scholarly journals State and evolution of the African rainforests between 1990 and 2010

2013 ◽  
Vol 368 (1625) ◽  
pp. 20120300 ◽  
Author(s):  
Philippe Mayaux ◽  
Jean-François Pekel ◽  
Baudouin Desclée ◽  
François Donnay ◽  
Andrea Lupi ◽  
...  
Keyword(s):  
West Africa ◽  
Forest Cover ◽  
Central Africa ◽  
Congo Basin ◽  
Landsat Images ◽  
Deforestation Rate ◽  
Rural And Urban ◽  
Moderate Resolution ◽  
Underlying Causes ◽  
Moderate Resolution Imaging Spectroradiometer

This paper presents a map of Africa's rainforests for 2005. Derived from moderate resolution imaging spectroradiometer data at a spatial resolution of 250 m and with an overall accuracy of 84%, this map provides new levels of spatial and thematic detail. The map is accompanied by measurements of deforestation between 1990, 2000 and 2010 for West Africa, Central Africa and Madagascar derived from a systematic sample of Landsat images—imagery from equivalent platforms is used to fill gaps in the Landsat record. Net deforestation is estimated at 0.28% yr −1 for the period 1990–2000 and 0.14% yr −1 for the period 2000–2010. West Africa and Madagascar exhibit a much higher deforestation rate than the Congo Basin, for example, three times higher for West Africa and nine times higher for Madagascar. Analysis of variance over the Congo Basin is then used to show that expanding agriculture and increasing fuelwood demands are key drivers of deforestation in the region, whereas well-controlled timber exploitation programmes have little or no direct influence on forest-cover reduction at present. Rural and urban population concentrations and fluxes are also identified as strong underlying causes of deforestation in this study.

scholarly journals Satellite monitoring of blue-ice extent near Byrd Glacier, Antarctica

2004 ◽  
Vol 39 ◽  
pp. 223-230 ◽  
Author(s):  
Ian C. Brown ◽  
Ted A. Scambos
Keyword(s):  
Snow Cover ◽  
Satellite Monitoring ◽  
Landsat Images ◽  
Moderate Resolution ◽  
Summer Maximum ◽  
Resolution Imaging ◽  
Snowfall Event ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Seasonal And Interannual Variations

AbstractWe use satellite images to track seasonal and interannual variations in blue-ice extent over the past 30 years near Byrd Glacier on the East Antarctic plateau. The study areas have low slope and few nearby nunataks, which may increase their climate sensitivity. A threshold-based algorithm sensitive to snow grain-size is used to analyze 56 Moderate Resolution Imaging Spectroradiometer (MODIS) images over three recent summer seasons. Seasonal blue-ice exposure grows rapidly in late spring, and peaks by late December. Exposure is relatively constant between late December and mid-January, then declines in February. We interpret this cycle as due to removal and re-accumulation of patchy snow. Interannual changes in blue-ice area may be estimated by tracking the near-constant summer maximum extent period. Fifteen mid-summer Landsat images, spanning 1974–2002, were analyzed to determine long-term variations. Interannual area changes are 10–30%; however, the MODIS data revealed that the exposed blue-ice area can be sharply reduced for up to 2 weeks after a snowfall event; and in the 2001/02 season, patchy snow cover persisted for the entire summer. The combination of MODIS seasonal and Landsat interannual data indicates that blue-ice areas can be climate-sensitive. The strong feedback between snow cover and surface energy balance implies that blue-ice areas could rapidly decrease due to climate-related increases in snowfall or reduced ablation.

scholarly journals Response of African humid tropical forests to recent rainfall anomalies

2013 ◽  
Vol 368 (1625) ◽  
pp. 20120306 ◽  
Author(s):  
Salvi Asefi-Najafabady ◽  
Sassan Saatchi
Keyword(s):  
West Africa ◽  
Tropical Forests ◽  
Large Scale ◽  
Forest Canopy ◽  
Central Africa ◽  
Extreme Rainfall ◽  
Research Unit ◽  
Congo Basin ◽  
West And Central Africa ◽  
Rainfall Anomalies

During the last decade, strong negative rainfall anomalies resulting from increased sea surface temperature in the tropical Atlantic have caused extensive droughts in rainforests of western Amazonia, exerting persistent effects on the forest canopy. In contrast, there have been no significant impacts on rainforests of West and Central Africa during the same period, despite large-scale droughts and rainfall anomalies during the same period. Using a combination of rainfall observations from meteorological stations from the Climate Research Unit (CRU; 1950–2009) and satellite observations of the Tropical Rainfall Measuring Mission (TRMM; 1998–2010), we show that West and Central Africa experienced strong negative water deficit (WD) anomalies over the last decade, particularly in 2005, 2006 and 2007. These anomalies were a continuation of an increasing drying trend in the region that started in the 1970s. We monitored the response of forests to extreme rainfall anomalies of the past decade by analysing the microwave scatterometer data from QuickSCAT (1999–2009) sensitive to variations in canopy water content and structure. Unlike in Amazonia, we found no significant impacts of extreme WD events on forests of Central Africa, suggesting potential adaptability of these forests to short-term severe droughts. Only forests near the savanna boundary in West Africa and in fragmented landscapes of the northern Congo Basin responded to extreme droughts with widespread canopy disturbance that lasted only during the period of WD. Time-series analyses of CRU and TRMM data show most regions in Central and West Africa experience seasonal or decadal extreme WDs (less than −600 mm). We hypothesize that the long-term historical extreme WDs with gradual drying trends in the 1970s have increased the adaptability of humid tropical forests in Africa to droughts.

scholarly journals Observations of Supermicron-Sized Aerosols Originating from Biomass Burning in South Central Africa

2021 ◽  
Author(s):  
Rose Marie Miller ◽  
Greg M. McFarquhar ◽  
Robert M. Rauber ◽  
Joseph R. O'Brien ◽  
Siddhant Gupta ◽  
...  
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Single Particle ◽  
Central Africa ◽  
Submicron Particles ◽  
Back Trajectories ◽  
Active Fire ◽  
South Central ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract. During the three years of the ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) campaign, the NASA Orion P-3 was equipped with a 2D-Stereo (2D-S) probe that imaged particles with maximum dimension (D) ranging from 10 < D < 1280 µm. The 2D-S recorded supermicron-sized aerosol particles (SAPs) outside of clouds within biomass burning plumes during flights over the Southeast Atlantic off Africa’s coast. Numerous SAPs with 10 < D < 1520 µm were observed in 2017 and 2018 at altitudes between 1230 m and 3500 m, 1000 km from the coastline mostly between 7–11° S. No SAPs were observed in 2016 as flights were conducted further south and further from the coastline. Number concentrations of black carbon (rBC) measured by a single particle soot photometer ranged from 200 to 1200 cm−3 when SAPs were observed. Transmission electron microscopy images of submicron particulates, collected on Holey carbon grid filters, revealed particles with potassium salts, black carbon and organics while energy-dispersive X-ray spectroscopy spectra detected potassium, a tracer for biomass burning, indicating that the submicron particles originated from biomass burning in addition to black carbon. NOAA Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) three-day back trajectories show a source in northern Angola for times when large SAPs were observed. Fire Information for Resource Management System Moderate Resolution Imaging Spectroradiometer (MODIS) 6 active fire maps showed extensive biomass burning at these locations. Given the back trajectories, the high number concentrations of rBC, and the presence of elemental tracers indicative of biomass burning, it is hypothesized that the SAPs imaged by the 2D-S are examples of unburned plant material previously seen in biomass burning smoke close to the source.

New simple approach to understand the spatial and vertical distribution of biomass burning CO emission based on the MOPITT vertical measurements

2020 ◽  
Author(s):  
Chuyong Lin ◽  
Jason Cohen
Keyword(s):  
South America ◽  
Biomass Burning ◽  
Large Scale ◽  
Central Africa ◽  
Western Africa ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Significant Spread ◽  
Spatial And Vertical Distribution

&lt;p&gt;A simple variance-maximization approach, based on 19 years of weekly Moderate Resolution Imaging spectroradiometer (MOPITT) CO vertical measurements, was employed to quantify the spatial distribution of the global seasonal biomass burning region. Results demonstrate there are a few large-scale and typical biomass burning regions responsible for most of the biomass burning emissions throughout the world, with the largest of these such regions located in Amazonian South America, Western Africa, Indonesia, and Northern Southeast Asia (Eastern India, Northern Myanmar, Laos, Vietnam and Eastern Bangladesh), which are highly associated with the results of Global Fire Emission Database(GFED). The CO is primarily lofted to and spreads downwind at 800mb or 700mb with three exceptions: The Maritime Continent and South America where there is significant spread at 300mb consistent with known deep- and pyro-convection; and Southern Africa where there is significant spread at 600mb. The total mass of CO lofted into the free troposphere ranges from 46% over Central Africa to 92% over Australia.&lt;/p&gt;

scholarly journals ValLAI_Crop, a validation dataset for coarse-resolution satellite LAI products over Chinese cropland

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Bowen Song ◽  
Liangyun Liu ◽  
Shanshan Du ◽  
Xiao Zhang ◽  
Xidong Chen ◽  
...  
Keyword(s):  
Field Measurements ◽  
Validation Dataset ◽  
Landsat Images ◽  
Area Index ◽  
Coarse Resolution ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Fine Resolution ◽  
Modis Lai

AbstractNumerous validation efforts have been conducted over the last decade to assess the accuracy of global leaf area index (LAI) products. However, such efforts continue to face obstacles due to the lack of sufficient high-quality field measurements. In this study, a fine-resolution LAI dataset consisting of 80 reference maps was generated during 2003–2017. The direct destructive method was used to measure the field LAI, and fine-resolution LAI images were derived from Landsat images using semiempirical inversion models. Eighty reference LAI maps, each with an area of 3 km × 3 km and a percentage of cropland larger than 75%, were selected as the fine-resolution validation dataset. The uncertainty associated with the spatial scale effect was also provided. Ultimately, the fine-resolution reference LAI dataset was used to validate the Moderate Resolution Imaging Spectroradiometer (MODIS) LAI product. The results indicate that the fine-resolution reference LAI dataset builds a bridge to link small sampling plots and coarse-resolution pixels, which is extremely important in validating coarse-resolution LAI products.

scholarly journals Fragmentation and clearance of Liberia's forests during 1986-2000

Oryx ◽  
2007 ◽  
Vol 41 (4) ◽  
pp. 539-543 ◽  
Author(s):  
T. Christie ◽  
M.K. Steininger ◽  
D. Juhn ◽  
A. Peal
Keyword(s):  
West Africa ◽  
Satellite Imagery ◽  
Conservation Planning ◽  
Forest Cover ◽  
Deforestation Rate ◽  
Landsat Satellite ◽  
Comprehensive Mapping

AbstractWe report estimates of the area and rate of loss and fragmentation of Liberian forests from 1986 to 2000. These estimates are based on comprehensive mapping using Landsat satellite imagery, which has a resolution of 28.5 m. We estimate a total forest cover of 4.65 million ha in 1986 and 4.33 million ha in 2000. Most of Liberia's remaining forest is in two large regions. These forests are very important biologically because they are the largest remaining forest areas in West Africa. The average deforestation rate was low at 0.2% per year during 1986–2000. Although the fragmentation of Liberia's forests is also relatively low, most of the remaining forest is readily accessible as it is within a few km of existing roads. This ease of accessibility suggests that the present low deforestation rate could increase if conservation planning is not effectively implemented.

scholarly journals Estimation of Seasonal Evapotranspiration for Crops in Arid Regions Using Multisource Remote Sensing Images

2020 ◽  
Vol 12 (15) ◽  
pp. 2398
Author(s):  
Mingxing Cha ◽  
Mengmeng Li ◽  
Xiaoqin Wang
Keyword(s):  
Remote Sensing ◽  
Arid Regions ◽  
Optimal Allocation ◽  
Irrigation Management ◽  
Accurate Estimation ◽  
Remote Sensing Images ◽  
Landsat Images ◽  
Moderate Resolution ◽  
Sebal Model ◽  
Moderate Resolution Imaging Spectroradiometer

An accurate estimation of evapotranspiration (ET) from crops is crucial in irrigation management, crop yield assessment, and optimal allocation of water resources, particularly in arid regions. This study explores the estimation of seasonal evapotranspiration for crops using multisource remote sensing images. The proposed estimation framework starts with estimating daily evapotranspiration (ETd) values, which are then used to calculate ET estimates during the crop growing season (ETs). We incorporated Landsat images into the surface energy balance algorithm over land (SEBAL) model, and we used the trapezoidal and sinusoidal methods to estimate the seasonal ET. The trapezoidal method used multitemporal ETd images, while the sinusoidal method employs time-series Moderate Resolution Imaging Spectroradiometer (MODIS) images and multitemporal ETd images. Experiments were implemented in the agricultural lands of the Kai-Kong River Basin, Xinjiang, China. The experimental results show that the obtained ETd estimates using the SEBAL model are comparable with those from the Penman–Monteith method. The ETs obtained using the trapezoidal and sinusoidal methods both have a relatively high spatial resolution of 30 m. The sinusoidal method performs better than the trapezoidal method when using low temporal resolution Landsat images. We observed that the omission of Landsat images during the middle stage of crop growth has the greatest impact on the estimation results of ETs using the sinusoidal method. Based on the results of the study, we conclude that the proposed sinusoidal method, with integrated multisource remote sensing images, offers a useful tool in estimating seasonal evapotranspiration for crops in arid regions.

scholarly journals Reforestation and Deforestation in Northern Luzon, Philippines: Critical Issues as Observed from Space

Forests ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1071
Author(s):  
Gay Jane Perez ◽  
Josefino C. Comiso ◽  
Lemnuel V. Aragones ◽  
Harry C. Merida ◽  
Perry S. Ong
Keyword(s):  
Vegetation Cover ◽  
Forest Cover ◽  
Old Growth ◽  
Old Growth Forest ◽  
Open Forest ◽  
Sierra Madre ◽  
Critical Issues ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Negative Impacts

Among the richest in biodiversity globally has been the Philippine rainforest, which used to cover about 90% of the country’s land area. During the last few decades, the forest cover has been reduced to less than 10% of the original, only a fraction of which is old-growth forest. The negative impacts of deforestation led to the launching of the National Greening Program (NGP) that involved the planting of more than a billion seedlings over a few million hectares of land from 2011 to 2016. To assess the success of the NGP, satellite data from Landsat and the Moderate Resolution Imaging Spectroradiometer (MODIS) were analyzed before, during, and after the NGP. Reforestation in the NGP sites was examined concurrently with observed deforestation in Luzon using forest loss data derived from Landsat for the period 2001 to 2018. The results show that losses declined from 2011 to 2015 but increased from 2016 to 2018. Because of such losses, the net effect is a balance of reforestation and deforestation or no significant gain from the NGP. Case studies were done in three sites in the Sierra Madre forest, where half of the remaining old-growth forest is located, using a combination of Landsat and Very High Resolution (VHR) data. The Landsat data were classified into closed forest, open forest, and other vegetation cover types. The conversion from one vegetation cover type to another was evaluated through the use of the Sankey Diagram. While some non-forest types became open or closed forests, the loss of open or closed forests is more pronounced. VHR data reveal critical issues happening within the NGP sites during the NGP period. More comprehensive data from MODIS also confirm that there was no significant increase in the forest cover in Luzon, Sierra Madre, and Cordillera from 2001 to 2018.

scholarly journals The ERA5’s Diurnal Cycle of Low-Level Clouds Over Western Central Africa During June-September: Dynamic and Thermodynamic Processes.

2021 ◽  
Author(s):  
Atanas Dommo ◽  
Derbetini A. Vondou ◽  
Nathalie Philippon ◽  
Ryan Eastman ◽  
Vincent Moron ◽  
...  
Keyword(s):  
Diurnal Cycle ◽  
Lower Layer ◽  
Central Africa ◽  
Cloud Formation ◽  
Atmospheric Conditions ◽  
Low Level ◽  
Low Cloud ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Low Cloud Cover

Abstract This paper analyzes the diurnal cycle of low cloud cover (LCC) and the atmospheric conditions under which it grows over Western Central Africa during the cloudiest season (June-September). Moderate Resolution Imaging Spectroradiometer (MODIS) observations, Extended Edited Clouds Reports Archive (EECRA) and the fifth generation of reanalysis of the European Centre for Medium Range Weather Forecasts (ECMWF), i.e., ERA5 are used. LCC peaks between 04LT and 07LT and tends to be less dense during the afternoon. The associated dynamic and thermodynamic ERA5 conditions reveal different processes. The strong low level (below 1000 m) southwesterly flow in the evening supplies the region with humidity from the ocean and leads to cloud formation. Relative humidity (RH) tendencies show that temperature contributes to 100% of RH changes : the strong cooling observed after sunset at 19LT increases RH in the area of about 8%/h in the lower layer (below 1000m). The nighttime cooling shows strong cooling rates of about -1.4K/h after sunset till 22 LT, then rates decrease during the night to reach a value of about -0.3K/h between 22LT and 07LT. The cloud formation is mostly related to horizontal air advection, strong convergence in the lower layer and turbulent upwards mixing of moisture, while cooling at the cloud-top helps to maintain the cloud deck once it has formed. During daytime, solar radiation suppressed cooling at the cloud-top, thereafter strong turbulent kinetic energy acts to partly destroy the cloud deck and cloud fraction.

scholarly journals Assessing MODIS Vegetation Continuous Fields tree cover product (collection 6): performance and applicability in tropical forests and savannas

2021 ◽  
Author(s):  
Rahayu Adzhar ◽  
Douglas I. Kelley ◽  
Ning Dong ◽  
Mireia Torello Raventos ◽  
Elmar Veenendaal ◽  
...  
Keyword(s):  
Field Data ◽  
Forest Cover ◽  
Tree Cover ◽  
Tropical Savannas ◽  
Moderate Resolution ◽  
Forest Cover Changes ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Continuous Fields ◽  
The Impact

Abstract. The Moderate Resolution Imaging Spectroradiometer vegetation continuous fields (MODIS VCF) Earth observation product is widely used to estimate forest cover changes, parameterise vegetation and Earth System models, and as a reference for validation or calibration where field data is limited. However, although limited independent validations of MODIS VCF have shown that MODIS VCF's accuracy decreases when estimating tree cover in sparsely-vegetated areas, such as in tropical savannas, no study has yet assessed the impact this may have on the VCF based tree cover distributions used by many in their research. Using tropical forest and savanna inventory data collected by the TROpical Biomes In Transition (TROBIT) project, we produce a series of corrections that take into account (i) the spatial disparity between the in-situ plot size and the MODIS VCF pixel, and (ii) the trees' spatial distribution within in-situ plots. We then applied our corrections to areas identified as forest or savanna in the International Geosphere-Biosphere Programme (IGBP) land cover mapping product. All IGBP classes identified as savanna show substantial increases in cover after correction, indicating that the most recent version of MODIS VCF consistently underestimates woody cover in tropical savannas. We estimate that MODIS VCF could be underestimating tropical tree cover by between 9–15 %. Models that use VCF as their benchmark could be underestimating the carbon uptake in forest-savanna areas and misrepresenting forest-savanna dynamics. While more detailed in-situ field data is necessary to produce more accurate and reliable corrections, we recommend caution when using MODIS VCF in tropical savannas.

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