) empirical functions of ecosystem-scale photosynthesis rates currently employed in models such as the Community Land Model (CLM).
Black carbon (BC) has been measured in snow and ice cores at levels that climate models predict a... more Black carbon (BC) has been measured in snow and ice cores at levels that climate models predict are high enough to be the second leading cause in arctic ice melt and glacial retreat after greenhouse gas warming. BC deposited on snow reduces the snow surface albedo; however, in addition to BC content, snow albedo also depends on sky cover, solar
The Tibetan Plateau (TP) has long been identified to be critical in regulating the Asian monsoon ... more The Tibetan Plateau (TP) has long been identified to be critical in regulating the Asian monsoon climate and hydrological cycle. The snowpack and glaciers over the TP provide fresh water to billions of Asian people, but the TP glaciers have been retreating faster than those anywhere else in the world. In this study a series of experiments with a global climate model are designed to simulate radiative forcing (RF) of black carbon (BC) in snow, and to assess the relative impacts of anthropogenic CO2 and carbonaceous particles in the atmosphere and snow on the snowpack over the TP and subsequent impacts on the Asian monsoon climate and hydrological cycle. Results show a large BC content in snow over the TP, especially the southern slope, with concentration larger than 100 µg/kg. Because of high aerosol content in snow and large incident solar radiation, the TP exhibits the largest surface RF induced by BC in snow compared to other snow-covered regions in the world. The BC-induced snow albedo perturbations generate surface RF of 5-15 W/m2 during spring. BC-in-snow increases the surface air temperature by around 1.0oC averaged over the TP and reduces spring snowpack over the TP more than pre-industrial to present CO2 increase and carbonaceous particles in the atmosphere. As a result, runoff increases during late winter and early spring but decreases during late spring and early summer, i.e. a trend toward earlier melt dates. The snowmelt efficacy, defined as the snowpack reduction per unit degree of warming induced by the forcing agent, is 1-4 times larger for BC-in-snow than CO2 increase during April-July, indicating that BC-in-snow more efficiently accelerates snowmelt because the increased net solar radiation induced by reduced albedo melts the snow more efficiently than snow melt due to warming in the air. The TP also influences the South (SAM) and East (EAM) Asian monsoon through its thermodynamical forcing. During boreal spring, aerosols are transported by southwesterly and some particles are deposited to the snowpack over the TP. While BC in the atmosphere directly absorb sunlight and warm the air, the darkened snow surface polluted by BC absorbs more solar radiation and increases the skin temperature, which warms the air above through sensible heating. Both effects enhance the upward motion of air and spur deep convection along the TP during the pre-monsoon season, resulting in earlier onset of the SAM and increase of moisture, cloudiness and convective precipitation over northern India. BC-in-snow has a more significant impact on the EAM in July than CO2 increase and carbonaceous particles in the atmosphere. Contributed by the significant increase of both sensible heat flux associated with warm skin temperature and latent heat flux associated with increased soil moisture with long memory, the role of the TP as a heat pump is elevated from spring through summer as the land-sea thermal contrast increases to strengthen the EAM. As a result, both southern China and northern China become wetter, but central China becomes drier - a near-zonal anomaly pattern that is consistent with the dominant mode of precipitation variability in East Asia.
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Papers by Mark Flanner