scholarly journals The direct radiative effect of biomass burning aerosols over southern Africa

2005 ◽  
Vol 5 (2) ◽  
pp. 1165-1211 ◽  
Author(s):  
S. J. Abel ◽  
E. J. Highwood ◽  
J. M. Haywood ◽  
M. A. Stringer
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Land Surface ◽  
General Circulation ◽  
Surface Albedo ◽  
Circulation Model ◽  
Radiative Effect ◽  
Aerosol Optical Properties ◽  
African Region ◽  
Biomass Smoke

Abstract. A multi-column radiative transfer code is used to assess the direct radiative effect of biomass burning aerosols over the southern African region during September. The horizontal distribution of biomass smoke is estimated from two sources; i) General Circulation Model (GCM) simulations combined with measurements from the Aerosol Robotic Network (AERONET) of Sun photometers; ii) data from the Moderate resolution Imaging Spectrometer (MODIS) satellite. Aircraft and satellite measurements are used to constrain the cloud fields, aerosol optical properties, vertical structure, and land surface albedo included in the model. The net regional direct effect of the biomass smoke is −3.1 to −3.6 Wm-2 at the top of atmosphere, and −14.4 to −17.0 Wm-2 at the surface for the MODIS and GCM distributions of aerosol. The direct radiative effect is shown to be highly sensitive to the prescribed vertical profiles and aerosol optical properties. The diurnal cycle of clouds and the spectral dependency of surface albedo are also shown to play an important role.

scholarly journals The direct radiative effect of biomass burning aerosols over southern Africa

2005 ◽  
Vol 5 (7) ◽  
pp. 1999-2018 ◽  
Author(s):  
S. J. Abel ◽  
E. J. Highwood ◽  
J. M. Haywood ◽  
M. A. Stringer
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Land Surface ◽  
General Circulation ◽  
Surface Albedo ◽  
Circulation Model ◽  
Radiative Effect ◽  
Aerosol Optical Properties ◽  
African Region ◽  
Biomass Smoke

Abstract. A multi-column radiative transfer code is used to assess the direct radiative effect of biomass burning aerosols over the southern African region during September. The horizontal distribution of biomass smoke is estimated from two sources; i) General Circulation Model (GCM) simulations combined with measurements from the Aerosol Robotic Network (AERONET) of Sun photometers; ii) data from the Moderate resolution Imaging Spectrometer (MODIS) satellite. Aircraft and satellite measurements are used to constrain the cloud fields, aerosol optical properties, vertical structure, and land surface albedo included in the model. The net regional direct effect of the biomass smoke is -3.1 to -3.6 Wm-2 at the top of atmosphere, and -14.4 to -17.0 Wm-2 at the surface for the MODIS and GCM distributions of aerosol. The direct radiative effect is shown to be highly sensitive to the prescribed vertical profiles and aerosol optical properties. The diurnal cycle of clouds and the spectral dependency of surface albedo are also shown to play an important role.

scholarly journals A new radiation infrastructure for the Modular Earth Submodel System (MESSy, based on version 2.51)

2016 ◽  
Author(s):  
Simone Dietmüller ◽  
Patrick Jöckel ◽  
Holger Tost ◽  
Markus Kunze ◽  
Cathrin Gellhorn ◽  
...  
Keyword(s):  
Optical Properties ◽  
Atmospheric Chemistry ◽  
Radiative Forcing ◽  
General Circulation ◽  
Circulation Model ◽  
Shortwave Radiation ◽  
Aerosol Optical Properties ◽  
On Line ◽  
User Friendly ◽  
Radiation Scheme

Abstract. The Modular Earth Submodel System (MESSy) provides an interface to couple submodels to a basemodel via a highly flexible data management facility (Jöckel et al., 2010). In the present paper we present the four new radiation related submodels RAD, AEROPT, CLOUDOPT and ORBIT. The submodel RAD (with shortwave radiation scheme RAD_FUBRAD) simulates the radiative transfer, the submodel AEROPT calculates the aerosol optical properties, the submodel CLOUDOPT calculates the cloud optical properties, and the submodel ORBIT is responsible for Earth orbit calculations. These submodels are coupled via the standard MESSy infrastructure and are largely based on the original radiation scheme of the general circulation model ECHAM5, however, expanded with additional features. These features comprise, among others, user-friendly and flexibly controllable (by namelists) on-line radiative forcing calculations by multiple diagnostic calls of the radiation routines. With this, it is now possible to calculate radiative forcing (instantaneous as well as stratosphere adjusted) of various greenhouse gases simultaneously in only one simulation, as well as the radiative forcing of cloud perturbations. Examples of on-line radiative forcing calculations in the ECHAM/MESSy Atmospheric Chemistry (EMAC) model are presented.

scholarly journals Background albedo dynamics improve simulated precipitation variability in the Sahel region

2013 ◽  
Vol 4 (2) ◽  
pp. 595-626
Author(s):  
F. S. E. Vamborg ◽  
V. Brovkin ◽  
M. Claussen
Keyword(s):  
Land Surface ◽  
General Circulation ◽  
Surface Albedo ◽  
Rainfall Variability ◽  
Circulation Model ◽  
Dynamic Background ◽  
Simulated Precipitation ◽  
Sst Forcing ◽  
Rainfall Anomalies ◽  
Sahel Region

Abstract. Using the general circulation model ECHAM5-JSBACH forced by observed sea surface temperatures (SSTs) for the 20th century, we investigate the role of vegetation and land surface albedo dynamics in shaping rainfall variability in the Sahel. We use two different land surface albedo schemes, one in which the albedo of the canopy is varying and one in which additionally the albedo changes of the surface below the canopy are taken into account. The SST-forcing provides the background for simulating the observed decadal signal in Sahelian rainfall, though the respone to SST-forcing only is not strong enough to fully capture the observed signal. The introduction of dynamic vegetation leads to an increase in inter-annual variability of the rainfall, and gives rise to an increased number of high amplitude rainfall anomaly events. The dynamic background albedo leads to an increased persistence of the rainfall anomalies. The increase in persistence means that the difference between the dry and the wet decades is increased compared to the other simulations, and thus more closely matching the observed absolute change between these two periods. These results highlight the need for a consistent representation of land surface albedo dynamics for capturing the full extent of rainfall anomalies in the Sahel.

scholarly journals Simulation of aerosol optical properties over a tropical urban site in India using a global model and its comparison with ground measurements

2011 ◽  
Vol 29 (5) ◽  
pp. 955-963 ◽  
Author(s):  
D. Goto ◽  
K. V. S. Badarinath ◽  
T. Takemura ◽  
T. Nakajima
Keyword(s):  
Optical Properties ◽  
General Circulation ◽  
Three Dimensional ◽  
Temporal Distribution ◽  
Circulation Model ◽  
Global Model ◽  
Atmospheric Environment ◽  
Urban Site ◽  
Aerosol Optical Properties ◽  
Aerosol Emission

Abstract. Aerosols have great impacts on atmospheric environment, human health, and earth's climate. Therefore, information on their spatial and temporal distribution is of paramount importance. Despite numerous studies have examined the variation and trends of BC and AOD over India, only very few have focused on their spatial distribution or even correlating the observations with model simulations. In the present study, a three-dimensional aerosol transport-radiation model coupled with a general circulation model. SPRINTARS, simulated atmospheric aerosol distributions including BC and aerosol optical properties, i.e., aerosol optical thickness (AOT), Ångström Exponent (AE), and single scattering albedo (SSA). The simulated results are compared with both BC measurements by aethalometer and aerosol optical properties measured by ground-based skyradiometer and by satellite sensor, MODIS/Terra over Hyderabad, which is a tropical urban area of India, for the year 2008. The simulated AOT and AE in Hyderabad are found to be comparable to ground-based measured ones. The simulated SSA tends to be higher than the ground-based measurements. Both these comparisons of aerosol optical properties between the simulations with different emission inventories and the measurements indicate that, firstly the model uncertainties derived from aerosol emission inventory cannot explain the gaps between the simulations and the measurements and secondly the vertical transport of BC and the treatment of BC-containing particles can be the main issue in the global model to solve the gap.

scholarly journals Assessment of Snow Cover and Surface Albedo in the ECHAM5 General Circulation Model

2006 ◽  
Vol 19 (16) ◽  
pp. 3828-3843 ◽  
Author(s):  
Andreas Roesch ◽  
Erich Roeckner
Keyword(s):  
Snow Cover ◽  
Land Surface ◽  
General Circulation ◽  
Surface Albedo ◽  
Climate Model ◽  
Circulation Model ◽  
Masking Effect ◽  
Second Phase ◽  
Snow Cover Area ◽  
Highly Nonlinear

Abstract Land surface albedo, snow cover fraction (SCF), and snow depth (SD) from two versions of the ECHAM climate model are compared to available ground-based and remote-sensed climatologies. ECHAM5 accurately reproduces the annual cycle of SD and correctly captures the timing of the snowmelt. ECHAM4, in contrast, simulates an excessive Eurasian snow mass in spring due to a delayed snowmelt. Annual cycles of continental snow cover area (SCA) are captured fairly well in both ECHAM4 and ECHAM5. The negative SCA trend observed during the last two decades of the twentieth century is evident also in the ECHAM5 simulation but less pronounced. ECHAM5 captures the interannual variability of SCA reasonably well, which is in contrast with results that were reported earlier for second-phase Atmospheric Model Intercomparison Project (AMIP II) models. An error analysis revealed that, for studies on SCA, it is essential to test the data records for their homogeneity and trends. The second part of the paper compares simulated surface albedos with remote-sensed climatologies derived from PINKER and the Moderate Resolution Imaging Spectroradiometer (MODIS). ECHAM5 is in better agreement with observations in the Himalayan–Tibetan area than ECHAM4. In contrast, the positive surface albedo bias over boreal forests under snow conditions in ECHAM4 is even more pronounced in ECHAM5. This deficiency is mainly due to the neglect of the snow-masking effect of stems and branches after trees have lost their foliage. The analysis demonstrates that positive biases in the SCA are not necessarily related to positive albedo biases. Furthermore, an overestimation of the area-averaged SD is not always related to positive SCF anomalies since the relationship between SD and SCF is highly nonlinear.

scholarly journals Background albedo dynamics improve simulated precipitation variability in the Sahel region

2014 ◽  
Vol 5 (1) ◽  
pp. 89-101 ◽  
Author(s):  
F. S. E. Vamborg ◽  
V. Brovkin ◽  
M. Claussen
Keyword(s):  
Land Surface ◽  
General Circulation ◽  
Surface Albedo ◽  
Rainfall Variability ◽  
Circulation Model ◽  
Dynamic Background ◽  
Simulated Precipitation ◽  
Sst Forcing ◽  
Rainfall Anomalies ◽  
Sahel Region

Abstract. Using the general circulation model ECHAM5–JSBACH forced by observed sea surface temperatures (SSTs) for the 20th century, we investigate the role of vegetation and land surface albedo dynamics in shaping rainfall variability in the Sahel. We use two different land surface albedo schemes, one in which the albedo of the canopy is varying and one in which the albedo changes of the surface below the canopy are also taken into account. The SST forcing provides the background for simulating the observed decadal signal in Sahelian rainfall, though the response to SST forcing only is not strong enough to fully capture the observed signal. The introduction of dynamic vegetation leads to an increase in interannual variability of the rainfall, and gives rise to an increased number of high-amplitude rainfall anomaly events. The dynamic background albedo leads to an increased persistence of the rainfall anomalies. The increase in persistence means that the difference between the dry and the wet decades is increased compared to the other simulations, and thus more closely matching the observed absolute change between these two periods. These results highlight the need for a consistent representation of land surface albedo dynamics for capturing the full extent of rainfall anomalies in the Sahel.

scholarly journals Aerosol optical properties at Lampedusa (Central Mediterranean) – 2. Determination of single scattering albedo at two wavelengths for different aerosol types

2005 ◽  
Vol 5 (4) ◽  
pp. 4971-5005 ◽  
Author(s):  
D. Meloni ◽  
A. di Sarra ◽  
G. Pace ◽  
F. Monteleone
Keyword(s):  
Optical Properties ◽  
Aerosol Optical Depth ◽  
Biomass Burning ◽  
Surface Albedo ◽  
Single Scattering ◽  
Asymmetry Factor ◽  
Aerosol Optical Properties ◽  
Central Mediterranean ◽  
Desert Dust ◽  
Aerosol Types

Abstract. Aerosol optical properties were retrieved from direct and diffuse spectral irradiance measurements made by a multi-filter rotating shadowband radiometer (MFRSR) at the island of Lampedusa (35.5° N, 12.6° E), in the Central Mediterranean, in the period July 2001–September 2003. In a companion paper (Pace et al., 2005) the aerosol optical depth (AOD) and Ångström exponent were used together with airmass backward trajectories to identify and classify different aerosol types. The MFRSR diffuse-to-direct ratio (DDR) at 415.6 nm and 868.7 nm for aerosol classified as biomass burning-urban/industrial, originating primarily from the European continent, and desert dust, originating from the Sahara, is used in this study to estimate the aerosol single scattering albedo (SSA). A detailed radiative transfer model is initialized with the measured aerosol optical depth; calculations are performed at the two wavelengths varying the SSA values until the modelled DDR matches the MFRSR observations. Sensitivity studies are performed to estimate how uncertainties on AOD, DDR, asymmetry factor (g), and surface albedo influence the retrieved SSA values. The results show that a 3% variation of AOD or DDR produce a change of about 0.02 in the retrieved SSA value at 415.6 and 868.7 nm; a ±0.06 variation of the asymmetry factor g produces a change of the estimated SSA of <0.04 at 415.6 nm, and <0.06 at 868.7 nm; finally, an increase of the assumed surface albedo of 0.05 gives very small changes (0.01–0.02) in the retrieved SSA. The calculations show that the SSA of desert dust (DD) increases with wavelength, from 0.81±0.05 at 415.6 nm to 0.94±0.05 at 868.7 nm; on the contrary, the SSA of urban/industrial (UN) aerosols decreases from 0.96±0.02 at 415.6 nm to 0.87±0.07 at 868.7 nm; the SSA of biomass burning (BB) particles is 0.82±0.04 at 415.6 nm and 0.80±0.05 at 868.7 nm. Episodes of UN aerosols occur usually in June and July; BB aerosol episodes with large AOD and long duration are observed mainly in July and August, the driest months of the year, when the development of fires is favoured.

scholarly journals A new radiation infrastructure for the Modular Earth Submodel System (MESSy, based on version 2.51)

2016 ◽  
Vol 9 (6) ◽  
pp. 2209-2222 ◽  
Author(s):  
Simone Dietmüller ◽  
Patrick Jöckel ◽  
Holger Tost ◽  
Markus Kunze ◽  
Catrin Gellhorn ◽  
...  
Keyword(s):  
Optical Properties ◽  
Atmospheric Chemistry ◽  
Radiative Forcing ◽  
General Circulation ◽  
Circulation Model ◽  
Shortwave Radiation ◽  
Earth Orbit ◽  
Aerosol Optical Properties ◽  
User Friendly ◽  
Radiation Scheme

Abstract. The Modular Earth Submodel System (MESSy) provides an interface to couple submodels to a base model via a highly flexible data management facility (Jöckel et al., 2010). In the present paper we present the four new radiation related submodels RAD, AEROPT, CLOUDOPT, and ORBIT. The submodel RAD (including the shortwave radiation scheme RAD_FUBRAD) simulates the radiative transfer, the submodel AEROPT calculates the aerosol optical properties, the submodel CLOUDOPT calculates the cloud optical properties, and the submodel ORBIT is responsible for Earth orbit calculations. These submodels are coupled via the standard MESSy infrastructure and are largely based on the original radiation scheme of the general circulation model ECHAM5, however, expanded with additional features. These features comprise, among others, user-friendly and flexibly controllable (by namelists) online radiative forcing calculations by multiple diagnostic calls of the radiation routines. With this, it is now possible to calculate radiative forcing (instantaneous as well as stratosphere adjusted) of various greenhouse gases simultaneously in only one simulation, as well as the radiative forcing of cloud perturbations. Examples of online radiative forcing calculations in the ECHAM/MESSy Atmospheric Chemistry (EMAC) model are presented.

scholarly journals Aerosol optical properties at Lampedusa (Central Mediterranean). 2. Determination of single scattering albedo at two wavelengths for different aerosol types

2006 ◽  
Vol 6 (3) ◽  
pp. 715-727 ◽  
Author(s):  
D. Meloni ◽  
A. di Sarra ◽  
G. Pace ◽  
F. Monteleone
Keyword(s):  
Optical Properties ◽  
Aerosol Optical Depth ◽  
Biomass Burning ◽  
Surface Albedo ◽  
Single Scattering ◽  
Asymmetry Factor ◽  
Aerosol Optical Properties ◽  
Central Mediterranean ◽  
Desert Dust ◽  
Aerosol Types

Abstract. Aerosol optical properties were retrieved from direct and diffuse spectral irradiance measurements made by a multi-filter rotating shadowband radiometer (MFRSR) at the island of Lampedusa (35.5° N, 12.6° E), in the Central Mediterranean, in the period July 2001–September 2003. In a companion paper (Pace et al., 2006) the aerosol optical depth (AOD) and Ångström exponent were used together with airmass backward trajectories to identify and classify different aerosol types. The MFRSR diffuse-to-direct ratio (DDR) at 415.6 nm and 868.7 nm for aerosol classified as "biomass burning-urban/industrial", originating primarily from the European continent, and desert dust, originating from the Sahara, is used in this study to estimate the aerosol single scattering albedo (SSA). A detailed radiative transfer model is initialised with the measured aerosol optical depth; calculations are performed at the two wavelengths varying the SSA values until the modelled DDR matches the MFRSR observations. Sensitivity studies are performed to estimate how uncertainties on AOD, DDR, asymmetry factor (g), and surface albedo influence the retrieved SSA values. The results show that a 3% variation of AOD or DDR produce a change of about 0.02 in the retrieved SSA value at 415.6 and 868.7 nm; a ±0.06 variation of the asymmetry factor g produces a change of the estimated SSA of <0.04 at 415.6 nm, and <0.06 at 868.7 nm; finally, an increase of the assumed surface albedo of 0.05 causes very small changes (0.01–0.02) in the retrieved SSA. The calculations show that the SSA of desert dust (DD) increases with wavelength, from 0.81±0.05 at 415.6 nm to 0.94±0.05 at 868.7 nm; on the contrary, the SSA of urban/industrial (UN) aerosols decreases from 0.96±0.02 at 415.6 nm to 0.87±0.07 at 868.7 nm; the SSA of biomass burning (BB) particles is 0.82±0.04 at 415.6 nm and 0.80±0.05 at 868.7 nm. Episodes of UN aerosols occur usually in June and July; long lasting BB aerosol episodes with large AOD are observed mainly in July and August, the driest months of the year, when the development of fires is frequent.

HAPEX—MOBILHY: A Hydrologic Atmospheric Experiment the Study of Water Budget and Evaporation Flux at the Climatic Scale

1986 ◽  
Vol 67 (2) ◽  
pp. 138-144 ◽  
Author(s):  
Jean-Claude André ◽  
Jean-Paul Goutorbe ◽  
Alain Perrier
Keyword(s):  
Remote Sensing ◽  
Soil Moisture ◽  
Land Surface ◽  
Water Budget ◽  
General Circulation ◽  
Circulation Model ◽  
Surface Energy Budget ◽  
Surface Hydrology ◽  
Land Surface Water ◽  
Evaporation Flux

The HAPEX-MOBILHY program is aimed at studying the hydrological budget and evaporation flux at the scale of a GCM (general circulation model) grid square, i.e., 104 km2. Different surface and subsurface networks will be operated during the year 1986, to measure and monitor soil moisture, surface-energy budget and surface hydrology, as well as atmospheric properties. A two-and-a-half-month special observing period will allow for detailed measurements of atmospheric fluxes and for intensive remote sensing of surface properties using well-instrumented aircraft. The main objective of the program, for which guest investigations are strongly encouraged, is to provide a data base against which parameterization schemes for the land-surface water budget will be tested and developed.

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