165 research outputs found
Adebiyi etal: absorption of shortwave radiation by North African dust
No full textThe codes and datasets contained here are for the paper with the information below
Titled: "North African dust absorbs substantially less solar radiation than estimated by climate models and remote-sensing retrievals"
Author: Adeyemi A. Adebiyi, Yue Huang, Bjørn H. Samset and Jasper F. Kok
Please see the ReadMe.txt for additional details.
------------------------
Corresponding Authors:
Adeyemi Adebiyi
Email: [email protected];
Department of Life and Environmental Sciences,
University of California-Merced,
5200 North Lake Road Merced, CA 95343
Corrigendum for: Patorani local knowledge system in fisheries resources conservation education in Galesong District South Sulawesi
No full textWe sincerely express our apology for the changes in the author list in the article entitled Patorani local knowledge system in fisheries resources conservation education in Galesong District South Sulawesi. This article was published on DOI: 10.17977/um017v28i12023p52-63, with the authors list consisting of Hasriyanti, Rusdi, Alonge Titus Adeyemi, Michel E. D. Chaves, and Erman Syarif. However, Michel E. D. Chaves issue a complaint regarding his involvement during the research and paper completion. He did not agree to the inclusion of his name in the author list. We have contacted the corresponding author for confirmation. Besides, the co-author has also confirmed the mistake in the writing of one of the author’s names, Alonge Titus Adeyemi, which should be Titus Adeyemi Alonge. The corresponding author has submitted a letter of author contribution signed by Hasriyanti, Rusdi, Titus Adeyemi Alonge, and Erman Syarif. The original article has been revised, and reasonable effort should be made to remove all references to this article
Portraits for an eagle: a festschrift in honour of Femi Osofisan
No full textTo mark the 60th birthday of Femi Osofisan, this unique collection of essays by friends and critics pays tribute to his many achievements as a director, teacher, essayist, novelist, poet, critic and one of the foremost playwrights from Africa. The essays provide an important insight into the man,his work and his valuable contributions to theatre and literature in Africa.
Femi Osofisan has taught, directed and had his plays performed in several countries including Australia, Canada, Germany, Ghana, Sierra Leone, Jamaica, Lesotho, Sri Lanka, United Kingdom and the USA. Author of more than fifty plays, two books for junior readers, four works of fiction, four collections of poetry anf four volumes of essays, Osofisan also has popular columns in a number of Nigerian newspapers. Currently the President of the Nigerian Centre of International PEN and a Patron of the Pan-African Writers' Association, he has been the President of the Association of Nigerian Authors. Osofisan is currently a Professor of Drama at the University of Ibadan, Nigeria.
Portraits For An Eagle is a definitive tribute to a man of the theatre. Contributors include fellow writers, distinguished academics and critics like Biodun Jeyifo, James Gibbs, Olu Obafemi, Barbara Goff and Martin Banham
Portraits for an eagle: a festschrift in honour of Femi Osofisan
No full textTo mark the 60th birthday of Femi Osofisan, this unique collection of essays by friends and critics pays tribute to his many achievements as a director, teacher, essayist, novelist, poet, critic and one of the foremost playwrights from Africa. The essays provide an important insight into the man,his work and his valuable contributions to theatre and literature in Africa.
Femi Osofisan has taught, directed and had his plays performed in several countries including Australia, Canada, Germany, Ghana, Sierra Leone, Jamaica, Lesotho, Sri Lanka, United Kingdom and the USA. Author of more than fifty plays, two books for junior readers, four works of fiction, four collections of poetry anf four volumes of essays, Osofisan also has popular columns in a number of Nigerian newspapers. Currently the President of the Nigerian Centre of International PEN and a Patron of the Pan-African Writers' Association, he has been the President of the Association of Nigerian Authors. Osofisan is currently a Professor of Drama at the University of Ibadan, Nigeria.
Portraits For An Eagle is a definitive tribute to a man of the theatre. Contributors include fellow writers, distinguished academics and critics like Biodun Jeyifo, James Gibbs, Olu Obafemi, Barbara Goff and Martin Banham
Recommended from our members
Chapter 6 - Future changes in precipitation distributions over Africa
No full textThe African continent is home to approximately 1.4 billion people, about 18% of the world's population. Monsoon precipitation is critical to African societies, contributing a large proportion of the average annual precipitation. Variations in monsoon precipitation have major impacts on, for example, agriculture, freshwater supply and sanitation, and hydropower generation. Unusually low precipitation can also lead to large and prolonged droughts across Africa, increasing mortality. Future changes in monsoon precipitation, therefore, have important societal implications. In this chapter, we summarize the impact of climate change on future changes in precipitation over Africa and for the end of the 21st century. Climate models show that precipitation is projected to increase over most of the African continent (the central Sahel, east and central Africa), while precipitation is projected to decrease over the western Sahel and south-eastern Africa. We document the impact of climate change on extreme precipitation events. We also explain the uncertainty in simulated changes in precipitation and discuss ways to improve the reliability of projections.</p
Dust Constraints from joint Observational-Modelling-experiMental analysis – DustCOMM Version 1
No full textDust Constraints from joint Observational-Modelling-experiMental analysis – DustCOMM Version 1
This is the version-1 of DustCOMM dataset (Adebiyi et al. Geoscientific Model Development), containing annual and seasonal climatologies of constrained dust aerosol properties, including spatially-varying dust size distribution, mass extinction efficiency, and atmospheric dust loading.
Please be aware that there will be future versions of DustCOMM that incorporates more observational, modeling and experimental constraints.
Please send an email to the corresponding authors if you have any question or would like to receive update of DustCOMM's future developments.
Below, we give a brief description of each data file. In each, we have included the mean, median, 1 and 2 sigma uncertainty estimates as a function of location. These uncertainty estimates are derived from probability distributions that describe the field over each location. Please contact the corresponding authors if you are interested in the full dataset.
The dimensions in these dataset are denoted as:
lon [144] -- Longitude. Unit of degrees_east. Global - 2.5 deg resolution.
lat [96] -- Latitude. Unit of degrees_north. Global - ~2 deg resolution
lev [35] -- Pressure levels. Unit of hPa. ~900 hPa to 100 hPa. Lower resolution in the boundary layer and higher resolution in the free troposphere.
D [200] -- Dust Geometric Diameter. Unit of microns. From 0.2-20 microns.
nseas [4] -- Seasons. They are DJF, MAM, JJA, and SON corresponding to December-January-February, March-April-May, June-July-August, and September-October-December respectively.
--------
Dust_Size_Distr_dVdD_annual.nc - Dimension: [lon, lat, lev, D]
Dust_Size_Distr_dVdD_seasonal.nc - Dimension: [nseas, lon, lat, lev, D]
-- DustCOMM annual and seasonal climatologies of 3-D normalized dust (volume) size distribution. Fields include:
-> dVdD_mean -- Mean Normalized Dust Volume Size Distribution
-> dVdD_median -- Median Normalized Dust Volume Size Distribution
-> dVdD_Pos1sig -- +1 Sigma Normalized Dust Volume Size Distribution
-> dVdD_Neg1sig -- -1 Sigma Normalized Dust Volume Size Distribution
-> dVdD_Pos2sig -- +2 Sigma Normalized Dust Volume Size Distribution
-> dVdD_Neg2sig -- -2 Sigma Normalized Dust Volume Size Distribution
--------
Dust_3D_MEE_annual.nc - Dimension: [lon, lat, lev]
Dust_3D_MEE_seasonal.nc - Dimension: [nseas, lon, lat, lev]
-- DustCOMM annual and seasonal climatologies of 3-D dust mass extinction efficiency (m2/g). Fields include:
-> MEE_mean -- Mean Dust 3D Mass Extinction Efficiency
-> MEE_median -- Median Dust 3D Mass Extinction Efficiency
-> MEE_Pos1sig -- +1 Sigma Dust 3D Mass Extinction Efficiency
-> MEE_Neg1sig -- -1 Sigma Dust 3D Mass Extinction Efficiency
-> MEE_Pos2sig -- +2 Sigma Dust 3D Mass Extinction Efficiency
-> MEE_Neg2sig -- -2 Sigma Dust 3D Mass Extinction Efficiency
--------
Dust_2D_MEE_annual.nc - Dimension: [lon, lat]
Dust_2D_MEE_seasonal.nc - Dimension: [nseas, lon, lat]
-- DustCOMM annual and seasonal climatologies of 2-D dust mass extinction efficiency (m2/g). Fields include:
-> MEE_mean -- Mean Dust 2D Mass Extinction Efficiency
-> MEE_median -- Median Dust 2D Mass Extinction Efficiency
-> MEE_Pos1sig -- +1 Sigma Dust 2D Mass Extinction Efficiency
-> MEE_Neg1sig -- -1 Sigma Dust 2D Mass Extinction Efficiency
-> MEE_Pos2sig -- +2 Sigma Dust 2D Mass Extinction Efficiency
-> MEE_Neg2sig -- -2 Sigma Dust 2D Mass Extinction Efficiency
--------
Dust_Load_annual.nc - Dimension: [lon, lat]
Dust_Load_seasonal.nc - Dimension: [nseas, lon, lat]
-- DustCOMM annual and seasonal climatologies of 2-D atmospheric dust loading (g/m2). Fields include:
-> Load_mean -- Mean Atmospheric Dust Loading
-> Load_median -- Median Atmospheric Dust Loading
-> Load_Pos1sig -- +1 Sigma Atmospheric Dust Loading
-> Load_Neg1sig -- -1 Sigma Atmospheric Dust Loading
-> Load_Pos2sig -- +2 Sigma Atmospheric Dust Loading
-> Load_Neg2sig -- -2 Sigma Atmospheric Dust Loading
==========================
Correspondng Authors:
Adeyemi Adebiyi and Jasper Kok
Department of Atmospheric and Oceanic Sciences,
University of California Los Angeles, CA, USA
Email: [email protected] and [email protected]</p
DustCOMM
No full text<p>Dust Constraints from joint Observational-Modelling-experiMental analysis – DustCOMM Version 1</p>
Recommended from our members
The Impact of Meteorology on Smoke and Low-level Clouds over the Southeast Atlantic
No full textIn this dissertation, we use radiosondes and satellite observation, reanalysis datasets, as well as radiative and trajectory models to document the relationship between the low-level clouds, smoke and meteorology over the southeast Atlantic. The southeast Atlantic presents a natural environment with one of the world’s largest marine low-level clouds, occurring along with the largest consumption of biomass fire over the adjacent southern African continent. This combination results in an extensive region of above-cloud biomass burning aerosols (predominantly smoke) over the marine low-level clouds, whereby the elevated smoke could lead to the stabilization of the lower troposphere, reduction of the cloud-top entrainment, and the build-up of water vapor within the boundary layer, which may eventually lead to increases in cloud fraction and decreases in cloud-top heights, in a process called semi-direct aerosol effect. The smokes are transported at a preferred altitude (∼750hPa – 550hPa) by a background easterly winds between July and October. During the same period, strong surface winds and ocean-influenced cold surface temperature characterize the meteorology within the boundary layer. The marine low-level cloud region is also associated with strong climatological subsidence above it, and cloud-top temperature inversion layer. The meteorological variations occurring above and below the low-level clouds are capable of influencing the cloud properties, and therefore may confound with the aerosol effects, making the separation of the aerosol and meteorological influences, on the low-level cloud, a very difficult challenge. We address this problem by identifying the dynamical and thermodynamical variations above the low-level clouds during the the peak aerosol months (July–October). Specifically, three areas are explored in this dissertation: the convolution of the dynamical and moisture effects with shortwave-absorbing aerosols over the low-level clouds; the role of the mid-tropospheric easterly-transporting system on both the elevated smoke and the low-level cloud environments; and the synoptic-scale sensitivity of the low-level clouds to a range of interacting meteorological conditions, with and without the presence of the elevated smoke. First, the analysis of the radiosondes at St. Helena Island, a small island located approximately 1800 km offshore of continental Africa (15.9◦S, 5.6◦W), shows the presence of mid-tropospheric moisture within the smoke layer, and above the low-level clouds. The smoke layer has previously been associated with hot and dry layer, perhaps in analogy to the Saharan air layer. The mid-tropospheric moisture over the south-east Atlantic has not been previously documented, and it occurs more than 70% of the time between September and October. During the same months, as the aerosol loading increases, the amount of the mid-tropospheric moisture also increases. The result of the radiative transfer calculations shows that the mid-tropospheric moisture-induced longwave cooling accounts for about 30% of the aerosol-induced shortwave warming, within the smoke layer. At the cloud top, increased mid-tropospheric moisture could increase cloud-top heights by enhancing the downwelling longwave radiation at the cloud top, and potentially reducing the turbulent mixing within the boundary layer, which may ultimately reduce the cloud fraction. This process essentially opposes the cloud-thickening semi-direct aerosol effect due to the elevated smoke alone.
Dynamical changes occurring during the polluted condition over the southeast Atlantic include enhanced above-cloud warm horizontal temperature advection, and reduced subsidence. The flow is from the warmer adjacent continent air, and the warm advection directly above the marine low-level cloud is also capable of the increases in cloudiness through its influence on stability, that is separate from the stability associated with semi-direct aerosol effect. In addition, though a previous modeling study focussing on the southeast Atlantic has similarly identified the association between the elevated shortwave-absorbing aerosols (smoke) and the reduced subsidence, it remains unclear if the reduced subsidence is a response of the elevated aerosols alone, or an associated change in the above-cloud meteorological features, or both. Here, we show that during the September–October period, the southeast Atlantic is characterized by the Southern African Easterly Jet (AEJ-S), a region of maximum mid-tropospheric easterly winds responsible for the westward transport of both the aerosols and the moisture above the low-level clouds. The AEJ-S can be thought of as a southern counterpart of a better-known northern African easterly jet, and using the wealth of information available for the northern African easterly jet, we show that the AEJ-S is associated with induced upward motion directly below the jet, between 5◦S-15◦S. The AEJ-S-induced upward motion strengthens the large-scale ascent over the land, and therefore enhances the efficiency of trajectory-derived aerosol lifting emissions into the free-troposphere. Over ocean, the induced upward motion also reduces the large-scale subsidence over the marine low-level cloud. All else equal, the reduction of the offshore subsidence can be associated with reduction in nearby cloud fraction and increases in cloud-top heights, between 5◦S-15◦S. Between the effects of AEJ-S and the elevated aerosols on subsidence, the AEJ-S can be associated with 16% reduction in subsidence compared to 7% reduction by the elevated smoke-aerosols, between 5◦S-15◦S. By isolating the independent effects of selected above-cloud and surface-based meteorological influences during July–October period, it is shown that increases in lower tropospheric stability (LTS, defined as θ800hP a − θ1000hP a ), cold surface advection and warm 800 hPa horizontal temperature advection, all lead to increases in marine low-level cloudiness over the southeast Atlantic. In addition, the mid-tropospheric moisture is shown to independently result in reduction of cloud fraction, especially in the near- coastal region. Enhanced subsidence independently leads to increased cloudiness north of 20◦S, but decreased cloudiness south of 20◦S. The subsidence-induced reduction in cloudiness, south of 20◦S, contributes significantly to counteracting the stability-induced increases in cloudiness over the same region. When aerosol is present north of 20◦S, the effect of LTS on the low-level cloud is increased by about 13% over the region where the elevated aerosols are more likely separated from the underlying clouds, and by about 32% when the aerosols are more likely in contact with the underlying cloud layer. The results of this dissertation provide a detailed, useful meteorological context, highlighting new information, for the several multi-national upcoming field campaigns planned over the southeast Atlantic region. It also provides a useful understanding of the background dynamics and basic physical connections between the aerosols, the low-level clouds and the meteorology over the southeast Atlantic, that can be used in future studies involving aerosol-cloud-radiation interactions, and ultimately in numerical climate models to improve the estimation of climate sensitivity to subtropical low-level clouds.</p
Low Cloud Cover Sensitivity to Biomass-Burning Aerosols and Meteorology over the Southeast Atlantic
No full textAbstract
Shortwave-absorbing aerosols seasonally cover and interact with an expansive low-level cloud deck over the southeast Atlantic. Daily anomalies of the MODIS low cloud fraction, fine-mode aerosol optical depth (AODf), and six ERA-Interim meteorological parameters (lower-tropospheric stability, 800-hPa subsidence, 600-hPa specific humidity, 1000- and 800-hPa horizontal temperature advection, and 1000-hPa geopotential height) are constructed spanning July–October (2001–12). A standardized multiple linear regression, whereby the change in the low cloud fraction to each component’s variability is normalized by one standard deviation, facilitates comparison between the different variables. Most cloud–meteorology relationships follow expected behavior for stratocumulus clouds. Of interest is the low cloud–subsidence relationship, whereby increasing subsidence increases low cloud cover between 10° and 20°S but decreases it elsewhere. Increases in AODf increase cloudiness everywhere, independent of other meteorological predictors. The cloud–AODf effect is partially compensated by accompanying increases in the midtropospheric moisture, which is associated with decreases in low cloud cover. This suggests that the free-tropospheric moisture affects the low cloud deck primarily through longwave radiation rather than mixing. The low cloud cover is also more sensitive to aerosol when the vertical distance between the cloud and aerosol layer is relatively small, which is more likely to occur early in the biomass burning season and farther offshore. A parallel statistical analysis that does not include AODf finds altered relationships between the low cloud cover changes and meteorology that can be understood through the aerosol cross-correlations with the meteorological predictors. For example, the low cloud–stability relationship appears stronger if aerosols are not explicitly included.</jats:p
The role of the southern African easterly jet in modifying the southeast Atlantic aerosol and cloud environments
No full textThe westward transport of biomass‐burning (BB) aerosols by mid‐tropospheric winds over the southeast Atlantic stratocumulus deck has long been recognized, but the coupling to the large‐scale circulation has yet to be investigated fully. This goal is furthered here using satellite observations and reanalysis datasets spanning 2001–2012, as well as 10 day forward trajectory calculations of satellite‐detected smoke emissions. The results highlight the important role of a mid‐tropospheric zonal wind maximum, the Southern African Easterly Jet (AEJ‐S), in transporting BB aerosol west off the African continent. The AEJ‐S, defined through daily‐mean 600 hPa easterly wind speeds exceeding 6 m s−1 between 5°S and 15°S and centred zonally on the coastline, is most pronounced during September–October. The AEJ‐S is part of a meridional circulation that is diabatically forced by the temperature–moisture gradient between the southern hot–dry and northern cool–moist convective structures over land. 45% of 24 264 total identified smoke trajectories exit the continent to its west between 5°S and 15°S. These thereafter follow three major pathways: northwestward (8%), directly westward (55%) and anticyclonically recirculated (37%). The AEJ‐S induces an upward motion directly below the jet that enhances prevailing updraughts over land, lifting emissions and transporting aerosols more efficiently over the southeast Atlantic. Offshore, the prevailing large‐scale mean subsidence is reduced, with an associated increase in the nearby cloud‐top heights and reduction in the nearby marine low‐level cloud fraction. Further from the jet, increased warm continental temperature advection at 800 hPa associated with the strengthened land‐based anticyclone decreases mean low‐level cloud heights.
Westward‐moving 600 hPa winds at the northern edge of a land‐based anticyclone become the southern African easterly jet (AEJ‐S, blue contours, 6‐10 m/s) in September‐October. 10‐day smoke trajectories (red to yellow indicating age), for September of 2007, visualize shortwave‐absorbing aerosol transport from satellite‐detected fire emissions (fire‐counts in maroon) far offshore, over the southeast Atlantic stratocumulus deck (greyscale, cloud fractions of 0.5 to 1.0). We further examine the impact of the AEJ‐S's secondary circulation on the stratocumulus clouds and aerosol distribution
- …
